Transcriber’s Note
Some spellings have been left as is e.g. Wavrille/Waville
Hyphenations have been standardised.
Changes made are noted at the end of the book.
AIRCRAFT
[Illustration:
_Courtesy of Aerial Age Weekly._
The NC-4 flying-boat, showing the arrangement of the motors.
It is equipped with four Liberty 450 h.-p. engines. It flew
from Rockaway, New York, to Plymouth, England, commanded by
Lieutenant-Commander A. C. Read, U. S. N.]
AIRCRAFT
ITS DEVELOPMENT IN WAR AND PEACE AND
ITS COMMERCIAL FUTURE
BY
EVAN JOHN DAVID
ASSOCIATE EDITOR OF “FLYING”
FULLY ILLUSTRATED
NEW YORK
CHARLES SCRIBNER’S SONS
1919
COPYRIGHT, 1919, BY
CHARLES SCRIBNER’S SONS
Copyright, 1919, by the CURTIS PUBLISHING CO.
Published September, 1919
[Illustration]
TO
ALL WHO HELPED ME TO OBTAIN
AN EDUCATION
PREFACE
The object of this book is to explain the fundamental principles
of aeronautics and to point out the historic development of both
the heavier-than-air and the lighter-than-air craft. The treatment
is simple. Technical phrases have been avoided wherever possible.
Emphasis has been laid on the changes in the design or construction
of aeroplanes and dirigibles, which show the evolution of flight and
aircraft from early experiments with balloons and gliders to the
transatlantic flights of the NC-4, the Vickers “Vimy” Bomber, and the
R-34. Only those things have been singled out which indicated a step
forward in the science of aeronautics. Emphasis is placed upon the
commercial accomplishments of the aeroplane and the dirigible, and
many of the present uses and future possibilities of aircraft as a
commercial vehicle have been pointed out.
I am indebted to many sources for the information contained herein.
Mr. Henry Woodhouse, the well-known aeronautical authority and editor
of _Flying Magazine_ and author of the text-books on military and
naval aeronautics, has been the source of much of my information, and
the volumes of _Flying Magazine_ have supplied me with much historic
data. _Aerial Age Weekly_ and Mr. G. Douglas Wardrop, the managing
editor, have also been very helpful. The British periodicals _Flight_,
_The Aeroplane_, and _Aeronautics_ have furnished me with many facts
regarding British aircraft. The articles of Mr. C. G. Grey, the editor
of _The Aeroplane_, dealing with the growth of heavier-than-air
machines, and of Mr. W. L. Wade on lighter-than-air craft, have been
the source of many of the facts regarding the evolution of aircraft.
Many other aeronautical authorities have afforded statistics, facts,
etc.
EVAN JOHN DAVID.
NEW YORK, August 12.
CONTENTS
CHAPTER PAGE
I. THE FIRST BALLOONS 1
THE DEVELOPMENT OF THE FREE BALLOON—THE
CAPTIVE BALLOON—THE DIRIGIBLE—THE BLIMP—THE
KITE BALLOON.
II. THE AEROPLANE 13
EXPERIMENTS WITH PLANES—LILLIENTHAL’S
GLIDER—LANGLEY’S AERODROME—SUCCESS OF
THE WRIGHTS—FIRST AEROPLANE FLIGHTS.
III. WHY AN AEROPLANE FLIES 25
THE HELICOPTER—THE ORNITHOPTER—WING
SURFACE—FLYING SPEED—LANDING SPEED—EFFECT
OF MOTORS—THE SEAPLANE.
IV. LEARNING TO FLY 34
EARLY METHODS—DEVELOPMENT OF SCHOOLS—STUDYING
STRUCTURE OF PLANES, MOTORS,
THEORY OF FLIGHT, AERODYNAMICS, MAP READING—FRENCH
SYSTEM—GOSPORT SYSTEM.
V. AEROPLANE DEVELOPMENT, 1903 TO 1918 47
ADER’S EXPERIMENTS—MAXIM’S MULTIPLANE—DUMONT’S
AEROPLANE—WRIGHTS’ 1908 PLANE—VOISIN
PUSHER—BLERIOT’S MONOPLANE—AVRO
TRIPLANE—FARMAN’S AILERONS—OTHER TYPES.
VI. DEVELOPMENT OF THE AEROPLANE FOR WAR PURPOSES 67
GERMAN AERIAL PREPAREDNESS—PRIZES GIVEN
FOR AERONAUTICS BY VARIOUS GOVERNMENTS—FIRST
USE OF PLANES IN WAR—FIRST AIRCRAFT
ARMAMENT.
VII. DEVELOPMENT OF THE LIBERTY AND OTHER
MOTORS 76
DEBATE IN REGARD TO ORIGIN OF LIBERTY MOTOR—LIBERTY-ENGINE
CONFERENCE, DESIGN, AND
TEST—MAKERS OF PARTS—HISPANO-SUIZA MOTOR—ROLLS-ROYCE—OTHER
MOTORS.
VIII. GROWTH OF AIRCRAFT MANUFACTURING IN
UNITED STATES 94
THE 1912 EXPOSITION—THE FIRST PAN-AMERICAN
EXPOSITION—THE MANUFACTURERS AIRCRAFT
EXPOSITION—DESCRIPTIONS OF EXHIBITORS—GROWTH
OF AIRCRAFT FACTORIES—NAVAL
AIRCRAFT FACTORY.
IX. THE DEVELOPMENT OF THE AERO MAIL 134
FIRST MAIL CARRIED BY AIRCRAFT—NEW
YORK—PHILADELPHIA—WASHINGTON SERVICE—NEW
YORK—CLEVELAND—CHICAGO SERVICE—FOREIGN
AERO MAIL ROUTES.
X. KINDS OF FLYING 151
NIGHT FLYING—FORMATION FLYING—STUNTING—IMMELMAN
TURN—NOSE DIVING—TAIL SPINNING—BARREL—FALLING
LEAF, ETC.
XI. AERIAL NAVIGATION 161
ATMOSPHERIC CONDITIONS—WINDS AND THEIR
WAYS—CLOUD FORMATIONS, NAMES, AND ALTITUDES.
XII. COMMERCIAL FLYING 169
BUSINESS POSSIBILITIES OF THE AEROPLANE—SOME
CELEBRATED AIR RECORDS—GERMANY’S
INITIAL ADVANTAGE—A HUGE INVESTMENT—CAUSES
OF ACCIDENTS—DISCOMFORTS OVERCOME—INEXPENSIVE
FLYABOUTS—THE SPORTS TYPE—ARCTIC-FLIGHT—NO
EAST OR WEST.
XIII. THE COMMERCIAL ZEPPELIN 203
THE AMBITION OF THE AGES REALIZED—A GIANT
GERMAN DIRIGIBLE—ZEPPELIN ACCOMPLISHMENTS—HIGH
COST OF ZEPPELINS—SAFETY OF
TRAVEL—SOME BRITISH PREDICTIONS—THE FUTURE
OF HELIUM—THE LIFE-BLOOD OF COMMERCE.
XIV. THE REGULATION OF AIR TRAFFIC 235
IMPORTANCE OF SAME—LAWS FORMED BY BRITISH
AERIAL TRANSPORT COMMITTEE LIKELY TO
BE BASES OF INTERNATIONAL AERIAL LAWS—COPY
OF SAME.
XV. THE TRANS-ATLANTIC FLIGHT 251
THE NC’S—THE LOSS OF THE C-5—READ’S STORY—BELLINGER’S
STORY—THE GREAT NAVAL
FLIGHT—HAWKER’S STORY—ALCOCK’S STORY—TO
AND FROM AMERICA—THE R-34.
APPENDIX I 327
UNITED STATES AIRCRAFT AND ENGINE PRODUCTION
FOR THE UNITED STATES AIR SERVICE.
APPENDIX II 354
RECORDS OF ALLIED AND ENEMY ACES WITH
NUMBER OF PLANES BROUGHT DOWN.
APPENDIX III 362
NOMENCLATURE FOR AERONAUTICS.
ILLUSTRATIONS
The NC-4 flying-boat, showing the arrangement of the
motors _Frontispiece_
FACING PAGE
Observation balloon about to ascend 10
The Wright flyer after the epoch-making flight at Kitty
Hawk, N. C., December, 1903 20
A Shortt “pusher” seaplane equipped with a one-and-a-half-pounder
gun 32
British-built Curtiss flying boat, at Brighton, England 32
The Farman “Goliath” contrasted with a Farman “Mosquito” 56
The huge four-motored Handley Page bomber 64
The Martin bomber 84
The pathfinding aerial mail flight, New York-Cleveland-Chicago 144
The reconstructed De Haviland biplane, showing the
limousine accommodations for passengers 146
Diagrams showing an “aerial skid,” “tail slide,” and the
“spinning dive” 154
The so-called “Immelman turn” 156
Diagrams illustrating the reversal of position effected by
a “loop” and the execution of the so-called “Immelman turn” 158
Interior view of the Graham White twenty-four-seater
aeroplane in flight 170
The Vickers-“Vimy” bomber 200
The C-5 leaving its hangar at Montauk Point en route to
accompany the NC’s on their trans-Atlantic flight 202
The R-34, the British rigid dirigible 222
AIRCRAFT
CHAPTER I
THE FIRST BALLOONS
THE DEVELOPMENT OF THE FREE BALLOON—THE CAPTIVE BALLOON—THE
DIRIGIBLE—THE BLIMP—THE KITE BALLOON
Ever since man first noticed the flight of a bird through the air he
has longed to fly. How often, during the countless ages of unrecorded
time, he attempted to soar above the earth we cannot know. That he
tried often and failed always we have ample proof; indeed, the phrase,
“might as well try to fly,” expressed the acme of the impossible.
That many scientific men for nearly two thousand years believed that
eventually a mechanical means could be devised to lift man off the
ground like the wings of a bird and to propel him through the air, we
have evidence in their writings and the history of their lives.
Ancient mythology is full of stories of the heroes who attempted to
imitate the flight of the fowls of the air. The earliest efforts of the
aeronauts themselves appear to have been along this line. Naturally
many of the experimenters lost their lives. A mere enumeration of their
names would take too much space for this volume.
Perhaps these struggles to use wings suggested to the tight-rope walker
Allard the possibility of performing a novel stunt. At any rate, in
1660 he successfully made several glides for exhibition purposes in
France. Seventeen years later another Frenchman named Bosnier also made
spectacular glides. These experiments, however, led to the invention
of the glider, which finally developed into the aeroplane or the
heavier-than-air machine.
A glider consists of a rigid rectangular plane constructed of frail
framework, similar to a kite, and covered with linen or cloth,
much like the wing of a modern aeroplane. This plane surface might
be a dozen or more feet long and two or more feet wide. The early
experimenters jumped off hills with this plane fastened to their arms
or shoulders, and balancing themselves in the centre, glided several
feet over the ground, keeping their equilibrium by means of their feet.
Later two planes fastened together like a box-kite were employed, with
the flier stretched out on his stomach on the lower planes. Lillienthal
and even the Wright brothers learned most about longitudinal and
lateral balance by gliding on gliders of the last type. A great deal of
sport can be had with these man-carrying kites even to-day.
The experiments of the two French brothers, Joseph and Jacques
Montgolfier, with paper bags inflated with hot air started a new period
of development in aeronautics, for the paper bags suggested the silk
ones, which were, of course, much lighter. On September 19, 1783, they
gave an exhibition before the royal family at Versailles.
The authors of the first ascension, the first actual step in the
conquest of the air, were two Frenchmen, Marquis d’Arlandes and Pilâtre
de Roziers, who made the first ascension near Paris on November 21,
1783. From that time on free ballooning became a very popular sport.
The escaping of the hot air or gas, forcing the balloon to descend
too suddenly, led to the invention of the parachute as a means of
descending slowly from the collapsing bag. The possibility of using
this type of balloon for observation purposes was realized by the
French, and the first recorded battle that the captive balloon was
employed in was at Fleurus June 26, 1794, thus supplying “aerial eyes”
for the French army to observe the movements of the Austrians.
The free balloon was, however, entirely at the mercy of the winds,
and the captive balloon could not be moved about readily, so that it
was thus limited in its sphere of observation, except when attached
to some movable conveyance. This showed the necessity of inventing
some means of propulsion and steering. The first experiments were
attempts to row ordinary spherical balloons, as you would a boat, but
the earliest record of any definite progress being achieved in forcing
a lighter-than-air craft through the air was the experiment in France
of two brothers named Robert in 1784. They constructed a melon-shaped
balloon, 52 feet long and 32 feet in diameter, made of proofed silk.
The gas employed was pure hydrogen. Underneath this envelope was
suspended a long, narrow car, in general idea not unlike that used on
some modern airships; and three pairs of oars with blades made like
racquet-frames covered with silk, and a rudder of similar material,
were the only implements for navigation.
The two brothers and their brother-in-law went up in the apparatus and
succeeded in describing a curve of one kilometre radius, which showed,
at any rate, that they could deviate slightly from the direction of the
feeble wind then prevailing.
The development of the steam-engine was potent with suggestions for
aerial navigation of a dirigible. Thus, on December 24, 1852, Henry
Gifford, another Frenchman, first ascended in a dirigible balloon.
It was spindle-shaped, 143 feet long and 39 feet in diameter. It was
driven by a 3 horse-power steam-engine and an 11-foot screw propeller.
He went out from the Hippodrome in Paris and made six miles per hour
relative to the air and several successful landings. This was the first
recorded dirigible flight.
A decade later, Tissandier, with a spindle-shaped balloon, much on
the lines of those of his predecessors, succeeded in reaching a
speed of eight miles an hour with the aid of an electric motor and a
bichromate-of-potash battery.
Captain Charles Renard brought the airship another stage toward
realization by building an envelope with a true stream-line. The method
of suspending the car was of the type adopted by later builders,
namely, to place an enormous sheet over the back of the airship and
to attach suspensory cords to its edges. This airship had a cubic
capacity of 66,000 feet, and was kept rigid by means of an internal
air balloonet or interior gas-bag which was confined to a definite
shape by an outer framework or cover. This balloonet was kept full by a
fan-blower coupled to the motor.
The car was 108 feet long, and really served as a spar employed in
later airships of what became known as the semirigid type.
An electric motor was installed, weighing 220 pounds, which developed 9
horse-power. The battery composed of chlorochromic salts, delivered one
shaft horse-power for each 88 pounds, and this great weight seriously
handicapped the performance of the airship. The first trials were made
in 1884, and apparently within the limits of its propulsive power the
airship was an unqualified success, so far as navigation was concerned.
On one occasion it flew around Paris at an average speed of 14½
miles an hour.
As early as 1872 Herr Hanlein, in Germany, built an airship of quite
reasonable proportions, propelled by a 6 horse-power Lenoir gas-engine.
Apparently the engine was run on gas from the envelope. A speed of 10
miles an hour or so was achieved.
In 1879 Baumgartner and Wolfert built an airship with a Daimler benzine
motor. An ascent was made at Leipzig in 1880, but owing to improper
load distribution the vessel got out of control and was smashed on the
ground.
The first rigid dirigible with aluminum framework was built by an
Austrian named Schwartz in 1897. This was the prototype of the
Zeppelin, and no practical rigid lighter-than-air ship could now be
lifted by hydrogen unless it had an aluminum framework.
The invention of the gasoline engine was another tremendous advantage
to the Zeppelin.
M. Santos Dumont built an extraordinary collection of small airships
during a period of several years commencing in 1898. His first effort
was a cylinder of varnished Japanese silk, 82½ feet long and 11
feet in diameter, with pointed ends, which gave it a capacity of about
6,300 cubic feet. It was fitted with the usual internal air balloonet
and a 3½ horse-power motor-cycle engine weighing 66 pounds. The
engine was fitted to an ordinary balloon basket, which hung beneath the
envelope and drove a two-blade propeller. The pilot also sat in the
basket. The poise of the vessel was controlled by shifting weights,
and steering was effected with a silk rudder stretched over a steel
frame. In September, 1898, this miniature airship left the Zoological
Gardens at Paris in the face of a gentle wind, and performed all sorts
of evolutions in the neighborhood.
M. Dumont’s No. 5 was fitted with a four-cylinder, air-cooled motor
driving an enormous propeller of 26 feet in diameter, which gave a
thrust of 120 pounds at 140 revolutions per minute. There is, however,
some difference between this number of revolutions and the 1,400 per
minute now generated by all the standard aeronautical motors. Among
other novelties water ballast was used and piano wires replaced the old
type suspension cords.
No account of the lighter-than-air machine would be complete without
mentioning the man after whom the Zeppelins were named. As a matter of
fact Count Zeppelin added nothing strikingly new to his airships—he
simply made them much larger than any of their predecessors; thus
increasing the net lifting power and multiplying the number of engines
and the horse-power.
Count Ferdinand von Zeppelin first began to experiment in 1898. His
first rigid dirigible was 410 feet and the gas-bags contained 400,000
cubic feet of hydrogen, and the net lifting power, after allowing for
the engines, fuel, gear, etc., was about two tons. The framework was
of aluminum latticework divided into seventeen compartments, fifteen
of which had gas-bags. Two cars were attached and in each was a 16
horse-power German Daimler gasoline motor driving two propellers,
and the machine gained a speed of 15 miles an hour, which was far in
advance of any airship of that period.
By this time practically all the fundamentals of construction of
dirigibles had been incorporated in these airships. Further refinements
were made, more engines and balloonets added, and the length of the
dirigible and the volume of hydrogen gas used for inflation was
increased, as was also the horse-power, but nothing more in the way of
radical changes was employed to the end of the Great War. Therefore
a description of the Zeppelin which was brought down in England will
serve as an excellent idea of the size of these mammoth airships.
The Zeppelin forced to land in Essex measured from 650 feet to 680
feet in length and measured 72 feet across its largest diameter.
The vessel was of the stream-line form, with a blunt, rounded nose,
and a tail that tapered off to a sharp point. The framework was made
of longitudinal latticework girders, connected together at intervals
by circumferential latticework ties, all made of an aluminum alloy
resembling duraluminum. The whole was braced together and stiffened by
a system of wires, arrangements being provided by which they could be
tightened up when required. The weight of the framework is reckoned to
be about 9 tons, or barely a fifth of the total of 50 tons attributed
to the airship complete with engines, fuel, guns, and crew. There were
24 balloonets arranged within the framework, and the hydrogen capacity
was 2,000,000 cubic feet.
A cat-walk, an arched passage with a footway nine inches wide, running
along the keel enabled the crew, which consisted of twenty-two men, to
move about the ship and get from one gondola to another. This footway
was covered with wood, a material which, however, was evidently avoided
as much as possible in the construction of the ship. The gondolas, made
of aluminum alloy, were four in number; one was placed forward on the
centre line, two were amidships, one on each side, and the fourth was
aft, again on the centre line.
The vessel was propelled—at a speed, it is thought, of about sixty
miles an hour in still air—by means of six Maybach-Mercedes gasoline
engines of 240 horse-power each, or 1,440 horse-power in all. Each had
six vertical cylinders with overhead valves and water cooling, and
weighed about 1,000 pounds. They were connected each to a propeller
shaft through a clutch and change-speed gear, and also to a dynamo
used either for lighting or for furnishing power to the wireless
installation. One of these engines with its propeller was placed at
the back of the large forward gondola, two were in the amidships
gondolas, and three were in the aft gondola. In the last case one of
the propellers was in the centre line of the ship, and the shafts of
the other two were stayed out, one on either side. With the object of
minimizing air resistance the stays were provided with a light but
strong casing of two or three ply wood, shaped in stream-line form.
The gasoline tanks had a capacity of 2,000 gallons, and the propeller
shafts were carried in ball bearings. The date, July 14, 1916, marked
on one of them, is thought to indicate the date of the launching or
commissioning of the vessel.
Forward of the engine-room of the forward gondola, but separated from
it by a small air space, was first the wireless operator’s cabin and
then the commander’s room. The latter was the navigating platform, and
in it were concentrated the controls of the elevators and rudder at
the stern, the arrangement for equalizing the levels in the gasoline
and water tanks, the engine-room telegraphs, and the switchboard of
the electrical gear for releasing the bombs. Provision was made for
carrying sixty of the latter in a compartment amidships, and there
was a sliding shutter, worked from the commander’s cabin, which was
withdrawn to allow them to fall freely. Nine machine-guns were carried.
Two of these, of 0.5-inch bore, were mounted on the top of the vessel,
and six of a smaller caliber were placed in the gondolas—two in the
forward, one each in the amidships ones, and two in the aft one. The
ninth was carried in the tail.
The separate gas-bags were a decided advantage over the free balloon
and earlier airships which carried all the gas in one compartment,
for if the latter sprang a leak for any reason it had to descend,
whereas the Zeppelin could keep afloat with several of the separate
compartments in a complete state of collapse.
Since the Zeppelin, like all airships, is buoyed up by hydrogen gas
which is .008 lighter than air, the dirigible was sent up by the simple
expedient of increasing the volume of gas in the envelope until the
vessel arose. This was done by releasing the gas for storage-tanks into
the gas-bags. In order to head the nose up, air was kept in certain
of the rear bags, thus making the tail heavier than the forward part,
which naturally rose first. Steering was done by means of the rudder or
the engines, or both, and the airship was kept on an even keel by use
of the lateral planes. The airship could be brought down by forcing the
gas out of the bags into the gas-tanks, thus decreasing the volume and
by increasing the air in the various compartments.
This airship had a flying radius of 800 miles and could climb to 12,000
feet, and could carry a useful load of four tons and could remain in
the air for fifty hours. Without a doubt it is one of the largest rigid
dirigibles ever built.
[Illustration:
_Courtesy of Flying Magazine._
Observation balloon about to ascend.
These balloons were stationed at intervals along the battle-fronts.]
Owing to the great amount of material used, the immense cost, and the
time necessary to construct a Zeppelin, under the urgent demands of
war, the British built and developed a small rigid dirigible measuring
between 200 and 250 feet in length, buoyed up by two balloonets,
one front and back, and carrying a fuselage and one aeromotor, and
propeller situated directly under the cigar-shaped airship. These
vessels made about fifty miles an hour, carried two men, were fitted
with wireless, and made excellent scouts over the North Sea and
waters contiguous to allied territory, looking for submarines. These
air-vessels were called Blimps.
The kite balloon was cigar-shaped and non-rigid, with only a basket
suspended underneath. It was attached to a rope and was lifted by the
gas and the wind which passed under the fins, which extended from the
sides near the rear. It combined the principle of the free balloon and
the man-lifting kites.
These balloons were used very extensively in the Great War for
observation purposes. Suspended at the end of a cable attached to a
donkey-engine or a windlass at an altitude of 3,000 feet, they afforded
the best observation for artillery-fire, and by means of the telephone
in the basket the observer could keep headquarters well informed of
troop movements within a radius of many miles.
Naturally it was the special delight of the aeroplanes to dive down on
these stationary balloons and by means of incendiary bullets to ignite
the gas. It was dangerous work for the heavier-than-air machines,
for all the way down the antiaircraft guns blazed away. It was also
dangerous work for the observers in the imprisoned balloon, who often
had to jump with their parachutes in order to escape.
Thus by 1918 man had devised an aircraft that could propel him through
the air faster than the eagle, farther than the sea-gull, and soar
aloft higher than the lark! No wonder he felt that no mechanical feat
was impossible.
CHAPTER II
THE AEROPLANE
EXPERIMENTS WITH PLANES—LILLIENTHAL’S GLIDER—LANGLEY’S
AERODROME—SUCCESS OF THE WRIGHTS—FIRST AEROPLANE FLIGHTS
The evolution of the heavier-than-air flying-machine, like that of the
lighter-than-air, covers a long period of time, and was fraught with
many difficulties and dangers. For ages many scientific men played with
the idea, but owing to the lack of motive power light enough to be
mounted on a glider yet supplying sufficient strength to drive a set
of planes through the air at 45 miles an hour, very little progress
was made until the perfection of the steam-engine and the development
of the gasoline motor. Indeed, such things as lateral and longitudinal
balance of planes, as well as steering by rudder, could only be worked
out to a successful conclusion by man-carrying gliders moving at a
sufficient velocity to keep them off the ground. Since no mechanical
device driven by man could supply this want, the science lacked
practical development until the last quarter of a century.
Perhaps the acrobatic tight-rope walker Allard, in 1660, was the first
to make long glides during an exhibition of his profession. But nothing
of material advantage to the science was accomplished.
In 1809 Sir George Cayley, an Englishman, planned an aeroplane with
oblique planes, resting on a wheeled chassis, fitted with propellers,
motors, and steering devices. The machine was never built.
In 1843 another Englishman, Samuel Henderson, designed and patented an
“aerial steam carriage,” which was to be an aeroplane of immense size
to be used for passenger carrying. Like the former it was never built.
M. Strongfellow, another Englishman, designed a triplane, which he
fitted with a tail and two propellers. A triplane differs from a
biplane only in that a third plane is superimposed over the second
plane at the same distance as the second plane was above the first or
monoplane. This model was shown at the exhibition of the Aeronautical
Society of Great Britain in 1868. As in the case of previous inventors,
nothing in this model indicated that he had any comprehension of
the principles of stability or knowledge of the lifting capacity of
surfaces, or the power required for dynamic flight.
In 1872 a French inventor, named Alphonse Penaud, constructed a
small monoplane. It was only a toy—two flimsy wings actuated by
a twisting rubber—but it had fore-and-aft stability. These model
aeroplanes, however, aided the science materially by demonstrating the
necessity for stability before planes could be steered through space.
Subsequently, in 1875, Penaud took out a patent on a monoplane fitted
with two propellers and having controlling devices. But this was
not built, principally because it would have required a light motor,
and the lightest available at that time weighed over 60 pounds per
horse-power. To-day most aeromotors weigh less than two pounds per
horse-power.
Louis Pierre Mouillard, a Frenchman, who had observed that large birds
in flight, while seeming at rest, could go forward against the wind
without a stroke of the wings, constructed a number of gliders built
on the principle of bird wings, and experimented with gliding. He
published a work called “L’Empire de l’Air,” which inspired many late
experiments with gliders.
The net results of all these designs and experiments of these inventors
demonstrated that thin, rigid surfaces of a certain shape, structure,
and design could support weights when driven through the air at a
sufficient velocity. Further than that they contributed practically
nothing to the science of aviation.
As a matter of fact, it was toward the close of the nineteenth century
before means were found to make an aeroplane rise from the ground,
maintain its equilibrium. These latter-day pioneers of aviation were
divided into two schools. The first sought to achieve soaring flights
by means of large kitelike apparatus, which enabled them to fly in the
air against winds, their machines being lifted up and supported by the
inertia of the air as kites are. The second sought to develop power
flight, that is, to send their kitelike machines through the air at
high speed, being tracted or propelled by revolving screws actuated by
motor power.
The most prominent experimenters of the first glider school were Otto
Lillienthal, a German, P. L. Pitcher, an Englishman, Octave Chanute,
and J. J. Montgomery.
Lillienthal was the first man to accomplish successful flights by
means of artificial wing surfaces. In 1894, after much experimenting,
he constructed rigid wings which he held to his shoulders. He used to
run down hills with them until the velocity he was moving at would
catch the air and lift him completely off the ground. By observation of
birds he saw that their wings were arched, which suggested reason for
failures of previous experiments in this line; so afterward his planes
were arched also. He was the first man to be lifted off the ground by
plane surfaces, and to demonstrate that arched surfaces were necessary
to sustained flight of heavier-than-air craft.
To the rigid wings Lillienthal fastened a rigid tail and this
constituted his glider. There were no control levers and the only way
he could steer was by shifting the balance, by use of his legs, in one
direction or another. By means of an artificial hill he had constructed
he could coast downward for some distance without striking the ground.
He was unfortunately killed in one of these experiments in 1896.
Chanute’s experiments in gliding were similar to Lillienthal’s, but
they were conducted on the sand-dunes along Lake Michigan, near
Chicago. His apparatus was more strongly constructed, of trussed
biplane type—a construction suggested to him by his experience
in bridge building, and one which persists to-day as the basis of
strength in our present military biplanes. In design it was similar to
a box kite, and it was the kind which the Wrights adopted for their
experiments.
The leaders of the second school were: Clement Ader (1890-97), Sir
Hiram Stevens Maxim (1890-94), and Samuel Pierpont Langley (1895-1903).
Clement Ader, the famous French scientist, under the auspices of the
French Government, conducted experiments from 1890 to 1897. In 1890
he filled his Arion, a boat-shaped machine with two propellers, with
a steam-engine, but the apparatus never flew. He finished his next
machine in 1897 after six years of hard work. It was large enough to
carry a man, but, like its predecessor, it never left the ground, and
the French Government refused to support his experiments further.
While Ader was making his experiments in France, Sir Hiram S. Maxim was
at work constructing a large multiplane for the English Government,
which he fitted with two steam-engines of 175 horse-power. But like
Ader’s experiments it toppled over at the first trial and was badly
damaged, and the British Government refused further backing.
The experience of Samuel Pierpont Langley in America is not unlike the
experience of Ader in France and Maxim in England. He was employed by
the Board of Ordnance and Fortification of the United States army to
construct the “Aerodrome” of his own invention. Congress appropriated
$50,000 for the purpose. Langley’s machine was a tandem monoplane, 48
feet from tip to tip, and 52 feet from bowsprit to the end of its tail.
It was fitted with a 50 horse-power engine and weighed 830 pounds.
The trials of this aerodrome, two attempts to launch it, were made on
October 7 and December 8, 1903. On both occasions the aerodrome became
entangled in the defective launching apparatus, and was thrown headlong
into the Potomac River—on which the launching trials were made.
Following the last failure, when the aerodrome was wrecked, the press
ridiculed the whole enterprise, and Congress refused to appropriate
money for further experiments. The Langley aerodrome, fitted with a
Curtiss motor and Curtiss controls, flew in 1913-14.
As with experiments of the first school they did not attain practical
results. The machines were usually wrecked at the first trial without
giving any clew to the nature or whereabouts of the trouble. Although
Langley’s machines were reconstructed and flown later this should not
detract in any way from the fame of the Wright brothers, Orville and
Wilbur, who really were the first to construct an aeroplane which was
driven by a gasoline motor, lifting a man off the ground, and pursuing
a steered and sustained flight through the air.
The experiments of Lillienthal and his death in his glider were
the direct incentives to the Wright brothers to conduct their
investigations with gliders. The Lillienthal way of balancing
the planes by swinging his legs they judged to be a poor means of
controlling the direction of the flight. So they set out to discover
another method of controlling the stability of the planes. Their
experiments began in the fall of 1900 at Kitty Hawk, North Carolina,
as Mr. Henry Woodhouse, the aeronautical authority, has pointed out.
They took all the theories of flight and tried them one by one, only to
find, after two years of hard, discouraging work, that they were based
more or less on guesswork. Thereupon they cast aside old theories and
patiently put the apparatus through innumerable gliding tests, ever
changing, adding, modifying—setting down the results; after each glide
comparing, changing again and again, until they finally constructed a
glider which was easy to balance both laterally and longitudinally.
But in order to control fore-and-aft balance they had to eliminate
Lillienthal’s method of swinging his legs and substitute a horizontal
elevator. This elevator was raised and lowered by a lever operated
by the pilot stretched out on the centre of the lower wing of the
glider. This device kept the glider level with respect to the ground.
In fact, this elevator was absolutely necessary to prevent the planes
from diving up or down, for if the pilot found the glider pitching
too much forward, tending to dive, he would tilt the elevator upward
by means of the lever, thus pulling the nose of the glider back into
its proper position. At first the Wrights built the elevator in front
of the planes so that they could see and study its effect. They soon
discovered that the control of the glider was much better with the
elevator. This elevator has been incorporated as a standard fin on the
tail of the fuselage of every aeroplane and is one of the chief factors
in steering up or down.
Having completely mastered this most important step, the Wrights next
took up the problem of lateral control. The natural tendency of the
glider was to flop about like a kite with too light a tail. In order
to correct this lateral instability the Wrights determined to make
the air itself, rather than gravity, supply this balance, instead
of Lillienthal’s method of swinging his legs from side to side by
observing closely the way in which a pigeon secures its lateral balance
by varying the angle of attack with its two wings, whereby one wing
would lift more forcibly than the other, thereby turning the bird in
any direction around any given axis of flight. In order to accomplish
this variation the Wrights made the ends of the glider loose while the
rest remained rigid. Then by a system of wires operated from a lever
they could warp these wing ends of the glider, one to present a greater
angle of attack to the air and the other a smaller angle, just as the
pigeon did. In other words, by pulling down the rear edge of the tip of
one wing and by pulling up the extreme edge of the other the angles of
the wings were varied with respect to the way in which they cut through
the air on very much the same principles as the tail elevator on the
fuselage. Also, if a flat surface moves through the air horizontal to
the ground, if you tipped the rear edge upward the air would strike it
on that edge and have a tendency to force it down, thus forcing the
forward edge upward. To pull it in the other direction would cause
the opposite effect. The Wrights were first to incorporate this in a
glider or aeroplane. They patented it, and although a hinge, called an
aileron, was later attached to the end of the wings of an aeroplane
to produce the same effect and at the same time to allow more rigid
construction of the ends of the wings, nevertheless this idea was
distinctly a Wright discovery and innovation.
[Illustration:
_Courtesy of Flying Magazine._
The Wright flyer after the epoch-making flight at Kitty Hawk, N. C.,
December, 1903.
This was the first successful motor-driven heavier-than-air craft to
lift a man off the ground and carry him over a steered course. It had
one 16 h.-p. motor with a chain-drive to two propellers. The elevators
were in front of the machine. The plane resembles a glider or a box
kite and the wings could be warped for steering.]
But that was not all the Wright brothers did to make man-flight over a
sustained and steered course in a heavier-than-air machine possible.
Directional control or power to steer the glider in a straight line
or to vary it had not yet been acquired, so the Wrights installed a
vertical rudder which they also operated by lever, just as the rudder
on a power-boat is controlled, and the effect on directional steering
was the same. Indeed, passage through the medium of the air is in many
ways similar to passage through water. Thus the moment the glider
swerved from right to left the rudder was pulled in the opposite
direction and the planes came back to the steered course.
But this was not invented at once nor installed until after the Wrights
discovered that whenever the glider was in flight the effect of warping
the wings to control the rolling had a serious unexpected secondary
effect, namely, a tendency for the high wing, which they desired to
bring down, to advance faster through the air than the low wing, and
solely by its higher velocity to develop a higher lifting capacity and
thus to neutralize the benefit of the warp. After much experimenting
they hit upon the rudder idea and that corrected the difficulty.
Thus the Wrights gained complete mastery of the glider; they could
steer it up and down, turn it from right to left, and bring it back
safely to the earth. This is the basis of the Wright patents to-day.
The next thing to be done was to install upon an aeroplane a power
plant sufficient to drive it through the air fast enough to make the
air lift it off the ground and sustain it in the “liquid blue” until
the pilot saw fit to glide to the earth again. This was by no means
a simple matter, for from 1900, when the Wrights began their glider
experiments, to 1903, when they made their first flight, the gasoline
motor was in its impotent infancy. They set about building a small
light motor, however, to install in their planes.
In the meantime they experimented further with wing surfaces. Langley
and Chanute had proved flat wings inefficient and curved wings
necessary for lifting capacity. Of course, those early experimenters
did not know how much those curvatures affected the climbing angle of
a glider, so the Wrights set out to find out by using the wind-tunnel
method and testing scale models in the same, with a blast of air
generated by an engine-driven fan. This tunnel was cylindrical in
form, sixteen inches in diameter. The smaller models of wings were
hung in the centre, the air-blast turned on, and the balance arm,
which projected into the tunnel and on which the wings were mounted,
measured the air forces and the efficiency of the varied wing shapes
from the standpoint of rounded wing tips and curvature.
Data acquired in experimenting with their six-inch model biplane in
this determined them to build their aeroplane on that scale, even
though it was discovered that two wings together were less efficient
than one wing by itself. The rigidity of two wings added a safety
factor, so they adopted the biplane or two-plane surface rather than
the monoplane or one-plane surface.
In these experiments the Wrights also discovered that all surfaces
shaped like a fish offered less resistance to the air than blunter
obtuse surfaces, so they adopted the stream-line method in construction
of struts or supports to the two wings, so that now all surfaces that
cut the air in the forward progress of the planes are rounded off so
that the air slips off with the least resistance. This was an important
discovery, for later when the enclosed fuselage or body in which the
aviator sits was constructed it had much to do in determining its shape
and design.
Propellers had already been experimented with as a means of propulsion
through the air. Because of the low horse-power at which they were
driven very little scientific data as to propeller efficiency had been
compiled. Because the first motor constructed by the Wrights had only
16 horse-power at maximum speed, which soon fell off to 12 horse-power,
the two propellers mounted on their first machine developed a
high propeller efficiency. To-day propeller efficiency has reached
approximately 70 per cent of efficiency, and much study has been
devoted to the propeller.
Because no gasoline motor was in existence light enough to mount on
their glider the Wrights built their own in their shops in Dayton. It
was a four-cylinder water-cooled upright motor, and it could develop
12 horse-power. The engine was mounted on the rear of the planes of
the glider and by a chain drive propelled the two blades mounted in
the rear of the two planes, thus making a pusher type of aeroplane.
The estimate of the total weight of the machine and the operator was
between 750 and 800 pounds.
With this machine, on December 17, 1903, Wilbur Wright made the
world’s first sustained steered flight of 852 feet in 59 seconds in a
heavier-than-air machine. To them really belongs the honor of having
invented the aeroplane and of having demonstrated the feasibility of
navigating the air in a heavier-than-air machine. It is true that the
Frenchman M. Bleriot was the man who covered the fuselage, put the
engine in front of the aviator, and constructed a monoplane similar
in shape to a bird. Nevertheless, it is the Wrights who built the
aeroplane which met all the fundamental requirements of flight through
the air.
CHAPTER III
WHY AN AEROPLANE FLIES
THE HELICOPTER—THE ORNITHOPTER—WING SURFACE—FLYING SPEED—LANDING
SPEED—EFFECT OF MOTORS—THE SEAPLANE
The heavier-than-air machines are divided into three classes. The
helicopter is a machine which theorists of that school believe can fly
straight up into the sky because its air screw propeller works on a
vertical axis. This type of aircraft has never been successful, for the
reason that the propeller does not lift. It simply pulls a stream-lined
surface through the air. The lifting must be done by planes.
The ornithopter is another heavier-than-air craft which seeks to fly by
flapping wings like a bird. The effort to build this type of machine is
as old as human desire to imitate the fowls of the air and it has been
as unsuccessful as the helicopter.
Before we begin to discuss the aeroplane we must remember that
before a modern machine leaves the ground it must be moving at least
thirty-five miles an hour with respect to the air. This forcing of
the edges of these broad-pitching, curved surfaces through the air at
such a velocity naturally drives the air downward and these particles
of atmosphere react in exactly the same degree upward, thus forcing
the planes and the attached apparatus upward. Therefore, as long as
the aeroplane rushes through the air at that or greater speed the
thousands of cubic feet of air forced down beneath the wings deliver
up a reaction that results in complete support. When an aircraft fails
to move at that velocity it loses “flying speed” and falls to the
earth. The net result of this reaction is called “lift,” and as long as
the machine sweeps forward at that momentum it has lift. The engine,
of course, must supply this forward movement, and when it stalls,
the heavier-than-air machine must glide to a landing-place or fall
perpendicular to the ground.
To understand why a heavier-than-air machine flies it is necessary
to remember that air or atmosphere has many of the characteristics
of water. Indeed, like the ocean, its pressure varies at different
altitudes. At sea-level a cubic foot in dry weather weighs 0.0807
pounds, but at a mile above sea-level it weighs only 0.0619 pounds,
and at five miles 0.0309 pounds per cubic foot and so on up. Therefore
machines designed to fly at sea-level often fail to get off the ground
at 12,000 feet above the sea in such countries as Mexico.
Air also has motion. Its tendency to remain motionless is called
inertia, and its characteristic desire to reoccupy its normal amount
of space is known as its elasticity, and the tendency of the particles
of air to resist separation is described as its viscosity. Thus we see
that air has practically the same characteristics as water, only it is
much lighter.
Without going into a technical discussion of all the forces that enter
into the flight of an aeroplane we must, however, realize that if the
pressure of the atmosphere is uniform in all directions, in order to
make the air forced under a wing or plane lift more than the air above
forces down, the wing of the plane must be curved in such a way that
the forward motion of the edge of the wing causes the air underneath
to force any particle of the surface upward, while the upper surface
is relieved of the pressure. This is done by curving the surface of
the planes so that the under surface is concave while the upper part
is almost convex, like the outspread wing of a bird. When this wing is
forced horizontally through the air it creates a vacuum immediately
behind the upper or convex part, the under pressure is still constant
and the surface is lifted upward. That is why a plane covered with a
curved surface will fly and a plane with a flat surface will not. In
short, a curved surface when moving through atmosphere causes eddies in
the air, and if the curvature of the wings is properly calculated, it
leaves a vacuum near the rear edge of the surface of the plane and it
climbs upward. The smaller the angle the smaller the lift or climbing
power of the plane. Thus a 15-degree angle will lift one pound; if
reduced to 10 degrees it will only lift two-thirds of a pound, but
because a wing is curved a plane could fly at several degrees less than
0 degree, but its “stalling” or critical angle beyond which it is not
safe to go is 15 degrees.
It must be borne in mind that the larger the wing surface the larger
load the aeroplane can carry, for the lift of a heavier-than-air
machine depends entirely on the number of square feet of surface in
the plane or wings. The larger the planes the more power is required
to force them through the air and the less easy they are to manœuvre
and land. The Nieuports, Spads, Sopwiths, and Fokkers, with their small
wing spread of less than 30 feet, made them much easier to fly, even
though they land faster than the “big busses.” Therefore every pound of
weight added to an aeroplane decreases its speed proportionately and
requires an equivalent increase in horse-power to force it through the
air. Of course, an increase of speed gives an increase in lift, so by
doubling the speed of a plane you increase the lift just four times.
There are, however, a number of factors which tend to decrease the
progress of a machine through the air: the head resistance of the
fuselage, the motor, the struts, the wires, the landing-gear, etc.
These things do not add to the lift and are described as “dead-head”
resistance. Stream-line, or the tapering of all surfaces which resist
the air, helps reduce this resistance, so that the design of the plane
has much to do with its speed, also as to whether the plane can climb
faster than fly straight ahead. Naturally the horse-power of the motor
determines the flying speed of the aeroplane as much as any other
factor.
To lift a plane off the ground it must be travelling at least 35 miles
an hour with respect to the air, as we have pointed out before. So if
a gale is blowing 20 miles an hour the aeroplane may be lifted off the
ground when moving no faster than 15 miles an hour with respect to the
earth. Likewise unless a machine is moving 35 miles an hour it will
lose flying speed and fall to the ground.
Machines do not all land at the same speed. The famous Morane monoplane
skimmed along the ground at anywhere from 45 to 90 miles an hour.
It is manifestly impossible to do more than suggest the fundamental
principles of aeroplane flight here. To be sure, the type of aircraft
has, as we have indicated, much to do with why and how it flies.
Because of its similarity to the bird and owing to the lack of struts,
etc., to increase the head resistance the monoplane or single-wing
plane is the fastest machine. The absence of struts and the few bracing
wires brings a greater strain on the wings and increases its chances of
breaking. The biplane, with its two parallel wings separated by struts,
is more easily braced and proportionately stronger. The lift is also
greater, due to the additional wing surface. The vacuum made over the
lower wing is interfered with by the upper plane, and thus neutralizes
somewhat the lifting and flying efficiency of the upper wing. Since a
plane must reverse all its stresses when looping, the double supports
of the biplane make it less susceptible to doubling up and falling.
These are some of the reasons for the popularity of the biplane.
The triplane is so called because it has three tiers of wing surfaces
set one above the other. This allows for even greater strength in
construction, and despite the resistance several very fast-climbing
triplanes have been built. The famous Caproni triplanes with three
motors have a wing spread of 127 feet. Many biplanes and flying-boats
also have approximately 126-foot wing spread. The well-known Handley
Page bomber and the NC-1, NC-2, NC-3, NC-4 Naval Flying Boats, which
tried the Atlantic flight, had a similar wing spread.
In the war the small aeroplane of the monoplane or biplane type with
a small wing spread and equipped with a rotary motor, whose nine or
more cylinders revolved with the propeller, or a small V-type motor,
was called a scout. These biplanes seldom had a wing spread of over 28
feet and the horse-power of the rotary motors seldom developed more
than 150 horse-power, whereas the stationary motors for these same
machines generated as much as 300 horse-power, as in the case of the
Hispano-Suiza. These machines were used for fighting because they made
as high as 150 miles an hour and responded so easily to the slightest
movement of the “joy stick” and, consequently, manœuvred so readily.
Since trick flying was absolutely essential to air duels these machines
were best for this purpose and for quickly getting information of troop
movements.
The next larger size, seating two men and driven by the same types of
motors or even larger twelve-cylinder Rolls-Royce or Liberty motors,
but with a wing spread of from 34 to 48 feet, was used for taking
photographs, directing artillery-fire, and general reconnaissance in
war. The multimotored machines, with a wing spread of anywhere from 48
to 150 feet, were used for bombing at night or during the day. Owing
to the size of these machines and because of their slow-flying speed
they were easy to land. Some of the scouts weighed, with petrol and two
hours’ fuel, less than 1,000 pounds, whereas the four-motored bombers,
with 127-foot wing spread, weighed over six tons and could carry a
useful load of three tons.
The hydroaeroplane does not differ fundamentally from the aeroplane
as regards flying principles. In structure it may be a biplane or
triplane, but owing to the supports necessary to carry the pontoons it
cannot be easily attached to a monoplane. Structurally, it differs from
the aeroplane only in having pontoons or a boat substituted for wheels
and landing chassis. Owing to the surfaces presented by the pontoons or
the hull of the boat, looping is practically eliminated and the spread
of these flying craft is much slower than land machines.
Although M. Fabre conducted experiments with aeroplanes carrying floats
instead of wheels, Mr. Glenn H. Curtiss was the first to successfully
construct and fly a hydroplane. At the time of his flight down the
Hudson River from Albany to New York he equipped his plane with a light
boat to protect himself in case of a forced landing on the water.
Encouraged by this experiment under the Alexander Graham Bell Aerial
Experiment Association, and by later attaching a canoe, he succeeded in
landing and getting off the water. Later he built a hydroaeroplane and
flew successfully at San Diego, Cal., thus establishing America as the
land which invented and developed the seaplane and flying-boat.
Structurally, the modern seaplane has two small pontoons on the
end of each wing and a small boat in the centre, or sometimes only
two pontoons in all which are side by side near the fuselage. The
flying-boat has one large boat instead of a fuselage, with a small
pontoon on the end of each wing. The former is used for fast flying,
but owing to the air resistance to the pontoons, and especially to the
boats, the speed cannot be compared to that of the scout aeroplanes.
Moreover, they are much harder to do stunts with and few are known to
have looped the loop. Like the big land bombers the flying-boats may be
equipped with as many as three motors. One of these has carried as many
as fifty passengers at one time.
Contrary to the accepted notion, these flying-boats are very hard to
land on the sea because it is so difficult to calculate the position of
the wave when you strike—both are moving so rapidly.
As we have already seen that due to the fact that a heavier-than-air
machine must be moving at least 35 miles an hour to get off the ground
or water, a strong and powerful motor is absolutely essential to make
aeroplane flying possible. We have already discovered that the Wrights
had to construct their own motor because none was light enough for an
aeroplane. Their 16 horse-power single-cylinder engine weighed over 200
pounds. To-day the Liberty is rated at from 400 to 450 horse-power, and
it weighs less than two pounds per horse-power. An Italian aeronautical
engine develops 700 horse-power, and one sixteen-cylinder American
motor generates 900 horse-power. This shows the tremendous development
of the motor for modern flying.
[Illustration: A Shortt “pusher” seaplane equipped with a
one-and-a-half-pounder gun.]
[Illustration:
_From a photograph by Bain News Service._
British-built Curtiss flying-boat, at Brighton, England.]
But, aside from the matter of weight and horse-power, the aeromotor has
been called upon to perform at altitudes of as high as 30,000 feet as
efficiently as on the ground. Since the atmospheric pressure at that
height weighs a great deal less than at sea-level the flow of gasoline
and lubricants is very much decreased, so that the efficiency of the
motor may fall off proportionately. To meet these requirements the
aviation motor must be especially designed, and since the vibration of
the propeller shakes the frail frame on which the engine is mounted,
the materials must have the greatest strength and resistance.
Nevertheless, in both types of motor, the rotary air-cooled and the
stationary V type, the engineers have succeeded in making engines that
would climb still higher than the 30,500 ceiling already made, if the
aviators could stand the cold or have enough hydrogen to keep them from
fainting.
The motor then is the heart of the heavier-than-air machine, and when
it stops the aeroplane must volplane or fall to the earth, a slave to
the laws of gravity.
CHAPTER IV
LEARNING TO FLY
EARLY METHODS—DEVELOPMENT OF SCHOOLS—STUDYING STRUCTURE OF
PLANES, MOTORS, THEORY OF FLIGHT, AERODYNAMICS, MAP READING—FRENCH
SYSTEM—GOSPORT SYSTEM
From the time of the first flight of the Wright brothers in 1903 to
the breaking out of the Great War in July, 1914, the art of flying
an aeroplane was not taught systematically either in private or
military schools, primarily because flying in a heavier-than-air
machine was regarded by civilians as a very dangerous sport and by
military authorities as hardly more than a dubious scout for locating
troop or train movements. For that reason very few civilians were
induced to take up aviation except a few of the more daring sportsmen.
Consequently, civilian flying on a large scale did not flourish.
It is true, however, that several small schools attached to
manufacturing plants did attempt to teach the rudiments of flight and
aircraft construction. These schools did not prosper because only a few
pupils who wished to give exhibition flights attended, and the art of
flying and aircraft development suffered.
In England several schools were started with indifferent success for
the same reason as obtained in America, and in France and Germany,
aside from a few aviators who were striving for new world’s records,
most of the flying training was in the army. Therefore most of the
great fliers, like the Wrights, Beachy, Martin, Curtiss, Farman,
Bleriot, Garros, Vedrines, Graham-White, Sopwith, A. V. Roe—to mention
only a very few—learned to fly themselves. For that reason the toll of
lives taken in flying was high. Nevertheless, that did not stop these
daring fliers from stunting and exploring all the aerial manœuvres
possible with a heavier-than-air machine. As a result Pegout looped
the loop; Ruth Law flew at night; Bleriot crossed the channel; Garros
the Mediterranean Sea; Vedrines flew from Paris via Constantinople to
Cairo; and in July, 1914, Heinrich Oelerich climbed to 26,246 feet
altitude in Germany, and in the same month another German flew for
twenty-four hours one minute, without stopping.
Meanwhile France had trained several hundred aviators for her army
and Germany had five or six hundred trained fliers, including those
in the Zeppelin service. The United States army had hardly more than
fifty fliers when the Mexican trouble broke out, and only half a dozen
aeroplanes to use on the Mexican border.
As soon as the war began and aircraft demonstrated that the side
which got control of the air could put out the eyes of the opposing
army and that the great struggle might be decided in the air, all the
belligerent nations began to train aviators for the war in the air.
France was the first to develop a school of flying, and the French
method, with slight variations, was adopted by England and the United
States. A description of their method will give a comprehensive
conception of the training necessary for a military flier in the war.
Early in the war most of the army, navy, and private aviation schools
of the United States adopted the penguin system of learning to
fly. That method, invented by the French, consisted of using as a
training-machine an aeroplane that had so small a wing spread or so
weak a motor that it merely hopped five or six feet off the ground when
the motor was wide open. The small wing spread caused it to zigzag
along the ground like a drunken man. For those reasons, perhaps, it was
named after the penguin, which does not remain long on the ground or in
the air and which has an irregular gait.
The first step in learning to fly consists in studying the structure of
the aeroplane and of the aeronautical engine, and aerodynamics, or the
science of the forces that aid or hinder the flight of heavier-than-air
machines. During the last half-dozen years many of the manufacturers
of aircraft maintained schools in order to encourage men to learn the
art of flying, and have given their pupils the chance to study at first
hand the designing, the building, and the assembling of aeroplanes
and hydroplanes. That has given the pupils a thorough knowledge of
every detail of the aircraft—an invaluable asset to an aviator who
has been compelled to make a forced landing far from a repair-shop.
In the “ground” schools conducted by the United States Government
for instructing aviation officers at the various institutions, like
Cornell, Massachusetts Institute of Technology, and Princeton, a great
deal of time was devoted to assembling aeroplanes.
Most of the manufacturers of aircraft in this country do not make
the motors used to propel their aeroplanes. The aeronautical motor
is one of the most difficult machines to build successfully. A motor
that runs as smoothly as a watch on the ground may hesitate and
sputter at an altitude of a thousand feet, and at three thousand feet
may stop altogether. Engineers say that that is because the change
in temperature and in atmospheric pressure causes a difference in
carburization. All these things the prospective flier had to learn as
well as the reasons for the same.
Contrary to the general notion, the construction of the aeronautical
motor differs radically from that of the automobile engine. In point
of weight the difference is marked. Seldom is any stipulation made
that limits the weight of the automobile motor in proportion to the
amount of horse-power; a few pounds more or less is not an important
consideration in a pleasure-car or a motor-truck. But in an aeroplane
every ounce of superfluous weight must be eliminated from the engine,
which must nevertheless be strong enough to withstand the most violent
strain.
The aeroplane motor is subject to far greater strains than the
automobile motor is. Except during a race, one rarely runs the engine
of an automobile at its maximum speed; the aeroplane motor, on the
contrary, usually runs at full speed from the moment the aeroplane
starts until the motor is shut off and begins to volplane down to the
earth. It is true that you can regulate the aeroplane engine by the
throttle to run from as low as three hundred revolutions a minute to
as high as sixteen hundred; but except when testing the motor there is
rarely any reason for slowing it up while in the air. The load that the
propeller of an aeroplane carries is much less than the load that the
shaft of an automobile carries, but, on account of the frail structure
of the plane, the vibration is much more violent. A battle plane seldom
weighs more than two thousand pounds, and a scouting machine of the
Nieuport type tips the scales at not more than one thousand pounds.
For these reasons aircraft require special kinds of motors. The V type
is so called because the cylinders are set in the form of that letter;
the rotary motor has the cylinders arranged in a circle like the spokes
of a wheel, and it revolves on its shaft like the propeller. The rotary
motor is used in scouting machines because it is light. The revolving
engine also revolves on its shaft, but it has a great many more
cylinders arranged side by side like the cylinders of an automobile
engine. It is much heavier than the rotary type; it may have as many as
thirty-two cylinders.
Of course, a knowledge of the automobile engine was an aid to the
prospective aviator; for, except in the process of cooling and the
revolution of the cylinders, the principles of the automobile motor and
those of the aeroplane are identical.
At aviation schools the pupils went thoroughly into all those
things and supplemented their knowledge by continually mounting and
dismounting engines and examining their most intricate parts. The
schools also kept on hand large aeroplane models, which the students
took apart and put together again. In the classroom the prospective
aviators studied the mathematics and the theory of aerodynamics.
All this work was very important, for an aeroplane is such a nicely
balanced machine that if it is not perfectly constructed mathematically
it will not fly safely.
For example, if the tail plane or flat, finlike surface that projects
from the sides of the tail of the body, or fuselage, has too much
“incidence,” or, in other words, is slanted at too sharp an angle
downward, it has a tendency in flight to lift the rear of the machine
and to make it dive. A seaplane, when properly constructed, is so
evenly balanced that, when the crane that lifts it off the mother
ship holds it suspended in the air, the machine is equipoised like a
bird with wings spread in flight. If the plane is heavier on one side
than on the other, it will, while “banking,” or turning a corner,
slide toward the centre of the circle; that sometimes causes a “tail
spin,” in which the machine whirls round as if it had been caught in a
whirlpool. That is a very difficult situation, for an aviator usually
ends in a smash at the bottom of the whirlpool unless the pilot has
altitude enough to flatten out his plane before it gets too close to
the ground. These things were all taught before the novice went up in
the air.
Map reading and air navigation were the next studies in military
aviation schools. First, the student learned how to judge the height
of hills and the size of towns from different altitudes, so that when
flying he could tell what part of the country he was passing over. Many
of the schools perched the prospective fliers high in the air in a
classroom and spread out a miniature landscape made of dirt and sand on
a map beneath them so they could get practice in perspective.
Of course, when an aviator is lost in the fog or above the clouds he
needs to use all the instruments on board to find his position. For
that purpose drift instruments are mounted on aircraft; those tell how
much the air-currents, which have the same effect on aircraft as the
tide has on a boat, have driven him off his course. A compass indicates
the direction in which he is travelling, and other instruments show
him whether his machine is climbing, diving, or “banking”; the aneroid
barometer indicates the altitude. It is essential, of course, for the
aviator to know how to read those instruments correctly. Without the
information they give him, he might not know, if flying at night or
in a cloud, that his craft was climbing at a dangerous angle until
wrenches or other loose implements began to fall out of the machine.
As the next step in the training the student learns the controls. To
do that he runs the “taxi” or “lawn-mower,” as the training-machine
is called, up and down the field. The “hopping” of this machine
familiarizes him with “getting off” and landing, and with the noise of
the propeller. After he has learned to steer his machine in a straight
line, he takes longer “hops” until he is thoroughly familiar with
the “joy stick” which pulls the elevators or ailerons up or down or
operates the rudder.
Soon afterward the student went up with an instructor for a long
flight. The purpose of the flight was to get the pupil used to higher
altitudes and to the motion of the aeroplane, and to give him a chance
to watch his teacher actually running the machine. Strange to relate,
many who have felt an uncontrollable desire to jump off high buildings
have no such feeling while in an aeroplane. That is because they sit
and look out horizontally instead of perpendicularly downward, and
because they move at such tremendous speed.
After several trips of that kind, the instructor let the student handle
the controls until he could climb, dive, and “bank,” or turn the
machine in the air. But the pupil was not permitted to land a machine
until near the end of his course; for next to getting out of a tail
spin, a dive, or a side slip, landing was the hardest task in flying.
Statistics show that more aviators have been killed in making landings
than in any other way. Many of the accidents, of course, were caused
by the nature of the ground, for when the engine of the aeroplane
stops, the aviator has to volplane or glide down wherever he can.
One of the difficulties of landing is owing to the fact that even
training-machines cannot land at a slower speed than thirty-five miles
an hour. If the wheels of the aeroplane, when they first touch ground,
do not skim over the surface of the field, the machine is liable to
“nose in” and turn a somersault. Indeed, that is why the pusher type of
training-machine, with the propeller in the rear of the pilot, is being
abandoned for the tractor machine, which has the propeller in front. If
an accident does occur with a tractor the engine does not “climb your
back.” One of the greatest dangers of flying a seaplane is due to the
fact that the engine is installed not in the hull but high above the
aviators’ heads, upon which it is apt to fall in case of a crash.
The student was next permitted to fly alone. Most machines were so
strongly built that accidents were seldom caused by breakage, although,
of course, before each flight the aviator and his mechanic critically
examined his machine for broken parts. With a reasonable amount of care
straight flying by daylight was comparatively safe.
In the French aviation schools, before the military birdman could pass
his final examinations, he had to climb twice to an altitude of six
thousand feet and spend an hour at a ten-thousand-foot altitude. If he
passed that test successfully, he had to fly over a triangular course
of one hundred and fifty miles and land at each corner of the triangle.
Before he could fly his machine on the battle-front the French flier
had to know how to loop, to fall or dive at such a steep angle that
his machine actually dropped through the air for several hundred
feet before it flattened out—a tremendous strain on the wings of a
machine—to side slip or round a curve with his machine banked at such
an angle that it gradually slid toward the centre of the circle, to
climb or tail dive at such a pitch that the aircraft actually slips
backward tail foremost. Indeed, in the last days of training the
student was encouraged to practise all kinds of stunts and tricks, for
when an enemy descended on you from the clouds above and was sitting
on your tail weaving a wreath of bullets from a machine-gun round you,
your only chance of escape was by means of a loop, a dive, a side slip,
or a roll.
Another interesting test a pilot had to undergo before he got his
license to do battle was to ascend fifteen hundred feet, cut off all
power, and volplane down in a spiral to a fixed point. To perform the
manœuvre successfully required great skill. All the members of the
famous Lafayette Escadrille had to undergo those tests before becoming
fighting aviators, and Americans who received their final training in
France had to go through the same training.
In our government flying-schools at Mineola in Long Island and the
other flying-fields in Texas and other parts of the country, at San
Diego in California, the students were put to similar tests of skill.
In the private civilian schools, however, instructors rarely attempt
to teach their pupils more than straight flying. But most aviators
agree that every flyer ought to know the “stunts” in order to meet
successfully any extraordinary situation that may confront him.
Of course the training for aerial observers, wireless operators, and
photographers was very different from that of the pilots. In each case
the instruction was peculiar to the science they were to practise, and
it had little to do with aviation, only in so far as it was actually
affected by flying. The men who took the pictures had to make a study
of the science of photography. The same was true of the wireless
operator. The observer, however, had to study topography and the use
of the machine-gun, and target practice such as characterized the work
of the pilot. In different countries this differed with the methods
developed there. In England the pilot often shot at toy balloons in the
air while chasing them with his machine or at targets on the ground.
The same method was employed by the United States. Nearly all the great
aces in the war were very clever shots, and Major Bishop attributed
most of his success to his skill with the machine-gun.
Finally the Gosport system of training aviators was adopted by the
British and the American armies because it permitted the training of
tens of thousands of fliers at the same time. The principles taught
were the same as those enumerated above. The system, however, reduces
the time spent on each operation to the minimum, specifying the number
of hours to be spent on each step in the course. Here is a sample of
the outline of the training under that system:
STANDARD OF TRAINING
PART 1. PILOTS—FLYING WINGS
1. _Ground Instruction._
1. Buzzing and Panneau
2. Artillery Observation
3. Gunnery
4. Aerial Navigation
5. Engine Running
6. Photography
7. Bombing and Camera Obscura
8. Air Force Knowledge
9. Engines and Rigging, Workshops Course
10. Drill and P. T.
2. _Air Tests._
1. Flying Instruction
2. Formation Flying
3. Cross Country
4. Reconnaissance
5. Photography
6. Bombing (Camera Obscura)
7. Ring Sights and Camera Gun
8. Altitude Test and Cloud Flying
9. Aerial Navigation
3. _Appendices._
A Flying Instruction
B Formation Flying
C Cross Country
D Bombing
E Wireless
F Gunnery
G Ring Sights and Camera Gun
H Aerial Navigation
I Photography
To insure a certain amount of continuous practice the following
minimum times will be spent on ground subjects. It must be realized,
however, that efficiency, and not time spent, is the ultimate passing
standard.
Buzzing and Panneau 30 hours
Artillery Observation 20”
Gunnery 60”
Aerial Navigation 20”
Engine Running 3”
Photography 2”
Bombing and Camera Obscura 1 hour
Engines and Rigging 12 hours (Workshops Course)
Military Knowledge 3”
Lectures will be given covering—
(1) All questions on above subjects.
(2) Practical wireless covering knowledge useful to a pilot.
(3) All ground signals as given on new Artillery Observation card,
40-W.O.-2584.
Thus every step in the education of the flier was provided for and thus
the United States turned out over 10,000 aviators.