permitted to know next to nothing was the so-called “gun camera,” the
invention of Thornton Pickard, of Altringham, England. This camera,
which was designed for the purpose of training aerial gunners, imitated
as closely as possible a Marlin aircraft machine-gun, and in order to
make a picture it was necessary for the operator to go through the same
movements as in firing a Marlin gun. The picture was made through a
circular graticule synchronized with the sight on the fixed machine-gun,
so if the film, upon being developed, showed that the gunner had scored
a “hit” with the camera, he would have been equally successful with an
actual machine-gun. The gun cameras as developed in the United States
were of two kinds: one, using a regular Brownie film, took one picture
each time the trigger was pulled; the other, which was virtually a
motion-picture camera so constructed as to exactly replace the magazine
on a Lewis gun, gave a “burst” of exposure with a rapidity equalling
that of a machine-gun firing a burst of shots, and was used for training
aviators in the handling of their flexibly mounted Lewis guns. The
resulting film, or bromide print, consisted of a string of silhouettes
of the supposed enemy plane, each with an image of the gun-sights
superimposed to show where the gun was held, with reference to the
target, at the instant the picture was taken.
The enormous numbers of pictures taken from the skies necessitated a
corresponding development and manufacture of travelling dark rooms,
seventy-five complete units of these machines being built and shipped
overseas. These consisted of mobile photo laboratories, having all the
equipment necessary for the rapid production of prints in the field,
for when important operations are in progress it is imperative that the
aero photographs reach the staff at the earliest possible moment after
they are taken. The dark rooms, which were mounted on trucks, were
equipped with apparatus for generating the current used in the lamps
and enlargers, while trailers were fitted with sinks, tanks, enlarging
cameras, and other necessary photographic apparatus. The fact should not
be overlooked, moreover, that provision had to be made for training the
vast and for the most part inexperienced personnel of the photographic
sections in the countless new and peculiar phases of taking pictures from
the skies.
In considering the development of military aeronautics it must be borne
in mind that the maximum altitudes attained by airplanes increased
enormously during the war. In 1914 the record for altitude was 26,246
feet, or slightly less than five miles. By January, 1919, the record had
been raised to 30,500 feet, an increase of more than four-fifths of a
mile. In 1915 the Western Front pilots worked at 7,000 feet without fear
of attack from the ground, and few machines flew at heights of more than
10,000 feet. In fact, the “ceiling” with the early equipment was about
12,000 feet. In the closing months of the war, however, as a result of
the development of the antiaircraft artillery, it became necessary for
aviators to climb to 15,000 feet over the enemy lines, and tactics of the
air made that machine safest which could fly highest.
Now it may not have occurred to you that the higher you ascend the
greater becomes the decrease in atmospheric pressure. At 19,000 feet
the pressure of the atmosphere is one-half the pressure at sea-level.
That means that a given amount of air in the lungs of an aviator flying
at that height gives only half the oxygen that it would were he on the
ground. It is, then, the lack of oxygen, and not, as many suppose, the
low pressure itself, which makes men weak and slow of action at high
altitudes. Though these facts have been determined by medical research,
it is a curious phase of the flyer’s psychology that most aviators laugh
at the idea. Yet any one who has crossed the Rockies or ascended one of
the Alpine peaks by funicular has noticed that as the altitude increases
the breathing becomes quicker and deeper, the heart beats faster and
faster. But though the pilot may, as he asserts, continue to feel
perfectly fit and well, he is not as efficient as when near the ground.
His reactions become slower, he is less prompt to judge distances, to
aim his guns, to fire, to manœuvre his plane—and this despite the fact
that he is usually quite unconscious of any impairment of his faculties.
He will feel dizzy but perfectly happy—autointoxication, I believe the
doctors call it—whereas, as a matter of fact, he has lost his judgment;
and if he attempts to stay at these altitudes he will gradually pass into
a condition of partial and sometimes total unconsciousness, lose control
of his machine, and come crashing to the earth.
The imperative necessity of maintaining flyers at the highest possible
efficiency was brought home to the aviation authorities through studying
the reports of English air-casualties during the first year of the war.
The records divided these as follows: 2 per cent were due to the enemy,
8 per cent were due to the plane, and 90 per cent were due to the men,
which clearly indicated that something was radically wrong with the
personnel and that prompt action was necessary. A thorough study of the
situation disclosed the fact that practically all of the flying personnel
was suffering from what is known to scientists as oxygen fatigue,
caused by flying for many hours a day at high altitudes where there
was not enough oxygen to feed the body. As a result of this discovery,
Lieutenant-Colonel Dreyer, of the Royal Army Medical Corps, designed an
oxygen apparatus for use by the British air forces, the manufacture of
which was immediately begun in Paris. So pressing was the need for these
apparatus that an automobile was kept waiting at the plant where they
were being manufactured to rush each one to the front as soon as it was
finished.
An original model of this apparatus was brought to the United States
shortly after we entered the war, but as it was made entirely by hand,
it had to be redesigned to meet our manufacturing conditions. The
perfected oxygen equipment, as used in the American Air Service, consists
of a small tank, or tanks, according to the amount of oxygen carried,
a pressure device, a face-mask covering the mouth and nose, and a tube
connecting the mask with the oxygen reservoir. The American mask has
combined with it the interphone whereby the pilot and observer can
converse with each other while in the air and, in certain cases, the
receiver of the radio telephone. In May, 1918, six complete apparatus
were sent overseas by special messenger to be tried out under battle
conditions, and when the war ended 5,000 had been manufactured and
accepted. All American military planes flying at an altitude of over
10,000 feet are now fitted for the installation of oxygen equipment.
This includes day-bombing, pursuit, and chase planes, and a percentage
of night-bombing and observation machines. So much importance was
attached by the military authorities to supplying our flying-men with
oxygen that a special oxygen division was organized and sent to France
for the purpose of installing the apparatus in the planes. Yet, as I
have previously remarked, the flyers themselves persist in regarding the
apparatus, probably because of the discomfort involved in wearing it,
with amused scepticism.
* * * * *
Of all the inventions which have sprung from the war, none is more
amazing, to my way of thinking, than the radio telephone. Think of
standing on the ground and holding a conversation in a normal tone of
voice with an aviator so high in the sky that you cannot see his airplane
with the naked eye. Think of it! Before we entered the war, any one
save a handful of enthusiastic scientists would have ridiculed such a
suggestion, yet to-day, at any one of a score of flying-fields, you can
sit at an office desk and converse with aviators in the clouds as easily
as though you were sitting opposite them at a dinner-table.
[Illustration: RADIO TELEPHONE APPARATUS IN OPERATION ON AN AIRPLANE.
The pilot and observer are able to talk to each other through the same
instrument by means of which they communicate with the ground.
_Photograph by Signal Corps, U. S. A._]
[Illustration: PRESIDENT WILSON TALKING WITH AN AVIATOR IN THE CLOUDS BY
MEANS OF THE RADIO TELEPHONE.
_Photograph by Signal Corps, U. S. A._]
[Illustration: A RANGE-FINDER FOR ASCERTAINING THE ALTITUDE AND SPEED OF
AIRPLANES.
One of the most remarkable inventions of the war. This instrument not
only ascertains the altitude and position of an airplane but by means of
an electric connection automatically sets the sights on the antiaircraft
gun.]
The enormous advantage which such an invention would give to the army
possessing it was early recognized by certain electrical engineers and a
few scientifically minded officers of the Signal Corps, and, as a result
of their enthusiasm, before the first contingent sailed for France work
had been begun on the development of a radiotelephone set for airplanes.
There is no necessity of recounting the innumerable experiments and
heart-breaking failures before the first real successes were obtained. So
far as the radio part of the problem was concerned, a solution was had in
a comparatively short time. But working this apparatus in a swift-moving
and terrifically noisy airplane was quite a different matter, it was
quickly discovered, from working it under ordinary conditions on the
ground, the roar of the engine and the rushing air making it impossible
to hear one’s own voice, much less the weak signals of the receiver. One
of the first problems to be solved, therefore, was to design a head-set
which would exclude these noises while at the same time permitting the
voice of the telephone to be heard. The answer was found in a form of
aviator’s helmet fitting the head so closely as to exclude virtually
all extraneous sounds save those coming through telephone-receivers
inserted in the helmet so as to fit the ears. No sooner was this
problem solved, however, than another one demanded solution. A means
had been devised for protecting the receivers from outside noises—but
how about the _transmitter_? Every one knows how sensitive the ordinary
telephone-transmitter is to extraneous sounds, so it does not require
much imagination to picture how impossible it would be for the aviator
to make his voice heard in a transmitter alongside a 200 horse-power
airplane engine. But a brilliant series of experiments, conducted
largely by Mr. J. P. Minton, of the Western Electric Company, resulted
in a form of telephone-transmitter or microphone which possessed the
remarkable quality of being insensible to engine and wind noises and at
the same time highly responsive to the tones of the voice. With these two
elements in hand it was thought that the problem was solved, but three
more months of unremitting work were required to perfect the apparatus
to a state where it was practicable for use by others than experts. At
last everything was ready, however, and in December, 1917, the officials
of the Aircraft Production Board and the joint Army and Navy Technical
Boards announced that they would witness an exhibition of the apparatus
at the Moraine Flying-Field at Dayton. Two days before the date set for
the demonstration a group of the engineers and mechanics who had been
working over the problem almost night and day during the preceding six
months descended, with many cases of paraphernalia, on the Ohio town.
Only the enthusiasts who for the preceding half-year had spent their days
working over the problem and their nights dreaming of it believed that
the exhibition would prove successful. Every one else was sceptical. The
plan was to have two planes, both carrying radio sets, in the air at the
same time, while the visiting officials listened in at a ground-station
located on the top of a near-by hill. That night the inventors and their
assistants congregated in a room of the hotel where they were staying and
worked out a scenario and held a rehearsal of the morrow’s programme.
A famous electrical expert represented one plane and a young engineer
represented the other, while the inventors, sitting in the middle of the
room, gave them their orders and sent them sailing over beds, chairs,
and tables as it was hoped their planes would manœuvre in the clouds the
next day. No one slept very well that night. The morning was cold and
dismal, in keeping with the spirits of all concerned. Upon the arrival of
the exalted ones, among whom were several of the foremost scientists and
inventors of America, they were shown the apparatus installed in the two
planes and were told what it was expected to do. They were then escorted
up to the little station on the hill, where a loud-speaking receiver
had been connected with the wireless apparatus, so that all could hear
without the use of head-sets. The planes left the ground, and after what
seemed an interminable length of time, there came from the receiver the
first faint sounds which indicated that they were ready to perform. The
officials, with their coat-collars about their ears, appeared only mildly
interested and several gave unmistakable signs of being bored. Suddenly,
without the slightest warning, out of the horn of the loud-speaker came
the words: “_Hello, ground-station! This is Plane Number One speaking.
Do you get me all right?_” The bored expressions on the faces of the
officials changed to expressions of amazement tinged with awe. Instead
of the confusing dash-dot-dash which they associated with wireless, here
was a human voice coming out of space clear and distinct—yet the speaker
was two miles in the air. Soon the same signal came from the other plane
and the exhibition was on. Under command from the ground the planes were
manœuvred all over that part of the country. They climbed and volplaned
and circled. They were sent on scouting expeditions and reported what
they saw as they travelled through the air. Continuous conversation was
carried on, even when the planes were out of sight, and finally, upon
command, they came tearing down the skies like two huge homing pigeons
and landed where directed. From that moment the radio telephone was sold
to the government. It was no longer a question as to whether it would
work, but how soon and in what quantity its manufacture could be started.
The primary object of the airplane telephone is to make it possible for
the commander of an air-squadron to control the movement of his men in
the air just as a drill-sergeant directs the evolutions of a platoon on
the ground. For this purpose extra-long range is not required or, indeed,
desired, the distance over which they can talk being purposely limited
to two or three miles, so that the enemy cannot overhear except when
actually engaged in combat. Then it does not matter.
Neither my space nor my knowledge of electrical engineering are
sufficient to permit of explaining in detail the working of the radio
telephone. It is enough to say that a wind-driven generator supplies
electric current to a couple of vacuum tubes mounted in a box filled
with coils and condensers. These tubes transform the dynamo current
into a high-frequency alternating current which is fed out into space
through the antenna. This antenna consists of a copper wire about 200
feet long, which with a lead weight on the end trails out behind the
airplane when it is in flight. Normally this wire is wound up on a reel,
being let out and wound in as occasion demands. With the special form of
telephone-transmitter already described, the words of the aviator are
impressed on this wire, the electric waves thus set in motion radiating
out into space, where they are picked up by similar antennæ either on
other planes or on masts on the ground. The receiving process is the
exact reverse of that used in sending, other vacuum tubes taking the
high-frequency current from the antenna and transforming it so that
it can be heard in the form of speech in the telephone fitted in the
aviator’s helmet or in the loud-speaking horn on the ground. That is
about as near as I can come to explaining the radio telephone without
writing a book.
* * * * *
One of boyhood’s most joyous recollections is that of “balloon day”
at the county fair, when the great yellow spheroid in the middle of
the race-track enclosure slowly filled (oh, so slowly, it seemed!),
bulged, tugged at its moorings, and at last rose majestically skyward,
the aeronaut, a lithe figure in spangled tights, waving down to the sea
of upturned faces as he swung at ease in his cobweb-like trapeze. But,
though the recollection of the balloonist’s skill and daring remains
sharp and clear in our minds, so much space has been devoted in the
war books and the news despatches to the exploits of the aviators that
we seem to have completely lost sight of the no less hazardous work of
those daring souls who, day after day, in heat and cold, in snow and
drenching rain, sat huddled in their frail baskets under the swaying
gas-bags, often a mile above the ground, and through their glasses
watched what the enemy was doing, heedless of the repeated attempts made
by the enemy’s gunners and flyers to bring them down. Though they have
received practically no share of the publicity and praise which has
been showered upon the flying-men, the officers and men of the Balloon
Section of the Air Service deserve from the public its deepest gratitude
and appreciation. The perilous nature of their work is shown by the fact
that in the last six weeks of the war twenty-one American balloons were
lost, six being destroyed by shell-fire and fifteen by enemy planes.
Its importance is emphasized by the fact that the Germans gave official
credit to their aviators of _one and a half planes for every balloon
brought down_.
[Illustration: A SENTINEL OF THE SKIES.
Those daring souls who day after day sat huddled in their frail baskets
and through their glasses watched what the enemy was doing.]
[Illustration: AN AMERICAN OBSERVATION BALLOON LEAVING ITS “BED” BEHIND
THE WESTERN FRONT.]
[Illustration: A BALLOON COMPANY MANŒUVRING A CAQUOT FROM WINCH POSITION
TO ITS BED.
_Photograph by U. S. Air Service._]
At the beginning of the war the artillery-fire of the Allies was directed
for the most part by airplanes. Their work, however, left much to be
desired. Though the plane observers could locate targets fairly well,
they frequently lost touch with their batteries through the difficulty of
sending and receiving wireless or visual signals from the swiftly moving
craft. Thus there came into use the captive balloon, which by the end of
the war had practically replaced the airplane as a director of gun-fire
wherever possible, thus making the artillery infinitely more efficient
than ever before. Sitting comfortably aloft, the observer in the basket
of a kite-balloon had the whole panorama of his particular station spread
beneath him like a map in bas-relief, being able to detect, with the aid
of powerful glasses, anything transpiring within a radius of ten miles
or more. He was constantly in touch with his batteries by telephone and
could not only give the gunners, by means of co-ordinated maps, the
exact location of their target and the effect of their bursting shells,
but could keep the staff informed of enemy troop movements, airplane
activities, and preparations for impending attacks. The balloonist
became, indeed, a veritable sentinel of the skies, hovering over the
battle-lines with the persistency and the keen, long-range vision of
a hawk. He played a less spectacular part in the great drama than the
airplane scout or fighter in the latter’s free and dazzling flights,
but his duties were scarcely less important. Nor did he suffer from
ennui during his stays aloft. When a kite-balloon went up along the
battle-front it at once became the subject of the keenest attention by
the enemy because it was known to be up on business and was certain to be
the cause of damage unless it was forced down. Long-range, high-velocity
guns were trained on it and, from the upper levels of the air, planes
came swooping down upon it in their attempts to dash through the screen
of shells from the antiaircraft guns and put an incendiary bullet into
the sausage-shaped, elephant-colored gas-bag which so insolently defied
them. And a bullet which got home meant the instant ignition of the
highly inflammable hydrogen, the quick destruction of the balloon and,
perhaps, the occupants of the basket as well, unless they could get away
in their parachute. From the moment the gas leaped into flame until the
fall of the balloon was rarely over fifteen or twenty seconds, so quick
thinking and quick work was called for if the men in the basket were to
jump to safety. The pilot of the airplane could dodge and swerve and
slip away from the guns by a hundred shrewd devices; not so the pilot
of the kite-balloon anchored to its windlass. He had to carry on his
abstruse mathematical calculations unconcernedly, his spare moments being
enlivened by watching the flash of an enemy gun on a distant hill and
then waiting twenty or thirty seconds for the whining messenger of death
to reach him, pondering, meanwhile, on the accuracy of that particular
gunner. As a matter of fact, few direct shell-hits on a balloon were
recorded during the war, most of the balloons which were brought down
having been accounted for by incendiary bullets from diving planes. Just
as some sportsmen devote their energies to moose and elk and grizzlies
while others specialize on smaller game, so some of the airplane pilots
made a specialty of hunting “sausages,” and at this thrilling and highly
perilous sport became amazingly expert. When the Crown Prince’s assaults
on Verdun were at their height, I saw eight French aviators start out to
bring down eight German balloons. Within less than thirty minutes seven
of the _drachen_ had come down in flames—which shows that a balloonist
was not a good life-insurance risk. The average life of an observation
balloon on the Western Front was estimated to be about fifteen days.
Sometimes it lasted only a few minutes. There is a record of an American
balloon passing unscathed through the whole period of American activity
on a busy sector, but it was generally considered that a balloon which
has seen five or six months of ordinary non-war service has done its duty
and is unsafe because of the deterioration of the fabric.
In August, 1914, Germany had perhaps a hundred kite or “sausage”
balloons, France and England a very few. The German type was known as
the “Drachen,” and consisted of a gas-cylinder of rubberized cloth
about sixty-five feet long and twenty-seven feet in diameter, with
hemispherical ends. For stability a lobe, about a third of the diameter
of the cylinder, was attached to the underbody of the gas-bag and curved
up around the end. This lobe, made of a lighter fabric than the bag
itself, automatically filled with air as the balloon ascended and acted
as a rudder to hold the balloon in line. For further stability three
tail-cups, one behind the other, with mouths open to the wind, were
attached to the rear of the balloon.
While the Drachen balloon was a rather clumsy affair and proved unstable
in high winds, its importance as an adjunct to the artillery was early
recognized by the Allies, for the results of its work daily became more
apparent. Though the armies of France, England, Italy, and the United
States made repeated experiments in an attempt to evolve a type which
should possess greater stability and permit of higher altitudes being
attained, it remained for Captain Caquot, of the French Army, to produce
a balloon which possessed both of these qualities, his name now being
used as a designation for the type which he invented and which was in
general used by the Allied armies during the last year of the war. The
Caquot received its greatest compliment from Germany when her army
adopted this type of balloon and discarded the Drachen.