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Title: Flying Machines: construction and operation; a practical book which shows, in illustrations, working plans and text, how to build and navigate the modern airship
Author: Russell, Thomas Herbert, 1862-1947, Jackman, William James, 1850-, Chanute, Octave, 1832-1910
Language: English
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*** Start of this LibraryBlog Digital Book "Flying Machines: construction and operation; a practical book which shows, in illustrations, working plans and text, how to build and navigate the modern airship" ***
FLYING MACHINE: CONSTRUCTION AND OPERATION
By W.J. Jackman and Thos. H. Russell
A Practical Book Which Shows, in Illustrations, Working Plans and Text,
How to Build and Navigate the Modern Airship.
W.J. JACKMAN, M.E., Author of "A B C of the Motorcycle," "Facts for
Motorists," etc. etc.
and
THOS. H. RUSSELL, A.M., M.E., Charter Member of the Aero Club of
Illinois, Author of "History of the Automobile," "Motor Boats:
Construction and Operation," etc. etc.
With Introductory Chapter By Octave Chanute, C.E., President Aero Club
of Illinois
1912
PREFACE.
This book is written for the guidance of the novice in aviation--the
man who seeks practical information as to the theory, construction and
operation of the modern flying machine. With this object in view the
wording is intentionally plain and non-technical. It contains some
propositions which, so far as satisfying the experts is concerned, might
doubtless be better stated in technical terms, but this would defeat the
main purpose of its preparation. Consequently, while fully aware of its
shortcomings in this respect, the authors have no apologies to make.
In the stating of a technical proposition so it may be clearly
understood by people not versed in technical matters it becomes
absolutely necessary to use language much different from that which an
expert would employ, and this has been done in this volume.
No man of ordinary intelligence can read this book without obtaining
a clear, comprehensive knowledge of flying machine construction and
operation. He will learn, not only how to build, equip, and manipulate
an aeroplane in actual flight, but will also gain a thorough
understanding of the principle upon which the suspension in the air of
an object much heavier than the air is made possible.
This latter feature should make the book of interest even to those who
have no intention of constructing or operating a flying machine. It will
enable them to better understand and appreciate the performances of the
daring men like the Wright brothers, Curtiss, Bleriot, Farman, Paulhan,
Latham, and others, whose bold experiments have made aviation an
actuality.
For those who wish to engage in the fascinating pastime of construction
and operation it is intended as a reliable, practical guide.
It may be well to explain that the sub-headings in the articles by Mr.
Chanute were inserted by the authors without his knowledge. The purpose
of this was merely to preserve uniformity in the typography of the book.
This explanation is made in justice to Mr. Chanute.
THE AUTHORS.
IN MEMORIAM.
Octave Chanute, "the father of the modern flying machine," died at his
home in Chicago on November 23, 1910, at the age of 72 years. His last
work in the interest of aviation was to furnish the introductory chapter
to the first edition of this volume, and to render valuable assistance
in the handling of the various subjects. He even made the trip from his
home to the office of the publishers one inclement day last spring,
to look over the proofs of the book and, at his suggestion, several
important changes were made. All this was "a labor of love" on Mr.
Chanute's part. He gave of his time and talents freely because he was
enthusiastic in the cause of aviation, and because he knew the authors
of this book and desired to give them material aid in the preparation of
the work--a favor that was most sincerely appreciated.
The authors desire to make acknowledgment of many courtesies in the way
of valuable advice, information, etc., extended by Mr. Octave Chanute,
C. E., Mr. E. L. Jones, Editor of Aeronautics, and the publishers of,
the New England Automobile Journal and Fly.
CONTENTS
Chapter
I. Evolution of the Two-Surface Flying Machine
Introductory Chapter by Octave Chanute, C. E.
II. Theory Development and Use
Origin of the Aeroplane--Developments by Chanute
and the Wrights--Practical Uses and Limits.
III. Mechanical Bird Action
What the Motor Does--Puzzle in Bird Soaring.
IV. Various Forms of Flying Machines
Helicopters, Ornithopters and Aeroplanes--
Monoplanes, Biplanes and Triplanes.
V. Constructing a Gliding Machine
Plans and Materials Required--Estimate of Cost--
Sizes and Preparation of Various Parts--Putting the
Parts Together
VI. Learning to Fly
How to Use the Glider--Effect of Body Movements
--Rules for Beginners--Safest Place to Glide.
VII. Putting On the Rudder
Its Construction, Application and Use.
VIII. The Real Flying Machine
Surface Area Required--Proper Size of Frame and
Auxiliaries--Installation of Motor--Cost of
Constructing Machine.
IX. Selection of the Motor
Essential Features--Multiplicity of Cylinders--Power
Required--Kind and Action of Propellers--Placing
of the Motor
X. Proper Dimensions of Machines
Figuring Out the Details--How to Estimate Load
Capacity--Distribution of the Weight--Measurements
of Leading Machines.
XI. Plane and Rudder Control
Various Methods in Use--Wheels and Hand and
Foot Levers
XII. How to Use the Machine
Rules of Leading Aviators--Rising from the Ground
--Reasonable Altitude--Preserving Equilibrium--
Learning to Steer.
XIII. Peculiarities of Aeroplane Power
Pressure of the Wind--How to Determine Upon
Power--Why Speed Is Required--Bird find Flying
Machine Areas.
XIV. About Wind Currents, Etc.
Uncertainty of Direct Force--Trouble With Gusty
Currents--Why Bird Action Is Imitated.
XV. The Element of Danger
Risk Small Under Proper Conditions--Two Fields
of Safety--Lessons in Recent Accidents.
XVI. Radical Changes Being Made
Results of Recent Experiments--New Dimensions
--Increased Speed--The One Governing Rule.
XVII. Some of the New Designs
Automatic Control of Plane Stability--Inventor
Herring's Devices--Novel Ideas of Students.
XVIII. Demand for Flying Machines
Wonderful Results in a Year--Factories Over-
crowded with Orders.
XIX. Law of the Airship
Rights of Property Owners--Some Legal
Peculiarities--Danger of Trespass.
XX. Soaring Flight
XXI. Flying Machines vs. Balloons
XXII. Problems of Aerial Flight
XXIII. Amateurs May Use Wright Patents
XXIV. Hints on Propeller Construction
XXV. New Motors and Devices
XXVI. Monoplanes, Triplanes, Multiplanes
XXVII. Records of Various Kinds
FLYING MACHINES: CONSTRUCTION and OPERATION
CHAPTER I. EVOLUTION OF TWO-SURFACE FLYING MACHINE.
By Octave Chanute.
I am asked to set forth the development of the "two-surface" type of
flying machine which is now used with modifications by Wright Brothers,
Farman, [1] Delagrange, Herring and others.
This type originated with Mr. F. H. Wenham, who patented it in
England in 1866 (No. 1571), taking out provisional papers only. In the
abridgment of British patent Aeronautical Specifications (1893) it is
described as follows:
"Two or more aeroplanes are arranged one above the other, and support a
framework or car containing the motive power. The aeroplanes are made of
silk or canvas stretched on a frame by wooden rods or steel ribs. When
manual power is employed the body is placed horizontally, and oars or
propellers are actuated by the arms or legs.
"A start may be obtained by lowering the legs and running down hill or
the machine may be started from a moving carriage. One or more screw
propellers may be applied for propelling when steam power is employed."
On June 27, 1866, Mr. Wenham read before the "Aeronautical Society of
Great Britain," then recently organized, the ablest paper ever presented
to that society, and thereby breathed into it a spirit which has
continued to this day. In this paper he described his observations of
birds, discussed the laws governing flight as to the surfaces and power
required both with wings and screws, and he then gave an account of his
own experiments with models and with aeroplanes of sufficient size to
carry the weight of a man.
Second Wenham Aeroplane.
His second aeroplane was sixteen feet from tip to tip. A trussed spar at
the bottom carried six superposed bands of thin holland fabric fifteen
inches wide, connected with vertical webs of holland two feet apart,
thus virtually giving a length of wing of ninety-six feet and one
hundred and twenty square feet of supporting surface. The man was placed
horizontally on a base board beneath the spar. This apparatus when tried
in the wind was found to be unmanageable by reason of the fluttering
motions of the fabric, which was insufficiently stiffened with crinoline
steel, but Mr. Wenham pointed out that this in no way invalidated
the principle of the apparatus, which was to obtain large supporting
surfaces without increasing unduly the leverage and consequent weight of
spar required, by simply superposing the surfaces.
This principle is entirely sound and it is surprising that it is,
to this day, not realized by those aviators who are hankering for
monoplanes.
Experiments by Stringfellow.
The next man to test an apparatus with superposed surfaces was Mr.
Stringfellow, who, becoming much impressed with Mr. Wenham's proposal,
produced a largish model at the exhibition of the Aeronautical Society
in 1868. It consisted of three superposed surfaces aggregating 28 square
feet and a tail of 8 square feet more. The weight was under 12 pounds
and it was driven by a central propeller actuated by a steam engine
overestimated at one-third of a horsepower. It ran suspended to a wire
on its trials but failed of free flight, in consequence of defective
equilibrium. This apparatus has since been rebuilt and is now in the
National Museum of the Smithsonian Institution at Washington. Linfield's
Unsuccessful Efforts.
In 1878 Mr. Linfield tested an apparatus in England consisting of a
cigar-shaped car, to which was attached on each side frames five feet
square, containing each twenty-five superposed planes of stretched and
varnished linen eighteen inches wide, and only two inches apart, thus
reminding one of a Spanish donkey with panniers. The whole weighed two
hundred and forty pounds. This was tested by being mounted on a flat car
behind a locomotive going 40 miles an hour. When towed by a line fifteen
feet long the apparatus rose only a little from the car and exhibited
such unstable equilibrium that the experiment was not renewed. The lift
was only about one-third of what it would have been had the planes been
properly spaced, say their full width apart, instead of one-ninth as
erroneously devised.
Renard's "Dirigible Parachute."
In 1889 Commandant Renard, the eminent superintendent of the French
Aeronautical Department, exhibited at the Paris Exposition of that year,
an apparatus experimented with some years before, which he termed a
"dirigible parachute." It consisted of an oviform body to which were
pivoted two upright slats carrying above the body nine long superposed
flat blades spaced about one-third of their width apart. When this
apparatus was properly set at an angle to the longitudinal axis of the
body and dropped from a balloon, it travelled back against the wind for
a considerable distance before alighting. The course could be varied
by a rudder. No practical application seems to have been made of this
device by the French War Department, but Mr. J. P. Holland, the
inventor of the submarine boat which bears his name, proposed in 1893
an arrangement of pivoted framework attached to the body of a flying
machine which combines the principle of Commandant Renard with the
curved blades experimented with by Mr. Phillips, now to be noticed, with
the addition of lifting screws inserted among the blades.
Phillips Fails on Stability Problem.
In 1893 Mr. Horatio Phillips, of England, after some very interesting
experiments with various wing sections, from which he deduced
conclusions as to the shape of maximum lift, tested an apparatus
resembling a Venetian blind which consisted of fifty wooden slats of
peculiar shape, 22 feet long, one and a half inches wide, and two inches
apart, set in ten vertical upright boards. All this was carried upon a
body provided with three wheels. It weighed 420 pounds and was driven
at 40 miles an hour on a wooden sidewalk by a steam engine of nine
horsepower which actuated a two-bladed screw. The lift was satisfactory,
being perhaps 70 pounds per horsepower, but the equilibrium was quite
bad and the experiments were discontinued. They were taken up again in
1904 with a similar apparatus large enough to carry a passenger, but the
longitudinal equilibrium was found to be defective. Then in 1907 a new
machine was tested, in which four sets of frames, carrying similar
sets of slat "sustainers" were inserted, and with this arrangement the
longitudinal stability was found to be very satisfactory. The whole
apparatus, with the operator, weighed 650 pounds. It flew about 200
yards when driven by a motor of 20 to 22 h.p. at 30 miles an hour,
thus exhibiting a lift of about 32 pounds per h.p., while it will be
remembered that the aeroplane of Wright Brothers exhibits a lifting
capacity of 50 pounds to the h.p.
Hargrave's Kite Experiments.
After experimenting with very many models and building no less than
eighteen monoplane flying model machines, actuated by rubber, by
compressed air and by steam, Mr. Lawrence Hargrave, of Sydney, New South
Wales, invented the cellular kite which bears his name and made it known
in a paper contributed to the Chicago Conference on Aerial Navigation
in 1893, describing several varieties. The modern construction is well
known, and consists of two cells, each of superposed surfaces with
vertical side fins, placed one behind the other and connected by a
rod or frame. This flies with great steadiness without a tail. Mr.
Hargrave's idea was to use a team of these kites, below which he
proposed to suspend a motor and propeller from which a line would be
carried to an anchor in the ground. Then by actuating the propeller the
whole apparatus would move forward, pick up the anchor and fly away. He
said: "The next step is clear enough, namely, that a flying machine with
acres of surface can be safely got under way or anchored and hauled to
the ground by means of the string of kites."
The first tentative experiments did not result well and emphasized the
necessity for a light motor, so that Mr. Hargrave has since been engaged
in developing one, not having convenient access to those which have been
produced by the automobile designers and builders.
Experiments With Glider Model.
And here a curious reminiscence may be indulged in. In 1888 the present
writer experimented with a two-cell gliding model, precisely similar to
a Hargrave kite, as will be confirmed by Mr. Herring. It was frequently
tested by launching from the top of a three-story house and glided
downward very steadily in all sorts of breezes, but the angle of descent
was much steeper than that of birds, and the weight sustained per square
foot was less than with single cells, in consequence of the lesser
support afforded by the rear cell, which operated upon air already set
in motion downward by the front cell, so nothing more was done with
it, for it never occurred to the writer to try it as a kite and he thus
missed the distinction which attaches to Hargrave's name.
Sir Hiram Maxim also introduced fore and aft superposed surfaces in his
wondrous flying machine of 1893, but he relied chiefly for the lift upon
his main large surface and this necessitated so many guys, to prevent
distortion, as greatly to increase the head resistance and this,
together with the unstable equilibrium, made it evident that the design
of the machine would have to be changed.
How Lilienthal Was Killed.
In 1895, Otto Lilienthal, the father of modern aviation, the man to
whose method of experimenting almost all present successes are due,
after making something like two thousand glides with monoplanes, added
a superposed surface to his apparatus and found the control of it much
improved. The two surfaces were kept apart by two struts or vertical
posts with a few guy wires, but the connecting joints were weak and
there was nothing like trussing. This eventually cost his most useful
life. Two weeks before that distressing loss to science, Herr Wilhelm
Kress, the distinguished and veteran aviator of Vienna, witnessed a
number of glides by Lilienthal with his double-decked apparatus. He
noticed that it was much wracked and wobbly and wrote to me after the
accident: "The connection of the wings and the steering arrangement were
very bad and unreliable. I warned Herr Lilienthal very seriously. He
promised me that he would soon put it in order, but I fear that he did
not attend to it immediately."
In point of fact, Lilienthal had built a new machine, upon a different
principle, from which he expected great results, and intended to make
but very few more flights with the old apparatus. He unwisely made one
too many and, like Pilcher, was the victim of a distorted apparatus.
Probably one of the joints of the struts gave way, the upper surface
blew back and Lilienthal, who was well forward on the lower surface, was
pitched headlong to destruction.
Experiments by the Writer.
In 1896, assisted by Mr. Herring and Mr. Avery, I experimented with
several full sized gliding machines, carrying a man. The first was a
Lilienthal monoplane which was deemed so cranky that it was discarded
after making about one hundred glides, six weeks before Lilienthal's
accident. The second was known as the multiple winged machine and
finally developed into five pairs of pivoted wings, trussed together at
the front and one pair in the rear. It glided at angles of descent of 10
or 11 degrees or of one in five, and this was deemed too steep. Then
Mr. Herring and myself made computations to analyze the resistances. We
attributed much of them to the five front spars of the wings and on
a sheet of cross-barred paper I at once drew the design for a new
three-decked machine to be built by Mr. Herring.
Being a builder of bridges, I trussed these surfaces together, in order
to obtain strength and stiffness. When tested in gliding flight the
lower surface was found too near the ground. It was taken off and the
remaining apparatus now consisted of two surfaces connected together
by a girder composed of vertical posts and diagonal ties, specifically
known as a "Pratt truss." Then Mr. Herring and Mr. Avery together
devised and put on an elastic attachment to the tail. This machine
proved a success, it being safe and manageable. Over 700 glides were
made with it at angles of descent of 8 to 10 degrees, or one in six to
one in seven.
First Proposed by Wenham.
The elastic tail attachment and the trussing of the connecting frame of
the superposed wings were the only novelties in this machine, for the
superposing of the surfaces had first been proposed by Wenham, but in
accordance with the popular perception, which bestows all the credit
upon the man who adds the last touch making for success to the labors
of his predecessors, the machine has since been known by many persons as
the "Chanute type" of gliders, much to my personal gratification.
It has since been improved in many ways. Wright Brothers, disregarding
the fashion which prevails among birds, have placed the tail in front
of their apparatus and called it a front rudder, besides placing the
operator in horizontal position instead of upright, as I did; and also
providing a method of warping the wings to preserve equilibrium. Farman
and Delagrange, under the very able guidance and constructive work of
Voisin brothers, then substituted many details, including a box tail for
the dart-like tail which I used. This may have increased the resistance,
but it adds to the steadiness. Now the tendency in France seems to be to
go back to the monoplane.
Monoplane Idea Wrong.
The advocates of the single supporting surface are probably mistaken. It
is true that a single surface shows a greater lift per square foot than
superposed surfaces for a given speed, but the increased weight due to
leverage more than counterbalances this advantage by requiring heavy
spars and some guys. I believe that the future aeroplane dynamic flier
will consist of superposed surfaces, and, now that it has been found
that by imbedding suitably shaped spars in the cloth the head resistance
may be much diminished, I see few objections to superposing three, four
or even five surfaces properly trussed, and thus obtaining a compact,
handy, manageable and comparatively light apparatus. [2]
CHAPTER II. THEORY, DEVELOPMENT, AND USE.
While every craft that navigates the air is an airship, all airships are
not flying machines. The balloon, for instance, is an airship, but it is
not what is known among aviators as a flying machine. This latter term
is properly used only in referring to heavier-than-air machines which
have no gas-bag lifting devices, and are made to really fly by the
application of engine propulsion.
Mechanical Birds.
All successful flying machines--and there are a number of them--are
based on bird action. The various designers have studied bird flight
and soaring, mastered its technique as devised by Nature, and the modern
flying machine is the result. On an exaggerated, enlarged scale the
machines which are now navigating the air are nothing more nor less than
mechanical birds.
Origin of the Aeroplane.
Octave Chanute, of Chicago, may well be called "the developer of the
flying machine." Leaving balloons and various forms of gas-bags out
of consideration, other experimenters, notably Langley and Lilienthal,
antedated him in attempting the navigation of the air on aeroplanes,
or flying machines, but none of them were wholly successful, and it
remained for Chanute to demonstrate the practicability of what was then
called the gliding machine. This term was adopted because the apparatus
was, as the name implies, simply a gliding machine, being without motor
propulsion, and intended solely to solve the problem of the best form of
construction. The biplane, used by Chanute in 1896, is still the basis
of most successful flying machines, the only radical difference being
that motors, rudders, etc., have been added.
Character of Chanute's Experiments.
It was the privilege of the author of this book to be Mr. Chanute's
guest at Millers, Indiana, in 1896, when, in collaboration with Messrs.
Herring and Avery, he was conducting the series of experiments which
have since made possible the construction of the modern flying machine
which such successful aviators as the Wright brothers and others are
now using. It was a wild country, much frequented by eagles, hawks, and
similar birds. The enthusiastic trio, Chanute, Herring and Avery, would
watch for hours the evolutions of some big bird in the air, agreeing
in the end on the verdict, "When we master the principle of that bird's
soaring without wing action, we will have come close to solving the
problem of the flying machine."
Aeroplanes of various forms were constructed by Mr. Chanute with the
assistance of Messrs. Herring and Avery until, at the time of the
writer's visit, they had settled upon the biplane, or two-surface
machine. Mr. Herring later equipped this with a rudder, and made other
additions, but the general idea is still the basis of the Wright,
Curtiss, and other machines in which, by the aid of gasolene motors,
long flights have been made.
Developments by the Wrights.
In 1900 the Wright brothers, William and Orville, who were then in
the bicycle business in Dayton, Ohio, became interested in Chanute's
experiments and communicated with him. The result was that the Wrights
took up Chanute's ideas and developed them further, making many
additions of their own, one of which was the placing of a rudder in
front, and the location of the operator horizontally on the machine,
thus diminishing by four-fifths the wind resistance of the man's
body. For three years the Wrights experimented with the glider before
venturing to add a motor, which was not done until they had thoroughly
mastered the control of their movements in the air.
Limits of the Flying Machine.
In the opinion of competent experts it is idle to look for a commercial
future for the flying machine. There is, and always will be, a limit to
its carrying capacity which will prohibit its employment for passenger
or freight purposes in a wholesale or general way. There are some, of
course, who will argue that because a machine will carry two people
another may be constructed that will carry a dozen, but those who make
this contention do not understand the theory of weight sustentation in
the air; or that the greater the load the greater must be the lifting
power (motors and plane surface), and that there is a limit to these--as
will be explained later on--beyond which the aviator cannot go.
Some Practical Uses.
At the same time there are fields in which the flying machine may be
used to great advantage. These are:
Sports--Flying machine races or flights will always be popular by reason
of the element of danger. It is a strange, but nevertheless a true
proposition, that it is this element which adds zest to all sporting
events.
Scientific--For exploration of otherwise inaccessible regions such as
deserts, mountain tops, etc.
Reconnoitering--In time of war flying machines may be used to advantage
to spy out an enemy's encampment, ascertain its defenses, etc.
CHAPTER III. MECHANICAL BIRD ACTION
In order to understand the theory of the modern flying machine one must
also understand bird action and wind action. In this connection the
following simple experiment will be of interest:
Take a circular-shaped bit of cardboard, like the lid of a hat box, and
remove the bent-over portion so as to have a perfectly flat surface with
a clean, sharp edge. Holding the cardboard at arm's length, withdraw
your hand, leaving the cardboard without support. What is the result?
The cardboard, being heavier than air, and having nothing to sustain
it, will fall to the ground. Pick it up and throw it, with considerable
force, against the wind edgewise. What happens? Instead of falling to
the ground, the cardboard sails along on the wind, remaining afloat so
long as it is in motion. It seeks the ground, by gravity, only as the
motion ceases, and then by easy stages, instead of dropping abruptly as
in the first instance.
Here we have a homely, but accurate illustration of the action of the
flying machine. The motor does for the latter what the force of your arm
does for the cardboard--imparts a motion which keeps it afloat. The only
real difference is that the motion given by the motor is continuous and
much more powerful than that given by your arm. The action of the latter
is limited and the end of its propulsive force is reached within a
second or two after it is exerted, while the action of the motor is
prolonged.
Another Simple Illustration.
Another simple means of illustrating the principle of flying machine
operation, so far as sustentation and the elevation and depression of
the planes is concerned, is explained in the accompanying diagram.
A is a piece of cardboard about 2 by 3 inches in size. B is a piece of
paper of the same size pasted to one edge of A. If you bend the paper
to a curve, with convex side up and blow across it as shown in Figure
C, the paper will rise instead of being depressed. The dotted lines show
that the air is passing over the top of the curved paper and yet, no
matter how hard you may blow, the effect will be to elevate the paper,
despite the fact that the air is passing over, instead of under the
curved surface.
In Figure D we have an opposite effect. Here the paper is in a curve
exactly the reverse of that shown in Figure C, bringing the concave side
up. Now if you will again blow across the surface of the card the action
of the paper will be downward--it will be impossible to make it rise.
The harder you blow the greater will be the downward movement.
Principle In General Use.
This principle is taken advantage of in the construction of all
successful flying machines. Makers of monoplanes and biplanes alike
adhere to curved bodies, with the concave surface facing downward.
Straight planes were tried for a time, but found greatly lacking in the
power of sustentation. By curving the planes, and placing the concave
surface downward, a sort of inverted bowl is formed in which the air
gathers and exerts a buoyant effect. Just what the ratio of the curve
should be is a matter of contention. In some instances one inch to the
foot is found to be satisfactory; in others this is doubled, and there
are a few cases in which a curve of as much as 3 inches to the foot has
been used.
Right here it might be well to explain that the word "plane" applied to
flying machines of modern construction is in reality a misnomer. Plane
indicates a flat, level surface. As most successful flying machines have
curved supporting surfaces it is clearly wrong to speak of "planes," or
"aeroplanes." Usage, however, has made the terms convenient and, as they
are generally accepted and understood by the public, they are used in
like manner in this volume.
Getting Under Headway.
A bird, on first rising from the ground, or beginning its flight from
a tree, will flap its wings to get under headway. Here again we have
another illustration of the manner in which a flying machine gets under
headway--the motor imparts the force necessary to put the machine into
the air, but right here the similarity ceases. If the machine is to be
kept afloat the motor must be kept moving. A flying machine will not
sustain itself; it will not remain suspended in the air unless it is
under headway. This is because it is heavier than air, and gravity draws
it to the ground.
Puzzle in Bird Soaring.
But a bird, which is also heavier than air, will remain suspended, in a
calm, will even soar and move in a circle, without apparent movement
of its wings. This is explained on the theory that there are generally
vertical columns of air in circulation strong enough to sustain a bird,
but much too weak to exert any lifting power on a flying machine, It is
easy to understand how a bird can remain suspended when the wind is
in action, but its suspension in a seeming dead calm was a puzzle
to scientists until Mr. Chanute advanced the proposition of vertical
columns of air.
Modeled Closely After Birds.
So far as possible, builders of flying machines have taken what may
be called "the architecture" of birds as a model. This is readily
noticeable in the form of construction. When a bird is in motion its
wings (except when flapping) are extended in a straight line at right
angles to its body. This brings a sharp, thin edge against the air,
offering the least possible surface for resistance, while at the same
time a broad surface for support is afforded by the flat, under side of
the wings. Identically the same thing is done in the construction of the
flying machine.
Note, for instance, the marked similarity in form as shown in the
illustration in Chapter II. Here A is the bird, and B the general
outline of the machine. The thin edge of the plane in the latter is
almost a duplicate of that formed by the outstretched wings of the bird,
while the rudder plane in the rear serves the same purpose as the bird's
tail.
CHAPTER IV. VARIOUS FORMS OF FLYING MACHINES.
There are three distinct and radically different forms of flying
machines. These are:
Aeroplanes, helicopters and ornithopers.
Of these the aeroplane takes precedence and is used almost exclusively
by successful aviators, the helicopters and ornithopers having been
tried and found lacking in some vital features, while at the same
time in some respects the helicopter has advantages not found in the
aeroplane.
What the Helicopter Is.
The helicopter gets its name from being fitted with vertical propellers
or helices (see illustration) by the action of which the machine is
raised directly from the ground into the air. This does away with the
necessity for getting the machine under a gliding headway before
it floats, as is the case with the aeroplane, and consequently the
helicopter can be handled in a much smaller space than is required for
an aeroplane. This, in many instances, is an important advantage, but it
is the only one the helicopter possesses, and is more than overcome
by its drawbacks. The most serious of these is that the helicopter is
deficient in sustaining capacity, and requires too much motive power.
Form of the Ornithopter.
The ornithopter has hinged planes which work like the wings of a bird.
At first thought this would seem to be the correct principle, and most
of the early experimenters conducted their operations on this line. It
is now generally understood, however, that the bird in soaring is in
reality an aeroplane, its extended wings serving to sustain, as well as
propel, the body. At any rate the ornithoper has not been successful in
aviation, and has been interesting mainly as an ingenious toy. Attempts
to construct it on a scale that would permit of its use by man in actual
aerial flights have been far from encouraging.
Three Kinds of Aeroplanes.
There are three forms of aeroplanes, with all of which more or less
success has been attained. These are:
The monoplane, a one-surfaced plane, like that used by Bleriot.
The biplane, a two-surfaced plane, now used by the Wrights, Curtiss,
Farman, and others.
The triplane, a three-surfaced plane This form is but little used,
its only prominent advocate at present being Elle Lavimer, a Danish
experimenter, who has not thus far accomplished much.
Whatever of real success has been accomplished in aviation may be
credited to the monoplane and biplane, with the balance in favor of
the latter. The monoplane is the more simple in construction and, where
weight-sustaining capacity is not a prime requisite, may probably be
found the most convenient. This opinion is based on the fact that the
smaller the surface of the plane the less will be the resistance offered
to the air, and the greater will be the speed at which the machine
may be moved. On the other hand, the biplane has a much greater plane
surface (double that of a monoplane of the same size) and consequently
much greater weight-carrying capacity.
Differences in Biplanes.
While all biplanes are of the same general construction so far as the
main planes are concerned, each aviator has his own ideas as to the
"rigging."
Wright, for instance, places a double horizontal rudder in front, with
a vertical rudder in the rear. There are no partitions between the
main planes, and the bicycle wheels used on other forms are replaced by
skids.
Voisin, on the contrary, divides the main planes with vertical
partitions to increase stability in turning; uses a single-plane
horizontal rudder in front, and a big box-tail with vertical rudder at
the rear; also the bicycle wheels.
Curtiss attaches horizontal stabilizing surfaces to the upper plane;
has a double horizontal rudder in front, with a vertical rudder
and horizontal stabilizing surfaces in rear. Also the bicycle wheel
alighting gear.
CHAPTER V. CONSTRUCTING A GLIDING MACHINE.
First decide upon the kind of a machine you want--monoplane, biplane,
or triplane. For a novice the biplane will, as a rule, be found the
most satisfactory as it is more compact and therefore the more easily
handled. This will be easily understood when we realize that the surface
of a flying machine should be laid out in proportion to the amount of
weight it will have to sustain. The generally accepted rule is that 152
square feet of surface will sustain the weight of an average-sized man,
say 170 pounds. Now it follows that if these 152 square feet of surface
are used in one plane, as in the monoplane, the length and width of this
plane must be greater than if the same amount of surface is secured by
using two planes--the biplane. This results in the biplane being more
compact and therefore more readily manipulated than the monoplane, which
is an important item for a novice.
Glider the Basis of Success.
Flying machines without motors are called gliders. In making a flying
machine you first construct the glider. If you use it in this form it
remains a glider. If you install a motor it becomes a flying machine.
You must have a good glider as the basis of a successful flying machine.
It will be well for the novice, the man who has never had any experience
as an aviator, to begin with a glider and master its construction and
operation before he essays the more pretentious task of handling a
fully-equipped flying machine. In fact, it is essential that he should
do so.
Plans for Handy Glider.
A glider with a spread (advancing edge) of 20 feet, and a breadth or
depth of 4 feet, will be about right to begin with. Two planes of this
size will give the 152 square yards of surface necessary to sustain a
man's weight. Remember that in referring to flying machine measurements
"spread" takes the place of what would ordinarily be called "length,"
and invariably applies to the long or advancing edge of the machine
which cuts into the air. Thus, a glider is spoken of as being 20 feet
spread, and 4 feet in depth. So far as mastering the control of the
machine is concerned, learning to balance one's self in the air, guiding
the machine in any desired direction by changing the position of the
body, etc., all this may be learned just as readily, and perhaps more
so, with a 20-foot glider than with a larger apparatus.
Kind of Material Required.
There are three all-important features in flying machine construction,
viz.: lightness, strength and extreme rigidity. Spruce is the wood
generally used for glider frames. Oak, ash and hickory are all stronger,
but they are also considerably heavier, and where the saving of weight
is essential, the difference is largely in favor of spruce. This will be
seen in the following table:
Weight Tensile Compressive
per cubic ft. Strength Strength
Wood in lbs. lbs. per sq. in. lbs. per sq in.
Hickory 53 12,000 8,500
Oak 50 12,000 9,000
Ash 38 12,000 6,000
Walnut 38 8,000 6,000
Spruce 25 8,000 5,000
Pine 25 5,000 4,500
Considering the marked saving in weight spruce has a greater percentage
of tensile strength than any of the other woods. It is also easier to
find in long, straight-grained pieces free from knots, and it is this
kind only that should be used in flying machine construction.
You will next need some spools or hanks of No. 6 linen shoe
thread, metal sockets, a supply of strong piano wire, a quantity of
closely-woven silk or cotton cloth, glue, turnbuckles, varnish, etc.
Names of the Various Parts.
The long strips, four in number, which form the front and rear edges of
the upper and lower frames, are called the horizontal beams. These are
each 20 feet in length. These horizontal beams are connected by upright
strips, 4 feet long, called stanchions. There are usually 12 of these,
six on the front edge, and six on the rear. They serve to hold the upper
plane away from the lower one. Next comes the ribs. These are 4 feet in
length (projecting for a foot over the rear beam), and while intended
principally as a support to the cloth covering of the planes, also
tend to hold the frame together in a horizontal position just as the
stanchions do in the vertical. There are forty-one of these ribs,
twenty-one on the upper and twenty on the lower plane. Then come the
struts, the main pieces which join the horizontal beams. All of these
parts are shown in the illustrations, reference to which will make the
meaning of the various names clear.
Quantity and Cost of Material.
For the horizontal beams four pieces of spruce, 20 feet long, 1 1/2
inches wide and 3/4 inch thick are necessary. These pieces must be
straight-grain, and absolutely free from knots. If it is impossible to
obtain clear pieces of this length, shorter ones may be spliced, but
this is not advised as it adds materially to the weight. The twelve
stanchions should be 4 feet long and 7/8 inch in diameter and rounded
in form so as to offer as little resistance as possible to the wind. The
struts, there are twelve of them, are 3 feet long by 11/4 x 1/2 inch.
For a 20-foot biplane about 20 yards of stout silk or unbleached muslin,
of standard one yard width, will be needed. The forty-one ribs are
each 4 feet long, and 1/2 inch square. A roll of No. 12 piano wire,
twenty-four sockets, a package of small copper tacks, a pot of glue, and
similar accessories will be required. The entire cost of this material
should not exceed $20. The wood and cloth will be the two largest
items, and these should not cost more than $10. This leaves $10 for the
varnish, wire, tacks, glue, and other incidentals. This estimate is
made for cost of materials only, it being taken for granted that the
experimenter will construct his own glider. Should the services of a
carpenter be required the total cost will probably approximate $60 or
$70.
Application of the Rudders.
The figures given also include the expense of rudders, but the details
of these have not been included as the glider is really complete without
them. Some of the best flights the writer ever saw were made by Mr. A.
M. Herring in a glider without a rudder, and yet there can be no doubt
that a rudder, properly proportioned and placed, especially a rear
rudder, is of great value to the aviator as it keeps the machine with
its head to the wind, which is the only safe position for a novice. For
initial educational purposes, however, a rudder is not essential as the
glides will, or should, be made on level ground, in moderate, steady
wind currents, and at a modest elevation. The addition of a rudder,
therefore, may well be left until the aviator has become reasonably
expert in the management of his machine.
Putting the Machine Together.
Having obtained the necessary material, the first move is to have the
rib pieces steamed and curved. This curve may be slight, about 2 inches
for the 4 feet. While this is being done the other parts should be
carefully rounded so the square edges will be taken off. This may be
done with sand paper. Next apply a coat of shellac, and when dry rub
it down thoroughly with fine sand paper. When the ribs are curved treat
them in the same way.
Lay two of the long horizontal frame pieces on the floor 3 feet apart.
Between these place six of the strut pieces. Put one at each end, and
each 4 1/2 feet put another, leaving a 2-foot space in the center. This
will give you four struts 4 1/2 feet apart, and two in the center 2 feet
apart, as shown in the illustration. This makes five rectangles. Be sure
that the points of contact are perfect, and that the struts are exactly
at right angles with the horizontal frames. This is a most important
feature because if your frame "skews" or twists you cannot keep it
straight in the air. Now glue the ends of the struts to the frame
pieces, using plenty of glue, and nail on strips that will hold the
frame in place while the glue is drying. The next day lash the joints
together firmly with the shoe thread, winding it as you would to mend a
broken gun stock, and over each layer put a coating of glue. This done,
the other frame pieces and struts may be treated in the same way, and
you will thus get the foundations for the two planes.
Another Way of Placing Struts.
In the machines built for professional use a stronger and more certain
form of construction is desired. This is secured by the placing the
struts for the lower plane under the frame piece, and those for the
upper plane over it, allowing them in each instance to come out flush
with the outer edges of the frame pieces. They are then securely
fastened with a tie plate or clamp which passes over the end of the
strut and is bound firmly against the surface of the frame piece by the
eye bolts of the stanchion sockets.
Placing the Rib Pieces.
Take one of the frames and place on it the ribs, with the arched side
up, letting one end of the ribs come flush with the front edge of the
forward frame, and the other end projecting about a foot beyond the rear
frame. The manner of fastening the ribs to the frame pieces is optional.
In some cases they are lashed with shoe thread, and in others clamped
with a metal clamp fastened with 1/2-inch wood screws. Where clamps and
screws are used care should be taken to make slight holes in the wood
with an awl before starting the screws so as to lessen any tendency to
split the wood. On the top frame, twenty-one ribs placed one foot apart
will be required. On the lower frame, because of the opening left for
the operator's body, you will need only twenty.
Joining the Two Frames.
The two frames must now be joined together. For this you will need
twenty-four aluminum or iron sockets which may be purchased at a
foundry or hardware shop. These sockets, as the name implies, provide
a receptacle in which the end of a stanchion is firmly held, and have
flanges with holes for eye-bolts which hold them firmly to the frame
pieces, and also serve to hold the guy wires. In addition to these
eye-bolt holes there are two others through which screws are fastened
into the frame pieces. On the front frame piece of the bottom plane
place six sockets, beginning at the end of the frame, and locating them
exactly opposite the struts. Screw the sockets into position with wood
screws, and then put the eye-bolts in place. Repeat the operation on the
rear frame. Next put the sockets for the upper plane frame in place.
You are now ready to bring the two planes together. Begin by inserting
the stanchions in the sockets in the lower plane. The ends may need a
little rubbing with sandpaper to get them into the sockets, but care
must be taken to have them fit snugly. When all the stanchions are in
place on the lower plane, lift the upper plane into position, and fit
the sockets over the upper ends of the stanchions.
Trussing with Guy Wires.
The next move is to "tie" the frame together rigidly by the aid of guy
wires. This is where the No. 12 piano wire comes in. Each rectangle
formed by the struts and stanchions with the exception of the small
center one, is to be wired separately as shown in the illustration. At
each of the eight corners forming the rectangle the ring of one of the
eye-bolts will be found. There are two ways of doing this "tieing," or
trussing. One is to run the wires diagonally from eye-bolt to eye-bolt,
depending upon main strength to pull them taut enough, and then twist
the ends so as to hold. The other is to first make a loop of wire
at each eye-bolt, and connect these loops to the main wires with
turn-buckles. This latter method is the best, as it admits of the
tension being regulated by simply turning the buckle so as to draw the
ends of the wire closer together. A glance at the illustration will make
this plain, and also show how the wires are to be placed. The proper
degree of tension may be determined in the following manner:
After the frame is wired place each end on a saw-horse so as to lift the
entire frame clear of the work-shop floor. Get under it, in the center
rectangle and, grasping the center struts, one in each hand, put your
entire weight on the structure. If it is properly put together it will
remain rigid and unyielding. Should it sag ever so slightly the tension
of the wires must be increased until any tendency to sag, no matter how
slight it may be, is overcome.
Putting on the Cloth.
We are now ready to put on the cloth covering which holds the air and
makes the machine buoyant. The kind of material employed is of small
account so long as it is light, strong, and wind-proof, or nearly so.
Some aviators use what is called rubberized silk, others prefer balloon
cloth. Ordinary muslin of good quality, treated with a coat of light
varnish after it is in place, will answer all the purposes of the
amateur.
Cut the cloth into strips a little over 4 feet in length. As you have
20 feet in width to cover, and the cloth is one yard wide, you will need
seven strips for each plane, so as to allow for laps, etc. This will
give you fourteen strips. Glue the end of each strip around the front
horizontal beams of the planes, and draw each strip back, over the ribs,
tacking the edges to the ribs as you go along, with small copper or
brass tacks. In doing this keep the cloth smooth and stretched tight.
Tacks should also be used in addition to the glue, to hold the cloth to
the horizontal beams.
Next, give the cloth a coat of varnish on the clear, or upper side, and
when this is dry your glider will be ready for use.
Reinforcing the Cloth.
While not absolutely necessary for amateur purposes, reinforcement
of the cloth, so as to avoid any tendency to split or tear out from
wind-pressure, is desirable. One way of doing this is to tack narrow
strips of some heavier material, like felt, over the cloth where it laps
on the ribs. Another is to sew slips or pockets in the cloth itself and
let the ribs run through them. Still another method is to sew 2-inch
strips (of the same material as the cover) on the cloth, placing them
about one yard apart, but having them come in the center of each piece
of covering, and not on the laps where the various pieces are joined.
Use of Armpieces.
Should armpieces be desired, aside from those afforded by the center
struts, take two pieces of spruce, 3 feet long, by 1 x 1 3/4 inches, and
bolt them to the front and rear beams of the lower plane about 14 inches
apart. These will be more comfortable than using the struts, as the
operator will not have to spread his arms so much. In using the struts
the operator, as a rule, takes hold of them with his hands, while with
the armpieces, as the name implies, he places his arms over them, one of
the strips coming under each armpit.
Frequently somebody asks why the ribs should be curved. The answer is
easy. The curvature tends to direct the air downward toward the rear
and, as the air is thus forced downward, there is more or less of an
impact which assists in propelling the aeroplane upwards.
CHAPTER VI. LEARNING TO FLY.
Don't be too ambitious at the start. Go slow, and avoid unnecessary
risks. At its best there is an element of danger in aviation which
cannot be entirely eliminated, but it may be greatly reduced and
minimized by the use of common sense.
Theoretically, the proper way to begin a glide is from the top of an
incline, facing against the wind, so that the machine will soar until
the attraction of gravitation draws it gradually to the ground. This is
the manner in which experienced aviators operate, but it must be kept in
mind that these men are experts. They understand air currents, know how
to control the action and direction of their machines by shifting the
position of their bodies, and by so doing avoid accidents which would be
unavoidable by a novice.
Begin on Level Ground.
Make your first flights on level ground, having a couple of men to
assist you in getting the apparatus under headway. Take your position in
the center rectangle, back far enough to give the forward edges of the
glider an inclination to tilt upward very slightly. Now start and run
forward at a moderately rapid gait, one man at each end of the glider
assisting you. As the glider cuts into the air the wind will catch under
the uplifted edges of the curved planes, and buoy it up so that it will
rise in the air and take you with it. This rise will not be great, just
enough to keep you well clear of the ground. Now project your legs a
little to the front so as to shift the center of gravity a trifle and
bring the edges of the glider on an exact level with the atmosphere.
This, with the momentum acquired in the start, will keep the machine
moving forward for some distance.
Effect of Body Movements.
When the weight of the body is slightly back of the center of gravity
the edges of the advancing planes are tilted slightly upward. The glider
in this position acts as a scoop, taking in the air which, in turn,
lifts it off the ground. When a certain altitude is reached--this varies
with the force of the wind--the tendency to a forward movement is
lost and the glider comes to the ground. It is to prolong the forward
movement as much as possible that the operator shifts the center of
gravity slightly, bringing the apparatus on an even keel as it were by
lowering the advancing edges. This done, so long as there is momentum
enough to keep the glider moving, it will remain afloat.
If you shift your body well forward it will bring the front edges of
the glider down, and elevate the rear ones. In this way the air will be
"spilled" out at the rear, and, having lost the air support or buoyancy,
the glider comes down to the ground. A few flights will make any
ordinary man proficient in the control of his apparatus by his body
movements, not only as concerns the elevating and depressing of the
advancing edges, but also actual steering. You will quickly learn,
for instance, that, as the shifting of the bodily weight backwards
and forwards affects the upward and downward trend of the planes, so a
movement sideways--to the left or the right--affects the direction in
which the glider travels.
Ascends at an Angle.
In ascending, the glider and flying machine, like the bird, makes an
angular, not a vertical flight. Just what this angle of ascension may be
is difficult to determine. It is probable and in fact altogether likely,
that it varies with the force of the wind, weight of the rising body,
power of propulsion, etc. This, in the language of physicists, is the
angle of inclination, and, as a general thing, under normal conditions
(still air) should be put down as about one in ten, or 5 3/4 degrees.
This would be an ideal condition, but it has not, as vet been reached.
The force of the wind affects the angle considerably, as does also the
weight and velocity of the apparatus. In general practice the angle
varies from 23 to 45 degrees. At more than 45 degrees the supporting
effort is overcome by the resistance to forward motion.
Increasing the speed or propulsive force, tends to lessen the angle at
which the machine may be successfully operated because it reduces the
wind pressure. Most of the modern flying machines are operated at an
angle of 23 degrees, or less.
Maintaining an Equilibrium.
Stable equilibrium is one of the main essentials to successful flight,
and this cannot be preserved in an uncertain, gusty wind, especially by
an amateur. The novice should not attempt a glide unless the conditions
are just right. These conditions are: A clear, level space, without
obstructions, such as trees, etc., and a steady wind of not exceeding
twelve miles an hour. Always fly against the wind.
When a reasonable amount of proficiency in the handling of the machine
on level ground has been acquired the field of practice may be changed
to some gentle slope. In starting from a slope it will be found easier
to keep the machine afloat, but the experience at first is likely to be
very disconcerting to a man of less than iron nerve. As the glider sails
away from the top of the slope the distance between him and the ground
increases rapidly until the aviator thinks he is up a hundred miles
in the air. If he will keep cool, manipulate his apparatus so as to
preserve its equilibrium, and "let nature take its course," he will come
down gradually and safely to the ground at a considerable distance
from the starting place. This is one advantage of starting from an
elevation--your machine will go further.
But, if the aviator becomes "rattled"; if he loses control of his
machine, serious results, including a bad fall with risk of death,
are almost certain. And yet this practice is just as necessary as the
initial lessons on level ground. When judgment is used, and "haste made
slowly," there is very little real danger. While experimenting with
gliders the Wrights made flights innumerable under all sorts of
conditions and never had an accident of any kind.
Effects of Wind Currents.
The larger the machine the more difficult it will be to control its
movements in the air, and yet enlargement is absolutely necessary as
weight, in the form of motor, rudder, etc., is added.
Air currents near the surface of the ground are diverted by every
obstruction unless the wind is blowing hard enough to remove the
obstruction entirely. Take, for instance, the case of a tree or shrub,
in a moderate wind of from ten to twelve miles an hour. As the wind
strikes the tree it divides, part going to one side and part going to
the other, while still another part is directed upward and goes over
the top of the obstruction. This makes the handling of a glider on
an obstructed field difficult and uncertain. To handle a glider
successfully the place of operation should be clear and the wind
moderate and steady. If it is gusty postpone your flight. In this
connection it will be well to understand the velocity of the wind, and
what it means as shown in the following table:
Miles per hour Feet per second Pressure per sq. foot
10 14.7 .492
25 36.7 3.075
50 73.3 12.300
100 146.6 49.200
Pressure of wind increases in proportion to the square of the velocity.
Thus wind at 10 miles an hour has four times the pressure of wind at
5 miles an hour. The greater this pressure the large and heavier the
object which can be raised. Any boy who has had experience in flying
kites can testify to this, High winds, however, are almost invariably
gusty and uncertain as to direction, and this makes them dangerous for
aviators. It is also a self-evident fact that, beyond a certain stage,
the harder the wind blows the more difficult it is to make headway
against it.
Launching Device for Gliders.
On page 195 will be found a diagram of the various parts of a launcher
for gliders, designed and patented by Mr. Octave Chanute. In describing
this invention in Aeronautics, Mr. Chanute says:
"In practicing, the track, preferably portable, is generally laid in
the direction of the existing wind and the car, preferably a
light platform-car, is placed on the track. The truck carrying
the winding-drum and its motor is placed to windward a suitable
distance--say from two hundred to one thousand feet--and is firmly
blocked or anchored in line with the portable track, which is preferably
80 or 100 feet in length. The flying or gliding machine to be launched
with its operator is placed on the platform-car at the leeward end of
the portable track. The line, which is preferably a flexible combination
wire-and-cord cable, is stretched between the winding-drum on the track
and detachably secured to the flying or gliding machine, preferably by
means of a trip-hoop, or else held in the hand of the operator, so that
the operator may readily detach the same from the flying-machine when
the desired height is attained."
How Glider Is Started.
"Then upon a signal given by the operator the engineer at the motor
puts it into operation, gradually increasing the speed until the line
is wound upon the drum at a maximum speed of, say, thirty miles an
hour. The operator of the flying-machine, whether he stands upright and
carries it on his shoulders, or whether he sits or lies down prone upon
it, adjusts the aeroplane or carrying surfaces so that the wind shall
strike them on the top and press downward instead of upward until the
platform-car under action of the winding-drum and line attains the
required speed.
"When the operator judges that his speed is sufficient, and this depends
upon the velocity of the wind as well as that of the car moving against
the wind, he quickly causes the front of the flying-machine to tip
upward, so that the relative wind striking on the under side of the
planes or carrying surfaces shall lift the flying machine into the air.
It then ascends like a kite to such height as may be desired by the
operator, who then trips the hook and releases the line from the
machine."
What the Operator Does.
"The operator being now free in the air has a certain initial velocity
imparted by the winding-drum and line and also a potential energy
corresponding to his height above the ground. If the flying or gliding
machine is provided with a motor, he can utilize that in his further
flight, and if it is a simple gliding machine without motor he can make
a descending flight through the air to such distance as corresponds to
the velocity acquired and the height gained, steering meanwhile by the
devices provided for that purpose.
"The simplest operation or maneuver is to continue the flight straight
ahead against the wind; but it is possible to vary this course to the
right or left, or even to return in downward flight with the wind to
the vicinity of the starting-point. Upon nearing the ground the operator
tips upward his carrying-surfaces and stops his headway upon the
cushion of increased air resistance so caused. The operator is in no way
permanently fastened to his machine, and the machine and the operator
simply rest upon the light platform-car, so that the operator is free
to rise with the machine from the car whenever the required initial
velocity is attained.
Motor For the Launcher.
"The motor may be of any suitable kind or construction, but is
preferably an electric or gasolene motor. The winding-drum is furnished
with any suitable or customary reversing-guide to cause the line to
wind smoothly and evenly upon the drum. The line is preferably a cable
composed of flexible wire and having a cotton or other cord core to
increase its flexibility. The line extends from the drum to the flying
or gliding machine. Its free end may, if desired, be grasped and held
by the operator until the flying-machine ascends to the desired height,
when by simply letting go of the line the operator may continue his
flight free. The line, however, is preferably connected to the flying
or gliding machine directly by a trip-hook having a handle or trip lever
within reach of the operator, so that when he ascends to the required
height he may readily detach the line from the flying or gliding
machine."
CHAPTER VII. PUTTING ON THE RUDDER.
Gliders as a rule have only one rudder, and this is in the rear. It
tends to keep the apparatus with its head to the wind. Unlike the rudder
on a boat it is fixed and immovable. The real motor-propelled flying
machine, generally has both front and rear rudders manipulated by wire
cables at the will of the operator.
Allowing that the amateur has become reasonably expert in the
manipulation of the glider he should, before constructing an actual
flying machine, equip his glider with a rudder.
Cross Pieces for Rudder Beam.
To do this he should begin by putting in a cross piece, 2 feet long by
1/4 x 3/4 inches between the center struts, in the lower plane. This may
be fastened to the struts with bolts or braces. The former method is
preferable. On this cross piece, and on the rear frame of the plane
itself, the rudder beam is clamped and bolted. This rudder beam is 8
feet 11 inches long. Having put these in place duplicate them in exactly
the same manner and dimensions from the upper frame The cross pieces on
which the ends of the rudder beams are clamped should be placed about
one foot in advance of the rear frame beam.
The Rudder Itself.
The next step is to construct the rudder itself. This consists of two
sections, one horizontal, the other vertical. The latter keeps
the aeroplane headed into the wind, while the former keeps it
steady--preserves the equilibrium.
The rudder beams form the top and bottom frames of the vertical rudder.
To these are bolted and clamped two upright pieces, 3 feet, 10 inches
in length, and 3/4 inch in cross section. These latter pieces are placed
about two feet apart. This completes the framework of the vertical
rudder. See next page (59).
For the horizontal rudder you will require two strips 6 feet long, and
four 2 feet long. Find the exact center of the upright pieces on the
vertical rudder, and at this spot fasten with bolts the long pieces of
the horizontal, placing them on the outside of the vertical strips. Next
join the ends of the horizontal strips with the 2-foot pieces, using
small screws and corner braces. This done you will have two of the
2-foot pieces left. These go in the center of the horizontal frame,
"straddling" the vertical strips, as shown in the illustration.
The framework is to be covered with cloth in the same manner as the
planes. For this about ten yards will be needed.
Strengthening the Rudder.
To ensure rigidity the rudder must be stayed with guy wires. For this
purpose the No. 12 piano wire is the best. Begin by running two of these
wires from the top eye-bolts of stanchions 3 and 4, page 37, to rudder
beam where it joins the rudder planes, fastening them at the bottom.
Then run two wires from the top of the rudder beam at the same point,
to the bottom eye-bolts of the same stanchions. This will give you
four diagonal wires reaching from the rudder beam to the top and bottom
planes of the glider. Now, from the outer ends of the rudder frame run
four similar diagonal wires to the end of the rudder beam where it rests
on the cross piece. You will then have eight truss wires strengthening
the connection of the rudder to the main body of the glider.
The framework of the rudder planes is then to be braced in the same way,
which will take eight more wires, four for each rudder plane. All the
wires are to be connected at one end with turn-buckles so the tension
may be regulated as desired.
In forming the rudder frame it will be well to mortise the corners, tack
them together with small nails, and then put in a corner brace in the
inside of each joint. In doing this bear in mind that the material to be
thus fastened is light, and consequently the lightest of nails, screws,
bolts and corner pieces, etc., is necessary.
CHAPTER VIII. THE REAL FLYING MACHINE.
We will now assume that you have become proficient enough to warrant an
attempt at the construction of a real flying machine--one that will not
only remain suspended in the air at the will of the operator, but make
respectable progress in whatever direction he may desire to go. The
glider, it must be remembered, is not steerable, except to a limited
extent, and moves only in one direction--against the wind. Besides this
its power of flotation--suspension in the air--is circumscribed.
Larger Surface Area Required.
The real flying machine is the glider enlarged, and equipped with
motor and propeller. The first thing to do is to decide upon the size
required. While a glider of 20 foot spread is large enough to sustain a
man it could not under any possible conditions, be made to rise with the
weight of the motor, propeller and similar equipment added. As the load
is increased so must the surface area of the planes be increased.
Just what this increase in surface area should be is problematical as
experienced aviators disagree, but as a general proposition it may be
placed at from three to four times the area of a 20-foot glider. [3]
Some Practical Examples.
The Wrights used a biplane 41 feet in spread, and 6 1/2 ft. deep. This,
for the two planes, gives a total surface area of 538 square feet,
inclusive of auxiliary planes. This sustains the engine equipment,
operator, etc., a total weight officially announced at 1,070 pounds. It
shows a lifting capacity of about two pounds to the square foot of plane
surface, as against a lifting capacity of about 1/2 pound per square
foot of plane surface for the 20-foot glider. This same Wright machine
is also reported to have made a successful flight, carrying a total load
of 1,100 pounds, which would be over two pounds for each square foot of
surface area, which, with auxiliary planes, is 538 square feet.
To attain the same results in a monoplane, the single surface would
have to be 60 feet in spread and 9 feet deep. But, while this is the
mathematical rule, Bleriot has demonstrated that it does not always hold
good. On his record-breaking trip across the English channel, July 25th,
1909, the Frenchman was carried in a monoplane 24 1/2 feet in spread,
and with a total sustaining surface of 150 1/2 square feet. The total
weight of the outfit, including machine, operator and fuel sufficient
for a three-hour run, was only 660 pounds. With an engine of (nominally)
25 horsepower the distance of 21 miles was covered in 37 minutes.
Which is the Best?
Right here an established mathematical quantity is involved. A small
plane surface offers less resistance to the air than a large one and
consequently can attain a higher rate of speed. As explained further
on in this chapter speed is an important factor in the matter of
weight-sustaining capacity. A machine that travels one-third faster
than another can get along with one-half the surface area of the latter
without affecting the load. See the closing paragraph of this chapter on
this point. In theory the construction is also the simplest, but this is
not always found to be so in practice. The designing and carrying
into execution of plans for an extensive area like that of a monoplane
involves great skill and cleverness in getting a framework that will be
strong enough to furnish the requisite support without an undue excess
of weight. This proposition is greatly simplified in the biplane and,
while the speed attained by the latter may not be quite so great as that
of the monoplane, it has much larger weight-carrying capacity.
Proper Sizes For Frame.
Allowing that the biplane form is selected the construction may be
practically identical with that of the 20-foot glider described in
Chapter V., except as to size and elimination of the armpieces. In
size the surface planes should be about twice as large as those of
the 20-foot glider, viz: 40 feet spread instead of 20, and 6 feet deep
instead of 3. The horizontal beams, struts, stanchions, ribs, etc.,
should also be increased in size proportionately.
While care in the selection of clear, straight-grained timber is
important in the glider, it is still more important in the construction
of a motor-equipped flying machine as the strain on the various parts
will be much greater.
How to Splice Timbers.
It is practically certain that you will have to resort to splicing the
horizontal beams as it will be difficult, if not impossible, to find
40-foot pieces of timber totally free from knots and worm holes, and of
straight grain.
If splicing is necessary select two good 20-foot pieces, 3 inches wide
and 1 1/2 inches thick, and one 10-foot long, of the same thickness and
width. Plane off the bottom sides of the 10-foot strip, beginning about
two feet back from each end, and taper them so the strip will be about
3/4 inch thick at the extreme ends. Lay the two 20-foot beams end to
end, and under the joint thus made place the 10-foot strip, with the
planed-off ends downward. The joint of the 20-foot pieces should be
directly in the center of the 10-foot piece. Bore ten holes (with a
1/4-inch augur) equi-distant apart through the 20-foot strips and the
10-foot strip under them. Through these holes run 1/4-inch stove bolts
with round, beveled heads. In placing these bolts use washers top and
bottom, one between the head and the top beam, and the other between the
bottom beam and the screw nut which holds the bolt. Screw the nuts down
hard so as to bring the two beams tightly together, and you will have a
rigid 40-foot beam.
Splicing with Metal Sleeves.
An even better way of making a splice is by tonguing and grooving the
ends of the frame pieces and enclosing them in a metal sleeve, but
it requires more mechanical skill than the method first named. The
operation of tonguing and grooving is especially delicate and calls for
extreme nicety of touch in the handling of tools, but if this dexterity
is possessed the job will be much more satisfactory than one done with a
third timber.
As the frame pieces are generally about 1 1/2 inch in diameter, the
tongue and the groove into which the tongue fits must be correspondingly
small. Begin by sawing into one side of one of the frame pieces about
4 inches back from the end. Make the cut about 1/2 inch deep. Then turn
the piece over and duplicate the cut. Next saw down from the end
to these cuts. When the sawed-out parts are removed you will have a
"tongue" in the end of the frame timber 4 inches long and 1/2 inch
thick. The next move is to saw out a 5/8-inch groove in the end of the
frame piece which is to be joined. You will have to use a small chisel
to remove the 5/8-inch bit. This will leave a groove into which the
tongue will fit easily.
Joining the Two Pieces.
Take a thin metal sleeve--this is merely a hollow tube of aluminum
or brass open at each end--8 inches long, and slip it over either the
tongued or grooved end of one of the frame timbers. It is well to have
the sleeve fit snugly, and this may necessitate a sand-papering of the
frame pieces so the sleeve will slip on.
Push the sleeve well back out of the way. Cover the tongue thoroughly
with glue, and also put some on the inside of the groove. Use plenty
of glue. Now press the tongue into the groove, and keep the ends firmly
together until the glue is thoroughly dried. Rub off the joint lightly
with sand-paper to remove any of the glue which may have oozed out, and
slip the sleeve into place over the joint. Tack the sleeve in position
with small copper tacks, and you will have an ideal splice.
The same operation is to be repeated on each of the four frame pieces.
Two 20-foot pieces joined in this way will give a substantial frame, but
when suitable timber of this kind can not be had, three pieces, each 6
feet 11 inches long, may be used. This would give 20 feet 9 inches, of
which 8 inches will be taken up in the two joints, leaving the frame 20
feet 1 inch long.
Installation of Motor.
Next comes the installation of the motor. The kinds and efficiency of
the various types are described in the following chapter (IX). All we
are interested in at this point is the manner of installation. This
varies according to the personal ideas of the aviator. Thus one man puts
his motor in the front of his machine, another places it in the center,
and still another finds the rear of the frame the best. All get
good results, the comparative advantages of which it is difficult
to estimate. Where one man, as already explained, flies faster than
another, the one beaten from the speed standpoint has an advantage in
the matter of carrying weight, etc.
The ideas of various well-known aviators as to the correct placing of
motors may be had from the following:
Wrights--In rear of machine and to one side.
Curtiss--Well to rear, about midway between upper and lower planes.
Raich--In rear, above the center.
Brauner-Smith--In exact center of machine.
Van Anden--In center.
Herring-Burgess--Directly behind operator.
Voisin--In rear, and on lower plane.
Bleriot--In front.
R. E. P.--In front.
The One Chief Object.
An even distribution of the load so as to assist in maintaining the
equilibrium of the machine, should be the one chief object in deciding
upon the location of the motor. It matters little what particular spot
is selected so long as the weight does not tend to overbalance the
machine, or to "throw it off an even keel." It is just like loading
a vessel, an operation in which the expert seeks to so distribute
the weight of the cargo as to keep the vessel in a perfectly upright
position, and prevent a "list" or leaning to one side. The more evenly
the cargo is distributed the more perfect will be the equilibrium of the
vessel and the better it can be handled. Sometimes, when not properly
stowed, the cargo shifts, and this at once affects the position of the
craft. When a ship "lists" to starboard or port a preponderating weight
of the cargo has shifted sideways; if bow or stern is unduly depressed
it is a sure indication that the cargo has shifted accordingly. In
either event the handling of the craft becomes not only difficult, but
extremely hazardous. Exactly the same conditions prevail in the handling
of a flying machine.
Shape of Machine a Factor.
In placing the motor you must be governed largely by the shape and
construction of the flying machine frame. If the bulk of the weight
of the machine and auxiliaries is toward the rear, then the natural
location for the motor will be well to the front so as to counterbalance
the excess in rear weight. In the same way if the preponderance of the
weight is forward, then the motor should be placed back of the center.
As the propeller blade is really an integral part of the motor, the
latter being useless without it, its placing naturally depends upon the
location selected for the motor.
Rudders and Auxiliary Planes.
Here again there is great diversity of opinion among aviators as to
size, location and form. The striking difference of ideas in this
respect is well illustrated in the choice made by prominent makers as
follows:
Voisin--horizontal rudder, with two wing-like planes, in front; box-like
longitudinal stability plane in rear, inside of which is a vertical
rudder.
Wright--large biplane horizontal rudder in front at considerable
distance--about 10 feet--from the main planes; vertical biplane rudder
in rear; ends of upper and lower main planes made flexible so they may
be moved.
Curtiss--horizontal biplane rudder, with vertical damping plane between
the rudder planes about 10 feet in front of main planes; vertical rudder
in rear; stabilizing planes at each end of upper main plane.
Bleriot--V-shaped stabilizing fin, projecting from rear of plane, with
broad end outward; to the broad end of this fin is hinged a vertical
rudder; horizontal biplane rudder, also in rear, under the fin.
These instances show forcefully the wide diversity of opinion existing
among experienced aviators as to the best manner of placing the rudders
and stabilizing, or auxiliary planes, and make manifest how hopeless
would be the task of attempting to select any one form and advise its
exclusive use.
Rudder and Auxiliary Construction.
The material used in the construction of the rudders and auxiliary
planes is the same as that used in the main planes--spruce for the
framework and some kind of rubberized or varnished cloth for the
covering. The frames are joined and wired in exactly the same manner
as the frames of the main planes, the purpose being to secure the same
strength and rigidity. Dimensions of the various parts depend upon the
plan adopted and the size of the main plane.
No details as to exact dimensions of these rudders and auxiliary planes
are obtainable. The various builders, while willing enough to supply
data as to the general measurements, weight, power, etc., of their
machines, appear to have overlooked the details of the auxiliary parts,
thinking, perhaps, that these were of no particular import to the
general public. In the Wright machine, the rear horizontal and front
vertical rudders may be set down as being about one-quarter (probably a
little less) the size of the main supporting planes.
Arrangement of Alighting Gear.
Most modern machines are equipped with an alighting gear, which not
only serves to protect the machine and aviator from shock or injury in
touching the ground, but also aids in getting under headway. All the
leading makes, with the exception of the Wright, are furnished with a
frame carrying from two to five pneumatic rubber-tired bicycle wheels.
In the Curtiss and Voisin machines one wheel is placed in front and two
in the rear. In the Bleriot and other prominent machines the reverse is
the rule--two wheels in front and one in the rear. Farman makes use of
five wheels, one in the extreme rear, and four, arranged in pairs, a
little to the front of the center of the main lower plane.
In place of wheels the Wright machine is equipped with a skid-like
device consisting of two long beams attached to the lower plane by
stanchions and curving up far in front, so as to act as supports to the
horizontal rudder.
Why Wood Is Favored.
A frequently asked question is: "Why is not aluminum, or some similar
metal, substituted for wood." Wood, particularly spruce, is preferred
because, weight considered, it is much stronger than aluminum, and this
is the lightest of all metals. In this connection the following table
will be of interest:
Compressive
Weight Tensile Strength Strength
per cubic foot per sq. inch per sq. inch
Material in lbs. in lbs. in lbs.
Spruce.... 25 8,000 5,000
Aluminum 162 16,000 ......
Brass (sheet) 510 23,000 12,000
Steel (tool) 490 100,000 40,000
Copper (sheet) 548 30,000 40,000
As extreme lightness, combined with strength, especially tensile
strength, is the great essential in flying-machine construction, it can
be readily seen that the use of metal, even aluminum, for the framework,
is prohibited by its weight. While aluminum has double the strength
of spruce wood it is vastly heavier, and thus the advantage it has in
strength is overbalanced many times by its weight. The specific gravity
of aluminum is 2.50; that of spruce is only 0.403.
Things to Be Considered.
In laying out plans for a flying machine there are five important points
which should be settled upon before the actual work of construction is
started. These are:
First--Approximate weight of the machine when finished and equipped.
Second--Area of the supporting surface required.
Third--Amount of power that will be necessary to secure the desired
speed and lifting capacity.
Fourth--Exact dimensions of the main framework and of the auxiliary
parts.
Fifth--Size, speed and character of the propeller.
In deciding upon these it will be well to take into consideration
the experience of expert aviators regarding these features as given
elsewhere. (See Chapter X.)
Estimating the Weights Involved.
In fixing upon the probable approximate weight in advance of
construction much, of course, must be assumed. This means that it will
be a matter of advance estimating. If a two-passenger machine is to be
built we will start by assuming the maximum combined weight of the two
people to be 350 pounds. Most of the professional aviators are lighter
than this. Taking the medium between the weights of the Curtiss and
Wright machines we have a net average of 850 pounds for the framework,
motor, propeller, etc. This, with the two passengers, amounts to 1,190
pounds. As the machines quoted are in successful operation it will be
reasonable to assume that this will be a safe basis to operate on.
What the Novice Must Avoid.
This does not mean, however, that it will be safe to follow these
weights exactly in construction, but that they will serve merely as
a basis to start from. Because an expert can turn out a machine,
thoroughly equipped, of 850 pounds weight, it does not follow that a
novice can do the same thing. The expert's work is the result of years
of experience, and he has learned how to construct frames and motor
plants of the utmost lightness and strength.
It will be safer for the novice to assume that he can not duplicate the
work of such men as Wright and Curtiss without adding materially to the
gross weight of the framework and equipment minus passengers.
How to Distribute the Weight.
Let us take 1,030 pounds as the net weight of the machine as against the
same average in the Wright and Curtiss machines. Now comes the question
of distributing this weight between the framework, motor, and other
equipment. As a general proposition the framework should weigh about
twice as much as the complete power plant (this is for amateur work).
The word "framework" indicates not only the wooden frames of the main
planes, auxiliary planes, rudders, etc., but the cloth coverings as
well--everything in fact except the engine and propeller.
On the basis named the framework would weigh 686 pounds, and the power
plant 344. These figures are liberal, and the results desired may be
obtained well within them as the novice will learn as he makes progress
in the work.
Figuring on Surface Area.
It was Prof. Langley who first brought into prominence in connection
with flying machine construction the mathematical principle that the
larger the object the smaller may be the relative area of support. As
explained in Chapter XIII, there are mechanical limits as to size which
it is not practical to exceed, but the main principle remains in effect.
Take two aeroplanes of marked difference in area of surface. The larger
will, as a rule, sustain a greater weight in relative proportion to
its area than the smaller one, and do the work with less relative
horsepower. As a general thing well-constructed machines will average
a supporting capacity of one pound for every one-half square foot of
surface area. Accepting this as a working rule we find that to sustain
a weight of 1,200 pounds--machine and two passengers--we should have 600
square feet of surface.
Distributing the Surface Area.
The largest surfaces now in use are those of the Wright, Voisin and
Antoinette machines--538 square feet in each. The actual sustaining
power of these machines, so far as known, has never been tested to the
limit; it is probable that the maximum is considerably in excess of what
they have been called upon to show. In actual practice the average is a
little over one pound for each one-half square foot of surface area.
Allowing that 600 square feet of surface will be used, the next question
is how to distribute it to the best advantage. This is another important
matter in which individual preference must rule. We have seen how the
professionals disagree on this point, some using auxiliary planes
of large size, and others depending upon smaller auxiliaries with an
increase in number so as to secure on a different plan virtually the
same amount of surface.
In deciding upon this feature the best thing to do is to follow the
plans of some successful aviator, increasing the area of the auxiliaries
in proportion to the increase in the area of the main planes. Thus, if
you use 600 square feet of surface where the man whose plans you
are following uses 500, it is simply a matter of making your planes
one-fifth larger all around.
The Cost of Production.
Cost of production will be of interest to the amateur who essays to
construct a flying machine. Assuming that the size decided upon is
double that of the glider the material for the framework, timber, cloth,
wire, etc., will cost a little more than double. This is because it must
be heavier in proportion to the increased size of the framework, and
heavy material brings a larger price than the lighter goods. If we allow
$20 as the cost of the glider material it will be safe to put down
the cost of that required for a real flying machine framework at $60,
provided the owner builds it himself.
As regards the cost of motor and similar equipment it can only be said
that this depends upon the selection made. There are some reliable
aviation motors which may be had as low as $500, and there are others
which cost as much as $2,000.
Services of Expert Necessary.
No matter what kind of a motor may be selected the services of an expert
will be necessary in its proper installation unless the amateur has
considerable genius in this line himself. As a general thing $25 should
be a liberal allowance for this work. No matter how carefully the engine
may be placed and connected it will be largely a matter of luck if it is
installed in exactly the proper manner at the first attempt. The chances
are that several alterations, prompted by the results of trials, will
have to be made. If this is the case the expert's bill may readily run
up to $50. If the amateur is competent to do this part of the work the
entire item of $50 may, of course, be cut out.
As a general proposition a fairly satisfactory flying machine, one that
will actually fly and carry the operator with it, may be constructed for
$750, but it will lack the better qualities which mark the higher priced
machines. This computation is made on the basis of $60 for material, $50
for services of expert, $600 for motor, etc., and an allowance of $40
for extras.
No man who has the flying machine germ in his system will be long
satisfied with his first moderate price machine, no matter how well it
may work. It's the old story of the automobile "bug" over again. The man
who starts in with a modest $1,000 automobile invariably progresses by
easy stages to the $4,000 or $5,000 class. The natural tendency is to
want the biggest and best attainable within the financial reach of the
owner.
It's exactly the same way with the flying machine convert. The more
proficient he becomes in the manipulation of his car, the stronger
becomes the desire to fly further and stay in the air longer than the
rest of his brethren. This necessitates larger, more powerful, and more
expensive machines as the work of the germ progresses.
Speed Affects Weight Capacity.
Don't overlook the fact that the greater speed you can attain the
smaller will be the surface area you can get along with. If a machine
with 500 square feet of sustaining surface, traveling at a speed of
40 miles an hour, will carry a weight of 1,200 pounds, we can cut the
sustaining surface in half and get along with 250 square feet, provided
a speed of 60 miles an hour can be obtained. At 100 miles an hour only
80 square feet of surface area would be required. In both instances the
weight sustaining capacity will remain the same as with the 500 square
feet of surface area--1,200 pounds.
One of these days some mathematical genius will figure out this problem
with exactitude and we will have a dependable table giving the maximum
carrying capacity of various surface areas at various stated speeds,
based on the dimensions of the advancing edges. At present it is largely
a matter of guesswork so far as making accurate computation goes.
Much depends upon the shape of the machine, and the amount of surface
offering resistance to the wind, etc.
CHAPTER IX. SELECTION OF THE MOTOR.
Motors for flying machines must be light in weight, of great strength,
productive of extreme speed, and positively dependable in action.
It matters little as to the particular form, or whether air or water
cooled, so long as the four features named are secured. There are at
least a dozen such motors or engines now in use. All are of the gasolene
type, and all possess in greater or lesser degree the desired qualities.
Some of these motors are:
Renault--8-cylinder, air-cooled; 50 horse power; weight 374 pounds.
Fiat--8-cylinder, air-cooled; 50 horse power; weight 150 pounds.
Farcot--8-cylinder, air-cooled; from 30 to 100 horse power, according to
bore of cylinders; weight of smallest, 84 pounds.
R. E. P.--10-cylinder, air-cooled; 150 horse power; weight 215 pounds.
Gnome--7 and 14 cylinders, revolving type, air-cooled; 50 and 100 horse
power; weight 150 and 300 pounds.
Darracq--2 to 14 cylinders, water cooled; 30 to 200 horse power; weight
of smallest 100 pounds.
Wright--4-cylinder, water-cooled; 25 horse power; weight 200 pounds.
Antoinette--8 and 16-cylinder, water-cooled; 50 and 100 horse power;
weight 250 and 500 pounds.
E. N. V.--8-cylinder, water-cooled; from 30 to 80 horse power, according
to bore of cylinder; weight 150 to 400 pounds.
Curtiss--8-cylinder, water-cooled; 60 horse power; weight 300 pounds.
Average Weight Per Horse Power.
It will be noticed that the Gnome motor is unusually light, being about
three pounds to the horse power produced, as opposed to an average of 4
1/2 pounds per horse power in other makes. This result is secured by
the elimination of the fly-wheel, the engine itself revolving, thus
obtaining the same effect that would be produced by a fly-wheel. The
Farcot is even lighter, being considerably less than three pounds per
horse power, which is the nearest approach to the long-sought engine
equipment that will make possible a complete flying machine the total
weight of which will not exceed one pound per square foot of area.
How Lightness Is Secured.
Thus far foreign manufacturers are ahead of Americans in the production
of light-weight aerial motors, as is evidenced by the Gnome and Farcot
engines, both of which are of French make. Extreme lightness is made
possible by the use of fine, specially prepared steel for the cylinders,
thus permitting them to be much thinner than if ordinary forms of steel
were used. Another big saving in weight is made by substituting what are
known as "auto lubricating" alloys for bearings. These alloys are made
of a combination of aluminum and magnesium.
Still further gains are made in the use of alloy steel tubing instead of
solid rods, and also by the paring away of material wherever it can be
done without sacrificing strength. This plan, with the exclusive use of
the best grades of steel, regardless of cost, makes possible a marked
reduction in weight.
Multiplicity of Cylinders.
Strange as it may seem, multiplicity of cylinders does not always add
proportionate weight. Because a 4-cylinder motor weighs say 100 pounds,
it does not necessarily follow that an 8-cylinder equipment will weigh
200 pounds. The reason of this will be plain when it is understood
that many of the parts essential to a 4-cylinder motor will fill the
requirements of an 8-cylinder motor without enlargement or addition.
Neither does multiplying the cylinders always increase the horsepower
proportionately. If a 4-cylinder motor is rated at 25 horsepower it is
not safe to take it for granted that double the number of cylinders
will give 50 horsepower. Generally speaking, eight cylinders, the bore,
stroke and speed being the same, will give double the power that can be
obtained from four, but this does not always hold good. Just why this
exception should occur is not explainable by any accepted rule.
Horse Power and Speed.
Speed is an important requisite in a flying-machine motor, as the
velocity of the aeroplane is a vital factor in flotation. At
first thought, the propeller and similar adjuncts being equal, the
inexperienced mind would naturally argue that a 50-horsepower engine
should produce just double the speed of one of 25-horsepower. That
this is a fallacy is shown by actual performances. The Wrights, using a
25-horsepower motor, have made 44 miles an hour, while Bleriot, with a
50-horsepower motor, has a record of a short-distance flight at the rate
of 52 miles an hour. The fact is that, so far as speed is concerned,
much depends upon the velocity of the wind, the size and shape of the
aeroplane itself, and the size, shape and gearing of the propeller. The
stronger the wind is blowing the easier it will be for the aeroplane
to ascend, but at the same time the more difficult it will be to make
headway against the wind in a horizontal direction. With a strong head
wind, and proper engine force, your machine will progress to a certain
extent, but it will be at an angle. If the aviator desired to keep
on going upward this would be all right, but there is a limit to the
altitude which it is desirable to reach--from 100 to 500 feet for
experts--and after that it becomes a question of going straight ahead.
Great Waste of Power.
One thing is certain--even in the most efficient of modern aerial motors
there is a great loss of power between the two points of production and
effect. The Wright outfit, which is admittedly one of the most effective
in use, takes one horsepower of force for the raising and propulsion of
each 50 pounds of weight. This, for a 25-horsepower engine, would give
a maximum lifting capacity of 1250 pounds. It is doubtful if any of
the higher rated motors have greater efficiency. As an 8-cylinder motor
requires more fuel to operate than a 4-cylinder, it naturally follows
that it is more expensive to run than the smaller motor, and a normal
increase in capacity, taking actual performances as a criterion, is
lacking. In other words, what is the sense of using an 8-cylinder motor
when one of 4 cylinders is sufficient?
What the Propeller Does.
Much of the efficiency of the motor is due to the form and gearing of
the propeller. Here again, as in other vital parts of flying-machine
mechanism, we have a wide divergence of opinion as to the best form. A
fish makes progress through the water by using its fins and tail; a
bird makes its way through the air in a similar manner by the use of its
wings and tail. In both instances the motive power comes from the body
of the fish or bird.
In place of fins or wings the flying machine is equipped with a
propeller, the action of which is furnished by the engine. Fins and
wings have been tried, but they don't work.
While operating on the same general principle, aerial propellers are
much larger than those used on boats. This is because the boat
propeller has a denser, more substantial medium to work in (water), and
consequently can get a better "hold," and produce more propulsive force
than one of the same size revolving in the air. This necessitates the
aerial propellers being much larger than those employed for marine
purposes. Up to this point all aviators agree, but as to the best form
most of them differ.
Kinds of Propellers Used.
One of the most simple is that used by Curtiss. It consists of two
pear-shaped blades of laminated wood, each blade being 5 inches wide
at its extreme point, tapering slightly to the shaft connection. These
blades are joined at the engine shaft, in a direct line. The propeller
has a pitch of 5 feet, and weighs, complete, less than 10 pounds. The
length from end to end of the two blades is 6 1/2 feet.
Wright uses two wooden propellers, in the rear of his biplane, revolving
in opposite directions. Each propeller is two-bladed.
Bleriot also uses a two-blade wooden propeller, but it is placed in
front of his machine. The blades are each about 3 1/2 feet long and have
an acute "twist."
Santos-Dumont uses a two-blade wooden propeller, strikingly similar to
the Bleriot.
On the Antoinette monoplane, with which good records have been made, the
propeller consists of two spoon-shaped pieces of metal, joined at the
engine shaft in front, and with the concave surfaces facing the machine.
The propeller on the Voisin biplane is also of metal, consisting of two
aluminum blades connected by a forged steel arm.
Maximum thrust, or stress--exercise of the greatest air-displacing
force--is the object sought. This, according to experts, is best
obtained with a large propeller diameter and reasonably low speed. The
diameter is the distance from end to end of the blades, which on the
largest propellers ranges from 6 to 8 feet. The larger the blade surface
the greater will be the volume of air displaced, and, following this,
the greater will be the impulse which forces the aeroplane ahead. In all
centrifugal motion there is more or less tendency to disintegration in
the form of "flying off" from the center, and the larger the revolving
object is the stronger is this tendency. This is illustrated in the many
instances in which big grindstones and fly-wheels have burst from being
revolved too fast. To have a propeller break apart in the air would
jeopardize the life of the aviator, and to guard against this it has
been found best to make its revolving action comparatively slow.
Besides this the slow motion (it is only comparatively slow) gives the
atmosphere a chance to refill the area disturbed by one propeller blade,
and thus have a new surface for the next blade to act upon.
Placing of the Motor.
As on other points, aviators differ widely in their ideas as to the
proper position for the motor. Wright locates his on the lower plane,
midway between the front and rear edges, but considerably to one side of
the exact center. He then counter-balances the engine weight by placing
his seat far enough away in the opposite direction to preserve the
center of gravity. This leaves a space in the center between the motor
and the operator in which a passenger may be carried without disturbing
the equilibrium.
Bleriot, on the contrary, has his motor directly in front and preserves
the center of gravity by taking his seat well back, this, with the
weight of the aeroplane, acting as a counter-balance.
On the Curtiss machine the motor is in the rear, the forward seat of the
operator, and weight of the horizontal rudder and damping plane in front
equalizing the engine weight.
No Perfect Motor as Yet.
Engine makers in the United States, England, France and Germany are all
seeking to produce an ideal motor for aviation purposes. Many of the
productions are highly creditable, but it may be truthfully said that
none of them quite fill the bill as regards a combination of the minimum
of weight with the maximum of reliable maintained power. They are all,
in some respects, improvements upon those previously in use, but the
great end sought for has not been fully attained.
One of the motors thus produced was made by the French firm of Darracq
at the suggestion of Santos Dumont, and on lines laid down by him.
Santos Dumont wanted a 2-cylinder horizontal motor capable of developing
30 horsepower, and not exceeding 4 1/2 pounds per horsepower in weight.
There can be no question as to the ability and skill of the Darracq
people, or of their desire to produce a motor that would bring new
credit and prominence to the firm. Neither could anything radically
wrong be detected in the plans. But the motor, in at least one important
requirement, fell short of expectations.
It could not be depended upon to deliver an energy of 30 horsepower
continuously for any length of time. Its maximum power could be secured
only in "spurts."
This tends to show how hard it is to produce an ideal motor for aviation
purposes. Santos Dumont, of undoubted skill and experience as an
aviator, outlined definitely what he wanted; one of the greatest
designers in the business drew the plans, and the famous house of
Darracq bent its best energies to the production. But the desired end
was not fully attained.
Features of Darracq Motor.
Horizontal motors were practically abandoned some time ago in favor of
the vertical type, but Santos Dumont had a logical reason for reverting
to them. He wanted to secure a lower center of gravity than would be
possible with a vertical engine. Theoretically his idea was correct as
the horizontal motor lies flat, and therefore offers less resistance to
the wind, but it did not work out as desired.
At the same time it must be admitted that this Darracq motor is a marvel
of ingenuity and exquisite workmanship. The two cylinders, having a bore
of 5 1-10 inches and a stroke of 4 7-10 inches, are machined out of a
solid bar of steel until their weight is only 8 4-5 pounds complete.
The head is separate, carrying the seatings for the inlet and exhaust
valves, is screwed onto the cylinder, and then welded in position. A
copper water-jacket is fitted, and it is in this condition that the
weight of 8 4-5 pounds is obtained.
On long trips, especially in regions where gasolene is hard to get,
the weight of the fuel supply is an important feature in aviation. As a
natural consequence flying machine operators favor the motor of greatest
economy in gasolene consumption, provided it gives the necessary power.
An American inventor, Ramsey by name, is working on a motor which
is said to possess great possibilities in this line. Its distinctive
features include a connecting rod much shorter than usual, and a crank
shaft located the length of the crank from the central axis of the
cylinder. This has the effect of increasing the piston stroke, and also
of increasing the proportion of the crank circle during which effective
pressure is applied to the crank.
Making the connecting rod shorter and leaving the crank mechanism the
same would introduce excessive cylinder friction. This Ramsey overcomes
by the location of his crank shaft. The effect of the long piston stroke
thus secured, is to increase the expansion of the gases, which in turn
increases the power of the engine without increasing the amount of fuel
used.
Propeller Thrust Important.
There is one great principle in flying machine propulsion which must
not be overlooked. No matter how powerful the engine may be unless the
propeller thrust more than overcomes the wind pressure there can be no
progress forward. Should the force of this propeller thrust and that of
the wind pressure be equal the result is obvious. The machine is at a
stand-still so far as forward progress is concerned and is deprived of
the essential advancing movement.
Speed not only furnishes sustentation for the airship, but adds to the
stability of the machine. An aeroplane which may be jerky and uncertain
in its movements, so far as equilibrium is concerned, when moving at
a slow gait, will readily maintain an even keel when the speed is
increased.
Designs for Propeller Blades.
It is the object of all men who design propellers to obtain the maximum
of thrust with the minimum expenditure of engine energy. With this
purpose in view many peculiar forms of propeller blades have been
evolved. In theory it would seem that the best effects could be secured
with blades so shaped as to present a thin (or cutting) edge when they
come out of the wind, and then at the climax of displacement afford a
maximum of surface so as to displace as much air as possible. While
this is the form most generally favored there are others in successful
operation.
There is also wide difference in opinion as to the equipment of the
propeller shaft with two or more blades. Some aviators use two and some
four. All have more or less success. As a mathematical proposition it
would seem that four blades should give more propulsive force than two,
but here again comes in one of the puzzles of aviation, as this result
is not always obtained.
Difference in Propeller Efficiency.
That there is a great difference in propeller efficiency is made readily
apparent by the comparison of effects produced in two leading makes of
machines--the Wright and the Voisin.
In the former a weight of from 1,100 to 1,200 pounds is sustained and
advance progress made at the rate of 40 miles an hour and more, with
half the engine speed of a 25 horse-power motor. This would be a
sustaining capacity of 48 pounds per horsepower. But the actual capacity
of the Wright machine, as already stated, is 50 pounds per horsepower.
The Voisin machine, with aviator, weighs about 1,370 pounds, and is
operated with a so-horsepower motor. Allowing it the same speed as the
Wright we find that, with double the engine energy, the lifting capacity
is only 27 1/2 pounds per horsepower. To what shall we charge this
remarkable difference? The surface of the planes is exactly the same in
both machines so there is no advantage in the matter of supporting area.
Comparison of Two Designs.
On the Wright machine two wooden propellers of two blades each (each
blade having a decided "twist") are used. As one 25 horsepower motor
drives both propellers the engine energy amounts to just one-half of
this for each, or 12 1/2 horsepower. And this energy is utilized at
one-half the normal engine speed.
On the Voisin a radically different system is employed. Here we have
one metal two-bladed propeller with a very slight "twist" to the blade
surfaces. The full energy of a 50-horsepower motor is utilized.
Experts Fail to Agree.
Why should there be such a marked difference in the results obtained?
Who knows? Some experts maintain that it is because there are two
propellers on the Wright machine and only one on the Voisin, and
consequently double the propulsive power is exerted. But this is not a
fair deduction, unless both propellers are of the same size. Propulsive
power depends upon the amount of air displaced, and the energy put into
the thrust which displaces the air.
Other experts argue that the difference in results may be traced to the
difference in blade design, especially in the matter of "twist."
The fact is that propeller results depend largely upon the nature of
the aeroplanes on which they are used. A propeller, for instance,
which gives excellent results on one type of aeroplane, will not work
satisfactorily on another.
There are some features, however, which may be safely adopted in
propeller selection. These are: As extensive a diameter as possible;
blade area 10 to 15 per cent of the area swept; pitch four-fifths of
the diameter; rotation slow. The maximum of thrust effort will be thus
obtained.
CHAPTER X. PROPER DIMENSIONS OF MACHINES.
In laying out plans for a flying machine the first thing to decide upon
is the size of the plane surfaces. The proportions of these must be
based upon the load to be carried. This includes the total weight of
the machine and equipment, and also the operator. This will be a rather
difficult problem to figure out exactly, but practical approximate
figures may be reached.
It is easy to get at the weight of the operator, motor and propeller,
but the matter of determining, before they are constructed, what the
planes, rudders, auxiliaries, etc., will weigh when completed is an
intricate proposition. The best way is to take the dimensions of some
successful machine and use them, making such alterations in a minor way
as you may desire.
Dimensions of Leading Machines.
In the following tables will be found the details as to surface area,
weight, power, etc., of the nine principal types of flying machines
which are now prominently before the public:
MONOPLANES.
Surface area Spread in Depth in
Make Passengers sq. feet linear feet linear
feet
Santos-Dumont.. 1 110 16.0 26.0
Bleriot..... 1 150.6 24.6 22.0
R. E. P..... 1 215 34.1 28.9
Bleriot..... 2 236 32.9 23.0
Antoinette.... 2 538 41.2 37.9
No. of Weight Without
Propeller
Make Cylinders Horse Power Operator
Diameter
Santos-Dumont.. 2 30 250 5.0
Bleriot..... 3 25 680 6.9
R. E. P..... 7 35 900 6.6
Bleriot..... 7 50 1,240 8.1
Antoinette... 8 50 1,040 7.2
BIPLANES.
Surface Area Spread in Depth
in
Make Passengers sq. feet linear feet linear
feet
Curtiss... 2 258 29.0
28.7
Wright.... 2 538 41.0
30.7
Farman.... 2 430 32.9
39.6
Voisin.... 2 538 37.9
39.6
No. of Weight Without
Propeller
Make Cylinders Horse Power Operator
Diameter
Curtiss... 8 50 600 6.0
Wright.... 4 25 1,100 8.1
Farman.... 7 50 1,200 8.9
Voisin.... 8 50 1,200 6.6
In giving the depth dimensions the length over all--from the extreme
edge of the front auxiliary plane to the extreme tip of the rear is
stated. Thus while the dimensions of the main planes of the Wright
machine are 41 feet spread by 6 1/2 feet in depth, the depth over all is
30.7.
Figuring Out the Details.
With this data as a guide it should be comparatively easy to decide
upon the dimensions of the machine required. In arriving at the maximum
lifting capacity the weight of the operator must be added. Assuming this
to average 170 pounds the method of procedure would be as follows:
Add the weight of the operator to the weight of the complete machine.
The new Wright machine complete weighs 900 pounds. This, plus 170, the
weight of the operator, gives a total of 1,070 pounds. There are 538
square feet of supporting surface, or practically one square foot of
surface area to each two pounds of load.
There are some machines, notably the Bleriot, in which the supporting
power is much greater. In this latter instance we find a surface area of
150 1/2 square feet carrying a load of 680 plus 170, or an aggregate of
850 pounds. This is the equivalent of five pounds to the square foot.
This ratio is phenomenally large, and should not be taken as a guide by
amateurs.
The Matter of Passengers.
These deductions are based on each machine carrying one passenger, which
is admittedly the limit at present of the monoplanes like those operated
for record-making purposes by Santos-Dumont and Bleriot. The biplanes,
however, have a two-passenger capacity, and this adds materially to the
proportion of their weight-sustaining power as compared with the surface
area. In the following statement all the machines are figured on the
one-passenger basis. Curtiss and Wright have carried two passengers on
numerous occasions, and an extra 170 pounds should therefore be added to
the total weight carried, which would materially increase the capacity.
Even with the two-passenger load the limit is by no means reached,
but as experiments have gone no further it is impossible to make more
accurate figures.
Average Proportions of Load.
It will be interesting, before proceeding to lay out the dimension
details, to make a comparison of the proportion of load effect with
the supporting surfaces of various well-known machines. Here are the
figures:
Santos-Dumont--A trifle under four pounds per square foot.
Bleriot--Five pounds.
R. E. P.--Five pounds.
Antoinette--About two and one-quarter pounds.
Curtiss--About two and one-half pounds.
Wright--Two and one-quarter pounds.
Farman--A trifle over three pounds.
Voisin--A little under two and one-half pounds.
Importance of Engine Power.
While these figures are authentic, they are in a way misleading, as the
important factor of engine power is not taken into consideration. Let us
recall the fact that it is the engine power which keeps the machine in
motion, and that it is only while in motion that the machine will remain
suspended in the air. Hence, to attribute the support solely to the
surface area is erroneous. True, that once under headway the planes
contribute largely to the sustaining effect, and are absolutely
essential in aerial navigation--the motor could not rise without
them--still, when it comes to a question of weight-sustaining power, we
must also figure on the engine capacity.
In the Wright machine, in which there is a lifting capacity of
approximately 2 1/4 pounds to the square foot of surface area, an engine
of only 25 horsepower is used. In the Curtiss, which has a lifting
capacity of 2 1/2 pounds per square foot, the engine is of 50
horsepower. This is another of the peculiarities of aerial construction
and navigation. Here we have a gain of 1/4 pound in weight-lifting
capacity with an expenditure of double the horsepower. It is this
feature which enables Curtiss to get along with a smaller surface area
of supporting planes at the expense of a big increase in engine power.
Proper Weight of Machine.
As a general proposition the most satisfactory machine for amateur
purposes will be found to be one with a total weight-sustaining power of
about 1,200 pounds. Deducting 170 pounds as the weight of the operator,
this will leave 1,030 pounds for the complete motor-equipped machine,
and it should be easy to construct one within this limit. This implies,
of course, that due care will be taken to eliminate all superfluous
weight by using the lightest material compatible with strength and
safety.
This plan will admit of 686 pounds weight in the frame work, coverings,
etc., and 344 for the motor, propeller, etc., which will be ample. Just
how to distribute the weight of the planes is a matter which must be
left to the ingenuity of the builder.
Comparison of Bird Power.
There is an interesting study in the accompanying illustration. Note
that the surface area of the albatross is much smaller than that of the
vulture, although the wing spread is about the same. Despite this the
albatross accomplishes fully as much in the way of flight and soaring as
the vulture. Why? Because the albaboss is quicker and more powerful in
action. It is the application of this same principle in flying machines
which enables those of great speed and power to get along with less
supporting surface than those of slower movement.
Measurements of Curtiss Machine.
Some idea of framework proportion may be had from the following
description of the Curtiss machine. The main planes have a spread
(width) of 29 feet, and are 4 1/2 feet deep. The front double surface
horizontal rudder is 6x2 feet, with an area of 24 square feet. To the
rear of the main planes is a single surface horizontal plane 6x2 feet,
with an area of 12 square feet. In connection with this is a vertical
rudder 2 1/2 feet square. Two movable ailerons, or balancing planes, are
placed at the extreme ends of the upper planes. These are 6x2 feet,
and have a combined area of 24 square feet. There is also a triangular
shaped vertical steadying surface in connection with the front rudder.
Thus we have a total of 195 square feet, but as the official figures are
258, and the size of the triangular-shaped steadying surface is unknown,
we must take it for granted that this makes up the difference. In
the matter of proportion the horizontal double-plane rudder is about
one-tenth the size of the main plane, counting the surface area of
only one plane, the vertical rudder one-fortieth, and the ailerons
one-twentieth.
CHAPTER XI. PLANE AND RUDDER CONTROL.
Having constructed and equipped your machine, the next thing is to
decide upon the method of controlling the various rudders and auxiliary
planes by which the direction and equilibrium and ascending and
descending of the machine are governed.
The operator must be in position to shift instantaneously the position
of rudders and planes, and also to control the action of the motor. This
latter is supposed to work automatically and as a general thing does
so with entire satisfaction, but there are times when the supply of
gasolene must be regulated, and similar things done. Airship navigation
calls for quick action, and for this reason the matter of control is an
important one--it is more than important; it is vital.
Several Methods of Control.
Some aviators use a steering wheel somewhat after the style of that used
in automobiles, and by this not only manipulate the rudder planes, but
also the flow of gasolene. Others employ foot levers, and still others,
like the Wrights, depend upon hand levers.
Curtiss steers his aeroplane by means of a wheel, but secures the
desired stabilizing effect with an ingenious jointed chair-back. This is
so arranged that by leaning toward the high point of his wing planes the
aeroplane is restored to an even keel. The steering post of the wheel is
movable backward and forward, and by this motion elevation is obtained.
The Wrights for some time used two hand levers, one to steer by and warp
the flexible tips of the planes, the other to secure elevation. They
have now consolidated all the functions in one lever. Bleriot also uses
the single lever control.
Farman employs a lever to actuate the rudders, but manipulates the
balancing planes by foot levers.
Santos-Dumont uses two hand levers with which to steer and elevate,
but manipulates the planes by means of an attachment to the back of his
outer coat.
Connection With the Levers.
No matter which particular method is employed, the connection between
the levers and the object to be manipulated is almost invariably by
wire. For instance, from the steering levers (or lever) two wires
connect with opposite sides of the rudder. As a lever is moved so as to
draw in the right-hand wire the rudder is drawn to the right and vice
versa. The operation is exactly the same as in steering a boat. It
is the same way in changing the position of the balancing planes. A
movement of the hands or feet and the machine has changed its course,
or, if the equilibrium is threatened, is back on an even keel.
Simple as this seems it calls for a cool head, quick eye, and steady
hand. The least hesitation or a false movement, and both aviator and
craft are in danger.
Which Method is Best?
It would be a bold man who would attempt to pick out any one of these
methods of control and say it was better than the others. As in other
sections of aeroplane mechanism each method has its advocates who dwell
learnedly upon its advantages, but the fact remains that all the various
plans work well and give satisfaction.
What the novice is interested in knowing is how the control is effected,
and whether he has become proficient enough in his manipulation of it to
be absolutely dependable in time of emergency. No amateur should attempt
a flight alone, until he has thoroughly mastered the steering and plane
control. If the services and advice of an experienced aviator are not to
be had the novice should mount his machine on some suitable supports so
it will be well clear of the ground, and, getting into the operator's
seat, proceed to make himself well acquainted with the operation of the
steering wheel and levers.
Some Things to Be Learned.
He will soon learn that certain movements of the steering gear produce
certain effects on the rudders. If, for instance, his machine is
equipped with a steering wheel, he will find that turning the wheel to
the right turns the aeroplane in the same direction, because the tiller
is brought around to the left. In the same way he will learn that a
given movement of the lever throws the forward edge of the main plane
upward, and that the machine, getting the impetus of the wind under the
concave surfaces of the planes, will ascend. In the same way it will
quickly become apparent to him that an opposite movement of the lever
will produce an opposite effect--the forward edges of the planes will be
lowered, the air will be "spilled" out to the rear, and the machine will
descend.
The time expended in these preliminary lessons will be well spent. It
would be an act of folly to attempt to actually sail the craft without
them.
CHAPTER XII. HOW TO USE THE MACHINE.
It is a mistaken idea that flying machines must be operated at extreme
altitudes. True, under the impetus of handsome prizes, and the incentive
to advance scientific knowledge, professional aviators have ascended to
considerable heights, flights at from 500 to 1,500 feet being now
common with such experts as Farman, Bleriot, Latham, Paulhan, Wright and
Curtiss. The altitude record at this time is about 4,165 feet, held by
Paulhan.
One of the instructions given by experienced aviators to pupils, and for
which they insist upon implicit obeyance, is: "If your machine gets more
than 30 feet high, or comes closer to the ground than 6 feet, descend at
once." Such men as Wright and Curtiss will not tolerate a violation of
this rule. If their instructions are not strictly complied with they
decline to give the offender further lessons.
Why This Rule Prevails.
There is good reason for this precaution. The higher the altitude the
more rarefied (thinner) becomes the air, and the less sustaining power
it has. Consequently the more difficult it becomes to keep in suspension
a given weight. When sailing within 30 feet of the ground sustentation
is comparatively easy and, should a fall occur, the results are not
likely to be serious. On the other hand, sailing too near the ground
is almost as objectionable in many ways as getting up too high. If the
craft is navigated too close to the ground trees, shrubs, fences and
other obstructions are liable to be encountered. There is also the
handicap of contrary air currents diverted by the obstructions referred
to, and which will be explained more fully further on.
How to Make a Start.
Taking it for granted that the beginner has familiarized himself with
the manipulation of the machine, and especially the control mechanism,
the next thing in order is an actual flight. It is probable that his
machine will be equipped with a wheeled alighting gear, as the skids
used by the Wrights necessitate the use of a special starting track.
In this respect the wheeled machine is much easier to handle so far as
novices are concerned as it may be easily rolled to the trial grounds.
This, as in the case of the initial experiments, should be a clear,
reasonably level place, free from trees, fences, rocks and similar
obstructions with which there may be danger of colliding.
The beginner will need the assistance of three men. One of these should
take his position in the rear of the machine, and one at each end. On
reaching the trial ground the aviator takes his seat in the machine and,
while the men at the ends hold it steady the one in the rear assists in
retaining it until the operator is ready. In the meantime the aviator
has started his motor. Like the glider the flying machine, in order to
accomplish the desired results, should be headed into the wind.
When the Machine Rises.
Under the impulse of the pushing movement, and assisted by the motor
action, the machine will gradually rise from the ground--provided it
has been properly proportioned and put together, and everything is in
working order. This is the time when the aviator requires a cool head,
At a modest distance from the ground use the control lever to bring the
machine on a horizontal level and overcome the tendency to rise. The
exact manipulation of this lever depends upon the method of control
adopted, and with this the aviator is supposed to have thoroughly
familiarized himself as previously advised in Chapter XI.
It is at this juncture that the operator must act promptly, but with the
perfect composure begotten of confidence. One of the great drawbacks in
aviation by novices is the tendency to become rattled, and this is much
more prevalent than one might suppose, even among men who, under other
conditions, are cool and confident in their actions.
There is something in the sensation of being suddenly lifted from the
ground, and suspended in the air that is disconcerting at the start,
but this will soon wear off if the experimenter will keep cool. A few
successful flights no matter how short they may be, will put a lot of
confidence into him.
Make Your Flights Short.
Be modest in your initial flights. Don't attempt to match the records
of experienced men who have devoted years to mastering the details of
aviation. Paulhan, Farman, Bleriot, Wright, Curtiss, and all the rest of
them began, and practiced for years, in the manner here described, being
content to make just a little advancement at each attempt. A flight of
150 feet, cleanly and safely made, is better as a beginning than one of
400 yards full of bungling mishaps.
And yet these latter have their uses, provided the operator is of a
discerning mind and can take advantage of them as object lessons. But,
it is not well to invite them. They will occur frequently enough under
the most favorable conditions, and it is best to have them come later
when the feeling of trepidation and uncertainty as to what to do has
worn off.
Above all, don't attempt to fly too high. Keep within a reasonable
distance from the ground--about 25 or 30 feet. This advice is not given
solely to lessen the risk of serious accident in case of collapse, but
mainly because it will assist to instill confidence in the operator.
It is comparatively easy to learn to swim in shallow water, but the
knowledge that one is tempting death in deep water begets timidity.
Preserving the Equilibrium.
After learning how to start and stop, to ascend and descend, the next
thing to master is the art of preserving equilibrium, the knack of
keeping the machine perfectly level in the air--on an "even keel," as
a sailor would say. This simile is particularly appropriate as all
aviators are in reality sailors, and much more daring ones than those
who course the seas. The latter are in craft which are kept afloat by
the buoyancy of the water, whether in motion or otherwise and, so long
as normal conditions prevail, will not sink. Aviators sail the air in
craft in which constant motion must be maintained in order to ensure
flotation.
The man who has ridden a bicycle or motorcycle around curves at anything
like high speed, will have a very good idea as to the principle of
maintaining equilibrium in an airship. He knows that in rounding curves
rapidly there is a marked tendency to change the direction of the motion
which will result in an upset unless he overcomes it by an inclination
of his body in an opposite direction. This is why we see racers lean
well over when taking the curves. It simply must be done to preserve the
equilibrium and avoid a spill.
How It Works In the Air.
If the equilibrium of an airship is disturbed to an extent which
completely overcomes the center of gravity it falls according to the
location of the displacement. If this displacement, for instance, is at
either end the apparatus falls endways; if it is to the front or rear,
the fall is in the corresponding direction.
Owing to uncertain air currents--the air is continually shifting and
eddying, especially within a hundred feet or so of the earth--the
equilibrium of an airship is almost constantly being disturbed to some
extent. Even if this disturbance is not serious enough to bring on
a fall it interferes with the progress of the machine, and should
be overcome at once. This is one of the things connected with aerial
navigation which calls for prompt, intelligent action.
Frequently, when the displacement is very slight, it may be overcome,
and the craft immediately righted by a mere shifting of the operator's
body. Take, for illustration, a case in which the extreme right end
of the machine becomes lowered a trifle from the normal level. It is
possible to bring it back into proper position by leaning over to the
left far enough to shift the weight to the counter-balancing point. The
same holds good as to minor front or rear displacements.
When Planes Must Be Used.
There are other displacements, however, and these are the most frequent,
which can be only overcome by manipulation of the stabilizing planes.
The method of procedure depends upon the form of machine in use. The
Wright machine, as previously explained, is equipped with plane ends
which are so contrived as to admit of their being warped (position
changed) by means of the lever control. These flexible tip planes move
simultaneously, but in opposite directions. As those on one end rise,
those on the other end fall below the level of the main plane. By this
means air is displaced at one point, and an increased amount secured in
another.
This may seem like a complicated system, but its workings are simple
when once understood. It is by the manipulation or warping of these
flexible tips that transverse stability is maintained, and any tendency
to displacement endways is overcome. Longitudinal stability is governed
by means of the front rudder.
Stabilizing planes of some form are a feature, and a necessary feature,
on all flying machines, but the methods of application and manipulation
vary according to the individual ideas of the inventors. They all tend,
however, toward the same end--the keeping of the machine perfectly level
when being navigated in the air.
When to Make a Flight.
A beginner should never attempt to make a flight when a strong wind is
blowing. The fiercer the wind, the more likely it is to be gusty and
uncertain, and the more difficult it will be to control the machine.
Even the most experienced and daring of aviators find there is a limit
to wind speed against which they dare not compete. This is not because
they lack courage, but have the sense to realize that it would be silly
and useless.
The novice will find a comparatively still day, or one when the wind is
blowing at not to exceed 15 miles an hour, the best for his experiments.
The machine will be more easily controlled, the trip will be safer, and
also cheaper as the consumption of fuel increases with the speed of the
wind against which the aeroplane is forced.
CHAPTER XIII. PECULIARITIES OF AIRSHIP POWER.
As a general proposition it takes much more power to propel an airship
a given number of miles in a certain time than it does an automobile
carrying a far heavier load. Automobiles with a gross load of 4,000
pounds, and equipped with engines of 30 horsepower, have travelled
considerable distances at the rate of 50 miles an hour. This is an
equivalent of about 134 pounds per horsepower. For an average modern
flying machine, with a total load, machine and passengers, of 1,200
pounds, and equipped with a 50-horsepower engine, 50 miles an hour
is the maximum. Here we have the equivalent of exactly 24 pounds per
horsepower. Why this great difference?
No less an authority than Mr. Octave Chanute answers the question in a
plain, easily understood manner. He says:
"In the case of an automobile the ground furnishes a stable support;
in the case of a flying machine the engine must furnish the support and
also velocity by which the apparatus is sustained in the air."
Pressure of the Wind.
Air pressure is a big factor in the matter of aeroplane horsepower.
Allowing that a dead calm exists, a body moving in the atmosphere
creates more or less resistance. The faster it moves, the greater is
this resistance. Moving at the rate of 60 miles an hour the resistance,
or wind pressure, is approximately 50 pounds to the square foot of
surface presented. If the moving object is advancing at a right angle
to the wind the following table will give the horsepower effect of the
resistance per square foot of surface at various speeds.
Horse Power
Miles per Hour per sq. foot
10 0.013
15 0 044
20 0.105
25 0.205
30 0.354
40 0.84
50 1.64
60 2.83
80 6.72
100 13.12
While the pressure per square foot at 60 miles an hour, is only 1.64
horsepower, at 100 miles, less than double the speed, it has increased
to 13.12 horsepower, or exactly eight times as much. In other words the
pressure of the wind increases with the square of the velocity. Wind at
10 miles an hour has four times more pressure than wind at 5 miles an
hour.
How to Determine Upon Power.
This element of air resistance must be taken into consideration in
determining the engine horsepower required. When the machine is under
headway sufficient to raise it from the ground (about 20 miles an hour),
each square foot of surface resistance, will require nearly nine-tenths
of a horsepower to overcome the wind pressure, and propel the machine
through the air. As shown in the table the ratio of power required
increases rapidly as the speed increases until at 60 miles an hour
approximately 3 horsepower is needed.
In a machine like the Curtiss the area of wind-exposed surface is about
15 square feet. On the basis of this resistance moving the machine at 40
miles an hour would require 12 horsepower. This computation covers only
the machine's power to overcome resistance. It does not cover the power
exerted in propelling the machine forward after the air pressure is
overcome. To meet this important requirement Mr. Curtiss finds it
necessary to use a 50-horsepower engine. Of this power, as has been
already stated, 12 horsepower is consumed in meeting the wind pressure,
leaving 38 horsepower for the purpose of making progress.
The flying machine must move faster than the air to which it is opposed.
Unless it does this there can be no direct progress. If the two forces
are equal there is no straight-ahead advancement. Take, for sake of
illustration, a case in which an aeroplane, which has developed a speed
of 30 miles an hour, meets a wind velocity of equal force moving in an
opposite direction. What is the result? There can be no advance because
it is a contest between two evenly matched forces. The aeroplane stands
still. The only way to get out of the difficulty is for the operator to
wait for more favorable conditions, or bring his machine to the ground
in the usual manner by manipulation of the control system.
Take another case. An aeroplane, capable of making 50 miles an hour in a
calm, is met by a head wind of 25 miles an hour. How much progress does
the aeroplane make? Obviously it is 25 miles an hour over the ground.
Put the proposition in still another way. If the wind is blowing harder
than it is possible for the engine power to overcome, the machine will
be forced backward.
Wind Pressure a Necessity.
While all this is true, the fact remains that wind pressure, up to
a certain stage, is an absolute necessity in aerial navigation. The
atmosphere itself has very little real supporting power, especially if
inactive. If a body heavier than air is to remain afloat it must move
rapidly while in suspension.
One of the best illustrations of this is to be found in skating over
thin ice. Every school boy knows that if he moves with speed he may
skate or glide in safety across a thin sheet of ice that would not
begin to bear his weight if he were standing still. Exactly the same
proposition obtains in the case of the flying machine.
The non-technical reason why the support of the machine becomes easier
as the speed increases is that the sustaining power of the atmosphere
increases with the resistance, and the speed with which the object is
moving increases this resistance. With a velocity of 12 miles an hour
the weight of the machine is practically reduced by 230 pounds. Thus, if
under a condition of absolute calm it were possible to sustain a weight
of 770 pounds, the same atmosphere would sustain a weight of 1,000
pounds moving at a speed of 12 miles an hour. This sustaining power
increases rapidly as the speed increases. While at 12 miles the
sustaining power is figured at 230 pounds, at 24 miles it is four times
as great, or 920 pounds.
Supporting Area of Birds.
One of the things which all producing aviators seek to copy is the
motive power of birds, particularly in their relation to the area of
support. Close investigation has established the fact that the larger
the bird the less is the relative area of support required to secure a
given result. This is shown in the following table:
Supporting
Weight Surface Horse area
Bird in lbs. in sq. feet power per lb.
Pigeon 1.00 0.7 0.012 0.7
Wild Goose 9.00 2.65 0.026 0.2833
Buzzard 5.00 5.03 0.015 1.06
Condor 17.00 9.85 0.043 0.57
So far as known the condor is the largest of modern birds. It has a wing
stretch of 10 feet from tip to tip, a supporting area of about 10 square
feet, and weighs 17 pounds. It. is capable of exerting perhaps 1-30
horsepower. (These figures are, of course, approximate.) Comparing the
condor with the buzzard with a wing stretch of 6 feet, supporting area
of 5 square feet, and a little over 1-100 horsepower, it may be seen
that, broadly speaking, the larger the bird the less surface area
(relatively) is needed for its support in the air.
Comparison With Aeroplanes.
If we compare the bird figures with those made possible by the
development of the aeroplane it will be readily seen that man has made a
wonderful advance in imitating the results produced by nature. Here are
the figures:
Supporting
Weight Surface Horse area
Machine in lbs. in sq. feet power per lb.
Santos-Dumont.. 350 110.00 30 0.314
Bleriot..... 700 150.00 25 0.214
Antoinette.... 1,200 538.00 50 0.448
Curtiss..... 700 258.00 60 0.368
Wright.....[4] 1,100 538.00 25 0.489
Farman...... 1,200 430.00 50 0.358
Voisin...... 1,200 538.00 50 0.448
While the average supporting surface is in favor of the aeroplane, this
is more than overbalanced by the greater amount of horsepower required
for the weight lifted. The average supporting surface in birds is about
three-quarters of a square foot per pound. In the average aeroplane it
is about one-half square foot per pound. On the other hand the average
aeroplane has a lifting capacity of 24 pounds per horsepower, while the
buzzard, for instance, lifts 5 pounds with 15-100 of a horsepower.
If the Wright machine--which has a lifting power of 50 pounds per
horsepower--should be alone considered the showing would be much more
favorable to the aeroplane, but it would not be a fair comparison.
More Surface, Less Power.
Broadly speaking, the larger the supporting area the less will be the
power required. Wright, by the use of 538 square feet of supporting
surface, gets along with an engine of 25 horsepower. Curtiss, who uses
only 258 square feet of surface, finds an engine of 50 horsepower is
needed. Other things, such as frame, etc., being equal, it stands
to reason that a reduction in the area of supporting surface will
correspondingly reduce the weight of the machine. Thus we have the
Curtiss machine with its 258 square feet of surface, weighing only 600
pounds (without operator), but requiring double the horsepower of
the Wright machine with 538 square feet of surface and weighing 1,100
pounds. This demonstrates in a forceful way the proposition that the
larger the surface the less power will be needed.
But there is a limit, on account of its bulk and awkwardness in
handling, beyond which the surface area cannot be enlarged. Otherwise
it might be possible to equip and operate aeroplanes satisfactorily with
engines of 15 horsepower, or even less.
The Fuel Consumption Problem.
Fuel consumption is a prime factor in the production of engine power.
The veriest mechanical tyro knows in a general way that the more power
is secured the more fuel must be consumed, allowing that there is no
difference in the power-producing qualities of the material used. But
few of us understand just what the ratio of increase is, or how it is
caused. This proposition is one of keen interest in connection with
aviation.
Let us cite a problem which will illustrate the point quoted: Allowing
that it takes a given amount of gasolene to propel a flying machine a
given distance, half the way with the wind, and half against it, the
wind blowing at one-half the speed of the machine, what will be the
increase in fuel consumption?
Increase of Thirty Per Cent.
On the face of it there would seem to be no call for an increase as the
resistance met when going against the wind is apparently offset by the
propulsive force of the wind when the machine is travelling with
it. This, however, is called faulty reasoning. The increase in fuel
consumption, as figured by Mr. F. W. Lanchester, of the Royal Society of
Arts, will be fully 30 per cent over the amount required for a similar
operation of the machine in still air. If the journey should be made at
right angles to the wind under the same conditions the increase would be
15 per cent.
In other words Mr. Lanchester maintains that the work done by the motor
in making headway against the wind for a certain distance calls for more
engine energy, and consequently more fuel by 30 per cent, than is saved
by the helping force of the wind on the return journey.
CHAPTER XIV. ABOUT WIND CURRENTS, ETC.
One of the first difficulties which the novice will encounter is the
uncertainty of the wind currents. With a low velocity the wind, some
distance away from the ground, is ordinarily steady. As the velocity
increases, however, the wind generally becomes gusty and fitful in its
action. This, it should be remembered, does not refer to the velocity of
the machine, but to that of the air itself.
In this connection Mr. Arthur T. Atherholt, president of the Aero
Club of Pennsylvania, in addressing the Boston Society of Scientific
Research, said:
"Probably the whirlpools of Niagara contain no more erratic currents
than the strata of air which is now immediately above us, a fact hard to
realize on account of its invisibility."
Changes In Wind Currents.
While Mr. Atherholt's experience has been mainly with balloons it is all
the more valuable on this account, as the balloons were at the mercy of
the wind and their varying directions afforded an indisputable guide as
to the changing course of the air currents. In speaking of this he said:
"In the many trips taken, varying in distance traversed from twenty-five
to 900 miles, it was never possible except in one instance to maintain
a straight course. These uncertain currents were most noticeable in
the Gordon-Bennett race from St. Louis in 1907. Of the nine aerostats
competing in that event, eight covered a more or less direct course
due east and southeast, whereas the writer, with Major Henry B. Hersey,
first started northwest, then north, northeast, east, east by south,
and when over the center of Lake Erie were again blown northwest
notwithstanding that more favorable winds were sought for at altitudes
varying from 100 to 3,000 meters, necessitating a finish in Canada
nearly northeast of the starting point.
"These nine balloons, making landings extending from Lake Ontario,
Canada, to Virginia, all started from one point within the same hour.
"The single exception to these roving currents occurred on October 21st,
of last year (1909) when, starting from Philadelphia, the wind shifted
more than eight degrees, the greatest variation being at the lowest
altitudes, yet at no time was a height of over a mile reached.
"Throughout the entire day the sky was overcast, with a thermometer
varying from fifty-seven degrees at 300 feet to forty-four degrees,
Fahrenheit at 5,000 feet, at which altitude the wind had a velocity of
43 miles an hour, in clouds of a cirro-cumulus nature, a landing finally
being made near Tannersville, New York, in the Catskill mountains, after
a voyage of five and one-half hours.
"I have no knowledge of a recorded trip of this distance and duration,
maintained in practically a straight line from start to finish."
This wind disturbance is more noticeable and more difficult to contend
with in a balloon than in a flying machine, owing to the bulk and
unwieldy character of the former. At the same time it is not conducive
to pleasant, safe or satisfactory sky-sailing in an aeroplane. This is
not stated with the purpose of discouraging aviation, but merely that
the operator may know what to expect and be prepared to meet it.
Not only does the wind change its horizontal course abruptly and without
notice, but it also shifts in a vertical direction, one second blowing
up, and another down. No man has as yet fathomed the why and wherefore
of this erratic action; it is only known that it exists.
The most stable currents will be found from 50 to 100 feet from the
earth, provided the wind is not diverted by such objects as trees,
rocks, etc. That there are equally stable currents higher up is true,
but they are generally to be found at excessive altitudes.
How a Bird Meets Currents.
Observe a bird in action on a windy day and you will find it continually
changing the position of its wings. This is done to meet the varying
gusts and eddies of the air so that sustentation may be maintained and
headway made. One second the bird is bending its wings, altering the
angle of incidence; the next it is lifting or depressing one wing at a
time. Still again it will extend one wing tip in advance of the other,
or be spreading or folding, lowering or raising its tail.
All these motions have a meaning, a purpose. They assist the bird in
preserving its equilibrium. Without them the bird would be just as
helpless in the air as a human being and could not remain afloat.
When the wind is still, or comparatively so, a bird, having secured the
desired altitude by flight at an angle, may sail or soar with no wing
action beyond an occasional stroke when it desires to advance. But, in a
gusty, uncertain wind it must use its wings or alight somewhere.
Trying to Imitate the Bird.
Writing in _Fly_, Mr. William E. White says:
"The bird's flight suggests a number of ways in which the equilibrium
of a mechanical bird may be controlled. Each of these methods of control
may be effected by several different forms of mechanism.
"Placing the two wings of an aeroplane at an angle of three to five
degrees to each other is perhaps the oldest way of securing lateral
balance. This way readily occurs to anyone who watches a sea gull
soaring. The theory of the dihedral angle is that when one wing is
lifted by a gust of wind, the air is spilled from under it; while
the other wing, being correspondingly depressed, presents a greater
resistance to the gust and is lifted restoring the balance. A fixed
angle of three to five degrees, however, will only be sufficient for
very light puffs of wind and to mount the wings so that the whole
wing may be moved to change the dihedral angle presents mechanical
difficulties which would be better avoided.
"The objection of mechanical impracticability applies to any plan
to preserve the balance by shifting weight or ballast. The center of
gravity should be lower than the center of the supporting surfaces,
but cannot be made much lower. It is a common mistake to assume that
complete stability will be secured by hanging the center of gravity very
low on the principle of the parachute. An aeroplane depends upon rapid
horizontal motion for its support, and if the center of gravity be far
below the center of support, every change of speed or wind pressure will
cause the machine to turn about its center of gravity, pitching forward
and backward dangerously.
Preserving Longitudinal Balance.
"The birds maintain longitudinal, or fore and aft balance, by elevating
or depressing their tails. Whether this action is secured in an
aeroplane by means of a horizontal rudder placed in the rear, or by
deflecting planes placed in front of the main planes, the principle is
evidently the same. A horizontal rudder placed well to the rear as in
the Antoinette, Bleriot or Santos-Dumont monoplanes, will be very much
safer and steadier than the deflecting planes in front, as in the Wright
or Curtiss biplanes, but not so sensitive or prompt in action.
"The natural fore and aft stability is very much strengthened by placing
the load well forward. The center of gravity near the front and a
tail or rudder streaming to the rear secures stability as an arrow is
balanced by the head and feathering. The adoption of this principle
makes it almost impossible for the aeroplane to turn over.
The Matter of Lateral Balance.
"All successful aeroplanes thus far have maintained lateral balance by
the principle of changing the angle of incidence of the wings.
"Other ways of maintaining the lateral balance, suggested by observation
of the flight of birds are--extending the wing tips and spilling the air
through the pinions; or, what is the same thing, varying the area of the
wings at their extremities.
"Extending the wing tips seems to be a simple and effective solution of
the problem. The tips may be made to swing outward upon a vertical axis
placed at the front edge of the main planes; or they may be hinged to
the ends of the main plane so as to be elevated or depressed through
suitable connections by the aviator; or they may be supported from a
horizontal axis parallel with the ends of the main planes so that they
may swing outward, the aviator controlling both tips through one lever
so that as one tip is extended the other is retracted.
"The elastic wing pinions of a bird bend easily before the wind,
permitting the gusts to glance off, but presenting always an even and
efficient curvature to the steady currents of the air."
High Winds Threaten Stability.
To ensure perfect stability, without control, either human or automatic,
it is asserted that the aeroplane must move faster than the wind is
blowing. So long as the wind is blowing at the rate of 30 miles an hour,
and the machine is traveling 40 or more, there will be little trouble as
regards equilibrium so far as wind disturbance goes, provided the wind
blows evenly and does not come in gusts or eddying currents. But when
conditions are reversed--when the machine travels only 30 miles an hour
and the wind blows at the rate of 50, look out for loss of equilibrium.
One of the main reasons for this is that high winds are rarely steady;
they seldom blow for any length of time at the same speed. They are
usually "gusty," the gusts being a momentary movement at a higher speed.
Tornadic gusts are also formed by the meeting of two opposing currents,
causing a whirling motion, which makes stability uncertain. Besides, it
is not unusual for wind of high speed to suddenly change its direction
without warning.
Trouble With Vertical Columns.
Vertical currents--columns of ascending air--are frequently encountered
in unexpected places and have more or less tendency, according to their
strength, to make it difficult to keep the machine within a reasonable
distance from the ground.
These vertical currents are most generally noticeable in the vicinity
of steep cliffs, or deep ravines. In such instances they are usually of
considerable strength, being caused by the deflection of strong winds
blowing against the face of the cliffs. This deflection exerts a back
pressure which is felt quite a distance away from the point of origin,
so that the vertical current exerts an influence in forcing the machine
upward long before the cliff is reached.
CHAPTER XV. THE ELEMENT OF DANGER.
That there is an element of danger in aviation is undeniable, but it is
nowhere so great as the public imagines. Men are killed and injured in
the operation of flying machines just as they are killed and injured
in the operation of railways. Considering the character of aviation the
percentage of casualties is surprisingly small.
This is because the results following a collapse in the air are very
much different from what might be imagined. Instead of dropping to the
ground like a bullet an aeroplane, under ordinary conditions will, when
anything goes wrong, sail gently downward like a parachute, particularly
if the operator is cool-headed and nervy enough to so manipulate the
apparatus as to preserve its equilibrium and keep the machine on an even
keel.
Two Fields of Safety.
At least one prominent aviator has declared that there are two fields
of safety--one close to the ground, and the other well up in the air. In
the first-named the fall will be a slight one with little chance of the
operator being seriously hurt. From the field of high altitude the the
descent will be gradual, as a rule, the planes of the machine serving to
break the force of the fall. With a cool-headed operator in control the
aeroplane may be even guided at an angle (about 1 to 8) in its descent
so as to touch the ground with a gliding motion and with a minimum of
impact.
Such an experience, of course, is far from pleasant, but it is by no
means so dangerous as might appear. There is more real danger in falling
from an elevation of 75 or 100 feet than there is from 1,000 feet, as
in the former case there is no chance for the machine to serve as a
parachute--its contact with the ground comes too quickly.
Lesson in Recent Accidents.
Among the more recent fatalities in aviation are the deaths of Antonio
Fernandez and Leon Delagrange. The former was thrown to the ground by a
sudden stoppage of his motor, the entire machine seeming to collapse. It
is evident there were radical defects, not only in the motor, but in the
aeroplane framework as well. At the time of the stoppage it is
estimated that Fernandez was up about 1,500 feet, but the machine got
no opportunity to exert a parachute effect, as it broke up immediately.
This would indicate a fatal weakness in the structure which, under
proper testing, could probably have been detected before it was used in
flight.
It is hard to say it, but Delagrange appears to have been culpable to
great degree in overloading his machine with a motor equipment much
heavier than it was designed to sustain. He was 65 feet up in the air
when the collapse occurred, resulting in his death. As in the case of
Fernandez common-sense precaution would doubtless have prevented the
fatality.
Aviation Not Extra Hazardous.
All told there have been, up to the time of this writing (April, 1910),
just five fatalities in the history of power-driven aviation. This is
surprisingly low when the nature of the experiments, and the fact that
most of the operators were far from having extended experience, is taken
into consideration. Men like the Wrights, Curtiss, Bleriot, Farman,
Paulhan and others, are now experts, but there was a time, and it was
not long ago, when they were unskilled. That they, with numerous
others less widely known, should have come safely through their many
experiments would seem to disprove the prevailing idea that aviation is
an extra hazardous pursuit.
In the hands of careful, quick-witted, nervy men the sailing of an
airship should be no more hazardous than the sailing of a yacht. A
vessel captain with common sense will not go to sea in a storm, or
navigate a weak, unseaworthy craft. Neither should an aviator attempt to
sail when the wind is high and gusty, nor with a machine which has not
been thoroughly tested and found to be strong and safe.
Safer Than Railroading.
Statistics show that some 12,000 people are killed and 72,000 injured
every year on the railroads of the United States. Come to think it over
it is small wonder that the list of fatalities is so large. Trains
are run at high speeds, dashing over crossings at which collisions are
liable to occur, and over bridges which often collapse or are swept away
by floods. Still, while the number of casualties is large, the actual
percentage is small considering the immense number of people involved.
It is so in aviation. The number of casualties is remarkably small in
comparison with the number of flights made. In the hands of competent
men the sailing of an airship should be, and is, freer from risk of
accident than the running of a railway train. There are no rails
to spread or break, no bridges to collapse, no crossings at which
collisions may occur, no chance for some sleepy or overworked employee
to misunderstand the dispatcher's orders and cause a wreck.
Two Main Causes of Trouble.
The two main causes of trouble in an airship leading to disaster may
be attributed to the stoppage of the motor, and the aviator becoming
rattled so that he loses control of his machine. Modern ingenuity is
fast developing motors that almost daily become more and more reliable,
and experience is making aviators more and more self-confident in their
ability to act wisely and promptly in cases of emergency. Besides this
a satisfactory system of automatic control is in a fair way of being
perfected.
Occasionally even the most experienced and competent of men in all
callings become careless and by foolish action invite disaster. This
is true of aviators the same as it is of railroaders, men who work in
dynamite mills, etc. But in nearly every instance the responsibility
rests with the individual; not with the system. There are some men
unfitted by nature for aviation, just as there are others unfitted to be
railway engineers.
CHAPTER XVI. RADICAL CHANGES BEING MADE.
Changes, many of them extremely radical in their nature, are continually
being made by prominent aviators, and particularly those who have won
the greatest amount of success. Wonderful as the results have been
few of the aviators are really satisfied. Their successes have merely
spurred them on to new endeavors, the ultimate end being the development
of an absolutely perfect aircraft.
Among the men who have been thus experimenting are the Wright Brothers,
who last year (1909) brought out a craft totally different as regards
proportions and weight from the one used the preceding year. One marked
result was a gain of about 3 1/2 miles an hour in speed.
Dimensions of 1908 Machine.
The 1908 model aeroplane was 40 by 29 feet over all. The carrying
surfaces, that is, the two aerocurves, were 40 by 6 feet, having a
parabolical curve of one in twelve. With about 70 square feet of surface
in the rudders, the total surface given was about 550 square feet.
The engine, which is the invention of the Wright brothers, weighed,
approximately, 200 pounds, and gave about 25 horsepower at 1,400
revolutions per minute. The total weight of the aeroplane, exclusive of
passenger, but inclusive of engine, was about 1,150 pounds. This result
showed a lift of a fraction over 2 1/4 pounds to the square foot of
carrying surface. The speed desired was 40 miles an hour, but the
machine was found to make only a scant 39 miles an hour. The upright
struts were about 7/8-inch thick, the skids, 2 1/2 by 1 1/4 inches
thick.
Dimensions of 1909 Machine.
The 1909 aeroplane was built primarily for greater speed, and relatively
heavier; to be less at the mercy of the wind. This result was obtained
as follows: The aerocurves, or carrying surfaces, were reduced in
dimensions from 40 by 6 feet to 36 by 5 1/2 feet, the curve remaining
the same, one in twelve. The upright struts were cut from seven-eighths
inch to five-eighths inch, and the skids from two and one-half by one
and one-quarter to two and one-quarter by one and three-eighths inches.
This result shows that there were some 81 square feet of carrying
surface missing over that of last year's model. and some 25 pounds loss
of weight. Relatively, though, the 1909 model aeroplane, while actually
25 pounds lighter, is really some 150 pounds heavier in the air than the
1908 model, owing to the lesser square feet of carrying surface.
Some of the Results Obtained.
Reducing the carrying surfaces from 6 to 5 1/2 feet gave two
results--first, less carrying capacity; and, second, less head-on
resistance, owing to the fact that the extent of the parabolic curve
in the carrying surfaces was shortened. The "head-on" resistance is
the retardance the aeroplane meets in passing through the air, and is
counted in square feet. In the 1908 model the curve being one in twelve
and 6 feet deep, gave 6 inches of head-on resistance. The plane being
40 feet spread, gave 6 inches by 40 feet, or 20 square feet of head-on
resistance. Increasing this figure by a like amount for each plane, and
adding approximately 10 square feet for struts, skids and wiring, we
have a total of approximately, 50 square feet of surface for "head-on"
resistance.
In the 1909 aeroplane, shortening the curve 6 inches at the parabolic
end of the curve took off 1 inch of head-on resistance. Shortening the
spread of the planes took off between 3 and 4 square feet of head-on
resistance. Add to this the total of 7 square feet, less curve surface
and about 1 square foot, less wire and woodwork resistance, and we
have a grand total of, approximately, 12 square feet of less "head-on"
resistance over the 1908 model.
Changes in Engine Action.
The engine used in 1909 was the same one used in 1908, though some minor
changes were made as improvements; for instance, a make and break spark
was used, and a nine-tooth, instead of a ten-tooth magneto gear-wheel
was used. This increased the engine revolutions per minute from 1,200 to
1,400, and the propeller revolutions per minute from 350 to 371, giving
a propeller thrust of, approximately, 170 foot pounds instead of 153, as
was had last year.
More Speed and Same Capacity.
One unsatisfactory feature of the 1909 model over that of 1908,
apparently, was the lack of inherent lateral stability. This was caused
by the lesser surface and lesser extent of curvatures at the portions
of the aeroplane which were warped. This defect did not show so plainly
after Mr. Orville Wright had become fully proficient in the handling of
the new machine, and with skillful management, the 1909 model aeroplane
will be just as safe and secure as the other though it will take a
little more practice to get that same degree of skill.
To sum up: The aeroplane used in 1909 was 25 pounds lighter, but really
about 150 pounds heavier in the air, had less head-on resistance, and
greater propeller thrust. The speed was increased from about 39 miles
per hour to 42 1/2 miles per hour. The lifting capacity remained about
the same, about 450 pounds capacity passenger-weight, with the 1908
machine. In this respect, the loss of carrying surface was compensated
for by the increased speed.
During the first few flights it was plainly demonstrated that it would
need the highest skill to properly handle the aeroplane, as first one
end and then the other would dip and strike the ground, and either tear
the canvas or slew the aeroplane around and break a skid.
Wrights Adopt Wheeled Gears.
In still another important respect the Wrights, so far as the output
of one of their companies goes, have made a radical change. All the
aeroplanes turned out by the Deutsch Wright Gesellschaft, according to
the German publication, _Automobil-Welt_, will hereafter be equipped
with wheeled running gears and tails. The plan of this new machine is
shown in the illustration on page 145. The wheels are three in number,
and are attached one to each of the two skids, just under the front edge
of the planes, and one forward of these, attached to a cross-member. It
is asserted that with these wheels the teaching of purchasers to operate
the machines is much simplified, as the beginners can make short flights
on their own account without using the starting derrick.
This is a big concession for the Wrights to make, as they have hitherto
adhered stoutly to the skid gear. While it is true they do not control
the German company producing their aeroplanes, yet the nature of their
connection with the enterprise is such that it may be taken for granted
no radical changes in construction would be made without their approval
and consent.
Only Three Dangerous Rivals.
Official trials with the 1909 model smashed many records and leave the
Wright brothers with only three dangerous rivals in the field, and with
basic patents which cover the curve, warp and wing-tip devices found on
all the other makes of aeroplanes. These three rivals are the Curtiss
and Voisin biplane type and the Bleriot monoplane pattern.
The Bleriot monoplane is probably the most dangerous rival, as this make
of machine has a record of 54 miles per hour, has crossed the English
channel, and has lifted two passengers besides the operator. The
latest type of this machine only weighs 771.61 pounds complete, without
passengers, and will lift a total passenger weight of 462.97 pounds,
which is a lift of 5.21 pounds to the square foot. This is a better
result than those published by the Wright brothers, the best noted being
4.25 pounds per square foot.
Other Aviators at Work.
The Wrights, however, are not alone in their efforts to promote the
efficiency of the flying machine. Other competent inventive aviators,
notably Curtiss, Voisin, Bleriot and Farman, are close after them. The
Wrights, as stated, have a marked advantage in the possession of
patents covering surface plane devices which have thus far been found
indispensable in flying machine construction. Numerous law suits growing
out of alleged infringements of these patents have been started, and
others are threatened. What effect these actions will have in deterring
aviators in general from proceeding with their experiments remains to be
seen.
In the meantime the four men named--Curtiss, Voisin, Bleriot and
Farman--are going ahead regardless of consequences, and the inventive
genius of each is so strong that it is reasonable to expect some
remarkable developments in the near future.
Smallest of Flying Machines.
To Santos Dumont must be given the credit of producing the smallest
practical flying machine yet constructed. True, he has done nothing
remarkable with it in the line of speed, but he has demonstrated the
fact that a large supporting surface is not an essential feature.
This machine is named "La Demoiselle." It is a monoplane of the dihedral
type, with a main plane on each side of the center. These main
planes are of 18 foot spread, and nearly 6 1/2 feet in depth, giving
approximately 115 feet of surface area. The total weight is 242
pounds, which is 358 pounds less than any other machine which has been
successfully used. The total depth from front to rear is 26 feet.
The framework is of bamboo, strengthened and held taut with wire guys.
Have One Rule in Mind.
In this struggle for mastery in flying machine efficiency all the
contestants keep one rule in mind, and this is:
"The carrying capacity of an aeroplane is governed by the peripheral
curve of its carrying surfaces, plus the speed; and the speed
is governed by the thrust of the propellers, less the 'head-on'
resistance."
Their ideas as to the proper means of approaching the proposition
may, and undoubtedly are, at variance, but the one rule in solving the
problem of obtaining the greatest carrying capacity combined with the
greatest speed, obtains in all instances.
CHAPTER XVII. SOME OF THE NEW DESIGNS.
Spurred on by the success attained by the more experienced and better
known aviators numerous inventors of lesser fame are almost daily
producing practical flying machines varying radically in construction
from those now in general use.
One of these comparatively new designs is the Van Anden biplane, made
by Frank Van Anden of Islip, Long Island, a member of the New York
Aeronautic Society. While his machine is wholly experimental, many
successful short flights were made with it last fall (1909). One flight,
made October 19th, 1909, is of particular interest as showing the
practicability of an automatic stabilizing device installed by the
inventor. The machine was caught in a sudden severe gust of wind and
keeled over, but almost immediately righted itself, thus demonstrating
in a most satisfactory manner the value of one new attachment.
Features of Van Anden Model.
In size the surfaces of the main biplane are 26 feet in spread, and 4
feet in depth from front to rear. The upper and lower planes are 4 feet
apart. Silkolene coated with varnish is used for the coverings. Ribs
(spruce) are curved one inch to the foot, the deepest part of the curve
(4 inches) being one foot back from the front edge of the horizontal
beam. Struts (also of spruce, as is all the framework) are elliptical in
shape. The main beams are in three sections, nearly half round in form,
and joined by metal sleeves.
There is a two-surface horizontal rudder, 2x2x4 feet, in front. This
is pivoted at its lateral center 8 feet from the front edge of the main
planes. In the rear is another two-surface horizontal rudder 2x2x2 1/2
feet, pivoted in the same manner as the front one, 15 feet from the rear
edges of the main planes.
Hinged to the rear central strut of the rear rudder is a vertical rudder
2 feet high by 3 feet in length.
The Method of Control.
In the operation of these rudders--both front and rear--and the
elevation and depression of the main planes, the Curtiss system is
employed. Pushing the steering-wheel post outward depresses the front
edges of the planes, and brings the machine downward; pulling the
steering-wheel post inward elevates the front edges of the planes and
causes the machine to ascend.
Turning the steering wheel itself to the right swings the tail rudder to
the left, and the machine, obeying this like a boat, turns in the same
direction as the wheel is turned. By like cause turning the wheel to the
left turns the machine to the left.
Automatic Control of Wings.
There are two wing tips, each of 6 feet spread (length) and 2 feet from
front to rear. These are hinged half way between the main surfaces to
the two outermost rear struts. Cables run from these to an automatic
device working with power from the engine, which automatically operates
the tips with the tilting of the machine. Normally the wing tips are
held horizontal by stiff springs introduced in the cables outside of the
device.
It was the successful working of this device which righted the Van
Anden craft when it was overturned in the squall of October 19th, 1909.
Previous to that occurrence Mr. Van Anden had looked upon the device as
purely experimental, and had admitted that he had grave uncertainty as
to how it would operate in time of emergency. He is now quoted as being
thoroughly satisfied with its practicability. It is this automatic
device which gives the Van Anden machine at least one distinctively new
feature.
While on this subject it will not be amiss to add that Mr. Curtiss does
not look kindly on automatic control. "I would rather trust to my own
action than that of a machine," he says. This is undoubtedly good
logic so far as Mr. Curtiss is concerned, but all aviators are not so
cool-headed and resourceful.
Motive Power of Van Anden.
A 50-horsepower "H-F" water cooled motor drives a laminated wood
propeller 6 feet in diameter, with a 17 degree pitch at the extremities,
increasing toward the hub. The rear end of the motor is about 6 inches
back from the rear transverse beam and the engine shaft is in a direct
line with the axes of the two horizontal rudders. An R. I. V. ball
bearing carries the shaft at this point. Flying, the motor turns at
about 800 revolutions per minute, delivering 180 pounds pull. A test of
the motor running at 1,200 showed a pull of 250 pounds on the scales.
Still Another New Aeroplane.
Another new aeroplane is that produced by A. M. Herring (an old-timer)
and W. S. Burgess, under the name of the Herring-Burgess. This is also
equipped with an automatic stability device for maintaining the balance
transversely. The curvature of the planes is also laid out on new
lines. That this new plan is effective is evidenced by the fact that the
machine has been elevated to an altitude of 40 feet by using one-half
the power of the 30-horsepower motor.
The system of rudder and elevation control is very simple. The aviator
sits in front of the lower plane, and extending his arms, grasps two
supports which extend down diagonally in front. On the under side of
these supports just beneath his fingers are the controls which operate
the vertical rudder, in the rear. Thus, if he wishes to turn to the
right, he presses the control under the fingers of his right hand; if to
the left, that under the fingers of his left hand. The elevating rudder
is operated by the aviator's right foot, the control being placed on a
foot-rest.
Motor Is Extremely Light.
Not the least notable feature of the craft is its motor. Although
developing, under load, 30-horsepower, or that of an ordinary
automobile, it weighs, complete, hardly 100 pounds. Having occasion to
move it a little distance for inspection, Mr. Burgess picked it up and
walked off with it--cylinders, pistons, crankcase and all, even the
magneto, being attached. There are not many 30-horsepower engines which
can be so handled. Everything about it is reduced to its lowest terms
of simplicity, and hence, of weight. A single camshaft operates not
only all of the inlet and exhaust valves, but the magneto and gear water
pump, as well. The motor is placed directly behind the operator, and the
propeller is directly mounted on the crankshaft.
This weight of less than 100 pounds, it must be remembered, is not for
the motor alone; it includes the entire power plant equipment.
The "thrust" of the propeller is also extraordinary, being between 250
and 260 pounds. The force of the wind displacement is strong enough to
knock down a good-sized boy as one youngster ascertained when he got
behind the propeller as it was being tested. He was not only knocked
down but driven for some distance away from the machine. The propeller
has four blades which are but little wider than a lath.
Machine Built by Students.
Students at the University of Pennsylvania, headed by Laurence J. Lesh,
a protege of Octave Chanute, have constructed a practical aeroplane of
ordinary maximum size, in which is incorporated many new ideas. The most
unique of these is to be found in the steering gear, and the provision
made for the accommodation of a pupil while taking lessons under an
experienced aviator.
Immediately back of the aviator is an extra seat and an extra steering
wheel which works in tandem style with the front wheel. By this
arrangement a beginner may be easily and quickly taught to have
perfect control of the machine. These tandem wheels are also handy for
passengers who may wish to operate the car independently of one another,
it being understood, of course, that there will be no conflict of
action.
Frame Size and Engine Power.
The frame has 36 feet spread and measures 35 feet from the front edge to
the end of the tail in the rear. It is equipped with two rear propellers
operated by a Ramsey 8-cylinder motor of 50 horsepower, placed
horizontally across the lower plane, with the crank shaft running clear
through the engine.
The "Pennsylvania I" is the first two-propeller biplane chainless
car, this scheme having been adopted in order to avoid the crossing of
chains. The lateral control is by a new invention by Octave Chanute
and Laurence J. Lesh, for which Lesh is now applying for a patent. The
device was worked out before the Wright brothers' suit was begun, and is
said to be superior to the Wright warping or the Curtiss ailerons. The
landing device is also new in design. This aeroplane will weigh about
1,500 pounds, and will carry fuel for a flight of 150 miles, and it is
expected to attain a speed of at least 45 miles an hour.
There are others, lots of them, too numerous in fact to admit of mention
in a book of this size.
CHAPTER XVIII. DEMAND FOR FLYING MACHINES.
As a commercial proposition the manufacture and sale of motor-equipped
aeroplanes is making much more rapid advance than at first obtained in
the similar handling of the automobile. Great, and even phenomenal,
as was the commercial development of the motor car, that of the flying
machine is even greater. This is a startling statement, but it is fully
warranted by the facts.
It is barely more than a year ago (1909) that attention was seriously
attracted to the motor-equipped aeroplane as a vehicle possible of
manipulation by others than professional aviators. Up to that time
such actual flights as were made were almost exclusively with the sole
purpose of demonstrating the practicability of the machine, and the
merits of the ideas as to shape, engine power, etc., of the various
producers.
Results of Bleriot's Daring.
It was not until Bleriot flew across the straits of Dover on July 25th,
1909, that the general public awoke to a full realization of the fact
that it was possible for others than professional aviators to indulge
in aviation. Bleriot's feat was accepted as proof that at last
an absolutely new means of sport, pleasure and research, had been
practically developed, and was within the reach of all who had the
inclination, nerve and financial means to adopt it.
From this event may be dated the birth of the modern flying machine into
the world of business. The automobile was taken up by the general public
from the very start because it was a proposition comparatively easy of
demonstration. There was nothing mysterious or uncanny in the fact that
a wheeled vehicle could be propelled on solid, substantial roads by
means of engine power. And yet it took (comparatively speaking) a long
time to really popularize the motor car.
Wonderful Results in a Year.
Men of large financial means engaged in the manufacture of automobiles,
and expended fortunes in attracting public attention to them through the
medium of advertisements, speed and road contests, etc. By these means
a mammoth business has been built up, but bringing this business to its
present proportions required years of patient industry and indomitable
pluck.
At this writing, less than a year from the day when Bleriot crossed the
channel, the actual sales of flying machines outnumber the actual sales
of automobiles in the first year of their commercial development. This
may appear incredible, but it is a fact as statistics will show.
In this connection we should take into consideration the fact that up to
a year ago there was no serious intention of putting flying machines
on the market; no preparations had been made to produce them on a
commercial scale; no money had been expended in advertisements with a
view to selling them.
Some of the Actual Results.
Today flying machines are being produced on a commercial basis, and
there is a big demand for them. The people making them are overcrowded
with orders. Some of the producers are already making arrangements to
enlarge their plants and advertise their product for sale the same as
is being done with automobiles, while a number of flying machine motor
makers are already promoting the sale of their wares in this way.
Here are a few actual figures of flying machine sales made by the more
prominent producers since July 25th, 1909.
Santos Dumont, 90 machines; Bleriot, 200; Farman, 130;
Clemenceau-Wright, 80; Voisin, 100; Antoinette, 100. Many of these
orders have been filled by delivery of the machines, and in others the
construction work is under way.
The foregoing are all of foreign make. In this country Curtiss and the
Wrights are engaged in similar work, but no actual figures of their
output are obtainable.
Larger Plants Are Necessary.
And this situation exists despite the fact that none of the producers
are really equipped with adequate plants for turning out their
machines on a modern, business-like basis. The demand was so sudden and
unexpected that it found them poorly prepared to meet it. This, however,
is now being remedied by the erection of special plants, the enlargement
of others, and the introduction of new machinery and other labor-saving
conveniences.
Companies, with large capitalization, to engage in the exclusive
production of airships are being organized in many parts of the world.
One notable instance of this nature is worth quoting as illustrative
of the manner in which the production of flying machines is being
commercialized. This is the formation at Frankfort, Germany, of the
Flugmaschine Wright, G. m. b. H., with a capital of $119,000, the
Krupps, of Essen, being interested.
Prices at Which Machines Sell.
This wonderful demand from the public has come notwithstanding the fact
that the machines, owing to lack of facilities for wholesale production,
are far from being cheap. Such definite quotations as are made are on
the following basis:
Santos Dumont--List price $1,000, but owing to the rush of orders agents
are readily getting from $1,300 to $1,500. This is the smallest machine
made.
Bleriot--List price $2,500. This is for the cross-channel type, with
Anzani motor.
Antoinette--List price from $4,000 to $5,000, according to size.
Wright--List price $5,600.
Curtiss--List price $5,000.
There is, however, no stability in prices as purchasers are almost
invariably ready to pay a considerable premium to facilitate delivery.
The motor is the most expensive part of the flying machine. Motor
prices range from $500 to $2,000, this latter amount being asked for the
Curtiss engine.
Systematic Instruction of Amateurs.
In addition to the production of flying machines many of the experienced
aviators are making a business of the instruction of amateurs. Curtiss
and the Wrights in this country have a number of pupils, as have also
the prominent foreigners. Schools of instruction are being opened in
various parts of the world, not alone as private money-making ventures,
but in connection with public educational institutions. One of these
latter is to be found at the University of Barcelona, Spain.
The flying machine agent, the man who handles the machines on a
commission, has also become a known quantity, and will soon be as
numerous as his brother of the automobile. The sign "John Bird, agent
for Skimmer's Flying Machine," is no longer a curiosity.
Yes, the Airship Is Here.
From all of which we may well infer that the flying machine in practical
form has arrived, and that it is here to stay. It is no exaggeration to
say that the time is close at hand when people will keep flying machines
just as they now keep automobiles, and that pleasure jaunts will be
fully as numerous and popular. With the important item of practicability
fully demonstrated, "Come, take a trip in my airship," will have more
real significance than now attaches to the vapid warblings of the
vaudeville vocalist.
As a further evidence that the airship is really here, and that its
presence is recognized in a business way, the action of life and
accident insurance companies is interesting. Some of them are
reconstructing their policies so as to include a special waiver of
insurance by aviators. Anything which compels these great corporations
to modify their policies cannot be looked upon as a mere curiosity or
toy.
It is some consolation to know that the movement in this direction is
not thus far widespread. Moreover it is more than probable that the
competition for business will eventually induce the companies to act
more liberally toward aviators, especially as the art of aviation
advances.
CHAPTER XIX. LAW OF THE AIRSHIP.
Successful aviation has evoked some peculiar things in the way of legal
action and interpretation of the law.
It is well understood that a man's property cannot be used without his
consent. This is an old established principle in common law which holds
good today.
The limits of a man's property lines, however, have not been so well
understood by laymen. According to eminent legal authorities such as
Blackstone, Littleton and Coke, the "fathers of the law," the owner of
realty also holds title above and below the surface, and this theory is
generally accepted without question by the courts.
Rights of Property Owners.
In other words the owner of realty also owns the sky above it without
limit as to distance. He can dig as deep into his land, or go as high
into the air as he desires, provided he does not trespass upon or injure
similar rights of others.
The owner of realty may resist by force, all other means having failed,
any trespass upon, or invasion of his property. Other people, for
instance, may not enter upon it, or over or under it, without his
express permission and consent. There is only one exception, and this is
in the case of public utility corporations such as railways which,
under the law of eminent domain, may condemn a right of way across the
property of an obstinate owner who declines to accept a fair price for
the privilege.
Privilege Sharply Confined.
The law of eminent domain may be taken advantage of only by corporations
which are engaged in serving the public. It is based upon the principle
that the advancement and improvement of a community is of more
importance and carries with it more rights than the interests of the
individual owner. But even in cases where the right of eminent domain is
exercised there can be no confiscation of the individual's property.
Exercising the right of eminent domain is merely obtaining by public
purchase what is held to be essential to the public good, and which
cannot be secured by private purchase. When eminent domain proceedings
are resorted to the court appoints appraisers who determine upon the
value of the property wanted, and this value (in money) is paid to the
owner.
How It Affects Aviation.
It should be kept in mind that this privilege of the "right of eminent
domain" is accorded only to corporations which are engaged in serving
the public. Individuals cannot take advantage of it. Thus far all
aviation has been conducted by individuals; there are no flying machine
or airship corporations regularly engaged in the transportation of
passengers, mails or freight.
This leads up to the question "What would happen if realty owners
generally, or in any considerable numbers, should prohibit the
navigation of the air above their holdings?" It is idle to say such
a possibility is ridiculous--it is already an actuality in a few
individual instances.
One property owner in New Jersey, a justice of the peace, maintains a
large sign on the roof of his house warning aviators that they must not
trespass upon his domain. That he is acting well within his rights in
doing this is conceded by legal authorities.
Hard to Catch Offenders.
But, suppose the alleged trespass is committed, what is the property
owner going to do about it? He must first catch the trespasser and this
would be a pretty hard job. He certainly could not overtake him, unless
he kept a racing aeroplane for this special purpose. It would be
equally difficult to identify the offender after the offense had been
committed, even if he were located, as aeroplanes carry no license
numbers.
Allowing that the offender should be caught the only recourse of the
realty owner is an action for damages. He may prevent the commission of
the offense by force if necessary, but after it is committed he can only
sue for damages. And in doing this he would have a lot of trouble.
Points to Be Proven.
One of the first things the plaintiff would be called upon to prove
would be the elevation of the machine. If it were reasonably close to
the ground there would, of course, be grave risk of damage to fences,
shrubbery, and other property, and the court would be justified in
holding it to be a nuisance that should be suppressed.
If, on the other hand; the machine was well up in the air, but going
slowly, or hovering over the plaintiff's property, the court might be
inclined to rule that it could not possibly be a nuisance, but right
here the court would be in serious embarrassment. By deciding that it
was not a nuisance he would virtually override the law against invasion
of a man's property without his consent regardless of the nature of the
invasion. By the same decision he would also say in effect that, if one
flying machine could do this a dozen or more would have equal right to
do the same thing. While one machine hovering over a certain piece of
property may be no actual nuisance a dozen or more in the same position
could hardly be excused.
Difficult to Fix Damages.
Such a condition would tend to greatly increase the risk of accident,
either through collision, or by the carelessness of the aviators in
dropping articles which might cause damages to the people or property
below. In such a case it would undoubtedly be a nuisance, and in
addition to a fine, the offender would also be liable for the damages.
Taking it for granted that no actual damage is done, and the owner
merely sues on account of the invasion of his property, how is the
amount of compensation to be fixed upon? The owner has lost nothing; no
part of his possessions has been taken away; nothing has been injured
or destroyed; everything is left in exactly the same condition as before
the invasion. And yet, if the law is strictly interpreted, the offender
is liable.
Right of Way for Airships.
Somebody has suggested the organization of flying-machine corporations
as common carriers, which would give them the right of eminent domain
with power to condemn a right of way. But what would they condemn? There
is nothing tangible in the air. Railways in condemning a right of way
specify tangible property (realty) within certain limits. How would an
aviator designate any particular right of way through the air a certain
number of feet in width, and a certain distance from the ground?
And yet, should the higher courts hold to the letter of the law and
decide that aviators have no right to navigate their craft over private
property, something will have to be done to get them out of the dilemma,
as aviation is too far advanced to be discarded. Fortunately there is
little prospect of any widespread antagonism among property owners so
long as aviators refrain from making nuisances of themselves.
Possible Solution Offered.
One possible solution is offered and that is to confine the path of
airships to the public highways so that nobody's property rights would
be invaded. In addition, as a matter of promoting safety for both
operators and those who may happen to be beneath the airships as they
pass over a course, adoption of the French rules are suggested. These
are as follows:
Aeroplanes, when passing, must keep to the right, and pass at a distance
of at least 150 feet. They are free from this rule when flying at
altitudes of more than 100 feet. Every machine when flying at night or
during foggy weather must carry a green light on the right, and a red
light on the left, and a white headlight on the front.
These are sensible rules, but may be improved upon by the addition of a
signal system of some kind, either horn, whistle or bell.
Responsibility of Aviators.
Mr. Jay Carver Bossard, in recent numbers of _Fly_, brings out some
curious and interesting legal points in connection with aviation, among
which are the following:
"Private parties who possess aerial craft, and desire to operate the
same in aerial territory other than their own, must obtain from land
owners special permission to do so, such permission to be granted only
by agreement, founded upon a valid consideration. Otherwise, passing
over another's land will in each instance amount to a trespass.
"Leaving this highly technical side of the question, let us turn to
another view: the criminal and tort liability of owners and operators to
airship passengers. If A invites B to make an ascension with him in his
machine, and B, knowing that A is merely an enthusiastic amateur and
far from being an expert, accepts and is through A's innocent negligence
injured, he has no grounds for recovery. But if A contracts with B, to
transport him from one place to another, for a consideration, and B is
injured by the poor piloting of A, A would be liable to B for damages
which would result. Now in order to safeguard such people as B, curious
to the point of recklessness, the law will have to require all airship
operators to have a license, and to secure this license airship pilots
will have to meet certain requirements. Here again is a question. Who
is going to say whether an applicant is competent to pilot a balloon or
airship?
Fine for an Aeronaut.
"An aeroplane while maneuvering is suddenly caught by a treacherous gale
and swept to the ground. A crowd of people hasten over to see if the
aeronaut is injured, and in doing so trample over Tax-payer Smith's
garden, much to the detriment of his growing vegetables and flowers. Who
is liable for the damages? Queer as it may seem, a case very similar to
this was decided in 1823, in the New York supreme court, and it was held
that the aeronaut was liable upon the following grounds: 'To render one
man liable in trespass for the acts of others, it must appear either
that they acted in concert, or that the act of the one, ordinarily and
naturally produced the acts of the others, Ascending in a balloon is not
an unlawful act, but it is certain that the aeronaut has no control
over its motion horizontally, but is at the sport of the wind, and is
to descend when and how he can. His reaching the earth is a matter of
hazard. If his descent would according to the circumstances draw a crowd
of people around him, either out of curiosity, or for the purpose
of rescuing him from a perilous situation, all this he ought to have
foreseen, and must be responsible for.'
Air Not Really Free.
"The general belief among people is, that the air is free. Not only free
to breathe and enjoy, but free to travel in, and that no one has any
definite jurisdiction over, or in any part of it. Now suppose this were
made a legal doctrine. Would a murder perpetrated above the clouds have
to go unpunished? Undoubtedly. For felonies committed upon the high seas
ample provision is made for their punishment, but new provisions will
have to be made for crimes committed in the air.
Relations of Owner and Employee.
"It is a general rule of law that a master is bound to provide
reasonably safe tools, appliances and machines for his servant. How this
rule is going to be applied in cases of aeroplanes, remains to be seen.
The aeroplane owner who hires a professional aeronaut, that is, one who
has qualified as an expert, owes him very little legal duty to supply
him with a perfect aeroplane. The expert is supposed to know as much
regarding the machine as the owner, if not more, and his acceptance of
his position relieves the owner from liability. When the owner hires an
amateur aeronaut to run the aeroplane, and teaches him how to manipulate
it, even though the prescribed manner of manipulation will make flight
safe, nevertheless if the machine is visibly defective, or known to be
so, any injury which results to the aeronaut the owner is liable for.
As to Aeroplane Contracts.
"At the present time there are many orders being placed with aeroplane
manufacturing companies. There are some unique questions to be raised
here under the law of contract. It is an elementary principle of law
that no one can be compelled to complete a contract which in itself is
impossible to perform. For instance, a contract to row a boat across
the Atlantic in two weeks, for a consideration, could never be enforced
because it is within judicial knowledge that such an undertaking is
beyond human power. Again, contracts formed for the doing of acts
contrary to nature are never enforcible, and here is where our
difficulty comes in. Is it possible to build a machine or species of
craft which will transport a person or goods through the air? The courts
know that balloons are practical; that is, they know that a bag
filled with gas has a lifting power and can move through the air at an
appreciable height. Therefore, a contract to transport a person in such
manner is a good contract, and the conditions being favorable could
undoubtedly be enforced. But the passengers' right of action for injury
would be very limited.
No Redress for Purchasers.
"In the case of giving warranties on aeroplanes, we have yet to see just
what a court is going to say. It is easy enough for a manufacturer to
guarantee to build a machine of certain dimensions and according to
certain specifications, but when he inserts a clause in the contract to
the effect that the machine will raise itself from the surface of the
earth, defy the laws of gravity, and soar in the heavens at the will of
the aviator, he is to say the least contracting to perform a miracle.
"Until aeroplanes have been made and accepted as practical, no court
will force a manufacturer to turn out a machine guaranteed to fly. So
purchasers can well remember that if their machines refuse to fly they
have no redress against the maker, for he can always say, 'The industry
is still in its experimental stage.' In contracting for an engine no
builder will guarantee that the particular engine will successfully
operate the aeroplane. In fact he could never be forced to live up to
such an agreement, should he agree to a stipulation of that sort. The
best any engine maker will guarantee is to build an engine according to
specifications."
CHAPTER XX. SOARING FLIGHT.
By Octave Chanute.
[5] There is a wonderful performance daily exhibited in southern climes
and occasionally seen in northerly latitudes in summer, which has
never been thoroughly explained. It is the soaring or sailing flight
of certain varieties of large birds who transport themselves on rigid,
unflapping wings in any desired direction; who in winds of 6 to 20
miles per hour, circle, rise, advance, return and remain aloft for hours
without a beat of wing, save for getting under way or convenience in
various maneuvers. They appear to obtain from the wind alone all the
necessary energy, even to advancing dead against that wind. This feat is
so much opposed to our general ideas of physics that those who have
not seen it sometimes deny its actuality, and those who have only
occasionally witnessed it subsequently doubt the evidence of their own
eyes. Others, who have seen the exceptional performances, speculate on
various explanations, but the majority give it up as a sort of "negative
gravity."
Soaring Power of Birds.
The writer of this paper published in the "Aeronautical Annual" for 1896
and 1897 an article upon the sailing flight of birds, in which he gave
a list of the authors who had described such flight or had advanced
theories for its explanation, and he passed these in review. He also
described his own observations and submitted some computations to
account for the observed facts. These computations were correct as
far as they went, but they were scanty. It was, for instance, shown
convincingly by analysis that a gull weighing 2.188 pounds, with a total
supporting surface of 2.015 square feet, a maximum body cross-section
of 0.126 square feet and a maximum cross-section of wing edges of 0.098
square feet, patrolling on rigid wings (soaring) on the weather side of
a steamer and maintaining an upward angle or attitude of 5 degrees to 7
degrees above the horizon, in a wind blowing 12.78 miles an hour, which
was deflected upward 10 degrees to 20 degrees by the side of the steamer
(these all being carefully observed facts), was perfectly sustained at
its own "relative speed" of 17.88 miles per hour and extracted from
the upward trend of the wind sufficient energy to overcome all the
resistances, this energy amounting to 6.44 foot-pounds per second.
Great Power of Gulls.
It was shown that the same bird in flapping flight in calm air, with an
attitude or incidence of 3 degrees to 5 degrees above the horizon and
a speed of 20.4 miles an hour was well sustained and expended 5.88
foot-pounds per second, this being at the rate of 204 pounds sustained
per horsepower. It was stated also that a gull in its observed
maneuvers, rising up from a pile head on unflapping wings, then plunging
forward against the wind and subsequently rising higher than his
starting point, must either time his ascents and descents exactly with
the variations in wind velocities, or must meet a wind billow rotating
on a horizontal axis and come to a poise on its crest, thus availing of
an ascending trend.
But the observations failed to demonstrate that the variations of the
wind gusts and the movements of the bird were absolutely synchronous,
and it was conjectured that the peculiar shape of the soaring wing of
certain birds, as differentiated from the flapping wing, might, when
experimented upon, hereafter account for the performance.
Mystery to be Explained.
These computations, however satisfactory they were for the speed of
winds observed, failed to account for the observed spiral soaring of
buzzards in very light winds and the writer was compelled to confess:
"Now, this spiral soaring in steady breezes of 5 to 10 miles per hour
which are apparently horizontal, and through which the bird maintains an
average speed of about 20 miles an hour, is the mystery to be explained.
It is not accounted for, quantitatively, by any of the theories which
have been advanced, and it is the one performance which has led some
observers to claim that it was done through 'aspiration.' i, e., that
a bird acted upon by a current, actually drew forward into that current
against its exact direction of motion."
Buzzards Soar in Dead Calm.
A still greater mystery was propounded by the few observers who asserted
that they had seen buzzards soaring in a dead calm, maintaining their
elevation and their speed. Among these observers was Mr. E. C. Huffaker,
at one time assistant experimenter for Professor Langley. The writer
believed and said then that he must in some way have been mistaken, yet,
to satisfy himself, he paid several visits to Mr. Huffaker, in Eastern
Tennessee and took along his anemometer. He saw quite a number of
buzzards sailing at a height of 75 to 100 feet in breezes measuring 5
or 6 miles an hour at the surface of the ground, and once he saw one
buzzard soaring apparently in a dead calm.
The writer was fairly baffled. The bird was not simply gliding,
utilizing gravity or acquired momentum, he was actually circling
horizontally in defiance of physics and mathematics. It took two years
and a whole series of further observations to bring those two sciences
into accord with the facts.
Results of Close Observations.
Curiously enough the key to the performance of circling in a light wind
or a dead calm was not found through the usual way of gathering human
knowledge, i. e., through observations and experiment. These had failed
because I did not know what to look for. The mystery was, in fact,
solved by an eclectic process of conjecture and computation, but once
these computations indicated what observations should be made, the
results gave at once the reasons for the circling of the birds, for
their then observed attitude, and for the necessity of an independent
initial sustaining speed before soaring began. Both Mr. Huffaker and
myself verified the data many times and I made the computations.
These observations disclosed several facts:
1st.--That winds blowing five to seventeen miles per hour frequently had
rising trends of 10 degrees to 15 degrees, and that upon occasions when
there seemed to be absolutely no wind, there was often nevertheless a
local rising of the air estimated at a rate of four to eight miles or
more per hour. This was ascertained by watching thistledown, and rising
fogs alongside of trees or hills of known height. Everyone will readily
realize that when walking at the rate of four to eight miles an hour in
a dead calm the "relative wind" is quite inappreciable to the senses and
that such a rising air would not be noticed.
2nd.--That the buzzard, sailing in an apparently dead horizontal calm,
progressed at speeds of fifteen to eighteen miles per hour, as measured
by his shadow on the ground. It was thought that the air was then
possibly rising 8.8 feet per second, or six miles per hour.
3rd.--That when soaring in very light winds the angle of incidence of
the buzzards was negative to the horizon--i. e., that when seen coming
toward the eye, the afternoon light shone on the back instead of on the
breast, as would have been the case had the angle been inclined above
the horizon.
4th.--That the sailing performance only occurred after the bird had
acquired an initial velocity of at least fifteen or eighteen miles per
hour, either by industrious flapping or by descending from a perch.
An Interesting Experiment.
5th.--That the whole resistance of a stuffed buzzard, at a negative
angle of 3 degrees in a current of air of 15.52 miles per hour, was 0.27
pounds. This test was kindly made for the writer by Professor A. F. Zahm
in the "wind tunnel" of the Catholic University at Washington, D. C.,
who, moreover, stated that the resistance of a live bird might be less,
as the dried plumage could not be made to lie smooth.
This particular buzzard weighed in life 4.25 pounds, the area of his
wings and body was 4.57 square feet, the maximum cross-section of
his body was 0.110 square feet, and that of his wing edges when fully
extended was 0.244 square feet.
With these data, it became surprisingly easy to compute the performance
with the coefficients of Lilienthal for various angles of incidence
and to demonstrate how this buzzard could soar horizontally in a dead
horizontal calm, provided that it was not a vertical calm, and that the
air was rising at the rate of four or six miles per hour, the lowest
observed, and quite inappreciable without actual measuring.
Some Data on Bird Power.
The most difficult case is purposely selected. For if we assume that the
bird has previously acquired an initial minimum speed of seventeen miles
an hour (24.93 feet per second, nearly the lowest measured), and that
the air was rising vertically six miles an hour (8.80 feet per second),
then we have as the trend of the "relative wind" encountered:
6
-- = 0.353, or the tangent of 19 degrees 26'.
17
which brings the case into the category of rising wind effects. But the
bird was observed to have a negative angle to the horizon of about 3
degrees, as near as could be guessed, so that his angle of incidence to
the "relative wind" was reduced to 16 degrees 26'.
The relative speed of his soaring was therefore:
Velocity = square root of (17 squared + 6 squared) = 18.03 miles per
hour.
At this speed, using the Langley co-efficient recently practically
confirmed by the accurate experiments of Mr. Eiffel, the air pressure
would be:
18.03 squared X 0.00327 = 1.063 pounds per square foot.
If we apply Lilienthal's co-efficients for an angle of 6 degrees 26', we
have for the force in action:
Normal: 4.57 X 1.063 X 0.912 = 4.42 pounds.
Tangential: 4.57 X 1.063 X 0.074 = - 0.359 pounds,
which latter, being negative, is a propelling force.
Results Astonish Scientists.
Thus we have a bird weighing 4.25 pounds not only thoroughly supported,
but impelled forward by a force of 0.359 pounds, at seventeen miles
per hour, while the experiments of Professor A. F. Zahm showed that the
resistance at 15.52 miles per hour was only 0.27 pounds,
17 squared
or 0.27 X ------- = 0.324 pounds, at seventeen miles an
15.52 squared
hour.
These are astonishing results from the data obtained, and they lead to
the inquiry whether the energy of the rising air is sufficient to make
up the losses which occur by reason of the resistance and friction of
the bird's body and wings, which, being rounded, do not encounter air
pressures in proportion to their maximum cross-section.
We have no accurate data upon the co-efficients to apply and estimates
made by myself proved to be much smaller than the 0.27 pounds resistance
measured by Professor Zahm, so that we will figure with the latter as
modified. As the speed is seventeen miles per hour, or 24.93 feet per
second, we have for the work:
Work done, 0.324 X 24.93 = 8.07 foot pounds per second.
Endorsed by Prof. Marvin.
Corresponding energy of rising air is not sufficient at four miles per
hour. This amounts to but 2.10 foot pounds per second, but if we assume
that the air was rising at the rate of seven miles per hour (10.26 feet
per second), at which the pressure with the Langley coefficient would be
0.16 pounds per square foot, we have on 4.57 square feet for energy of
rising air: 4.57 X 0.16 X 10.26 = 7.50 foot pounds per second, which
is seen to be still a little too small, but well within the limits of
error, in view of the hollow shape of the bird's wings, which receive
greater pressure than the flat planes experimented upon by Langley.
These computations were chiefly made in January, 1899, and were
communicated to a few friends, who found no fallacy in them, but thought
that few aviators would understand them if published. They were then
submitted to Professor C. F. Marvin of the Weather Bureau, who is well
known as a skillful physicist and mathematician. He wrote that they
were, theoretically, entirely sound and quantitatively, probably, as
accurate as the present state of the measurements of wind pressures
permitted. The writer determined, however, to withhold publication until
the feat of soaring flight had been performed by man, partly because he
believed that, to ensure safety, it would be necessary that the machine
should be equipped with a motor in order to supplement any deficiency in
wind force.
Conditions Unfavorable for Wrights.
The feat would have been attempted in 1902 by Wright brothers if the
local circumstances had been more favorable. They were experimenting on
"Kill Devil Hill," near Kitty Hawk, N. C. This sand hill, about 100
feet high, is bordered by a smooth beach on the side whence come the
sea breezes, but has marshy ground at the back. Wright brothers were
apprehensive that if they rose on the ascending current of air at the
front and began to circle like the birds, they might be carried by the
descending current past the back of the hill and land in the marsh.
Their gliding machine offered no greater head resistance in proportion
than the buzzard, and their gliding angles of descent are practically as
favorable, but the birds performed higher up in the air than they.
Langley's Idea of Aviation.
Professor Langley said in concluding his paper upon "The Internal Work
of the Wind":
"The final application of these principles to the art of aerodromics
seems, then, to be, that while it is not likely that the perfected
aerodrome will ever be able to dispense altogether with the ability
to rely at intervals on some internal source of power, it will not be
indispensable that this aerodrome of the future shall, in order to go
any distance--even to circumnavigate the globe without alighting--need
to carry a weight of fuel which would enable it to perform this journey
under conditions analogous to those of a steamship, but that the fuel
and weight need only be such as to enable it to take care of itself in
exceptional moments of calm."
Now that dynamic flying machines have been evolved and are being brought
under control, it seems to be worth while to make these computations and
the succeeding explanations known, so that some bold man will attempt
the feat of soaring like a bird. The theory underlying the performance
in a rising wind is not new, it has been suggested by Penaud and others,
but it has attracted little attention because the exact data and
the maneuvers required were not known and the feat had not yet been
performed by a man. The puzzle has always been to account for the
observed act in very light winds, and it is hoped that by the present
selection of the most difficult case to explain--i. e., the soaring in a
dead horizontal calm--somebody will attempt the exploit.
Requisites for Soaring Flights.
The following are deemed to be the requisites and maneuvers to master
the secrets of soaring flight:
1st--Develop a dynamic flying machine weighing about one pound per
square foot of area, with stable equilibrium and under perfect control,
capable of gliding by gravity at angles of one in ten (5 3/4 degrees) in
still air.
2nd.--Select locations where soaring birds abound and occasions where
rising trends of gentle winds are frequent and to be relied on.
3rd.--Obtain an initial velocity of at least 25 feet per second before
attempting to soar.
4th.--So locate the center of gravity that the apparatus shall assume a
negative angle, fore and aft, of about 3 degrees.
Calculations show, however, that sufficient propelling force may still
exist at 0 degrees, but disappears entirely at +4 degrees.
5th.--Circle like the bird. Simultaneously with the steering, incline
the apparatus to the side toward which it is desired to turn, so that
the centrifugal force shall be balanced by the centripetal force. The
amount of the required inclination depends upon the speed and on the
radius of the circle swept over.
6th.--Rise spirally like the bird. Steer with the horizontal rudder, so
as to descend slightly when going with the wind and to ascend when going
against the wind. The bird circles over one spot because the rising
trends of wind are generally confined to small areas or local chimneys,
as pointed out by Sir H. Maxim and others.
7th.--Once altitude is gained, progress may be made in any direction by
gliding downward by gravity.
The bird's flying apparatus and skill are as yet infinitely superior
to those of man, but there are indications that within a few years the
latter may evolve more accurately proportioned apparatus and obtain
absolute control over it.
It is hoped, therefore, that if there be found no radical error in the
above computations, they will carry the conviction that soaring flight
is not inaccessible to man, as it promises great economies of motive
power in favorable localities of rising winds.
The writer will be grateful to experts who may point out any mistake
committed in data or calculations, and will furnish additional
information to any aviator who may wish to attempt the feat of soaring.
CHAPTER XXI. FLYING MACHINES VS. BALLOONS.
While wonderful success has attended the development of the dirigible
(steerable) balloon the most ardent advocates of this form of aerial
navigation admit that it has serious drawbacks. Some of these may be
described as follows:
Expense and Other Items.
Great Initial Expense.--The modern dirigible balloon costs a fortune.
The Zeppelin, for instance, costs more than $100,000 (these are official
figures).
Expense of Inflation.--Gas evaporates rapidly, and a balloon must
be re-inflated, or partially re-inflated, every time it is used. The
Zeppelin holds 460,000 cubic feet of gas which, even at $1 per thousand,
would cost $460.
Difficulty of Obtaining Gas.--If a balloon suddenly becomes deflated, by
accident or atmospheric conditions, far from a source of gas supply, it
is practically worthless. Gas must be piped to it, or the balloon carted
to the gas house--an expensive proceeding in either event.
Lack of Speed and Control.
Lack of Speed.--Under the most favorable conditions the maximum speed
of a balloon is 30 miles an hour. Its great bulk makes the high speed
attained by flying machines impossible.
Difficulty of Control.--While the modern dirigible balloon is readily
handled in calm or light winds, its bulk makes it difficult to control
in heavy winds.
The Element of Danger.--Numerous balloons have been destroyed by
lightning and similar causes. One of the largest of the Zeppelins was
thus lost at Stuttgart in 1908.
Some Balloon Performances.
It is only a matter of fairness to state that, under favorable
conditions, some very creditable records have been made with modern
balloons, viz:
November 23d, 1907, the French dirigible Patrie, travelled 187 miles in
6 hours and 45 minutes against a light wind. This was a little over 28
miles an hour.
The Clement-Bayard, another French machine, sold to the Russian
government, made a trip of 125 miles at a rate of 27 miles an hour.
Zeppelin No. 3, carrying eight passengers, and having a total lifting
capacity of 5,500 pounds of ballast in addition to passengers, weight
of equipment, etc., was tested in October, 1906, and made 67 miles in 2
hours and 17 minutes, about 30 miles an hour.
These are the best balloon trips on record, and show forcefully the
limitations of speed, the greatest being not over 30 miles an hour.
Speed of Flying Machines.
Opposed to the balloon performances we have flying machine trips (of
authentic records) as follows:
Bleriot--monoplane--in 1908--52 miles an hour.
Delagrange--June 22, 1908--10 1/2 miles in 16 minutes, approximately 42
miles an hour.
Wrights--October, 1905--the machine was then in its infancy--24 miles
in 38 minutes, approximately 44 miles an hour. On December 31, 1908, the
Wrights made 77 miles in 2 hours and 20 minutes.
Lambert, a pupil of the Wrights, and using a Wright biplane, on October
18, 1909, covered 29.82 miles in 49 minutes and 39 seconds, being at
the rate of 36 miles an hour. This flight was made at a height of 1,312
feet.
Latham--October 21, 1909--made a short flight, about 11 minutes, in
the teeth of a 40 mile gale, at Blackpool, Eng. He used an Antoniette
monoplane, and the official report says: "This exhibition of nerve,
daring and ability is unparalled in the history of aviation."
Farman--October 20, 1909--was in the air for 1 hour, 32 min., 16
seconds, travelling 47 miles, 1,184 yards, a duration record for
England.
Paulhan--January 18, 1901--47 1/2 miles at the rate of 45 miles an hour,
maintaining an altitude of from 1,000 to 2,000 feet.
Expense of Producing Gas.
Gas is indispensable in the operation of dirigible balloons, and gas
is expensive. Besides this it is not always possible to obtain it in
sufficient quantities even in large cities, as the supply on hand is
generally needed for regular customers. Such as can be had is either
water or coal gas, neither of which is as efficient in lifting power as
hydrogen.
Hydrogen is the lightest and consequently the most buoyant of all known
gases. It is secured commercially by treating zinc or iron with dilute
sulphuric or hydrochloric acid. The average cost may be safely placed
at $10 per 1,000 feet so that, to inflate a balloon of the size of the
Zeppelin, holding 460,000 cubic feet, would cost $4,600.
Proportions of Materials Required.
In making hydrogen gas it is customary to allow 20 per cent for loss
between the generation and the introduction of the gas into the balloon.
Thus, while the formula calls for iron 28 times heavier than the weight
of the hydrogen required, and acid 49 times heavier, the real quantities
are 20 per cent greater. Hydrogen weighs about 0.09 ounce to the cubic
foot. Consequently if we need say 450,000 cubic feet of gas we must have
2,531.25 pounds in weight. To produce this, allowing for the 20 percent
loss, we must have 35 times its weight in iron, or over 44 tons. Of acid
it would take 60 times the weight of the gas, or nearly 76 tons.
In Time of Emergency.
These figures are appalling, and under ordinary conditions would be
prohibitive, but there are times when the balloon operator, unable to
obtain water or coal gas, must foot the bills. In military maneuvers,
where the field of operation is fixed, it is possible to furnish
supplies of hydrogen gas in portable cylinders, but on long trips
where sudden leakage or other cause makes descent in an unexpected spot
unavoidable, it becomes a question of making your own hydrogen gas or
deserting the balloon. And when this occurs the balloonist is up against
another serious proposition--can he find the necessary zinc or iron? Can
he get the acid?
Balloons for Commercial Use.
Despite all this the balloon has its uses. If there is to be such a
thing as aerial navigation in a commercial way--the carrying of freight
and passengers--it will come through the employment of such monster
balloons as Count Zeppelin is building. But even then the carrying
capacity must of necessity be limited. The latest Zeppelin creation,
a monster in size, is 450 feet long, and 42 1/2 feet in diameter. The
dimensions are such as to make all other balloons look like pigmies;
even many ocean-going steamers are much smaller, and yet its passenger
capacity is very small. On its 36-hour flight in May, 1909, the
Zeppelin, carried only eight passengers. The speed, however, was quite
respectable, 850 miles being covered in the 36 hours, a trifle over 23
miles an hour. The reserve buoyancy, that is the total lifting capacity
aside from the weight of the airship and its equipment, is estimated at
three tons.
CHAPTER XXII. PROBLEMS OF AERIAL FLIGHT.
In a lecture before the Royal Society of Arts, reported in Engineering,
F. W. Lanchester took the position that practical flight was not the
abstract question which some apparently considered it to be, but a
problem in locomotive engineering. The flying machine was a locomotive
appliance, designed not merely to lift a weight, but to transport it
elsewhere, a fact which should be sufficiently obvious. Nevertheless one
of the leading scientific men of the day advocated a type in which
this, the main function of the flying machine, was overlooked. When
the machine was considered as a method of transport, the vertical screw
type, or helicopter, became at once ridiculous. It had, nevertheless,
many advocates who had some vague and ill-defined notion of subsequent
motion through the air after the weight was raised.
Helicopter Type Useless.
When efficiency of transport was demanded, the helicopter type was
entirely out of court. Almost all of its advocates neglected the effect
of the motion of the machine through the air on the efficiency of the
vertical screws. They either assumed that the motion was so slow as not
to matter, or that a patch of still air accompanied the machine in its
flight. Only one form of this type had any possibility of success. In
this there were two screws running on inclined axles--one on each
side of the weight to be lifted. The action of such inclined screw was
curious, and in a previous lecture he had pointed out that it was almost
exactly the same as that of a bird's wing. In high-speed racing craft
such inclined screws were of necessity often used, but it was at
a sacrifice of their efficiency. In any case the efficiency of the
inclined-screw helicopter could not compare with that of an aeroplane,
and that type might be dismissed from consideration so soon as
efficiency became the ruling factor of the design.
Must Compete With Locomotive.
To justify itself the aeroplane must compete, in some regard or other,
with other locomotive appliances, performing one or more of the purposes
of locomotion more efficiently than existing systems. It would be no use
unless able to stem air currents, so that its velocity must be greater
than that of the worst winds liable to be encountered. To illustrate the
limitations imposed on the motion of an aeroplane by wind velocity, Mr.
Lanchester gave the diagrams shown in Figs. 1 to 4. The circle in each
case was, he said, described with a radius equal to the speed of the
aeroplane in still air, from a center placed "down-wind" from the
aeroplane by an amount equal to the velocity of the wind.
Fig. 1 therefore represented the case in which the air was still, and
in this case the aeroplane represented by _A_ had perfect liberty of
movement in any direction
In Fig. 2 the velocity of the wind was half that of the aeroplane, and
the latter could still navigate in any direction, but its speed against
the wind was only one-third of its speed with the wind.
In Fig. 3 the velocity of the wind was equal to that of the aeroplane,
and then motion against the wind was impossible; but it could move to
any point of the circle, but not to any point lying to the left of the
tangent _A_ _B_. Finally, when the wind had a greater speed than the
aeroplane, as in Fig. 4, the machine could move only in directions
limited by the tangents _A_ _C_ and _A_ _D_.
Matter of Fuel Consumption.
Taking the case in which the wind had a speed equal to half that of the
aeroplane, Mr. Lanchester said that for a given journey out and home,
down wind and back, the aeroplane would require 30 per cent more fuel
than if the trip were made in still air; while if the journey was made
at right angles to the direction of the wind the fuel needed would be 15
per cent more than in a calm. This 30 per cent extra was quite a heavy
enough addition to the fuel; and to secure even this figure it was
necessary that the aeroplane should have a speed of twice that of the
maximum wind in which it was desired to operate the machine. Again, as
stated in the last lecture, to insure the automatic stability of the
machine it was necessary that the aeroplane speed should be largely in
excess of that of the gusts of wind liable to be encountered.
Eccentricities of the Wind.
There was, Mr. Lanchester said, a loose connection between the average
velocity of the wind and the maximum speed of the gusts. When the
average speed of the wind was 40 miles per hour, that of the gusts might
be equal or more. At one moment there might be a calm or the direction
of the wind even reversed, followed, the next moment, by a violent gust.
About the same minimum speed was desirable for security against gusts as
was demanded by other considerations. Sixty miles an hour was the least
figure desirable in an aeroplane, and this should be exceeded as much as
possible. Actually, the Wright machine had a speed of 38 miles per hour,
while Farman's Voisin machine flew at 45 miles per hour.
Both machines were extremely sensitive to high winds, and the speaker,
in spite of newspaper reports to the contrary, had never seen either
flown in more than a gentle breeze. The damping out of the oscillations
of the flight path, discussed in the last lecture, increased with the
fourth power of the natural velocity of flight, and rapid damping
formed the easiest, and sometimes the only, defense against dangerous
oscillations. A machine just stable at 35 miles per hour would have
reasonably rapid damping if its speed were increased to 60 miles per
hour.
Thinks Use Is Limited.
It was, the lecturer proceeded, inconceivable that any very extended use
should be made of the aeroplane unless the speed was much greater than
that of the motor car. It might in special cases be of service,
apart from this increase of speed, as in the exploration of countries
destitute of roads, but it would have no general utility. With an
automobile averaging 25 to 35 miles per hour, almost any part of Europe,
Russia excepted, was attainable in a day's journey. A flying machine
of but equal speed would have no advantages, but if the speed could be
raised to 90 or 100 miles per hour, the whole continent of Europe
would become a playground, every part being within a daylight flight of
Berlin. Further, some marine craft now had speeds of 40 miles per hour,
and efficiently to follow up and report movements of such vessels an
aeroplane should travel at 60 miles per hour at least. Hence from
all points of view appeared the imperative desirability of very high
velocities of flight. The difficulties of achievement were, however,
great.
Weight of Lightest Motors.
As shown in the first lecture of his course, the resistance to motion
was nearly independent of the velocity, so that the total work done in
transporting a given weight was nearly constant. Hence the question of
fuel economy was not a bar to high velocities of flight, though should
these become excessive, the body resistance might constitute a large
proportion of the total. The horsepower required varied as the
velocity, so the factor governing the maximum velocity of flight was
the horsepower that could be developed on a given weight. At present the
weight per horsepower of feather-weight motors appeared to range from
2 1/4 pounds up to 7 pounds per brake horsepower, some actual figures
being as follows:
Antoinette........ 5 lbs.
Fiat.............. 3 lbs.
Gnome....... Under 3 lbs.
Metallurgic....... 8 lbs.
Renault........... 7 lbs.
Wright.............6 lbs.
Automobile engines, on the other hand, commonly weighed 12 pounds to 13
pounds per brake horsepower.
For short flights fuel economy was of less importance than a saving
in the weight of the engine. For long flights, however, the case
was different. Thus, if the gasolene consumption was 1/2 pound per
horsepower hour, and the engine weighed 3 pounds per brake horsepower,
the fuel needed for a six-hour flight would weigh as much as the engine,
but for half an hour's flight its weight would be unimportant.
Best Means of Propulsion.
The best method of propulsion was by the screw, which acting in air
was subject to much the same conditions as obtained in marine work.
Its efficiency depended on its diameter and pitch and on its position,
whether in front of or behind the body propelled. From this theory
of dynamic support, Mr. Lanchester proceeded, the efficiency of each
element of a screw propeller could be represented by curves such as were
given in his first lecture before the society, and from these curves the
over-all efficiency of any proposed propeller could be computed, by mere
inspection, with a fair degree of accuracy. These curves showed that the
tips of long-bladed propellers were inefficient, as was also the portion
of the blade near the root. In actual marine practice the blade from
boss to tip was commonly of such a length that the over-all efficiency
was 95 per cent of that of the most efficient element of it.
Advocates Propellers in Rear.
From these curves the diameter and appropriate pitch of a screw could
be calculated, and the number of revolutions was then fixed. Thus, for a
speed of 80 feet per second the pitch might come out as 8 feet, in which
case the revolutions would be 600 per minute, which might, however, be
too low for the motor. It was then necessary either to gear down the
propeller, as was done in the Wright machine, or, if it was decided to
drive it direct, to sacrifice some of the efficiency of the propeller.
An analogous case arose in the application of the steam turbine to the
propulsion of cargo boats, a problem as yet unsolved. The propeller
should always be aft, so that it could abstract energy from the wake
current, and also so that its wash was clear of the body propelled. The
best possible efficiency was about 70 per cent, and it was safe to rely
upon 66 per cent.
Benefits of Soaring Flight.
There was, Mr. Lanchester proceeded, some possibility of the aeronaut
reducing the power needed for transport by his adopting the principle of
soaring flight, as exemplified by some birds. There were, he continued,
two different modes of soaring flight. In the one the bird made use of
the upward current of air often to be found in the neighborhood of steep
vertical cliffs. These cliffs deflected the air upward long before it
actually reached the cliff, a whole region below being thus the seat of
an upward current. Darwin has noted that the condor was only to be found
in the neighborhood of such cliffs. Along the south coast also the gulls
made frequent use of the up currents due to the nearly perpendicular
chalk cliffs along the shore.
In the tropics up currents were also caused by temperature differences.
Cumulus clouds, moreover, were nearly always the terminations of such
up currents of heated air, which, on cooling by expansion in the upper
regions, deposited their moisture as fog. These clouds might, perhaps,
prove useful in the future in showing the aeronaut where up currents
were to be found. Another mode of soaring flight was that adopted by
the albatross, which took advantage of the fact that the air moved
in pulsations, into which the bird fitted itself, being thus able to
extract energy from the wind. Whether it would be possible for the
aeronaut to employ a similar method must be left to the future to
decide.
Main Difficulties in Aviation.
In practical flight difficulties arose in starting and in alighting.
There was a lower limit to the speed at which the machine was stable,
and it was inadvisable to leave the ground till this limit was attained.
Similarly, in alighting it was inexpedient to reduce the speed below the
limit of stability. This fact constituted a difficulty in the adoption
of high speeds, since the length of run needed increased in proportion
to the square of the velocity. This drawback could, however, be
surmounted by forming starting and alighting grounds of ample size.
He thought it quite likely in the future that such grounds would be
considered as essential to the flying machine as a seaport was to an
ocean-going steamer or as a road was to the automobile.
Requisites of Flying Machine.
Flying machines were commonly divided into monoplanes and biplanes,
according as they had one or two supporting surfaces. The distinction
was not, however, fundamental. To get the requisite strength some
form of girder framework was necessary, and it was a mere question of
convenience whether the supporting surface was arranged along both
the top and the bottom of this girder, or along the bottom only. The
framework adopted universally was of wood braced by ties of pianoforte
wire, an arrangement giving the stiffness desired with the least
possible weight. Some kind of chassis was also necessary.
CHAPTER XXIII. AMATEURS MAY USE WRIGHT PATENTS.
Owing to the fact that the Wright brothers have enjoined a number of
professional aviators from using their system of control, amateurs have
been slow to adopt it. They recognize its merits, and would like to use
the system, but have been apprehensive that it might involve them in
litigation. There is no danger of this, as will be seen by the following
statement made by the Wrights:
What Wright Brothers Say.
"Any amateur, any professional who is not exhibiting for money, is at
liberty to use our patented devices. We shall be glad to have them do
so, and there will be no interference on our part, by legal action, or
otherwise. The only men we proceed against are those who, without our
permission, without even asking our consent, coolly appropriate the
results of our labors and use them for the purpose of making money.
Curtiss, Delagrange, Voisin, and all the rest of them who have used our
devices have done so in money-making exhibitions. So long as there
is any money to be made by the use of the products of our brains, we
propose to have it ourselves. It is the only way in which we can get
any return for the years of patient work we have given to the problem of
aviation. On the other hand, any man who wants to use these devices for
the purpose of pleasure, or the advancement of science, is welcome to do
so, without money and without price. This is fair enough, is it not?"
Basis of the Wright Patents.
In a flying machine a normally flat aeroplane having lateral marginal
portions capable of movement to different positions above or below the
normal plane of the body of the aeroplane, such movement being about
an axis transverse to the line of flight, whereby said lateral marginal
portions may be moved to different angles relatively to the normal
plane of the body of the aeroplane, so as to present to the atmosphere
different angles of incidence, and means for so moving said lateral
marginal portions, substantially as described.
Application of vertical struts near the ends having flexible joints.
Means for simultaneously imparting such movement to said lateral
portions to different angles relatively to each other.
Refers to the movement of the lateral portions on the same side to the
same angle.
Means for simultaneously moving vertical rudder so as to present to
the wind that side thereof nearest the side of the aeroplane having the
smallest angle of incidence.
Lateral stability is obtained by warping the end wings by moving the
lever at the right hand of the operator, connection being made by wires
from the lever to the wing tips. The rudder may also be curved or warped
in similar manner by lever action.
Wrights Obtain an Injunction.
In January, 1910, Judge Hazel, of the United States Circuit Court,
granted a preliminary injunction restraining the Herring-Curtiss
Co., and Glenn H. Curtiss, from manufacturing, selling, or using for
exhibition purposes the machine known as the Curtiss aeroplane. The
injunction was obtained on the ground that the Curtiss machine is an
infringement upon the Wright patents in the matter of wing warping and
rudder control.
It is not the purpose of the authors to discuss the subject pro or con.
Such discussion would have no proper place in a volume of this kind. It
is enough to say that Curtiss stoutly insists that his machine is not
an infringement of the Wright patents, although Judge Hazel evidently
thinks differently.
What the Judge Said.
In granting the preliminary injunction the judge said:
"Defendants claim generally that the difference in construction of their
apparatus causes the equilibrium or lateral balance to be maintained and
its aerial movement secured upon an entirely different principle from
that of complainant; the defendants' aeroplanes are curved, firmly
attached to the stanchions and hence are incapable of twisting or
turning in any direction; that the supplementary planes or so-called
rudders are secured to the forward stanchion at the extreme lateral ends
of the planes and are adjusted midway between the upper and lower
planes with the margins extending beyond the edges; that in moving the
supplementary planes equal and uniform angles of incidence are presented
as distinguished from fluctuating angles of incidence. Such claimed
functional effects, however, are strongly contradicted by the expert
witness for complainant.
Similar to Plan of Wrights.
"Upon this contention it is sufficient to say that the affidavits for
the complainant so clearly define the principle of operation of the
flying machines in question that I am reasonably satisfied that there
is a variableness of the angle of incidence in the machine of defendants
which is produced when a supplementary plane on one side is tilted
or raised and the other stimultaneously tilted or lowered. I am also
satisfied that the rear rudder is turned by the operator to the side
having the least angle of incidence and that such turning is done at the
time the supplementary planes are raised or depressed to prevent tilting
or upsetting the machine. On the papers presented I incline to the view,
as already indicated, that the claims of the patent in suit should be
broadly construed; and when given such construction, the elements of
the Wright machine are found in defendants' machine performing the
same functional result. There are dissimilarities in the defendants'
structure--changes of form and strengthening of parts--which may be
improvements, but such dissimilarities seem to me to have no bearing
upon the means adopted to preserve the equilibrium, which means are the
equivalent of the claims in suit and attain an identical result.
Variance From Patent Immaterial.
"Defendants further contend that the curved or arched surfaces of the
Wright aeroplanes in commercial use are departures from the patent,
which describes 'substantially flat surfaces,' and that such a
construction would be wholly impracticable. The drawing, Fig. 3,
however, attached to the specification, shows a curved line inward of
the aeroplane with straight lateral edges, and considering such drawing
with the terminology of the specification, the slight arching of the
surface is not thought a material departure; at any rate, the patent in
issue does not belong to the class of patents which requires narrowing
to the details of construction."
"June Bug" First Infringement.
Referring to the matter of priority, the judge said:
"Indeed, no one interfered with the rights of the patentees by
constructing machines similar to theirs until in July, 1908, when
Curtiss exhibited a flying machine which he called the 'June Bug.' He
was immediately notified by the patentees that such machine with its
movable surfaces at the tips of wings infringed the patent in suit, and
he replied that he did not intend to publicly exhibit the machine for
profit, but merely was engaged in exhibiting it for scientific purposes
as a member of the Aerial Experiment Association. To this the patentees
did not object. Subsequently, however, the machine, with supplementary
planes placed midway between the upper and lower aeroplanes, was
publicly exhibited by the defendant corporation and used by Curtiss in
aerial flights for prizes and emoluments. It further appears that the
defendants now threaten to continue such use for gain and profit, and to
engage in the manufacture and sale of such infringing machines, thereby
becoming an active rival of complainant in the business of constructing
flying machines embodying the claims in suit, but such use of the
infringing machines it is the duty of this court, on the papers
presented, to enjoin.
"The requirements in patent causes for the issuance of an injunction
pendente lite--the validity of the patent, general acquiescence by the
public and infringement by the defendants--are so reasonably clear that
I believe if not probable the complainant may succeed at final hearing,
and therefore, status quo should be preserved and a preliminary
injunction granted.
"So ordered."
Points Claimed By Curtiss.
That the Herring-Curtiss Co. will appeal is a certainty. Mr. Emerson R.
Newell, counsel for the company, states its case as follows:
"The Curtiss machine has two main supporting surfaces, both of which are
curved * * * and are absolutely rigid at all times and cannot be moved,
warped or distorted in any manner. The front horizontal rudder is used
for the steering up or down, and the rear vertical rudder is used only
for steering to the right or left, in the same manner as a boat is
steered by its rudder. The machine is provided at the rear with a fixed
horizontal surface, which is not present in the machine of the patent,
and which has a distinct advantage in the operation of defendants'
machine, as will be hereafter discussed.
Does Not Warp Main Surface.
"Defendants' machine does not use the warping of the main supporting
surfaces in restoring the lateral equilibrium, but has two comparatively
small pivoted balancing surfaces or rudders. When one end of the machine
is tipped up or down from the normal, these planes may be thrown in
opposite directions by the operator, and so steer each end of the
machine up or down to its normal level, at which time tension upon them
is released and they are moved back by the pressure of the wind to their
normal position.
Rudder Used Only For Steering.
"When defendants' balancing surfaces are moved they present equal angles
of incidence to the normal rush of air and equal resistances, at each
side of the machine, and there is therefore no tendency to turn around a
vertical axis as is the case of the machine of the patent, consequently
no reason or necessity for turning the vertical rear rudder in
defendants' machine to counteract any such turning tendency. At any
rate, whatever may be the theories in regard to this matter, the fact is
that the operator of defendants' machine does not at any time turn his
vertical rudder to counteract any turning tendency clue to the side
balancing surfaces, but only uses it to steer the machine the same as a
boat is steered."
Aero Club Recognizes Wrights.
The Aero Club of America has officially recognized the Wright patents.
This course was taken following a conference held April 9th, 1910,
participated in by William Wright and Andrew Freedman, representing the
Wright Co., and the Aero Club's committee, of Philip T. Dodge, W. W.
Miller, L. L. Gillespie, Wm. H. Page and Cortlandt F. Bishop.
At this meeting arrangements were made by which the Aero Club recognizes
the Wright patents and will not give its section to any open meet
where the promoters thereof have not secured a license from the Wright
Company.
The substance of the agreement was that the Aero Club of America
recognizes the rights of the owners of the Wright patents under
the decisions of the Federal courts and refuses to countenance the
infringement of those patents as long as these decisions remain in
force.
In the meantime, in order to encourage aviation, both at home and
abroad, and in order to permit foreign aviators to take part in aviation
contests in this country it was agreed that the Aero Club of America, as
the American representative of the International Aeronautic Federation,
should approve only such public contests as may be licensed by the
Wright Company and that the Wright Company, on the other hand, should
encourage the holding of open meets or contests where ever approved as
aforesaid by the Aero Club of America by granting licenses to promoters
who make satisfactory arrangements with the company for its compensation
for the use of its patents. At such licensed meet any machine of any
make may participate freely without securing any further license or
permit. The details and terms of all meets will be arranged by the
committee having in charge the interests of both organizations.
CHAPTER XXIV. HINTS ON PROPELLER CONSTRUCTION.
Every professional aviator has his own ideas as to the design of
the propeller, one of the most important features of flying-machine
construction. While in many instances the propeller, at a casual glance,
may appear to be identical, close inspection will develop the fact
that in nearly every case some individual idea of the designer has been
incorporated. Thus, two propellers of the two-bladed variety, while of
the same general size as to length and width of blade, will vary greatly
as to pitch and "twist" or curvature.
What the Designers Seek.
Every designer is seeking for the same result--the securing of the
greatest possible thrust, or air displacement, with the least possible
energy.
The angles of any screw propeller blade having a uniform or true pitch
change gradually for every increased diameter. In order to give a
reasonably clear explanation, it will be well to review in a primary way
some of the definitions or terms used in connection with and applied to
screw propellers.
Terms in General Use.
Pitch.--The term "pitch," as applied to a screw propeller, is the
theoretical distance through which it would travel without slip in one
revolution, and as applied to a propeller blade it is the angle at
which the blades are set so as to enable them to travel in a spiral path
through a fixed distance theoretically without slip in one revolution.
Pitch speed.--The term "pitch speed" of a screw propeller is the speed
in feet multiplied by the number of revolutions it is caused to make
in one minute of time. If a screw propeller is revolved 600 times
per minute, and if its pitch is 7 ft., then the pitch speed of such a
propeller would be 7x600 revolutions, or 4200 ft. per minute.
Uniform pitch.--A true pitch screw propeller is one having its blades
formed in such a manner as to enable all of its useful portions, from
the portion nearest the hub to its outer portion, to travel at a uniform
pitch speed. Or, in other words, the pitch is uniform when the projected
area of the blade is parallel along its full length and at the same time
representing a true sector of a circle.
All screw propellers having a pitch equal to their diameters have the
same angle for their blades at their largest diameter.
When Pitch Is Not Uniform.
A screw propeller not having a uniform pitch, but having the same angle
for all portions of its blades, or some arbitrary angle not a true
pitch, is distinguished from one having a true pitch in the variation of
the pitch speeds that the various portions of its blades are forced to
travel through while traveling at its maximum pitch speed.
On this subject Mr. R. W. Jamieson says in Aeronautics:
"Take for example an 8-foot screw propeller having an 8-foot pitch at
its largest diameter. If the angle is the same throughout its entire
blade length, then all the porions of its blades approaching the hub
from its outer portion would have a gradually decreasing pitch. The
2-foot portion would have a 2-foot pitch; the 3-foot portion a 3-foot
pitch, and so on to the 8-foot portion which would have an 8-foot pitch.
When this form of propeller is caused to revolve, say 500 r.p.m., the
8-foot portion would have a calculated pitch speed of 8 feet by 500
revolutions, or 4,000 feet per min.; while the 2-foot portion would have
a calculated pitch speed of 500 revolutions by 2 feet, or 1,000 feet per
minute.
Effect of Non-Uniformity.
"Now, as all of the portions of this type of screw propeller must travel
at some pitch speed, which must have for its maximum a pitch speed
in feet below the calculated pitch speed of the largest diameter, it
follows that some portions of its blades would perform useful work
while the action of the other portions would be negative--resisting
the forward motion of the portions having a greater pitch speed. The
portions having a pitch speed below that at which the screw is traveling
cease to perform useful work after their pitch speed has been exceeded
by the portions having a larger diameter and a greater pitch speed.
"We might compare the larger and smaller diameter portions of this form
of screw propeller, to two power-driven vessels connected with a line,
one capable of traveling 20 miles per hour, the other 10 miles per hour.
It can be readily understood that the boat capable of traveling 10 miles
per hour would have no useful effect to help the one traveling 20 miles
per hour, as its action would be such as to impose a dead load upon the
latter's progress."
The term "slip," as applied to a screw propeller, is the distance
between its calculated pitch speed and the actual distance it travels
through under load, depending upon the efficiency and proportion of its
blades and the amount of load it has to carry.
The action of a screw propeller while performing useful work might be
compared to a nut traveling on a threaded bolt; little resistance is
offered to its forward motion while it spins freely without load, but
give it a load to carry; then it will take more power to keep up its
speed; if too great a load is applied the thread will strip, and so
it is with a screw propeller gliding spirally on the air. A propeller
traveling without load on to new air might be compared to the nut
traveling freely on the bolt. It would consume but little power and it
would travel at nearly its calculated pitch speed, but give it work to
do and then it will take power to drive it.
There is a reaction caused from the propeller projecting air backward
when it slips, which, together with the supporting effect of the blades,
combine to produce useful work or pull on the object to be carried.
A screw propeller working under load approaches more closely to its
maximum efficiency as it carries its load with a minimum amount of slip,
or nearing its calculated pitch speed.
Why Blades Are Curved.
It has been pointed out by experiment that certain forms of curved
surfaces as applied to aeroplanes will lift more per horse power, per
unit of square foot, while on the other hand it has been shown that a
flat surface will lift more per horse power, but requires more area of
surface to do it.
As a true pitch screw propeller is virtually a rotating aeroplane, a
curved surface may be advantageously employed when the limit of size
prevents using large plane surfaces for the blades.
Care should be exercised in keeping the chord of any curve to be used
for the blades at the proper pitch angle, and in all cases propeller
blades should be made rigid so as to preserve the true angle and not be
distorted by centrifugal force or from any other cause, as flexibility
will seriously affect their pitch speed and otherwise affect their
efficiency.
How to Determine Angle.
To find the angle for the proper pitch at any point in the diameter of
a propeller, determine the circumference by multiplying the diameter by
3.1416, which represent by drawing a line to scale in feet. At the end
of this line draw another line to represent the desired pitch in feet.
Then draw a line from the point representing the desired pitch in feet
to the beginning of the circumference line. For example:
If the propeller to be laid out is 7 feet in diameter, and is to have
a 7-foot pitch, the circumference will be 21.99 feet. Draw a diagram
representing the circumference line and pitch in feet. If this diagram
is wrapped around a cylinder the angle line will represent a true thread
7 feet in diameter and 7 feet long, and the angle of the thread will be
17 3/4 degrees.
Relation of Diameter to Circumference.
Since the areas of circles decrease as the diameter lessens, it follows
that if a propeller is to travel at a uniform pitch speed, the volume of
its blade displacement should decrease as its diameter becomes less, so
as to occupy a corresponding relation to the circumferences of larger
diameters, and at the same time the projected area of the blade must be
parallel along its full length and should represent a true sector of a
circle.
Let us suppose a 7-foot circle to be divided into 20 sectors, one of
which represents a propeller blade. If the pitch is to be 7 feet, then
the greatest depth of the angle would be 1/20 part of the pitch, or 4
2/10 inch. If the line representing the greatest depth of the angle is
kept the same width as it approaches the hub, the pitch will be uniform.
If the blade is set at an angle so its projected area is 1/20 part of
the pitch, and if it is moved through 20 divisions for one revolution,
it would have a travel of 7 feet.
CHAPTER XXV. NEW MOTORS AND DEVICES.
Since the first edition of this book was printed, early in 1910, there
has been a remarkable advance in the construction of aeroplane motors,
which has resulted in a wonderful decrease in the amount of surface area
from that formerly required. Marked gain in lightness and speed of
the motor has enabled aviators to get along, in some instances, with
one-quarter of the plane supporting area previously used. The first
Wright biplane, propelled by a motor of 25 h.p., productive of a fair
average speed of 30 miles an hour, had a plane surface of 538 square
feet. Now, by using a specially designed motor of 65 h. p., capable
of developing a speed of from 70 to 80 miles an hour, the Wrights are
enabled to successfully navigate a machine the plane area of which is
about 130 square feet. This apparatus is intended to carry only one
person (the operator). At Belmont Park, N. Y., the Wrights demonstrated
that the small-surfaced biplane is much faster, easier to manage in the
hands of a skilled manipulator, and a better altitude climber than the
large and cumbersome machines with 538 square feet of surface heretofore
used by them.
In this may be found a practical illustration of the principle that
increased speed permits of a reduction in plane area in mathematical
ratio to the gain in speed. The faster any object can be made to move
through the air, the less will be the supporting surface required to
sustain a given weight. But, there is a limit beyond which the plane
surface cannot be reduced with safety. Regard must always be had to
the securing of an ample sustaining surface so that in case of motor
stoppage there will be sufficient buoyancy to enable the operator to
descend safely.
The baby Wright used at the Belmont Park (N. Y.) aviation meet in the
fall of 1910, had a plane length of 19 feet 6 inches, and an extreme
breadth of 21 feet 6 inches, with a total surface area of 146 square
feet. It was equipped with a new Wright 8-cylinder motor of 60 h. p.,
and two Wright propellers of 8 feet 6 inches diameter and 500 r. p. m.
It was easily the fastest machine at the meet. After the tests, Wilbur
Wright said:
"It is our intention to put together a machine with specially designed
propellers, specially designed gears and a motor which will give us 65
horsepower at least. We will then be able, after some experimental work
we are doing now, to send forth a machine that will make a new speed
record."
In the new Wright machines the front elevating planes for up-and-down
control have been eliminated, and the movements of the apparatus are now
regulated solely by the rear, or "tail" control.
A Powerful Light Motor.
Another successful American aviation motor is the aeromotor,
manufactured by the Detroit Aeronautic Construction. Aeromotors are made
in four models as follows:
Model 1.--4-cylinder, 30-40 h. p., weight 200 pounds.
Model 2.--4-cylinder, (larger stroke and bore) 40-50 h. p., weight 225
pounds.
Model 3.--6-cylinder. 50-60 h. p., weight 210 pounds.
Model 4.--6-cylinder, 60-75 h. p., weight 275 pounds.
This motor is of the 4-cycle, vertical, water-cooled type. Roberts
Aviation Motor.
One of the successful aviation motors of American make, is that produced
by the Roberts Motor Co., of Sandusky, Ohio. It is designed by E. W.
Roberts, M. E., who was formerly chief assistant and designer for Sir
Hiram Maxim, when the latter was making his celebrated aeronautical
experiments in England in 1894-95. This motor is made in both the
4- and 6-cylinder forms. The 4-cylinder motor weighs complete with Bosch
magneto and carbureter 165 pounds, and will develop 40 actual brake
h. p. at 1,000 r. p. m., 46 h. p. at 1,200 and 52 h. p. at 1,400. The
6-cylinder weighs 220 pounds and will develop 60 actual brake h. p. at
1,000 r. p. m., 69 h. p. at 1,200 and 78 h. p. at 1,500.
Extreme lightness has been secured by doing away with all superfluous
parts, rather than by a shaving down of materials to a dangerous
thinness. For example, there is neither an intake or exhaust manifold on
the motor. The distributing valve forms a part of the crankcase as
does the water intake, and the gear pump. Magnalium takes the place of
aluminum in the crankcase, because it is not only lighter but stronger
and can be cast very thin. The crankshaft is 2 1/2-inch diameter with a
2 1/4-inch hole, and while it would be strong enough in ordinary 40
per cent carbon steel it is made of steel twice the strength of that
customarily employed. Similar care has been exercised on other parts and
the result is a motor weighing 4 pounds per h. p.
The Rinek Motor.
The Rinek aviation motor, constructed by the Rinek Aero Mfg. Co., of
Easton, Pa., is another that is meeting with favor among aviators. Type
B-8 is an 8-cylinder motor, the cylinders being set at right angles,
on a V-shaped crank case. It is water cooled, develops 50-60 h. p., the
minimum at 1,220 r. p. m., and weighs 280 pounds with all accessories.
Type B-4, a 4-cylinder motor, develops 30 h. p. at 1,800 r. p. m., and
weighs 130 pounds complete. The cylinders in both motors are made of
cast iron with copper water jackets.
The Overhead Camshaft Boulevard.
The overhead camshaft Boulevard is still another form of aviation motor
which has been favorably received. This is the product of the Boulevard
Engine Co., of St. Louis. It is made with 4 and 8 cylinders. The former
develops 30-35 h. p. at 1,200 r. p. m., and weighs 130 pounds. The
8-cylinder motor gives 60-70 h. p. at 1,200 r. p. m., and weighs 200
pounds. Simplicity of construction is the main feature of this motor,
especially in the manipulation of the valves.
CHAPTER XXVI. MONOPLANES, TRIPLANES, MULTIPLANES.
Until recently, American aviators had not given serious attention to
any form of flying machines aside from biplanes. Of the twenty-one
monoplanes competing at the International meet at Belmont Park, N. Y.,
in November, 1910, only three makes were handled by Americans. Moissant
and Drexel navigated Bleriot machines, Harkness an Antoinette, and Glenn
Curtiss a single decker of his own construction. On the other hand the
various foreign aviators who took part in the meet unhesitatingly gave
preference to monoplanes.
Whatever may have been the cause of this seeming prejudice against
the monoplane on the part of American air sailors, it is slowly being
overcome. When a man like Curtiss, who has attained great success with
biplanes, gives serious attention to the monoplane form of construction
and goes so far as to build and successfully operate a single surface
machine, it may be taken for granted that the monoplane is a fixture in
this country.
Dimensions of Monoplanes.
The makes, dimensions and equipment of the various monoplanes used at
Belmont Park are as follows:
Bleriot--(Moissant, operator)--plane length 23 feet, extreme breadth 28
feet, surface area 160 square feet, 7-cylinder, 50 h. p. Gnome engine,
Chauviere propeller, 7 feet 6 inches diameter, 1,200 r. p. m.
Bleriot--(Drexel, operator)--exactly the same as Moissant's machine.
Antoinette--(Harkness, operator)--plane length 42 feet, extreme breadth
46 feet, surface area 377 square feet, Emerson 6-cylinder, 50 h. p.
motor, Antoinette propeller, 7 feet 6 inches diameter, 1,200 r. p. m.
Curtiss--(Glenn H. Curtiss, operator)--plane length 25 feet, extreme
breadth 26 feet, surface area 130 square feet, Curtiss 8-cylinder, 60 h.
p. motor, Paragon propeller, 7 feet in diameter, 1,200 r. p. m.
With one exception Curtiss had the smallest machine of any of those
entering into competition. The smallest was La Demoiselle, made by
Santos-Dumont, the proportions of which were: plane length 20 feet,
extreme breadth 18 feet, surface area 100 square feet, Clement-Bayard
2-cylinder, 30 h. p. motor, Chauviere propeller, 6 feet 6 inches in
diameter, 1,100 r. p. m.
Winnings Made with Monoplanes.
Operators of monoplanes won a fair share of the cash prizes. They won
$30,283 out of a total of $63,250, to say nothing about Grahame-White's
winnings. The latter won $13,600, but part of his winning flights were
made in a Bleriot monoplane, and part in a Farman machine. Aside from
Grahame-White the winnings were divided as follows: Moissant (Bleriot)
$13,350; Latham (Antoinette) $8,183; Aubrun (Bleriot) $2,400; De Lesseps
(Bleriot) $2,300; Drexel (Bleriot) $1,700; Radley (Bleriot) $1,300;
Simon (Bleriot) $750; Andemars (Clement-Bayard) $100; Barrier (Bleriot)
$100.
Out of a total of $30,283, operators of Bleriot machines won $21,900,
again omitting Grahame-White's share. If the winnings with monoplane and
biplane could be divided so as to show the amount won with each type
of machine the credit side of the Bleriot account would be materially
enlarged.
The Most Popular Monoplanes.
While the number of successful monoplanes is increasing rapidly, and
there is some feature of advantage in nearly all the new makes, interest
centers chiefly in the Santos-Dumont, Antoinette and Bleriot machines.
This is because more has been accomplished with them than with any of
the others, possibly because they have had greater opportunities.
For the guidance of those who may wish to build a machine of the
monoplane type after the Santos-Dumont or Bleriot models, the following
details will be found useful.
Santos-Dumont--The latest production of this maker is called the "No. 20
Baby." It is of 18 feet spread, and 20 feet over all in depth. It stands
4 feet 2 inches in height, not counting the propeller. When this latter
is in a vertical position the extreme height of the machine is 7 feet
5 inches. It is strictly a one-man apparatus. The total surface area
is 115 square feet. The total weight of the monoplane with engine and
propeller is 352 pounds. Santos-Dumont weighs 110 pounds, so the entire
weight carried while in flight is 462 pounds, or about 3.6 pounds per
square foot of surface.
Bamboo is used in the construction of the body frame, and also for the
frame of the tail. The body frame consists of three bamboo poles about
2 inches in diameter at the forward end and tapering to about 1 inch at
the rear. These poles are jointed with brass sockets near the rear of
the main plane so they may be taken apart easily for convenience in
housing or transportation. The main plane is built upon four transverse
spars of ash, set at a slight dihedral angle, two being placed on each
side of the central bamboo. These spars are about 2 inches wide by 1
1/8-inch deep for a few feet each side of the center of the machine, and
from there taper down to an inch in depth at the center bamboo, and at
their outer ends, but the width remains the same throughout their entire
length. The planes are double surfaced with silk and laced above and
below the bamboo ribs which run fore and aft under the main spars and
terminate in a forked clip through which a wire is strung for lacing on
the silk. The tail consists of a horizontal and vertical surface placed
on a universal joint about 10 feet back of the rear edge of the main
plane. Both of these surfaces are flat and consist of a silk covering
stretched upon bamboo ribs. The horizontal surface is 6 feet 5 inches
across, and 4 feet 9 inches from front to back. The vertical surface
is of the same width (6 feet 5 inches) but is only 3 feet 7 inches
from front to back. All the details of construction are shown in the
accompanying illustration.
Power is furnished by a very light (110 pounds) Darracq motor, of the
double-opposed-cylinder type. It has a bore of 4.118 inches, and stroke
of 4.724 inches, runs at 1,800 r. p. m., and with a 6 1/2-foot propeller
develops a thrust of 242 1/2 pounds when the monoplane is held steady.
Bleriot--No. XI, the latest of the Bleriot productions, and the greatest
record maker of the lot, is 28 feet in spread of main plane, and depth
of 6 feet in largest part. This would give a main surface of 168 square
feet, but as the ends of the plane are sharply tapered from the rear,
the actual surface is reduced to 150 square feet. Projecting from
the main frame is an elongated tail (shown in the illustration) which
carries the horizontal and vertical rudders. The former is made in three
sections. The center piece is 6 feet 1 inch in spread, and 2 feet 10
inches in depth, containing 17 square feet of surface. The end sections,
which are made movable for warping purposes, are each 2 feet 10 inches
square, the combined surface area in the entire horizontal rudder
being 33 square feet. The vertical rudder contains 4 1/2 square feet of
surface, making the entire supporting area 187 1/2 square feet.
From the outer end of the propeller shaft in front to the extreme rear
edge of the vertical rudder, the machine is 25 feet deep. Deducting
the 6-foot depth of the main plane leaves 19 feet as the length of the
rudder beam and rudders. The motor equipment consists of a 3-cylinder,
air-cooled engine of about 30 h. p. placed at the front end of the body
frame, and carrying on its crankshaft a two-bladed propeller 6 feet 8
inches in diameter. The engine speed is about 1,250 r. p. m. at which
the propeller develops a thrust of over 200 pounds.
The Bleriot XI complete weighs 484 pounds, and with operator and fuel
supply ready for a 25- or 30-mile flight, 715 pounds. One peculiarity of
the Bleriot construction is that, while the ribs of the main plane are
curved, there is no preliminary bending of the pieces as in other forms
of construction. Bleriot has his rib pieces cut a little longer than
required and, by springing them into place, secures the necessary
curvature. A good view of the Bleriot plane framework is given on page
63.
Combined Triplane and Biplane.
At Norwich, Conn., the Stebbins-Geynet Co., after several years of
experiment, has begun the manufacture of a combination triplane and
biplane machine. The center plane, which is located about midway
between the upper and lower surfaces, is made removable. The change
from triplane to biplane, or vice versa, may be readily made in a few
minutes. The constructors claim for this type of air craft a large
supporting surface area with the minimum of dimensions in planes.
Although this machine has only 24-foot spread and is only 26 feet over
all, its total amount of supporting area is 400 square feet; weight, 600
pounds in flying order, and lifting capacity approximately 700 pounds
more.
The frame is made entirely of a selected grade of Oregon spruce,
finished down to a smooth surface and varnished. All struts are
fish-shaped and set in aluminum sockets, which are bolted to top and
lower beams with special strong bolts of small diameter. The middle
plane is set inside the six uprights and held in place by aluminum
castings. A flexible twisted seven-strand wire cable and Stebbins-Geynet
turnbuckles are used for trussing.
The top plane is in three sections, laced together. It has a 24-foot
spread and is 7 feet in depth. The middle plane is in two sections each
of 7 1/2 feet spread and 6 feet in depth. The center ends of the middle
plane sections do not come within 5 feet of joining, this open space
being left for the engine. The bottom plane is of 16 feet spread and 5
feet in depth. It will thus be seen that the planes overhang one another
in depth, the bottom one being the smallest in this respect. The planes
are set at an angle of 9 degrees, and there is a clear space of 3 1/2
feet between each, making the total distance from the bottom to the top
plane a trifle over 7 feet. The total supporting surface in the main
planes is 350 square feet. By arranging the three plane surfaces at
an angle as described and varying their size, the greatest amount of
lifting area is secured above the center of gravity, and the greatest
weight carried below.
The ribs are made of laminated spruce, finished down to 1/2x3/4-inch
cross section dimensions, with a curvature of about 1 in 20, and
fastened to the beams with special aluminum castings. Number 2 Naiad
aeroplane cloth is used in covering the planes, with pockets sewn in for
the ribs.
Two combination elevating rudders are set up well in front, each having
18 square feet of supporting area. These rudders are arranged to work
in unison, independently, or in opposite directions. In the Model B
machine, there are also two small rear elevating rudders, which work in
unison with the front rudders. One vertical rudder of 10 square feet is
suspended in the rear of a small stationary horizontal plane in Model A,
while the vertical rudder on Model B is only 6 square feet in size. The
elevating rudders are arranged so as to act as stabilizing planes when
the machine is in flight. The wing tips are held in place with a special
two-piece casting which forms a hinge, and makes a quick detachable
joint. Wing tips are also used in balancing.
Model A is equipped with a Cameron 25-30 h. p., 4-cylinder, air-cooled
motor. On Model B a Holmes rotary 7-cylinder motor of 4x4-inch bore and
stroke is used.
Positive control is secured by use of the Stebbins-Geynet "auto-control"
system. A pull or push movement operates the elevating rudders, while
the balancing is done by means of side movements or slight turns. The
rear vertical rudder is manipulated by means of a foot lever.
New Cody Biplane.
Among the comparatively new biplanes is one constructed by Willard F.
Cody, of London, Eng., the principal distinctive feature of which is an
automatic control which works independently of the hand levers. For the
other control a long lever carrying a steering wheel furnishes all the
necessary control movements, there being no footwork at all. The lever
is universally jointed and when moved fore and aft operates the two
ailerons as if they were one; when the shaft is rotated it moves the
tail as a whole. The horizontal tail component is immovable. When the
lever is moved from side to side it works not only the ailerons and
the independent elevators, but also through a peculiar arrangement, the
vertical rear rudder as well.
The spread of the planes is 46 feet 6 inches and the width 6 feet 6
inches. The ailerons jut out 1 foot 6 inches on each side of the machine
and are 13 feet 6 inches long. The cross-shaped tail is supported by an
outrigger composed of two long bamboos and of this the vertical plane
is 9 feet by 4 feet, while the horizontal plane is 8 feet by 4 feet. The
over-all length of the machine is 36 feet. The lifting surface is 857
square feet. It will weigh, with a pilot, 1,450 pounds. The distance
between the main planes is 8 feet 6 inches, which is a rather notable
feature in this flyer.
The propeller has a diameter of 11 feet and 2 inches with a 13-foot
6-inch pitch; it is driven at 560 revolutions by a chain, and the gear
reduction between the chain and propeller shaft is two to one.
The machine from elevator to tail plane bristles in original points. The
hump in the ribs has been cut away entirely, so that although the plane
is double surfaced, the surfaces are closest together at a point which
approximates the center of pressure. The plane is practically of two
stream-line forms, of which one is the continuation of the other.
This construction, claims the inventor, will give increased lift, and
decreased head resistance. The trials substantiate this, as the angle of
incidence in flying is only about one in twenty-six.
The ribs in the main planes are made of strips of silver spruce one-half
by one-half inch, while those in the ailerons are solid and one-fourth
inch thick. In the main planes the fabric is held down with thin wooden
fillets. Cody's planes are noted for their neatness, rigidity and
smoothness. Pegamoid fabric is used throughout.
Pressey Automatic Control.
Another ingenious system of automatic control has been perfected by Dr.
J. B. Pressey, of Newport News, Va. The aeroplane is equipped with a
manually operated, vertical rudder, (3), at the stern, and a horizontal,
manually operated, front control, (4), in front. At the ends of the main
plane, and about midway between the upper and lower sections thereof,
there are supplemental planes, (5).
In connection with these supplemental planes (5), there is employed a
gravity influenced weight, the aviator in his seat, for holding them in
a horizontal, or substantially horizontal, position when the main plane
is traveling on an even keel; and for causing them to tip when the main
plane dips laterally, to port or starboard, the planes (5) having
a lifting effect upon the depressed end of the main plane, and a
depressing effect upon the lifted end of the main plane, so as to
correct such lateral dip of the main plane, and restore it to an even
keel. To the forward, upper edge of planes (5) connection is made by
means of rod (13) to one arm of a bellcrank lever, (14) the latter being
pivotally mounted upon a fore and aft pin (15), supported from the main
plane; and the other arms of the port and starboard bellcrank levers
(16), are connected by rod (17), which has an eye (18), for receiving
the segmental rod (19), secured to and projecting from cross bar on seat
supporting yoke (7). When, therefore, the main plane tips downwardly on
the starboard side, the rod (17) will be moved bodily to starboard, and
the starboard balancing plane (5) will be inclined so as to raise its
forward edge and depress its rear edge, while, at the same time, the
port balancing plane (5), will be inclined so as to depress its forward
edge, and raise its rear edge, thereby causing the starboard balancing
plane to exert a lifting effect, and the port balancing plane to exert a
depressing effect upon the main plane, with the result of restoring the
main plane to an even keel, at which time the balancing planes (5), will
have resumed their normal, horizontal position.
When the main plane dips downwardly on the port side, a reverse action
takes place, with the like result of restoring the main plane to an even
keel. In order to correct forward and aft dip of the main plane, fore
and aft balancing planes (20) and (23) are provided. These planes are
carried by transverse rock shafts, which may be pivotally mounted in
any suitable way, upon structures carried by main plane. In the present
instance, the forward balancing plane is pivotally mounted in extensions
(21) of the frame (22) which carries the forward, manually operated,
horizontal ascending and descending plane
It is absolutely necessary, in making a turn with an aeroplane, if that
turn is to be made in safety, that the main plane shall be inclined, or
"banked," to a degree proportional to the radius of the curve and to the
speed of the aeroplane. Each different curve, at the same speed, demands
a different inclination, as is also demanded by each variation in speed
in rounding like curves. This invention gives the desired result with
absolute certainty.
The Sellers' Multiplane.
Another innovation is a multiplane, or four-surfaced machine, built and
operated by M. B. Sellers, formerly of Grahn, Ky., but now located at
Norwood, Ga. Aside from the use of four sustaining surfaces, the novelty
in the Sellers machine lies in the fact that it is operated successfully
with an 8 h. p. motor, which is the smallest yet used in actual flight.
In describing his work, Mr. Sellers says his purpose has been to develop
the efficiency of the surfaces to a point where flight may be obtained
with the minimum of power and, judging by the results accomplished,
he has succeeded. In a letter written to the authors of this book, Mr.
Sellers says:
"I dislike having my machine called a quadruplane, because the number of
planes is immaterial; the distinctive feature being the arrangement
of the planes in steps; a better name would be step aeroplane, or step
plane.
"The machine as patented, comprises two or more planes arranged in step
form, the highest being in front. The machine I am now using has four
planes 3 ft. x 18 ft.; total about 200 square feet; camber (arch) 1 in
16.
"The vertical keel is for lateral stability; the rudder for direction.
This is the first machine (so far as I know) to have a combination
of wheels and runners or skids (Oct. 1908). The wheels rise up
automatically when the machine leaves the ground, so that it may alight
on the runners.
"A Duthirt & Chalmers 2-cylinder opposed, 3 1/8-inch engine was used
first, and several hundred short flights were made. The engine gave
four brake h. p., which was barely sufficient for continued flight. The
aeroplane complete with this engine weighed 78 pounds. The engine now
used is a Bates 3 5/8-inch, 2-cylinder opposed, showing 8 h. p., and
apparently giving plenty of power. The weight of aeroplane with this
engine is now 110 pounds. Owing to poor grounds only short flights have
been made, the longest to date (Dec. 31, 1910) being about 1,000 feet.
"In building the present machine, my object was to produce a safe, slow,
light, and small h. p. aeroplane, a purpose which I have accomplished."
CHAPTER XXVII. 1911 AEROPLANE RECORDS.
THE WORLD AT LARGE.
Greatest Speed Per Hour, Whatever Length of Flight, Aviator Alone--E.
Nieuport, Mourmelon, France, June 21, Nieuport Machine, 82.72 miles;
with one passenger, E. Nieuport, Moumlelon, France, June 12, Nieuport
Machine, 67.11 miles; with two passengers, E. Nieuport, Mourmelon,
France, March 9, Nieuport Machine, 63.91 miles; with three passengers,
G. Busson, Rheims, France, March 10, Deperdussin Machine, 59.84 miles;
with four passengers, G. Busson, Rheims, France, March 10, Deperdussin
Machine, 54.21 miles.
Greatest Distance Aviator Alone--G. Fourny, no stops, Buc, France,
September 2, M. Farman Machine, 447.01 miles; E. Helen, three stops,
Etampes, France, September 8, Nieuport Machine, 778.45 miles; with
one passenger, Lieut. Bier, Austria, October 2, Etrich Machine, 155.34
miles; with two passengers, Lieut. Bier, Austria, October 4, Etrich
Machine, 69.59 miles; with three passengers, G. Busson, Rheims, France,
March 10, Deperdussin Machine, 31.06 miles; with four passengers, G.
Busson, Rheims, France, March 10, Deperdussin Machine, 15.99 miles.
Greatest Duration Aviator Alone--G. Fourny, no stops, Buc, France,
September 2, M. Farman Machine, 11 hours, 1 minute, 29 seconds, E.
Helen, three stops, Etampes, France, September 8, Nieuport Machine, 14
hours, 7 minutes, 50 seconds, 13 hours, 17 minutes net time; with one
passenger, Suvelack, Johannisthal, Germany, December 8, 4 hours, 23
minutes; with two passengers, T. de W. Milling, Nassau Boulevard, New
York, September 26, Burgess-Wright Machine, 1 hour, 54 minutes, 42 3-5
seconds; with three passengers, Warchalowski, Wiener-Neustadt, Aust.,
October 30, 45 minutes, 46 seconds; with four passengers, G. Busson,
Rheims, France, March 10, Deperdussin Machine, 17 minutes, 28 1-5
seconds.
Greatest Altitude Aviator Alone--Garros, St. Malo, France, September
4, Bleriot Machine, 13,362 feet; with one passenger, Prevost, Courcy,
France, December 2, 9,840 feet; with two passengers, Lieut. Bier,
Austria, Etrich Machine, 4,010 feet.
AMERICAN RECORDS.
Greatest Speed Per Hour, Whatever Length of Flight, Aviator Alone--A.
Leblanc, Belmont Park, N. Y., October 29, Bleriot Machine, 67.87 miles;
with one passenger, C. Grahame-White, Squantum, Mass., September 4,
Nieuport Machine, 63.23 miles; with two passengers, T. O. M. Sopwith,
Chicago, Ill., August 15, Wright Machine, 34.96 miles.
Greatest Distance Aviator Alone--St. Croix Johnstone, Mineola, N. Y.,
July 27, Moisant (Bleriot Type) Machine, 176.23 miles.
Greatest Duration Aviator Alone--Howard W. Gill, Kinloch, Mo., October
19, Wright Machine, 4 hours, 16 minutes, 35 seconds; with one passenger,
G. W. Beatty, Chicago, Ill., August 19, Wright Machine, 3 hours, 42
minutes, 22 1-5 seconds; with two passengers, T. de W. Milling, Nassau
Boulevard, N. Y., September 26, Burgess-Wright Machine, 1 hour, 54
minutes, 42 3-5 seconds.
Greatest Altitude Aviator Alone--L. Beachy, Chicago, Ill., August 20,
Curtiss Machine, 11,642 feet; with one passenger, C. Grahame-White,
Nassau Boulevard, N. Y., September 30, Nieuport Machine, 3,347 feet.
Weight Carrying--P. O. Parmelee, Chicago, III., August 19, Wright
Machine, 458 lbs.
AVIATION DEVELOPMENT.
The wonderful progress made in the science of aviation during the
year 1911 far surpasses any twelve months' advancement recorded. The
advancement has not been confined to any country or continent, since
every part of the world is taking its part in aviation history making.
The rapidly increasing interest in aviation has brought forth schools
for the instruction of flying in both the old and new world, and
licensed air pilots before they receive their sanctions from the
governing aero clubs of their country are required to pass an extremely
trying examination in actual flights. Exhibition flights and races
were common in all parts of the world during 1911, and touring aviators
visited India, China, Japan, South Africa, Australia and South America,
giving exhibitions and instruction.
Europe was the scene of a number of cross-country races in which entries
ranging from ten to twenty aviators flew from city to city around a
given circuit, which in some instances exceeded 1,000 miles in distance.
Cross-country flights with and without passengers became so common that
those of less than two hours' duration attracted little attention.
There were fewer attempts at high altitude soaring, although the world's
record in this department of aviation was bettered several times. In
place of these high flights, the aviators devoted more attention to
speed, duration and spectacular manoeuvres, which appeared to satisfy
the spectators. The prize money won during 1911 exceeded $1,000,000, but
owing to the increased number of aviators the individual winnings were
not as large as in 1910.
It is estimated that within the past twelve months more than 300,000
miles have been covered in aeroplane flights and more than seven
thousand persons, classed either as aviators or passengers, taken up
into the air. The aeroplane of today ranges through monoplane, biplane,
triplane and even quadraplane, and more than two hundred types of these
machines are in use.
Aeroplanes are becoming a factor of international commerce. The records
of the Bureau of Statistics show that more than $50,000 worth of
aeroplanes were imported into, and exported from, the United States in
the months of July, August and September, 1911. The Bureau of Statistics
only began the maintenance of a separate record of this comparatively
new article of commerce with the opening of the fiscal year 1911-12.
Two of the prominent developments of 1911 were the introduction of
the hydro-aeroplane and the motorless glider experiments of the
Wright brothers at Killdevil Hills, N. C., where during the two weeks'
experiments numerous flights with and against the wind were made,
culminating in the establishing of a record by Orville Wright on October
25, 1911, when in a 52-mile per hour blow he reached an elevation of 225
feet and remained in the air 10 minutes and 34 seconds. The search
for the secret of automatic stability still continues, and though some
remarkable progress has been made the solution has not yet been reached.
NOTABLE CROSS-COUNTRY FLIGHTS OF 1911.
One of the important features of 1911 in aviation was the rapid increase
in the number and distance of cross-country flights made either for the
purpose of exhibition, testing, instruction or pleasure. Flights between
cities in almost every country of the world became common occurrences.
So great was the number that only those of more than ordinary importance
because of speed, distance or duration are recorded. The flights of
Harry N. Atwood from Boston to Washington and from St. Louis to New
York, and C. P. Rodgers from New York to Los Angeles were the most
important events of the kind in this country. The St Louis to New York
flight was a distance by air route, 1,266 miles. Duration of flight, 12
days. Net flying time, 28 hours 53 minutes. Average daily flight, 105.5
miles. Average speed, 43.9 miles per hour.
Transcontinental Flight of Calbraith P. Rodgers.--All world records
for cross-country flying were broken during the New York to Los Angeles
flight of Calbraith P. Rodgers, who left Sheepshead Bay, N. Y., on
Sunday, September 17, 1911, and completed his flight to the Pacific
Coast on Sunday, November 5, at Pasadena, Cal. Rodgers flew a Wright
biplane, and during his long trip the machine was repeatedly repaired,
so great was the strain of the long journey in the air. Rodgers is
estimated to have covered 4,231 miles, although the actual route as
mapped out was but 4,017 miles. Elapsed time to Pasadena, Cal., 49 days;
actual time in the air, 4,924 minutes, equivalent to 3 days 10 hours 4
minutes; average speed approximating 51 miles per hour. Rodgers' longest
flight in one day was from Sanderson to Sierra Blanca, Texas, on October
28, when he covered 231 miles. On November 12, Rodgers fell at Compton,
Cal., and was badly injured, causing a delay of 28 days.
European Circuit Race.--Started from Paris on June 18, 1911. Distance,
1,073 miles, via Paris to Liege; Liege to Spa to Liege; Liege to
Utrecht, Holland; Utrecht to Brussels, Belgium; Brussels to Roubaix;
Roubaix to Calais; Calais to London; London to Calais and Calais to
Paris. Three aeronauts were killed either at the start or shortly after
the race was in progress. They were Capt. Princetau, M. Le Martin and
M. Lendron. Three others were injured by falls. Seven hundred thousand
spectators witnessed the start from the aviation field at Vincennes,
near Paris. There were more than forty starters, of which eight
finished. The winner, Lieut. Jean Conneau, who flies under the name of
"Andre Beaumont," completed the circuit on July 7; his actual net flying
time for the distance being 58h. 38m. 4-5s.
Circuit of England Race--1,010 Miles in Five Sections.--
Start, July 22. Finish, July 26. Prize, $50,000. Twenty-eight entries
and eighteen starters. Seventeen finished the first section from
Brooklands to Hendon, a distance of twenty miles. Five reached
Edinburgh, the second section, a distance of 343 miles, and four
completed the entire circuit.
Paris to Madrid Race.--This race was started at the Paris aviation
held at Issy-les-Moulineaux on Sunday, May 21. There were twenty-one
entrants, and fully 300,000 spectators gathered to witness the initial
flight of the aerial races. The race was divided into three stages as
follows: Paris to Angouleme, 248 miles; Angouleme to St. Sebastian, 208
miles, and from St. Sebastian to Madrid, 386 miles, a total distance
of 842 miles. After three of the entrants had safely left the field,
Aviator Train lost control of his plane, and in falling struck and
killed M. Berteaux, the French Minister of War, and seriously injured
Premier Monis. The accident caused the withdrawal of all but six of the
original entrants, and of these but one finished. The race called for
a flight over the Pyrenees Mountains, and Vedrines, the winner, had to
rise to a height of more than 7,000 feet to pass the mountain barrier
near Somosierra Pass. Both Vedrines and Gibert, another competitor, were
attacked by eagles during the latter stages of the flight. Vedrines,
who started from Paris on Monday, May 22, finished the long and perilous
race at 8:06 a. m. Friday, May 26. Vedrines net flying time, all
controls and enforced stops subtracted, was 14h. 55m. 18s. The various
prizes to the winner aggregated $30,000.
The Paris-Rome-Turin Race.--The conditions of this race called for a
flight between the cities of Paris, Rome and Turin, covering a distance
of 1,300 miles. The aviators were permitted by the rules to alight
whenever and wherever they desired and the time limit was set from
May 28 to June 15. A prize of $100,000 was offered the winner, but the
contest was never finished, as one after another the aviators dropped
out until Frey fell near Roncigilione, France, breaking both arms and
legs and unofficially ending the contest. There were twenty-one entries
and twelve actual starters.
International Speed Cup Race.--The third annual international James
Gordon Bennett speed cup race was held at Eastchurch, England, on July
1, 1911, and for the second time was won by an American aviator, C. T.
Weymann, in a French racing aeroplane. The distance was 150 kilometres
equivalent to 94 miles, and the winner's time of 1h. 11m. 36s. showed an
average speed of 78.77 miles per hour. The first race was held in 1909
and was won by Glenn Curtiss, who flew the twenty kilometres (12.4
miles) in 15 minutes 50 2-5 seconds at an average speed of 47 miles per
hour. In 1910 the winner was Grahame-White, who covered 100 kilometres
(62 miles) at Belmont Park, L. I., in 60 minutes 47 3-5 seconds, an
average speed of 61.3 miles per hour. In the 1911 race there were six
starters: three from France, two from Great Britain and one from the
United States.
Milan to Turin to Milan Race.--This race which was started from Milan,
Italy, on October 29, was restricted to Italian aviators and had six
starters. The distance was approximately 177 miles and won by Manissero
in a Bleriot machine in 3h. 16m. 2 4-5s.
New York to Philadelphia Race.--The first intercity aeroplane race ever
held in the United States was started from New York City on August
5, and finished in Philadelphia the same day. The prize of $5,000 was
offered by a commercial concern with stores in the two cities: Three
entrants competed from the Curtiss Exhibition Company. The distance was
approximately 83 miles and won by L. Beachey in a Curtiss machine in 1h.
50m. at an average speed of 45 miles per hour.
Tri-State Race.--The tri-state race was the feature event of the Harvard
Aviation Society meet held at Squantum, Mass., August 26 to September
6. It was held Labor Day, September 4, over a course of 174 miles, from
Boston to Nashua to Worcester to Providence to Boston. Four competitors
started, of which two finished, the winner, E. Ovington, in a Bleriot
machine. Ovington's net flying time, 3h. 6m. 22 1-5s. Winner's prize,
$10,000.
AEROPLANES AND DIRIGIBLE BALLOONS IN WARFARE.
Wonderful progress has been made in the development of the aeroplane in
this country and in Europe since 1903, and within the last two or three
years the leading powers of the world have entered upon extensive tests
and experiments to determine its availability and usefulness in land and
naval warfare.
At the present time all the great powers are building or purchasing
aeroplanes on an extensive scale. They have established government
schools for the instruction of their army and navy officers and for
experimental work. So-called "Airship Fleets" have been constructed and
placed in commission as auxiliaries to the armies and navies. The fleets
of France and Germany are about equal and are larger by far than those
of any of the other powers. The length of the dirigibles composing these
fleets runs from 150 to 500 feet; they are equipped with engines of from
50 to 500 horse-power, with a rate of speed ranging from 20 to 30 miles
per hour. Their approximate range is from 200 to 900 miles; the longest
actual run (made by the Zeppelin II, Germany) is 800 miles.
A British naval airship, one of the largest yet built, was completed
last summer. It has cost over $200,000, and it was in course of
designing and construction two years. It is 510 feet long; can carry 22
persons, and has a lift of 21 tons.
The relative value of the dirigible balloon and the aeroplane in actual
war is yet to be determined. The dirigible is considered to be the
safer, yet several large balloons of this class in Germany and France
have met with disaster, involving loss of lives. The capacity of the
dirigible for longer flights and its superior facilities for carrying
apparatus and operators for wireless telegraphy are distinct advantages.
There has not yet been much opportunity to test the airship in actual
warfare. The aeroplane has been used by the Italians in Tripoli for
scouting and reconnoitering and is said to have justified expectations.
On several occasions the Italian military aviators followed the
movements of the enemy, in one instance as far as forty miles inland. At
the time of the attack by the Turks a skillful aeroplane reconnaissance
revealed the approach of a large Turkish force, believed to be at the
time sixty miles away in the mountains.
Aeroplanes and airships, as they exist today, would doubtless render
very valuable service in a time of war, both over land and water, in
scouting, reconnoitering, carrying dispatches, and as some experts
believe, in locating submarines and mines placed by the enemy in
channels of exits from ports. A "coast aeroplane" could fly out 30 or 40
miles from land, and rising to a great height, descry any hostile ships
on the distant horizon, observe their number, strength, formation and
direction, and return within two hours with a report to obtain which
would require several swift torpedo-boat destroyers and a much greater
time. The question as to whether it would be practicable to bombard an
enemy on land or sea with explosive bombs dropped or discharged from
flying machines or airships, is one which is much discussed but hardly
yet determined.
Aeroplanes have been constructed with floats in the place of runners and
several attempts have been made, in some cases successfully, to light
with them on and to rise from the water. Mr. Curtiss did this at San
Francisco, in January, 1911. Attempts have also been made with the
aeroplane to alight on and to take flight from the deck of a warship.
Toward the end of 1910 Aviator Ely flew to land from the cruiser
Birmingham, and in January, 1911, he flew from land and alighted on the
cruiser Pennsylvania. But in these cases special arrangements were made
which would be hardly practicable in a time of actual war.
In November, 1911, a test was made at Newport, R. I., by Lieut. Rodgers,
of the navy, of a "hydro-areoplane" as an auxiliary to a battleship. The
idea of the test was to alight alongside of the ship, hoist the machine
aboard, put out to sea and launch the machine again with the use of a
crane. Lieut. Rodgers came down smoothly alongside the Ohio, his machine
was easily drawn aboard with a crane, and the Ohio steamed down to
the open sea, where it was blowing half a gale. But, owing to the
misjudgment of the ship's headway, one of the wings of the machine when
it struck the water after being released from the crane, went under the
water and was snapped off. Lieut. Rodgers was convinced that this method
was too risky and that some other must be devised.
CHAPTER XXVIII. GLOSSARY OF AERONAUTICAL TERMS.
Aerodrome.--Literally a machine that runs in the air. Aerofoil.--The
advancing transverse section of an aeroplane.
Aeroplane.--A flying machine of the glider pattern, used in
contra-distinction to a dirigible balloon.
Aeronaut.--A person who travels in the air.
Aerostat.--A machine sustaining weight in the air. A balloon is an
aerostat.
Aerostatic.--Pertaining to suspension in the air; the art of aerial
navigation.
Ailerons.--Small stabilizing planes attached to the main planes to
assist in preserving equilibrium.
Angle of Incidence.--Angle formed by making comparison with a
perpendicular line or body.
Angle of Inclination.--Angle at which a flying machine rises. This
angle, like that of incidence, is obtained by comparison with an
upright, or perpendicular line.
Auxiliary Planes.--Minor plane surfaces, used in conjunction with the
main planes for stabilizing purposes.
Biplane.--A flying-machine of the glider type with two surface planes.
Blade Twist.--The angle of twist or curvature on a propeller blade.
Cambered.--Curve or arch in plane, or wing from port to starboard.
Chassis.--The under framework of a flying machine; the framework of the
lower plane.
Control.--System by which the rudders and stabilizing planes are
manipulated.
Dihedral.--Having two sides and set at an angle, like dihedral planes,
or dihedral propeller blades.
Dirigible.--Obedient to a rudder; something that may be steered or
directed.
Helicopter.--Flying machine the lifting power of which is furnished by
vertical propellers.
Lateral Curvature.--Parabolic form in a transverse direction.
Lateral Equilibrium or Stability.--Maintenance of the machine on an even
keel transversely. If the lateral equilibrium is perfect the extreme
ends of the machine will be on a dead level.
Longitudinal Equilibrium or Stability.--Maintenance of the machine on an
even keel from front to rear.
Monoplane.--Flying machine with one supporting, or surface plane.
Multiplane.--Flying machine with more than three surface planes.
Ornithopter.--Flying machine with movable bird-like wings.
Parabolic Curves.--Having the form of a parabola--a conic section.
Pitch of Propeller Blade.--See "Twist."
Ribs.--The pieces over which the cloth covering is stretched.
Spread.--The distance from end to end of the main surface; the
transverse dimension.
Stanchions.--Upright pieces connecting the upper and lower frames.
Struts.--The pieces which hold together longitudinally the main frame
beams.
Superposed.--Placed one over another.
Surface Area.--The amount of cloth-covered supporting surface which
furnishes the sustaining quality.
Sustentation.--Suspension in the air. Power of sustentation; the quality
of sustaining a weight in the air.
Triplane.--Flying machine with three surface planes.
Thrust of Propeller.--Power with which the blades displace the air.
Width.--The distance from the front to the rear edge of a flying
machine.
Wind Pressure.--The force exerted by the wind when a body is moving
against it. There is always more or less wind pressure, even in a calm.
Wing Tips.--The extreme ends of the main surface planes. Sometimes these
are movable parts of the main planes, and sometimes separate auxiliary
planes.
Footnotes:
[Footnote 1: Now dead.]
[Footnote 2: Aeronautics.]
[Footnote 3: See Chapter XXV.]
[Footnote 4: The Wrights' new machine weighs only 900 pounds.]
[Footnote 5: Aeronautics.]
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