to the air. They have fins on their tails to steady them lest they
tumble over and over. On the smaller types of bombing planes, such as
the De Haviland-4, the bombs were usually carried underneath the lower
wings or under the fuselage, hanging horizontally by hooks or fastened
by bands around the bodies of the bombs, according to their type. The
bombs were dropped by a quick-release mechanism operated by a small
lever within the fuselage. The production of these release mechanisms,
of which several types were made, was one of the troublesome jobs in
connection with the airplane bombing.
All bombs are carried on the planes either suspended under the wings or
fuselage of the plane or in a compartment in the fuselage. The manner
of carrying and the design of the release mechanism is determined by
the type of plane used. Since the weight-carrying capacity of the
planes is limited, release mechanisms must be designed with a view
to lightness as well as safety. These mechanisms are so designed
that the observer can release any desired number of bombs either as
a salvo or in a "trail fire," and the order of releasing must be so
arranged that the balance of the plane will be disturbed as little as
possible; that is, if bombs are carried under the wings they should be
released alternately from each wing. All bombs are fitted with a safety
mechanism which enables the observer to drop them either "armed" or
"safe," i. e., so that they will explode or not as desired. An occasion
might develop where the aviator would have to get rid of his bombs over
his own lines. These various points are all taken care of in the design
of the release mechanism and are controlled by the observer with an
operating-control handle placed in the observer's cockpit.
All of the bombs used by our fliers and by the fliers of the other
nations at war were of three distinctive types--demolition bombs,
fragmentation bombs, and incendiary bombs.
Our Ordnance Department built demolition bombs in five different
weights: 50 pounds, 100 pounds, 250 pounds, 500 pounds, and, finally,
the enormous bomb weighing 1,000 pounds--half a ton. The most
frequently used demolition bombs, however, were those of the 100-pound
and 250-pound sizes. The demolition bombs were for use against
ammunition dumps, railways, roads, buildings, and all sorts of heavy
structures where a high-explosive charge is desired. These bombs had a
shell of light steel which was filled with trinitrotoluol--T. N. T., as
it is more commonly known--or some other explosive of great destructive
power. The charge was set off by a detonator held apart from the
dangerous contents of the bomb by a pin. As the bomb was released by
the mechanism the pin was automatically drawn out, and the detonator
slid down into position so as to explode the bomb the instant it struck
its object.
The first contract let for drop bombs of any type was given to the
Marlin-Rockwell Corporation of Philadelphia in June, 1917. This
contract was for the construction of 5,000 heavy drop bombs of the
design known as the Barlow, and also for 250 sets of release mechanisms
for this bomb. We were able to go ahead with the production of this
bomb at this early date since it was the only one of which we had
completed designs and working drawings when we entered the war. In
November, 1917, this order was increased to 13,000, and in April, 1918,
to 28,000.
The Barlow bomb, however, was destined never to cut any figure in our
fighting in France. The production was slow, due to the necessity of
constant experimentation to simplify a firing mechanism which was
regarded as too complicated by the experts of the War Department.
Finally, in June, 1918, when 9,000 of these bombs and 250 sets of
release mechanisms had been produced, a cablegram came from the
American Expeditionary Forces canceling the entire contract.
Meanwhile, the final type of demolition bomb, known variously as the
Mark I, II, III, IV, V, or VI, depending upon its size, had been
developed here. In December, 1917, a contract for 70,000 of the size
known as Mark II, weighing 25 pounds, was given to the Marlin-Rockwell
Corporation. But in June the American Expeditionary Forces informed us
that this bomb would not be of value to the Air Service abroad because
of its small explosive charge, and the contract was cut down to 40,000
bombs, which number the Army could use in training its aviators. By the
end of November, 1918, bomb bodies of the Mark II size to the number of
36,840 had been completed.
By the end of March, 1918, we had developed here a series of demolition
bombs that promised to meet every need of our Air Service abroad in
projectiles of their class. We let contracts for the manufacture of
300,000 of the 50-pound Mark III size, these contracts being reduced
later to a total of 220,000. The manufacturers were the A. O. Smith
Corporation, an automobile parts concern of Milwaukee, Wis.; the
Edward G. Budd Manufacturing Co. of Philadelphia; and Hale & Kilburn
of Philadelphia. Six months later the A. O. Smith Corporation had
reached a production of 1,200 of these bombs a day, and completed their
contract in October. Both the other concerns also completed their
contracts in the autumn of 1918.
[Illustration: TWO OF THE LARGEST DEMOLITION DROP BOMBS.
The larger of these two bombs weighs 1,000 pounds and carries
570 pounds of explosive. The smaller weighs 550 pounds and
carries 280 pounds of explosive. They are both made with a
heavy cast-steel nose and pressed metal rear body.]
[Illustration: MARK II BOMB RELEASE MECHANISM FOR HANDLEY-PAGE MACHINE,
SHOWING MARK I AND MARK IV BOMBS IN PLACE.]
[Illustration: MARK IX-A RELEASE MECHANISM AS ATTACHED TO MARK II
RELEASE FOR HANDLEY-PAGE PLANE.]
The A. O. Smith Corporation had tooled up their factory so as to become
one of our largest producers of airplane bombs. In addition to the
contract already mentioned, during 1918 this concern received orders
for approximately 300,000 demolition bombs of the 100-pound (Mark I)
size. By November 11, 1918, they had turned out 153,000 of these and
had developed a capacity for building 7,000 drop bombs daily. Another
large manufacturer of drop bombs was McCord & Co., of Chicago, a
concern which in 1918 received orders for nearly 100,000 bombs of the
250-pound, 550-pound, and 1000-pound sizes. By the day the armistice
was signed this concern had produced 39,400 completed bombs. These
bombs were the heaviest and largest ones intended for use by our
service abroad.
The fragmentation bombs differ from the demolition bombs in that they
have thick metal walls and consequently smaller charges of explosive.
They throw showers of fragments like those of high-explosive artillery
shell. The demolition bombs contain, on the other hand, the maximum
possible amount of explosive and produce destruction by the force
of explosion. Fragmentation bombs always have instantaneous firing
mechanisms, while demolition bombs are usually provided with delayed
fuses, allowing them to penetrate the target before explosion.
The fragmentation bombs produced by the Ordnance Bureau were smaller
than the demolition type, the size most commonly used weighing 24
pounds. These bombs had thick cases and were constructed so that they
would explode a few inches above the ground. As the bombs reach a
velocity downward of over 500 feet per second, the mechanism had to
operate to an accuracy of less than one-thousandth of a second. They
were designed for use against bodies of troops.
The fragmentation bombs were a late development in this class of
work. The timing device to explode the bomb at the proper distance
from the ground was undertaken by three concerns. The contracts for
approximately 600,000 of these devices were let in July, 1918. The
John Thomson Press Co. of New York City completed its contract for
100,000 mechanisms by the end of October, 1918. The National Tool &
Manufacturing Co. of St. Louis completed its contract for 100,000
shortly after the armistice was signed. The Yale & Towne Manufacturing
Co., Stamford, Conn., which had contracted to build approximately
400,000 of these devices, had turned out 150,000 by the end of
November, 1918. Other concerns which manufactured various parts for
the fragmentation bombs were the American Seating Co. of Grand Rapids,
Mich., makers of school desks and seats, and the Dail Steel Products
Co. of Lansing, Mich.
Some idea of the quantity of fragmentation bombs in our program may
be gained from the fact that the contract for the Cordeau-Bickford
fuse used in the fragmentation bomb, let to the Ensign-Bickford Co. of
Simsbury, Conn., called for the manufacture of 550,000 linear feet of
fuse, or more than 100 miles of it. The contracts for fuse were placed
in August and September, 1918, and the Ensign-Bickford Co. finished up
the job on November 7, four days before the armistice was signed.
The Government discovered that 3-inch shell rejected for various
reasons could be re-machined and used to make these airplane
fragmentation bombs. The various arsenals had a large supply of them
in storage. In August and September, 1918, contracts were let to
large numbers of concerns to convert over 500,000 of these shell into
fragmentation bombs, and by November 30, nearly 21,000 of the new bombs
had been delivered.
These bombs, made from the 3-inch shell, as far as the machining of
the bodies is concerned were turned out in various quantities by the
following firms:
Vermont Farm Machinery Co., Bellows Falls, Vt.
Richmond Forgings Corporation, Richmond, Va.
Bethlehem Steel Co., Bethlehem, Pa.
Consolidated Car Heating Co., Albany, N. Y.
S. A. Woods Machine Co., South Boston, Mass.
Westfield Manufacturing Co., Westfield, Mass.
Wheeling Mold & Foundry Co., Wheeling, W. Va.
A. P. Smith Manufacturing Co., East Orange, N. J.
Watervliet Arsenal, Watervliet, N. Y.
Keystone Machine Co., York, Pa.
McKiernan Terry Drill Co., Dover, N. J.
The nose-firing mechanism for these bombs was produced by the Yale
& Towne Manufacturing Co., Stamford, Conn.; the National Tool &
Manufacturing Co., St. Louis, Mo.; and the John Thomson Press Co., New
York City; while the rear cap stabilizer assemblies were produced by
the Dail Steel Products Co., Lansing, Mich., and the American Seating
Co., Grand Rapids, Mich.
The last item on the bomb program to come into production was the
fragmentation bomb Mark II-B, which was an exact copy of the British
Cooper bomb, the most effective bomb of this type in use by the allied
nations. Contracts for this bomb were not let until August 17, 1918,
to the Lycoming Foundry & Machine Co., of Williamsport, Pa., and the
Paige-Detroit Motor Car Co., of Detroit, Mich. The former company by
December 1 was producing these bombs at the rate of 500 per day and
the latter was just coming into quantity production the first week in
December.
[Illustration: TWO VIEWS, MARK V RELEASE TRAP (RIGHT HAND) WITH
UNIVERSAL NOSE AND TAIL BEAM, MOUNTED ON T-RAILS UNDER RIGHT WING OF
DH-4 PLANE.
Upper--Front view, showing operating tube connected to
alternating cam in fuselage. Two Mark III demolition drop bombs
(150 pounds) held by supporting straps; one bomb released,
showing free supporting strap. Lower--Rear view, showing method
of retaining stabilizer by tail clip with three Mark III
demolition drop bombs.]
[Illustration: TWO VIEWS OF MARK X RELEASE TRAP ON PLANES.
Shows Mark X release trap (Cooper) mounted upon T-rails under
wing of DH-4 plane. Bowden control wire and casing connected
to fuselage. Two Mark II-B fragmentation bombs suspended--one
arming vane retained, the other free.]
When the United States entered the war no satisfactory incendiary bombs
had yet been produced by any country, and consequently a long period
had to be given over to experimentation before quantity production
could be attained. We produced two types of incendiary bombs, the first
being of the scatter type, designed for use against light structures,
grain fields, and the like, and the second of the intensive type, for
use against large structures. Later on in our program we abandoned the
manufacture of the scatter type incendiary bombs on cable instructions
from abroad, as it was found that the wet climate made a bomb of
this type of little value. The American intensive bomb, while it had
not yet come up to our ideal and was in process of evolution during
its manufacture, nevertheless was regarded by our officers as more
effective than any other bomb of its type in existence, since it
produced a larger and hotter flame.
Our intensive incendiary bombs weighed about 40 pounds each and
contained charges of oil emulsion, thermit, and metallic sodium, a
combination of chemicals that burns with intense heat. These bombs were
used against ammunition depots or any structures of an inflammable
nature. The sodium in the charge was designed to have a discouraging
effect upon anyone who attempted to put out the fire of the burning
charge, since metallic sodium explodes with great violence if water is
poured upon it.
Of the scatter bombs we built 45,000 before abandoning the manufacture,
an action taken in September, 1918. When hostilities ceased we had out
contracts for 122,886 of the intensive bombs and about 86,000 of them
had been delivered ready for loading.
One of the large manufacturers of incendiary bombs was the
Conron-McNeal Co., of Kokomo, Ind., manufacturers of skates. The
company had to equip its plant with new machinery especially for
handling this novel manufacturing enterprise. In all, they produced
50,000 bombs and were turning them out at the rate of 400 per day
when the armistice was signed. This concern was the pioneer in the
manufacture, the subsequent contractors profiting by the experience of
the Conron-McNeal Co., and consequently being able to obtain quantity
production more quickly than the Kokomo plant had been able to reach
it. The Globe Machine & Stamping Co., of Cleveland, Ohio, built 30,000
bombs and 36,400 firing mechanisms before hostilities closed, and
eventually reached a production rate of 500 bombs and 1,000 firing
mechanisms per day. Parrish & Bingham, also of Cleveland, produced
13,000, and were turning them out at the rate of 400 daily when the
production was stopped. The C. R. Wilson Body Co., of Detroit, built
42,562 of the intensive bombs and reached a daily production of 500.
The New Home Sewing Machine Co., of Orange, Mass., manufactured 20,000
firing mechanisms for the scatter-type bombs.
One of the interesting phases of the bomb manufacturing program grew
out of the necessity for target practice for our aviators. For this
work we built dummy bombs of terra cotta, costing about a dollar
apiece. Instead of loading these bombs with explosive, we placed in
each a small charge of phosphorus and a loaded paper shotgun shell, so
that the bomb would eject a puff of smoke when it hit its object. The
aviators could see the smoke puffs and thereby determine the accuracy
of their aim.
The Gathmann Ammunition Co. of Texas, Md., was the first contractor
for dummy bombs, building 10,000, which were delivered in the spring
of 1918. In the spring and summer of 1918, the Atlantic Terra Cotta
Co., the New Jersey Terra Cotta Co., both of Perth Amboy, N. J., and
the Federal Terra Cotta Co. of Woodbridge, N. J., each built 25,000 of
these bombs. In September additional contracts for 50,000 dummy bombs
were given to each of these three concerns, while another contract for
25,000 went to the Northwestern Terra Cotta Co. of Chicago. By the end
of November these concerns had delivered nearly 34,000 of the 175,000
bombs contracted for, and were turning them out at the rate of 1,300
per day.
The Essex Specialty Co. manufactured 10,000 phosphorus rolls for dummy
bombs, and the Remington Arms-U. M. C. Co. supplied 10,000 shotgun
shells for the first bombs produced. Later the Remington Arms Co.
produced 100,000 shotgun shells for dummy bombs.
AIRPLANE PHOTOGRAPHIC SUPPLIES.
In four days of the final drive of the Yankee troops in the Argonne
district the American photographic sections of the Air Service made
and delivered 100,000 prints from negatives freshly taken from the air
above the battle lines. This circumstance is indicative of the progress
made by military intelligence from the days when a commander secured
information of the enemy's positions only by sending out patrols,
or from spies. The coming of the airplane destroyed practically all
possibility for the concealment by day of moving bodies of men or of
military works. Mere observation by the unaided eye of the airmen,
however, soon proved inadequate to utilize properly the vantage point
of the plane. The insufficient and often crude and inaccurate drawings
brought in by the airplane observer were early succeeded by the almost
daily photographing of the entire enemy terrain by cameras, which
recorded each minute feature far more accurately than the human eye
could possibly do. The airplane, to quote the common saying, had become
the eye of the Army, but the camera was the eye of the airplane.
This development in military information-getting from start to finish
was entirely the product and an evolution of the great war. When
the war broke out in 1914 there were no precedents for the military
photographer to go by, nor had any specialized apparatus ever been
designed by either side for this purpose. As a result the first crude
makeshifts were rapidly succeeded by more and more highly developed
equipment.
At the outset of the war, before antiaircraft guns were brought
to efficiency, it was possible for the observation planes of the
British, the French, and the Germans to fly at low altitudes and take
satisfactory pictures with such photographic appliances as were then
in common use. But as the "Archies" forced the planes to go higher in
the air, special equipment had to be designed for longer distance work
under the adverse conditions of vibration and speed, such as exist on
airplanes. It is a tribute to the photographic technicians of the world
that they were able to produce at all times equipment to meet these
increasing demands.
[Illustration: TYPE DR-4, DE RAM CAMERA.]
[Illustration: TYPE A-3, HAND-HELD AIRPLANE CAMERA.]
[Illustration: TYPE L, 4 x 5 PLATE CAMERA.]
[Illustration: MOBILE FIELD PHOTOGRAPHIC OUTFIT, USED FOR AIR SERVICE.
It includes a dark room, printing lantern, and light-generating plant.]
As the airplanes moved into higher altitudes, longer focus lenses
had to be employed, special dry plates developed, and special color
filters provided to overcome the haze created by humidity in the long
spaces between the cameras and the ground. When the war ended, cameras
were in common use taking photographs at an altitude of 4 miles with
such microscopic fidelity as to show even where a single soldier had
recently walked across a field.
The American Army came into the war almost innocent of any information
at all on the subject of war photography. Such technical information as
the allied nations had developed during the war had been most carefully
guarded from us and all other neutral countries, with the result that
what information we had was of a meager and conflicting sort.
Although in the early months of our participation in the war the
Signal Corps, which then had charge of all phases of aerial warfare,
made large purchases of motion-picture cameras, hand cameras, and
view cameras, it was not until the end of 1917 that our officers were
able to begin their real development of aerial photography. By this
time we had received much valuable information from the foreign high
commissions and samples of their earlier apparatus. Aerial photography
had become one of the leading activities of the air service. Thus
in April, 1917, the British service made 280,000 pictures at the
front, and a great part of all flying was done to secure photographs.
Moreover, the art was advancing at such a pace that practices in
approved use one week at the front appeared likely to become obsolete
the next, as new methods and new equipment superseded the old.
For years America had been second to none as a photographic country,
and it was to be expected that this country would make notable
contributions to the new science. It may indeed be wondered why, with
the experimental laboratories and the skilled technicians at our
command, we did not start at once to develop our own aerial designs
and equipment. Our officers, however, felt that such a course would
be likely to duplicate much of the work already done by the allied
countries, who stood ready then to furnish to us the results of their
experiences. While original research work might result in the invention
here of certain equipment of superlative merit, yet we would be sure,
in the course of such an undertaking, to adopt methods which had been
tried and discarded by the allies and which we ourselves would have to
discard when experience had proven them to be without value.
The information in our hands in December, 1917, showed that the
British system of air photography differed radically from that of the
French. The French cameras made a relatively large negative, 18 by 24
centimeters in dimension, on a glass plate. The magazines of the French
cameras held 12 plates, and extra magazines were carried in the plane.
These cameras were fitted with lenses of relatively long focus--20
inches. Three operations were necessary to make an exposure. The
photographer must change the plate, set the focal plane shutter, and
press the release. When the negatives were developed, fixed, washed,
and dried, prints were made by contact.
The British used a smaller-sized plate, 4 by 5 inches in size. Their
cameras were equipped with the only lenses available in England in
the early part of the war--lenses of relatively short focus, ranging
from 8 to 12 inches in this respect. Instead of making contact prints
from these plates, the British made enlargements, measuring 6½ by 8½
inches. In the earlier period of our development of aerial photographic
apparatus, we were in the same position as the British as regards
lenses. We had no adequate supply of long-focus lenses. Consequently we
followed the British designs of cameras and adopted the British system
almost explicitly in the training of aerial photographers.
It had been our first thought to use films to a great extent on
the front, since America was the country which had perfected the
photographic film, and was therefore, presumably, best equipped in
skill to adapt it to war uses. But plates had been used practically
exclusively by the British, the French, and the Italians; and it
appeared wisest to follow their experience at first, though all agreed
that film, with its small bulk and weight, would be greatly superior
for airplane use.
The Photographic Experimental Department of the Air Service, which was
organized in January, 1918, had as its major problems the design and
test of aerial cameras and all their parts and accessories. Equally
important with this problem was that of sensitive plates, papers,
color filters, and photographic chemicals. The corps of photographic
and optical experts, into whose hands these matters were placed,
early secured the active cooperation of the chief manufacturers
of photographic apparatus and materials in this country. In the
laboratories in Washington, D. C, Langley Field, Va., and Rochester, N.
Y., comprehensive development work was inaugurated, leading ultimately
to perfection of new designs of cameras and the development of plates
and other photographic materials equal or superior to any available
abroad.
The first airplane camera which it was decided to put into production
in America was a close copy of the British type "L," which use had
proven to be one of the best mechanisms employed at the front. The
operation of this camera was semiautomatic, the operator having nothing
to do except to press the shutter-release to keep the camera at work.
The operating power was derived from a small windmill or air propeller
driven by the rush of air past the plane. The automatic mechanism
changed the plate and set the shutter after each exposure. Because of
the situation with respect to lenses these cameras were constructed
to use lenses of 8-inch to 12-inch focus, and the English 4 by 5
plate. Some 750 of these cameras were constructed. They played an
indispensable part in the training of nearly 3,000 aerial photographers
in this country. They were also used by our bombing squadrons at the
front.
At the same time it was generally agreed that we should plan to follow
the French practice as soon as lenses of greater focal length could be
manufactured in this country. Increase in focal length was becoming
imperative, because aerial photographers were being compelled to
make exposures from much greater heights than in the earlier part of
the war. For the sake of those unacquainted with photography it may
be stated here that lenses of short focal lengths will not record
the details of objects a great distance away from the camera, the
longer-focus, rarer, and more expensive lenses being required for
distance work.
As a basis for the design of cameras of longer focus a sample of the
20-inch focus camera used by the French had been sent to this country
by the American Expeditionary Forces. The first camera authorized of
this focal length was similar in general character to this French
camera. It was constructed on the unit system, each part--shutter,
camera body, lens cone, and magazine--being of standardized dimensions.
It was understood that these standard dimensions were to be followed in
all subsequent cameras both in this country and in the countries of the
allies.
The idea constantly put before all designers of aerial cameras has been
that of the automatic type, in the use of which the observer or pilot
will have a minimum of work. Late in 1917 the Photographic Section of
the Air Service, American Expeditionary Forces, secured the rights
for the manufacture of an ingenious design of automatic plate camera
invented by Lieut. DeRam, of the French Army, and requested that this
be put in production. In this camera the magazine, which carries 50
plates, 18 by 24 centimeters in size, rotates between each exposure,
while the exposed plate is removed from the front of the pile and
carried to the back. After some study here of the incomplete model,
this camera was redesigned in such form as to fit it for methods of
American manufacture. It was made semiautomatic in operation; that is,
the work of the observer or pilot consisted merely in releasing the
shutter at will, a fresh plate always being in place. At the time of
the armistice 200 of these cameras were rapidly approaching completion.
Meanwhile experiments were actively pushed in the matter of the
utilization of film. Various difficulties and problems had to be solved
before film could be considered practical. Considerable time was
consumed in overcoming the peculiar static electrical discharges which
occur on film in cold, dry regions, such as in high mountains or the
upper atmosphere, and fog the sensitive surface by their light. The
film camera finally decided upon was based on a fundamental design by
the Folmer & Schwing organization of the Eastman Kodak Co.
This camera, known as the "K" type, carries a film on which 100
exposures, 18 by 24 centimeters in dimension, can be made at one
loading. The film is held flat by an ingenious device. The film strip
passes over a flat perforated sheet behind which a partial vacuum is
set up by a suction, or "Venturi," tube extending outside the body
of the airplane. The camera is entirely automatic, and is driven
either by a wind turbine of adjustable aperture or, in war planes, by
electric current from the heating and lighting circuit. The observer
in the airplane needs only to start the camera and regulate its speed
according to the speed with which the airplane is passing over the
ground below, and the camera thereafter will, of itself, take pictures
at such intervals as to map completely the terrain under observation.
In conjunction with the use of film in cameras came the question of
handling the film in the dark-room; that is, the ordinary manipulations
of developing, fixing, washing, and drying--a serious problem when the
large dimensions of the film, its length, and difficult characteristics
in handling are taken into consideration. This problem was attacked and
a film developing, handling, and drying machine was produced.
Some 200 of these automatic film cameras were on order at the close
of the war. Altogether over 1,100 airplane cameras of all types had
been and were about to be delivered when the armistice came. These
were built by the Eastman Kodak Co., Rochester; the Burke & James Co.,
Chicago; the G. E. M. Engineering Co., of Philadelphia; and Arthur
Brock, jr., of Philadelphia.
One of the most serious problems in aerial photography is the proper
mounting of the camera in the plane. Not only does the plane travel
at great speed, which makes necessary exceedingly short exposures and
therefore highly sensitive photographic materials, but the motor causes
a continuous vibration which, communicated to the camera itself, would
be fatal to obtaining sharp pictures.
The experimenters of the Air Service carried out a long, extensive,
and most interesting investigation at Langley Field to make clear the
whole question of preventing the vibration of the airplane camera. The
scientists worked out a method of making the camera itself record the
vibrations communicated to it by the plane when the box was not held by
a proper vibration-neutralizing suspension.
The plan adopted was to send up a camera thus mounted on an airplane,
focus it on a light on the ground below, open the shutter, and take a
time exposure from the swiftly-flying plane. The result, of course, was
a streak, or trail, written on the plate by the point of light below,
the jagged or wavy character of this trail indicating the vibrations of
the camera and determining the proper principles of a suitable mounting.
The first thought was to do this work at night, as the British had
done, when the light below would pierce the darkness distinctly. But
night flying is hazardous, and a better plan was called for. Nor would
the proposal to use an extremely strong light in broad daylight do,
because, while the light would indeed be photographed continuously
across the plate, so also would the surrounding ground, and the general
result would be a fogging or blurring of the outlines of the streak.
Finally the problem was solved by conducting the aerial experimental
work over woodland in the late afternoon. A strong, reddish light was
placed in the woods so as to be visible from above. The surrounding
green foliage supplied a frame of sufficient contrast to the light to
make its impression distinct on the plate. To emphasize the contrast,
the camera lens was covered with a reddish colored ray filter, and this
brought out sharply the outline of the streak.
These tests resulted in the design and production of new and unique
camera mountings which successfully stopped all vibrations of the
camera.
A problem on which it was necessary to have the closest cooperation
of the plane designers was that of installing the large 20-inch focus
cameras in the airplane. There is little room at best in a plane,
and the demands for armament, wireless, and bombing space all had to
receive attention. In the American service a distinct advance was made
in the design of a special plane intended primarily for photographic
reconnaissance. Several of these planes, which were the most completely
equipped for photographic purposes of any designed during the war, were
built and would have been put into quantity production in the late fall
of 1918.
Parallel with this development of apparatus went studies of the
sensitive materials and methods of photography from the air. Because of
the swift motion of the plane extremely short exposures are imperative.
Consequently, the most advanced technique of instantaneous photography
had to be applied. The cooperation of various plate manufacturers was
obtained, who brought out especially for the Government several new
plates which showed on test to be superior to any which had appeared
in the war on either side.
As an airplane rises higher and higher in the sky, the moisture
of the intervening atmosphere between the machine and the ground
creates a haze which makes aerial photography above a certain height
unsatisfactory and even impossible with the naked lenses as used on
the ground. The problem of finding the best means for piercing aerial
haze occupied the attention of a corps of experts working both in the
laboratory and in the field. The solution lay in the use of special
color filters of general yellow hue which obscured the bluish light
characteristic of haze. Filters of new materials specially adapted to
airplane use were made available as a result of this study.
Field equipment of quite new and special design for performing
photographic operations had to be designed and built. Among the most
interesting of these developments was the photographic truck or mobile
photographic laboratory. This consisted of a specially designed truck
and trailer containing all the equipment necessary for the rapid
production of prints in the field. The truck body was equipped with a
dynamo for furnishing the electrical current required for lights and
drying fans, while each unit was provided with an acetylene generator
for emergency use, if the electrical apparatus should break down. The
mobile dark room carried on the trailer of each unit was equipped with
tanks, enlarging camera, printing boxes, and other necessary apparatus.
In all, some 75 of these field laboratories were constructed.
While the development of apparatus and new materials was from a popular
standpoint in many ways the most interesting phase of the work of the
photographic scientists, nevertheless it should be remembered that the
great problem in this, as in all other fields of American endeavor, was
to produce the supplies in tremendous quantities. In October, 1918,
we shipped overseas 1,500,000 sheets of photographic printing paper,
300,000 dry plates and 20,000 rolls of film. We also sent 20 tons of
photographic chemicals. These were merely the principal items in the
consignment. Besides paper, plates and chemicals, the field force
required developing tents, trays, printing machines, stereoscopes, and
travelling dark rooms, to name only some of the principal items. Much
of the material already on the market was not suitable for the purpose,
a fact requiring the production of specially manufactured supplies.
THE FIREWORKS OF FLYING.
It is interesting to consider that without fireworks, and particularly
some of the familiar forms of them used to celebrate the Fourth of
July, war flying would have lost much of its efficiency. Night flying
would have been well-nigh impossible, while day flying would have had
to invent substitutes for fireworks had the latter not been available.
[Illustration: MARLIN MACHINE GUN WITH FIXED MOUNTING, ON A JN-4
FUSELAGE.]
[Illustration: TWO LEWIS MACHINE GUNS WITH MOVABLE MOUNTING, IN THE
OBSERVER'S COCKPIT OF A DE HAVILAND-4.]
[Illustration: AIRPLANE FLARE.]
[Illustration: HOLT WING-TIP FLARE HOLDER.]
The squadron fields near the front were kept as dark as possible at
night for obvious reasons. The first inkling that a squadron commander
might have of the approach of one of his aviators at night would be
the sudden appearance high in the air of a green or red or white
Roman-candle ball. This would be the signal inquiring if the landing
field were clear. A pyrotechnic star of a predetermined color, shot
from the ground, would answer the homing birdman; and, if the signal
were in the affirmative, he would descend through the sheer blackness,
unable to see clearly, yet confident that he would make his landing
safely.
As the plane neared the ground suddenly under one of the wings a flare
of dazzling power would commence to burn, for a few seconds flooding
the field with light. In that brief space of time the plane would have
made its landing, and soon field and quarters would again be obscured
under the protecting blanket of darkness.
Every service airplane at the front was equipped with one or more
signaling pistols. In appearance these weapons were more murderous than
the "gat" carried by a desperado of the movies, but, like the prize
bulldog with the undershot jaw, they were more deadly in looks than
in deeds. Their formidable-appearing cartridges were larger than the
shells used in shotguns, resembling the latter almost identically in
appearance; but every one of these shells contained only a Roman-candle
ball and a sufficient charge of powder to eject the star a good
distance into the air. The sound of the discharge was a mere whisper
of the shattering roar that might be expected from such a redoubtable
piece of ordnance. These aviation pistols were similar to the Very
signal pistols used in the trenches.
The stars shot were three colors, red, green and white, and the color
of a cartridge's star was painted on the end of the shell. This base
was also ridged with a different pattern for each color, so that the
aviator at night could feel with his fingers and tell the color of the
cartridge without seeing it.
Codes of numerous messages were worked out in different combinations
of these three colors. The stars were quite visible in broad daylight,
too, and were used for many signaling purposes. They indicated the
position of enemy troops or the presence of hostile aircraft, they
called for help from other airplanes, and they signaled squadron orders
when the machines were flying in formation.
But the signal pistol had a more sinister use. If the pilot were driven
down in enemy territory, it became his duty to destroy his machine. In
some cases the signal pistol was used effectively to set airplanes on
fire under such conditions. The pilot had only to open his gasoline
tank and fire a Roman candle ball into the escaping fluid. In other
cases when the aviator landed amid enemy troops he was able to hold
them at bay with his signal pistol until his plane was burned beyond
the possibility of salvage.
While we manufactured Very pistols in this country, all of those
actually used by our fliers in France were purchased abroad.
Night-flying is one of the most hazardous duties of the aviator, the
chief danger being in landing. The fields well back of the front were
usually brightly illuminated by flood lights at night, but those nearer
the enemy were left in darkness, as a rule, to protect them from the
attacks of hostile aircraft. The aviator at night can usually see the
ground faintly, but he is unable to make an accurate judgment of the
distance of his machine above the ground. This danger was greatly
alleviated when the wing-tip flares were invented. The wing-tip flare
consisted of a small cylinder of magnesium material in a metallic
holder, one flare being fitted under each lower wing of the plane. Each
flare was controlled by a push button in the pilot's cockpit. Pressure
on the button sent an electric spark into the magnesium and touched it
off.
When the descending pilot at night judged that he was near the ground
he pushed one of the buttons. Immediately the flare ignited and burned
for about 50 seconds with the brilliant light of 20,000 candle power.
Being hidden by the wing, this light did not dazzle the eyes of the
aviator, but the reflection from the under surface of the wing lighted
up the field for an adequate distance in all directions.
Another important use of pyrotechnics occurred in those enterprises
known as night-bombing raids. Since both sides kept their vulnerable
ammunition dumps and their important buildings completely unlighted
at night, even though the night raider knew he was in the general
vicinity of his objective, hits from bombs dropped from aloft were
almost accidental. To enable the night bomber to see his target
the interesting piece of pyrotechnics known as the airplane flare
was invented. This was a great charge of magnesium light held in a
cylindrical sheet-iron case nearly four feet long and half a foot in
diameter, the exact dimensions being 46 inches by 5 inches. The flare
weighed 32 pounds. Within the cylinder was not only the magnesium stick
but also a silk parachute 20 feet in diameter. The entire cartridge
was attached to the airplane by a release mechanism similar to those
holding the drop-bombs.
When over his objective at night the pilot or observer touched a button
and the entire cartridge, iron case and all, dropped from the plane. A
pin wheel on the lower end of the case was instantly spun by the rush
of air, and the resulting power not only ignited the magnesium but at
the same time detonated a charge of black powder sufficient in force
to eject from the case the flare and its tightly rolled parachute. The
parachute immediately opened; and the burning flare descended slowly,
flooding a large area of the ground below with a light of 320,000
candlepower, this light burning for about 10 minutes.
Such a light not only enabled the bomber to drop his destructive
missiles accurately, but it was found by experience that it dazzled the
eyes of antiaircraft gunners below and made their aim inaccurate. The
light of this flare was so strong that it was possible for the airplane
above to obtain photographs of good detail on the darkest of nights.
We were just starting to produce these flares when the war ended. In
fact the actual production of pyrotechnic supplies in this country was
small, the American Expeditionary Forces depending almost exclusively
for these supplies upon French and British sources.
KEEPING OUR FLIERS WARM.
When the commander of an airplane squadron sends an aviator into the
high altitudes, he sends him into climate that much of the year is
colder and more severe than any known on earth, even at the North Pole.
Not only is the temperature of the air likely to be many degrees below
zero at the heights which war planes attained, but the flier must face
this bitter cold in the gale of wind that is never blowing less than
100 miles per hour.
Consequently when we trained a corps of aviators to fly at altitudes of
18,000 to 20,000 feet above the western front, it was necessary for us
to design and manufacture for them the warmest clothing ever made. They
were dressed more warmly than any Polar exploration party that ever set
forth, more warmly in fact than any other class of men in the world.
For we not only gave them the protection of all the fine wool, leather,
and fur that they could wear without hindering their movements, but in
addition we literally wrapped them in flexible electric heaters.
The first purchases of aviators' flying clothes were made by the
coordinated action of the Council of National Defense and the
Quartermaster's Department. It was soon apparent that the design of
such clothing was a special matter which the aviation authorities
themselves should control, and purchases thereafter were all made by
the Bureau of Aircraft Production. There were no standard styles at the
time, so it became necessary for us to develop our own equipment. This
development resulted in an output for the flier that became standard.
In moderate weather the flier wore upon his head a woolen hood, or
helmet, extending well down over the forehead to the eyes, and around
the neck to the shoulders. In cold weather, or for high-flight work,
this headgear was augmented by a silk helmet of double thickness,
having between its layers an electrically heated pad connected by
copper wire to the electric generator on the plane's engine. Outside of
this was worn a soft leather helmet lined with fur, extending down over
the back of the head, covering the ears and cheeks, and fastening under
the chin. Then the face was entirely covered with a leather face mask
lined with wool and having an opening for the eyes, over which were
worn a pair of goggles. When the pilot was also required to operate
the radio system, in place of the fur-lined helmet he wore the radio
helmet. This was of leather and resembled the other in appearance, but
it contained the receiver of the wireless telephone, enabling the flier
to hear what was spoken to him in an ordinary tone of voice several
miles away.
In addition to this equipment the aviator who went up to the great
heights wore the oxygen mask. This was of rubber, and, besides
supplying oxygen, it contained a transmitter, allowing him to speak as
well as to hear by wireless.
Over the body was worn a one-piece flying suit extending from the feet
to the throat, belted and buttoned tight at the ankles and wrists. The
outer material of this suit was waterproof, and when it was buttoned on
there were no gaps through which the air might penetrate. This suit was
lined throughout with fur.
It was a considerable problem to find a fur of extreme warmth with a
pelt strong enough to withstand rough usage and still not be too great
in bulk, and purchasable at a price not too extravagant. After the
furs of many beasts had been examined and tested, it was determined
that the hide and fur of a Chinese Nuchwang dog met these requirements
better than any other. We were making so many of these suits that we
required all of the dogskins we could get, not only in this country,
but in China. Merely the final purchase of these pelts before the
armistice was signed was for nearly 500,000 of them, and that many dogs
in an interior Chinese province gave up their lives that the American
aviation warfare might succeed.
With its waterproof outer surface and its furry lining, it might
seem that such a garment would be warm enough for any work. But the
aircraft authorities of the United States were not content until they
had installed between the fur and the outer covering thin, flexible,
electric-heat units connected by silk-covered wire with the dynamo
on the engine. Similar heating pads were placed in the gloves and
moccasins of the fliers.
On their hands, besides the electrically heated gloves, the fliers wore
gauntlets of muskrat fur, these extending well up the arms and being
of special design which allowed the fingers of each glove to remain in
a fur-lined pocket or to be withdrawn from the pocket without removing
the gloves from the hand. Over the electrically heated moccasins were
worn leather moccasins extending well up the calf of the leg and lined
with heavy sheep wool. These were fastened with straps and buckles.
Thus clad, our aviators were acknowledged generally to be the most
warmly and efficiently equipped of any at the front.
Besides these special garments for warmth, the fliers required many
other items of clothing, such as sweaters, leather coats, fur-lined
coats, helmets, and many styles of goggles.
The total cost of air clothing, provided or in course of manufacture
on November 11, 1918, was over $5,000,000. Some of the major items in
round numbers were 50,000 fur-lined flying suits (at $36.25), 100,000
leather helmets, an equal number of leather coats, costing anywhere
from $10 to $30 each, and over 80,000 goggles at $3.50 apiece.
PROTECTION IN HIGH ALTITUDE FLYING.
Even to-day the veteran of the air squadron scoffs at the newfangled
outfits of oxygen masks and tanks carried in an experimental way on
some of the high-flying planes at the western front when hostilities
ceased. Nevertheless, had the war continued a few months longer, it
is probably true that the oxygen apparatus would have been included
in the indispensable equipment of every airplane in the front areas.
Such a development, had it occurred, would have been due largely to the
efforts of the American Aircraft Service.
Many aviators who have gone into high altitudes, fought there, and
lived to tell about it, doubt the necessity of oxygen-supplying
apparatus, since they themselves returned safely without it.
Nevertheless the experiments conducted by the Bureau of Aircraft
Production demonstrated conclusively that the flyer artificially
supplied with oxygen in the high altitudes is much more efficient than
one who is without it. These experiments were conducted in a room
which duplicated the conditions at high altitudes. At 19,000 feet the
pressure of the atmosphere is one-half the atmospheric pressure at sea
level. The lack of pressure in itself causes no appreciable physical or
mental reaction; but the reduced pressure at 19,000 feet means that in
a given amount of air there is only one-half the oxygen that there is
in a similar amount at sea level. The lack of oxygen is serious.
Experienced aviators were placed in an air-tight chamber under the
observation of Government scientists. The air in this chamber was then
exhausted until it corresponded to the atmosphere at the 19,000 feet
level. The subjects were then set at small mechanical tests, such as
the pushing of certain buttons when different colored lights were
turned on, these tasks requiring a degree of mental concentration. In
this and similar tests it was discovered that not only do the subjects
lose accuracy in the attenuated air, but their movements become
conspicuously slower. In the parlance of the pilot they become "dopey."
More than one returning aviator has confessed to this feeling when at a
high altitude.
When the British analyzed their air casualties during the first year
of the war they found that 2 of each 100 fliers in the casualty list
were killed or hurt by the enemy, 8 of them owed their misfortune to
defects in the planes, while the other 90 came to the hospital or the
grave because of themselves, their carelessness or recklessness, their
physical failings, and all other things which may be summed up in the
human equation. A thorough study on the part of the British disclosed
the fact that practically all of the flying personnel was suffering
from what became known as oxygen fatigue, caused by flying so many
hours each day in altitudes where there was not enough oxygen to feed
the body properly.
Before the war broke out the aviation record was 26,246 feet above sea
level. In January, 1919, this record had been lifted nearly a mile, the
high point being an altitude of 30,500 feet. Early in the war pilots
at the 7,000 feet level could laugh at antiaircraft fire, and few
machines ever went above 10,000 feet. Thus with the first equipment the
"ceiling"--that is, the average high level to which every day flying
goes--was about 12,000 feet.
When the war closed, a pilot was not safe under the 15,000 feet level,
due to the development of antiaircraft guns, and the safest machine
had become that which could fly highest. The aviators were demanding a
working ceiling of 18,000 feet, and were obtaining it, too, from the
latest type of planes. It was evident that the reduced oxygen at this
ceiling was responsible for casualties among the fliers, and we could
expect the ceiling to be pushed even higher as antiaircraft guns became
more powerful. The need of oxygen equipment was plainly indicated.
Even at 18,000 feet the aviator relying upon the normal oxygen supply
at that altitude, while he may feel perfectly fit, is actually slow to
judge distances, to aim his guns, to fire them, and to maneuver his
plane.
The first oxygen apparatus was designed for the British Air Service
and was made at the plant of de Lestang in Paris. The demand for the
apparatus was so great that an automobile was constantly kept waiting
at the factory that as soon as each set was finished it could be rushed
straight to the front. The first British squadron which used oxygen
equipment reported that its men gave six times the service of any other
British squadron.
Our Air Service adopted the Dreyer oxygen apparatus, which was the
original device produced by the British. We found it to be a hand-made
appliance, but under our direction we adapted it to American methods of
manufacture. The British apparatus was built to supply oxygen to one
man only. We changed it to take care of two men. The model received
was too heavy; we reduced the weight. Finally we added improvements to
make it more efficient and reliable and redesigned it to meet American
factory methods.
[Illustration: GUNNER IN COCKPIT EQUIPPED WITH OXYGEN HELMET AND
TELEPHONE RECEIVER, OPERATING MOVABLE MACHINE GUN.]
[Illustration: AVIATOR'S OXYGEN HELMET EQUIPPED WITH TELEPHONE
RECEIVER.]
[Illustration: OXYGEN APPARATUS FOR BREATHING AT HIGH ALTITUDES.]
Such an equipment has to be entirely automatic in its operation and as
reliable as human ingenuity can make it. The Dreyer device embodies
several instruments all of which must work perfectly under widely
varying conditions. In use its tanks will contain oxygen under pressure
ranging from 100 pounds to 2,250 pounds per square inch, yet the
mechanism must deliver the oxygen to the aviator at a constant rate
regardless of its tank pressure. Then the whole apparatus is subjected
to temperatures that may be as high as 80° above zero or as low as
30° below. It must function evenly in the atmospheric pressure at any
altitude up to 30,000 feet, delivering more oxygen as the atmosphere
thins. Such was the problem of manufacture. Yet, taking up the work
in January, 1918, we turned out six complete equipments by May 3,
1918, sending them overseas by special messenger for actual test on
the front. Twenty-eight days later we shipped 200 sets. By the end of
the war we had built 5,000 complete oxygen equipments. Of this number
3,600 had been sent to ports of embarkation awaiting shipment, and over
2,300 of these had been shipped overseas. In October we had reached a
production rate of 1,000 sets per month.
Some of the difficulties of this production may be read in the
description of the complicated character of the apparatus. The
equipment consists of a small tank or tanks, the pressure apparatus,
the tube leading from the reservoir, and finally the face mask
covering the mouth and nose. The mask has combined with it either the
interphone, a mechanism which cuts off the roar of the engine from
the ears of the passengers and allows the pilot and observer to talk
freely with each other, or in certain cases the receiver of the radio
telephone or telegraph.
The flow-regulating apparatus consists of five parts. In front of the
pilot is a high-pressure gauge to indicate the supply of oxygen in the
tank. In the tank there is a high-pressure valve with an upper chamber
which compensates for the temperature. There is also a shut-off valve,
hand operated, which can be set to provide a flow of oxygen to one
man, to two men, or to none at all. Then there is a regulating valve
operated by an aneroid barometer which adjusts the oxygen flow to the
altitude, the flow increasing as the machine goes higher. Finally in
the pilot's view there is a flow indicator consisting of a small fan
wheel which tells the aviator that the oxygen is actually flowing.
The mask presented a difficult problem, as it must be big enough to
contain the radio receivers and still enable the aviator to see and
work. Yet the mask must keep its adjustment in a gale of wind at least
100 miles per hour in velocity.
The actual use of the equipment on the front was just starting when the
armistice was signed. We sent across to France a special division of
experts to take charge of the installation of these equipments on the
planes. At the close of hostilities we required all military planes
flying above an altitude of 10,000 feet to be equipped with oxygen
apparatus. This class included day bombing, pursuit, and chassé planes,
and a certain number of night bombing planes, and Army and corps
observation planes.
[Illustration: TWO VIEWS OF BOMB SIGHTS USED ON AIRPLANES.
Upper picture shows bomb sight on De Haviland 4. Lower
picture shows high-altitude bomb sight. Set from readings of
instruments showing altitude and air speed. It indicates to the
bomber the precise instant for release of the bomb in order to
reach the target.]
[Illustration: AVIATORS EQUIPPED WITH TELEPHONE TRANSMITTERS AND HEAD
SETS TO COMMUNICATE WITH EACH OTHER.]
CHAPTER VI.
THE AIRPLANE RADIO TELEPHONE.
Electrical science was called upon to furnish marvels and prodigies
indeed during the recent war as aids to the American arms, but in no
respect did it respond in more successful and spectacular fashion than
it did when asked to produce a wireless telephone system that would
make possible the transmission of human speech to and from moving
airplanes. It is doubtful if any other branch of science enlisted for
war work produced any instrument or mechanism so far in advance of what
was known before the war as the airplane wireless phone was in its
class.
To be sure, we had the radio telephone some time before America entered
the war or even before the war broke out in Europe in 1914. Ever since
the scientists began experimenting with wireless electricity it has
been axiomatic that, at least theoretically, whatever you can do with
wires you can do without wires. And so following the development of
the wireless telegraph came the production of the wireless telephone,
and the invention had been so perfected in 1915 and 1916 that in the
United States Navy's official test at the Arlington Station, across
the Potomac River from Washington, human speech sent out by the
transmitters there was heard simultaneously at the Eiffel Tower in
Paris and at the Government's own wireless station in Hawaii.
But there is a vast difference between using the wireless telephone in
the quiet of the radio rooms aboard ship or in the shore stations and
using it amid the roar of the powerful engine propelling an airplane.
The equipment, too, that had been used on the ground was altogether too
cumbersome to go into the fuselage of an airplane.
As early as August, 1910, American genius had successfully accomplished
wireless telegraph transmission from airplane to ground, and in October
of the same year the idea of aerial fleet command by telephone was
conceived and plans for its development discussed by Army officers on
duty at the International Aviation Tournament at Belmont Park, Long
Island. In 1911 a message was successfully transmitted from an Army
airplane over a distance of 2 miles. In 1912 the Signal Corps had
increased the distance to 50 miles. Two years later, in the Philippine
Islands, a message had been successfully received on an airplane in
flight over a distance of 6 miles.
In 1915 the Aviation Section entered upon a definite plan of
development of aircraft wireless at the Signal Corps Aviation School,
San Diego, Calif. This plan was based upon the Belmont Park idea
and discussions, with the voice-commanded tactical air fleet as the
ultimate goal. The airplane had changed from the pusher to the tractor
type, with the noise of the motor of the latter driven back by the
blast of the propeller into the face of the aviator. The airplane
wireless problem was thus quite completely changed. Under these new
conditions, however, the development was entered upon, and it has since
been continuous. In October a spring-driven dictaphone was taken into
the air and a record of speech made in the noise of the motor. This was
contemporaneous with the successful long-range experiments in radio
telephony at Arlington, referred to above. A study of this dictaphone
record convinced the aviation officers that the idea of the radio
telephone for airplanes was entirely practicable. Experiments during
the fall and winter with various means of driving the wireless power
plant resulted in a decision to develop the air fan as a source of
power rather than the gear or belt system.
This development continuing through 1916, transmission by telegraph
from airplane was accomplished up to 140 miles, means for receiving
in the noise of the motor were worked out, and a message successfully
telegraphed between airplanes in flight. The radio telephone was under
construction, and in February, 1917, the voice was first transmitted by
telephone from airplane to ground. Like Alexander Graham Bell's first
wire telephone, the apparatus was crude. But the door was unlocked and
ready to be opened upon the new field of development.
When on May 22, 1917, Gen. Squier, the Chief Signal Officer of the
Army, called upon the scientists to develop at once an airplane
telephone, he was not only introducing them into what was to many of
them a new field, but he was asking them to produce what the science
of Europe had been unable to create in nearly three full years of
acquaintance with the successful ground system, although the needs
of airplane fighting demanded this invention as they demanded almost
nothing else.
It will thus be seen that when we began this development as a war
measure we had a considerable basis of experience to work upon. The
Army had established the foundation of operation on the airplane,
made a study of the tactical requirements, and knew what it wanted.
The Western Electric Co. in 1914 and 1915 had conducted extensive
experiments with the radio wireless telephone at a ground station
at Montauk, Long Island, and had played an important part in the
long-range experiments at the Arlington station. There had been
wireless voice communication before this time, but the apparatus and
systems perfected at Montauk set the standard on which all subsequent
development was built. The French Scientific Mission and other officers
of the allies had arrived and enabled us to check up what had been done
abroad and to confirm or modify our ideas of the tactical requirements.
At the conference with Gen. Squier in May was Col. Rees of the Royal
Air Force of Great Britain; Col. C. C. Culver, United States Army, then
a captain; and F. B. Jewett and E. B. Craft, respectively the chief
engineer and the assistant chief engineer of the Western Electric Co.
At this meeting Gen. Squier outlined the future of the part the
airplane was to play in the war, and pointed out how invaluable would
be a successful means of communication between battle planes when
flying in squadron formation. Mr. Jewett had received his commission as
a major in the Signal Corps, and he was ordered to take charge of the
work of developing radio communication for aircraft.
Capt. Culver had taken part in the 1910 experiments and discussions,
and since 1915 had been conducting the Army development of airplane
wireless at the aviation school at San Diego, Calif. He was detailed to
work with Maj. Jewett and his engineers, bringing to their assistance
the result of his experience and the point of view of the trained
military man and the aviator.
The first development was carried on in the laboratories of the Western
Electric Co. on West Street, in New York. Men and materials were
drafted from every department of the company, and the laboratories
were soon seething with activity. In a few weeks the first makeshift
apparatus was assembled, and the first practical test of a radio
phone on an airplane was made at Langley Field at Hampton, Va., less
than six weeks after the Signal Corps had given the go-ahead. Three
employees of the Western Electric Co. on that day established telephone
communication between an airplane in flight and the ground. A few days
later the first apparatus produced successful communication between
planes in the air.
It is not possible here to go into a technical description of the
wireless telephone. The most vital part of the apparatus, however, and
the essential factor in airplane wireless telephone communication is a
vacuum tube containing an incandescent filament, a wire mesh or grid,
and a metal plate. By means of electrical current the wire filament is
heated to incandescence. The tube has the property of receiving the
energy of the direct current of a dynamo and, through the medium of the
wireless antennæ, of throwing it out into space as a high-frequency
alternating current. Such is the sending tube. A modification of the
same tube picks up from the antennæ the high-frequency alternating
vibrations from another sending apparatus and transforms them into
direct current, carrying the sound waves of the human voice along with
them.
The design of the radio apparatus itself was relatively simple for
the experts who had undertaken the work, for the company had already
developed some highly successful forms of vacuum tubes, and it was
an easy matter for these technicians to assemble tubes with the
necessary coils, condensers, and other apparatus of the transmitting
and receiving elements and produce a system of such small compass that
it could be carried on an airplane. But working this apparatus under
ordinary conditions in the quiet laboratories and in a swift-moving and
tremendously noisy airplane were two different propositions.
One of the first problems was to design a comfortable head set which
would exclude all undesirable noises and admit only the telephone talk.
A form of helmet was finally devised with telephone receivers inserted
to fit the ears of the pilot or observer. Cushions and pads adjusted
the receiver to the ears, and the helmet fitted close to the face so as
to prevent as far as possible the transmission of undesirable sounds
either through the ear passages or through the bony structure of the
head, these bones acting as a sort of sounding board. The designers
finally developed a helmet that solved this portion of the problem.
Not only was it necessary to exclude the roar of the engine and the
rattle of the machine gun from the ears of the men receiving the radio
communication, but it was also necessary to filter out these sounds
from the telephone transmitter. Every person who has ever shouted into
a telephone knows how sensitive the ordinary telephone transmitter is
to extraneous noises. It requires no wide stretch of the imagination
to hear in fancy how an ordinary transmitter would behave when beside
the exhaust of a 400-horsepower Liberty engine. A brilliant line of
experimentation conducted by one of the scientists at the laboratory
resulted in a telephone transmitter or microphone which possessed the
extraordinary quality of being insensitive to engine and wind noises
and at the same time highly responsive to the tones of the human voice.
With the receiver and the transmitter perfected the scientists thought
that the problem of airplane telephoning was solved; but nevertheless
three months of hard work were required before the entire system
could be adjusted and put in such shape that it might be considered a
practical device for everyday use.
The question of weight was of utmost importance, and a structure that
would adequately house and protect the delicate parts of the mechanism
from the vibration and jars of flying and landing and at the same time
not be too heavy for practical use on the plane was a difficult problem
in mechanical design. Day after day the inventors took the mechanism up
in flying machines and brought it back night after night for more work
in the laboratory.
[Illustration: INTERIOR VIEW. AIRPLANE RADIO TELEPHONE SET BOX.]
[Illustration: EXTERIOR VIEW OF SAME.]
This was a period, however, of rapid progress. Officials appearing
on Langley Field from time to time witnessed informal demonstrations
of this development. In August Mr. Baker, Secretary of War, and Gen.
Scott, Chief of Staff, listened to a conversation being carried on
in the air, and some six weeks later Brig. Gen. Foulois witnessed
a similar demonstration and from the ground directed the movements
of the airplane in flight. The experimental apparatus had reached
such a state of efficiency that on October 16, at Langley Field,
communication by voice was carried on between airplanes in flight 25
miles apart and from airplane to ground over a distance of 45 miles.
By September cables had been sent abroad telling of the progress made
in this country on the development of this apparatus. Our officers
abroad were skeptical and could not believe that this country could
outdistance the scientists of the allies who had had three years of
war experience to draw upon. By October the designers had brought the
system to a perfection where they were willing to risk its use in
actual war flying, and Col. Culver took to the American Expeditionary
Forces in France several trunk-loads of the apparatus to acquaint those
abroad with what had been done and to test the apparatus under service
conditions. Meanwhile the development work continued in this country.
Early in December the operation of the apparatus was exhibited in an
official test at the Morraine Flying Field at Dayton, Ohio.
A large number of military and civilian officials not only of our own
country but of the allies had been invited to witness this test. It
must be remembered that at this time even those who had heard about
the progress being made were skeptical of the possibilities of the
successful adaptation of the radio telephone to airplane work. The
designers of aircraft never look with favor upon additional equipment
which may clutter up the machine with trailing wires and the like and
possibly compel alterations in standard lines. The pilots, also, do not
usually give a friendly reception to new equipment for their planes.
The exhibitors at Dayton planned to have two planes in the air at once,
so that the officials might listen in on their conversation at a ground
station located on the top of a hill near the flying field. By hard
work the inventors got their equipment installed, and just at dark
on the evening before the day of the trial one machine equipped with
wireless went up into the air and held successful communication with
the ground.
The next morning when the official party arrived the members viewed
the apparatus in the planes while the inventors explained what it was
expected to do. The visitors were then conducted to the station on
the hill, where those who were putting on the show had rigged up a
megaphone attached to the wireless receiver so that everyone could hear
without putting on a head set.
The attitude of some of the officials, particularly those from the
foreign nations who had had experience in war flying, was skeptical,
if not bored. The planes left the ground, and when the machines had
gone up so high that they were but specks in the sky the receiver began
emitting the premonitory noises that indicated that the men in the
planes were getting ready to perform. Suddenly out of the horn of the
loud-speaking receiver came the words: "Hello, ground station! This is
plane No. 1 speaking. Do you get me all right?"
Looks of amazement came over the faces of all those who had never heard
the wireless phone in operation before. Soon came the signal from plane
No. 2, and then the demonstration was on. Under command from the ground
the planes were maneuvered over much of that part of the country. They
were sent on scouting expeditions and reported what they saw as they
traveled through the air. Continuous conversation was carried on, and
finally, upon command, the planes came back out of space and landed as
directed.
From that moment there was nothing but enthusiasm in all quarters for
the radiophone upon airplanes. It was no longer a question whether
the device would work or was any good, but a question of how soon the
company could start manufacture and in what quantities the device could
be produced.
The demonstrations Col. Culver had been conducting in France began,
too, to bear fruit. Both the British and the French had developed
experimental apparatus by this time and this was examined and tested.
Then cablegrams began to arrive from abroad requisitioning the American
apparatus in large quantities--convincing evidence that it had greater
promise than any other.
But still difficulties were ahead, for at this stage the wireless
telephone consisted of a few experimental parts built by hand. It
remained a heavy task to standardize the equipment and perfect the
multitude of designs and drawings that must be in existence before
quantity manufacture could begin. All sorts of mechanical details
slighted in the experimenting and taken care of by makeshift devices
had to be worked out as practical manufacturing undertakings. It was
another case of day-and-night work to put the mechanism into condition
for production. The factory of the Western Electric Co. is in Chicago
but its drafting rooms and laboratories are in New York. As soon as any
detail was finally worked out the drawings were taken by messengers
and rushed to Chicago where the work of producing the manufacturing
tools had begun. Only the fastest passenger trains between New York and
Chicago were patronized in this part of the development.
As every detail was perfected it had to be checked by actual test in
the field, so that the company's engineers were almost constantly in
the air. One of these experts made 302 flights himself; and a total of
690 flights, of a combined duration of 484 hours, was required in the
experimental stage of the mechanism.
Immediately after the official trial in December the Government ordered
thousands of sets of the radio telephone. In spite of the enormous
detail involved in making ready for production, the first systems were
turned out early in 1918, well ahead of the delivery of the airplanes
in which they were to be used.
All through this development the designers had to confine their
activities within limits set by the producers of the aircraft. This in
itself created some puzzling problems. For instance, a constant current
of electricity must be supplied to heat the filaments of the vacuum
tubes and to operate the transmitter. A simple way to provide this
current would seem to be to connect a dynamo with the driving shaft
of the airplane engine, but the airplane constructors would not allow
any such connection with the engine. Current could be supplied from
storage batteries, but the planes were already loaded down with all the
gear they could carry, and the use of heavy batteries was out of the
question. Therefore it was the task of the phone designers to supply
a dynamo plant that would not add appreciably to the weight of the
plane. This was done by installing on the outside of the plane a wind
propeller, which was driven by the rushing air and had power enough to
turn the dynamo.
The dynamo must deliver a constant and unvarying voltage to the radio
phone, if its operation is to be possible, yet a wind propeller on
the airplane would be driven by air rushing by at speeds varying from
90 or 100 to 160 miles per hour, the latter figure being the speed
of a diving plane. This meant that the wind propeller, and hence the
armature of the dynamo, would revolve at a speed varying from 4,000
to 14,000 revolutions per minute. It would seem to be impossible to
procure current at a constant rate from a dynamo varying so widely
in its speed of operation; yet one of the experts engaged in this
enterprise solved the problem, and the dynamo thereafter performed
always in a most steady going and dependable manner.
Incidentally as a sort of by-product of the undertaking the special
transmitter and helmet may be employed as a means of communication
between the pilot and observer in a two-seated machine. When the helmet
is used for this purpose, the wireless is not employed at all, but
the head sets are connected by wires so that notwithstanding the fact
that one can not hear himself talk because of the noise on the plane
the pilot and observer can converse over the telephone with ease. Then
at any time by throwing a switch they can connect themselves with the
radio apparatus and talk with the men in another plane 3 or 4 miles
away or to their squadron headquarters on the ground.
One good result of the airplane telephone was to speed up the training
of aviators in this country and to make that training safer. But the
primary object of the wireless phone was to make it possible for the
leader of an air squadron at the front to control the movements of his
men in the air. For this purpose extra-long range was not required, and
the distance over which the machines could talk was purposely limited
to 2 or 3 miles so that the enemy could not overhear the conversation
except when the planes were actually engaged in fighting each other.
The Navy made use of the wireless telephone sets in the seaplanes, and
here the range of the equipment was made greater. The Navy also adopted
a modified form of the set for the 110-foot submarine chasers. The
subchasers hunted the submarines in packs, and by means of the radio
telephone the commanders of the boats kept in constant touch with each
other, thereby greatly increasing the effectiveness of their operations.
Altogether there were produced for the Army airplanes about 3,000
combined transmitting and receiving sets of the radio telephone and
about 6,500 receiving sets alone.
CHAPTER VII.
BALLOONS.
When Stephen Montgolfier and his brother Joseph, in November, 1782,
sent a sheep, a rooster, and a duck into the sky, lifted by a paper bag
inflated with hot air, these Columbuses of ballooning could scarcely
foresee the importance that their invention was to have in the great
war 135 years later. To the humble observation balloon in France rather
than to his dashing hero of a cousin, the airplane, must go the chief
credit for that marvelous accuracy which long-range artillery attained
during the great struggle.
The balloon itself was spectacular enough once its true character was
known. The fact that the American production of observation balloons
during our 19 months as a belligerent was a complete and unqualified
success makes the story of ballooning in France of particular interest
to the American reader.
After the animals of the Montgolfier barnyard had made their ascent,
two friends of the brothers, M. Pilatre de Rozier and Girond de
Villette, essayed to be the first human beings to take an aerial
flight, ascending to a height of 300 feet and returning to earth sound
of limb and body. Thereafter and until the great war in Europe the
balloon remained the awe of the circus and country fair grounds and
the delight of the handful of sportsmen who took up the adventurous
pursuit; but, except for a limited use of captive balloons in our Civil
War and in the siege of Paris, in 1870 and 1871, the balloon had no
important military use.
The hot-air balloon never could have become of great value to armies.
In the first place, it would descend when the balloon cooled off. This
defect was overcome by the use of lighter-than-air gas. Moreover, the
free balloon was subject to the whims of the breezes. To overcome this
characteristic the balloon must be fastened by a cable or propelled by
a portable engine. It was obvious, however, to military experts that a
stationary observation post anchored thousands of feet in the air would
be ideal in war operations; yet for all of this obvious need, until
the great war military science had perfected nothing better than the
spherical balloon. The spherical, anchored to a cable, bobbed aloft in
the gales and zephyrs as a cork does on the ocean waves. Although there
had been some experimentation with kite balloons before 1914, it was
not until the great war had been in progress for some months that the
principles of streamline shape were applied to the captive balloon; and
the kite balloon, the well-known "sausage," made its appearance, to be
the target for enemy aerial operations and the chief dependence of its
own Artillery.
The term "kite balloon" effectively describes the captive observation
balloon as we knew it in the war. It rides the air on the end of its
cable much in the manner of an ordinary kite, and some of the early
"sausages" even flaunted steadying tails such as kites carry. These
principles applied to the captive balloon gave to its observation
basket a stability unknown by the pioneer aeronauts under their
spherical bags.
In the first stages of the war the Artillery relied principally upon
airplanes for firing directions. But, while the airplane observers
could locate the targets fairly well, they frequently lost touch with
their batteries because of the difficulty of sending and receiving
wireless or visual signals upon their swiftly moving craft. This
disadvantage brought the captive balloon into use, gradually at
first, but before the end of the war on a scale which had practically
displaced the airplane as a director of gun fire. The balloon came to
be the very eye of the Artillery, which, thanks to the development of
this apparatus, reciprocated with an efficiency beyond anything known
before in the history of warfare.
Sitting comfortably aloft, the observer in the kite balloon basket
had the whole panorama of his particular station spread before him.
His powerful glasses could note accurately everything transpiring in
a radius of 10 miles or more. He was constantly in touch with his
batteries by telephone and not only could give by coordinated maps the
exact location of the target and the effect of the bursting shell, but
could and often did supply most valuable information of enemy troop
movements, airplane attacks, and the like. He was a sentinel of the sky
with the keen, long-range vision of the hawk. He played a part less
spectacular than the scout airplane with its free and dazzling flights,
but his duties were not less important.
Nor did he suffer from ennui during his period aloft. When a kite
balloon went up it became the subject of alert attention by the enemy,
because it was up there on hostile and damaging business. Long-range
high-velocity guns turned their muzzles on it, and planes swooped down
upon it from dizzy heights, seeking to pass through the barrier of
shell from antiaircraft guns and get an incendiary bullet through the
fabric of the gas bag, an eventuality which meant the ignition of the
highly inflammable hydrogen gas, the quick destruction of the balloon
and perhaps of the luckless occupants of the basket as well, unless
they could get away in their parachutes.
Only quick work could save the men in the basket in such a case. From
the time the gas leaped into flame until the explosion and fall of the
balloon there was an interval of rarely over 15 or 20 seconds. The
pilot of the airplane could dodge and slip away from the guns, but
not so the pilot of the kite balloon anchored to a windlass from 2 to
5 miles behind his own lines. He had to take what was coming to him
without means of defense. He must carry on his scientific calculations
unconcernedly and in his spare moments experience the questionable
pleasure of watching on some distant hill the flash of an enemy gun
trained upon him and then of waiting the 20 or 30 seconds for the
whizzing messenger to reach him, the while he pondered on the accuracy
of the enemy gunner's aim.
While the artillery on both sides paid considerable attention to the
observation balloons, the fact was that few of them were brought down
by direct shell hits. The diving airplane with its incendiary bullets
was a far more deadly enemy to the balloon than the ground artillery.
Certain pilots in all the air services made a specialty of hunting
sausages, the nickname given to kite balloons because of their shape.
In the 17 days between September 26 and November 11, 1918, our Army
lost 21 balloons, of which 15 were destroyed by enemy planes and 6
by enemy shell. But it may be noted that our aviators and artillery
exacted a toll of 50 German balloons in the same period and on the
same front. Of 100 balloons lost at the front, an average of 65 were
destroyed by enemy attacks and 35 by natural wear and tear.
The German general staff so strongly appreciated the work of the allied
kite balloons that in its system of rating aviators it ranked a balloon
brought down as the equal of one and one-half planes.
The average life of a kite balloon on an active sector of the western
front was estimated to be about 15 days. Some of them lived only a few
minutes. One American balloon passed unscathed through the whole period
of American activity on a busy sector. While ordinarily five or six
months of nonwar service will deteriorate the balloon fabric, there are
many cases of useful service longer than this.
When the war broke out Germany is said to have had about 100 balloons
of the kite type. France and England had few of them. The German
balloon was known as the Drachen. Its gas cylinder of rubberized cotton
cloth was approximately 65 feet long and 27 feet in diameter, the ends
being rounded. To give it a kite-like stability in the air a lobe,
which was a tube of rubberized fabric, of a diameter approximately
one-third of the diameter of the main balloon, was attached to the
underbody of the gas bag as a sort of rudder, which curved up around
the end of the balloon. This lobe was not filled with gas, but the
forward end of it was open so that when the balloon rose the breeze
filled the lobe with air. The inflated rudder then held the Drachen
in line. The lobe automatically met the emergency. In calm, windless
weather the balloon needed no steadying and the lobe was limp. Let the
gale blow, and the lobe inflated and held the nose of the Drachen into
the wind. As a further stabilizer three tailcups, with mouths open
to the breeze, were attached 10 feet apart on a line descending from
the rear of the balloon. In a strong wind these helped to keep the
contrivance from swinging.
The tail-cup was made of rubberized fabric, circular in shape, about 4
feet in diameter, and about 2 feet deep when inflated by the breeze. It
looked like an inverted umbrella, and was attached to the tail end of
the balloon for exactly the same purpose and with the same effect as
the tail attached to a kite.
The Drachen type of balloon was still in the experimental stage here
and in France and England when the Germans swept over Belgium. The
Drachen balloon was clumsy and relatively unstable in high winds, yet
its importance to the Artillery could not be ignored by the allies.
The results of its work daily became more apparent. The first effort
of the allies was to improve the Drachen to give it greater stability
and permit it to go to higher altitudes. While this work was going on,
Capt. Caquot, of the French Army, produced a kite balloon so superior
that it quickly superseded what had been in use. Germany clung to the
Drachen for a time, but finally abandoned it for the Caquot principles
of design.
The earlier balloons of the sausage type had been merely cylinders
with hemispherical ends. Now for the first time, in the Caquot model,
appeared a captive that was sharply stream lined. Stream lines are
lines so curved as to offer the least possible resistance to the medium
through which a mobile object, such as a yacht, an automobile, or an
airship, moves. The Caquot gas bag was 93 feet long, as compared with
the Drachen's 65 feet of length, yet its largest diameter was only
28 feet, being but a foot thicker than the pioneer German type. The
Caquot, as all balloons developed in the war, was made of rubberized
cotton cloth. Its capacity of 37,500 cubic feet of hydrogen gas lifted
the mooring cable, the basket, two observers, and the mass of necessary
equipment, and in good weather the balloon could ascend to a maximum
altitude of over 5,000 feet.
The principal innovation in the design of the Caquot balloon was the
location of the balloonette or air chamber within the main body of
the gas envelope. This chamber was in the forward instead of the rear
part of the bag and along the bottom of the envelope. It was separated
from the gas chamber by a diaphragm of rubberized cotton cloth, which
was sewn, cemented, and taped to the inner envelope somewhat below the
"equator" or median line from the nose to the tail of the gas bag.
[Illustration: CAQUOT, TYPE R, CAPTIVE OBSERVATION BALLOON.
This balloon is 93 feet long and 28 feet in diameter. Its gross lifting
power is 2,600 pounds.]
[Illustration: BALLOON CONTROLLED BY WINDLASS ON A MOTOR TRUCK.]
[Illustration: WINDLASS FOR CAQUOT BALLOON MADE BY JAMES CUNNINGHAM &
SONS.]
When a balloon of the Caquot type is fully inflated, the diaphragm
rests upon the underbody of the gas envelope, and there is no air in
the balloonette. Then, as the balloon begins to ascend, at the higher
levels the surrounding air pressure is reduced and the gas in the
balloon expands. This expansion would normally burst the envelope when
the balloon is at a high altitude, except for a safety valve which
pops at the danger point and relieves the pressure. Also, when the
balloon is anchored it gradually loses gas, since no fabric can be made
entirely gas-tight. A flabby balloon in a gale of wind is dangerous to
the men in the basket. This flabbiness might be expected to increase,
too, as the balloon was hauled down into the heavier air pressures.
It was to overcome this flabbiness that the interior balloonette was
first invented, but the new location not only accomplished this end but
increased the stability, lessened the tension on the cable and allowed
an almost horizontal position of the balloon itself. As the balloon
rises the wind blows into the balloonette through a simple scoop
placed under the nose of the balloon. This forces up the diaphragm and
compensates for any loss of gas from the envelope above. If the day is
calm and no air is driven into the balloonette, there is no danger from
a flabby balloon anyhow, and hence no need for the air chamber. The
thing is automatic.
The Caquot was equipped with lobes of rubberized fabric to act as
rudders. These lobes, which were spaced equidistantly around the
circumference of the rear third of the balloon, filled with wind
when wind was blowing and there was need of rudders. In calm weather
the lobes, particularly the two upper ones, hung loosely, resembling
elephant ears. On account of this characteristic the Caquots were
nicknamed "elephants" by the soldiers.
The Caquot maintained its stability without tailcups, and its
construction caused it to ride nearly horizontally and directly above
its mooring, regardless of winds. In this position it put much less
strain on the anchoring cable than the old-fashioned sausage. This
balloon has been operated successfully in winds as high as 70 miles an
hour, so that apparently no gale could keep it on the ground.
When we went into the war both our Army and Navy were practically
without observation balloons, and we knew little about their
construction, although we had been watching the developments in Europe.
One local National Guard organization had taken to the Mexican border
a locally designed captive balloon, the gift of the Goodyear Tire &
Rubber Co., of Akron, Ohio.
In April, 1917, the total production capacity of the United States
was for only two or three military observation balloons in a month.
But when the emergency came the various concerns whose plants were
adaptable to this class of manufacture--the list including the Goodyear
and Goodrich organizations at Akron, the United States Rubber Co., the
Firestone Tire & Rubber Co., the Connecticut Aircraft Co., and the
Knabenshue Manufacturing Co.--all joined wholeheartedly with the Signal
Corps to solve our balloon problems.
One of these problems was the production of balloon cloth, for which
there had never been any commercial call in this country. Such cloth
obviously must be of cotton, for in cotton we had our largest supply
of textile raw material. The cloth must be closely woven, smooth, and
strong, to serve as a base for the rubberizing process. The standard
balloon cloth should have a weave of approximately 140 threads to the
inch both ways. In our vast cotton industry only a few mills had ever
made such a cloth, and then only in small quantities. In fact we found
only a few looms in existence capable of weaving such cloth, which
must be from 38 to 45 inches wide. A single loom could turn out only
an average of ten yards of this cloth in a day. Our balloon program
was to call for millions of yards of high-count cloth, and this meant
the construction of thousands of new looms, as well as the training of
hundreds of weavers.
Naturally our cotton manufacturers were reluctant to undertake such
a production, and their fears were justified when we found that the
earliest deliveries of balloon cloth were frequently as high as 67
per cent imperfect. By the middle of 1918, however, the mills had
so perfected their methods that the wastage amounted to only 10 per
cent of the cloth woven. This wastage was largely caused by "slubs,"
knots, and other imperfections which prevented an even surface for
rubberizing. Because of the lives which depended upon having perfect
balloon cloth, the fabric was literally inspected inch by inch, and
hundreds of men and women had to be educated especially in this
inspection work.
The development of the new art of weaving balloon cloth was an
achievement of no mean degree. In April, 1917, all of our cotton mills
put together could produce only enough cloth to build two balloons a
week. In November, 1918, our looms were turning out cloth sufficient
for 10 balloons a day, an expansion in the industry amounting to 3,000
per cent in 19 months. This expansion proceeded at a rate that always
kept us a little ahead of the military schedule. To produce 10 balloons
a day the cotton mills had to turn out 600,000 yards of special cloth a
month. In addition to the small army of weavers, this production called
into service 3,200 looms.
Had the war continued another year, we would have reached our goal of
15 complete new kite balloons produced every day. Our complete project
of balloons and dirigibles of all types called for a total output
of 20,000,000 yards of balloon cloth. Had we reached the quantity
production planned, we would have been able to supply not only our
own needs but also all of the balloon needs of the allies in Europe.
America had the raw materials necessary for the whole anti-German
balloon program.
[Illustration: CUTTING AND CEMENTING BALLOON PANELS IN THE GOODRICH
PLANT AT AKRON.]
[Illustration: SPREADER ROOM AT THE U. S. RUBBER CO. FACTORY, SHOWING
MACHINES THAT RUBBERIZE THE CLOTH.]
[Illustration: FINAL BALLOON ASSEMBLY ROOM AT GOODRICH FACTORY.]
As it was, we supplied to France and England a considerable number of
balloons when the materials shortage in those countries was becoming
acute. The foreign users of this American made equipment reported that
it was equal to the best European product. It should have been. No
war material was ever manufactured more conscientiously than this. In
addition to the painstaking care of the producers, from start to finish
a large force of inspectors watched every step in the construction of
each balloon, and when America sent a balloon to the front it was right
for the work it had to perform.
The weaving of the cloth was but the first step in the production of
the balloon fabric. The fabric of the balloon envelope resembles a
sandwich in its construction, there being a thin film of specially
compounded rubber between two plies of the cotton cloth. The outer ply
of the cloth is cut on the bias. This method prevents any long straight
tear down the grain of the fabric. The threads of the inner ply are set
at an angle of 45° to those of the outer ply, thus distributing strain
sufficiently to stop a "snag" practically where it starts.
The cotton cloth alone can not resist the seepage of gas, and,
therefore, it is necessary to rubberize it, the rubber film being
really the gas-resisting envelope. In this rubberizing process the
cloth must be run through the spreading machine 30 to 35 times in order
to build up the thin rubber film without a flaw in it of any kind. The
outside ply of the balloon fabric is "spread," that is, painted with a
rubber compound containing a coloring matter. This compound makes the
fabric waterproof; it gives also protective coloring to the balloon
when in the air, making it less visible to the enemy; and, finally and
most important, this coloring absorbs the actinic rays of the sun which
are so fatal to the life of rubber. In some of the fabric the rubber
film itself was colored to withstand both the heat and ultra-violet
rays, thus both protecting the rubber and reflecting the heat which
would otherwise expand the gas in the balloon.
While in general we adopted the European standards of construction,
we had to develop our own rubber compounds and cures as well as our
various fabrication processes. The latest reports we received from the
front stated that the American fabric not only was successful, but that
it had an added characteristic which was a direct means of saving life.
It was discovered that the American fabric burned more slowly than the
European balloon fabric, giving the men in the observation basket more
time to get away in the parachutes when the balloons were destroyed by
hostile attack.
When we went into the war we had never built a windlass for a kite
balloon. The ability of the American manufacturer solved this problem
as it did almost every other problem in the development of war
instruments. Steam was the motive power first used for windlasses, but
before the fighting came to an end America had developed both gas and
electric windlasses which were thoroughly efficient.
The best known type of gasoline windlass was that having two motors,
one to turn the cable drum controlling the balloon's ascent and
descent, and one for moving the windlass itself along the road. A
record pull-down speed of 1,600 feet a minute, or more than three times
the speed of the fastest passenger elevator, has been attained by the
gasoline windlass.
The electric windlass, while pulling down the balloon at the slower
rate of 1,200 feet per minute, was smoother in operation. The mobile
windlass would move on a road under its own power at 20 miles an hour
and could tow the balloon in the air at the rate of 5 miles an hour, or
even faster if necessity demanded.
To play on the safe side at the start, we adopted a satisfactory
windlass that had been developed in France. It was difficult to
manufacture this entirely French machine with American materials
and methods; yet James Cunningham, Sons & Co., of Rochester, N. Y.,
succeeded in obtaining a delivery of four complete windlasses per week.
In addition to this windlass we designed two of our own. One of these
was the product of the United States Army Balloon School and was
manufactured by the McKeen Motor Car Co., of Omaha, Nebr.; the other
windlass was designed and manufactured by the N. C. L. Engineering Co.,
of Providence, R. I. Both were put into quantity production, assuring
us a sufficient number of the best windlasses ever manufactured.
The first cable used to hold the balloon captive was approximately a
quarter-inch in diameter, weighed 1 pound for each 8 feet of length
had a breaking strength of 6,900 pounds, and was made of seven twisted
strands of plow-steel wire, containing in all 133 separate wires. This
cable, while it accomplished the original purpose, was early seen to
have fine possibilities of development. The observers in the basket
must be kept in constant communication with the Artillery and their
own windlass and this communication could best and most efficiently be
obtained by means of the telephone. The balloon telephone, as first
used, was an entirely individual unit with its own separate cable
from the basket to the ground. In this way communication was indeed
established, but only at the cost of a decrease in possible altitude,
increased cable resistance, and the necessity of an extra windlass for
winding and unwinding the telephone cable.
[Illustration: BALLOONISTS READY TO ASCEND.
The picture shows balloonist with telephone equipment, also a parachute
on side of basket.]
[Illustration: BALLOON PACKED FOR OVERSEAS SHIPMENT.]
[Illustration: BALLOON IN GOODRICH FACTORY INFLATED TO BE SUBJECTED TO
AIR TEST.]
[Illustration: NURSE BALLOON CONTAINING 5,000 CUBIC FEET OF GAS.
It is used in the field to replenish kite balloons with hydrogen.]
Previous to the entrance of the United States in the war, preliminary
experiments in France were being made with the view of putting the
telephone wires in the center of the main cable, thus doing away
entirely with the second cable and windlass. But there had never
been developed a satisfactory cable of this construction. American
inventiveness at the John A. Roebling Sons Co. and the American Steel
& Wire Co. was set to work on this problem with the result that not
only was a satisfactory cable developed but a steady production was
attained, 50,000 feet per week being delivered regularly by the John
A. Roebling Sons Co. alone. This new cable consisted of 114 separate
wires of special steel besides the telephone center of 3 copper wires
properly insulated and armored. The specifications demanded a breaking
strength of 7,200 pounds while the actual test of the finished Roebling
cable showed 8,250 pounds.
Another of the balloon problems was the supply of hydrogen gas. Before
the war only a little hydrogen was used in this country, the element
being a by-product in the manufacture of commercial oxygen. We met
the additional demand for millions of cubic feet of hydrogen for our
balloons by establishing Government gas plants and expanding privately
owned plants already in existence. There were two methods of supplying
hydrogen to our balloon units at home and abroad. One of these was by
furnishing portable plants which would generate hydrogen at the place
where it was to be used. The other was to take the hydrogen from the
stationary plants, condense it by pressure in steel cylinders, and
ship it to points of demand. By far the greater part of the gas which
we used not only in this country but in France was produced at the
permanent supply stations and shipped in cylinders. Each cylinder held
about 191 cubic feet of gas under a pressure of 2,000 pounds per square
inch at 68° F. temperature. When the war ended we had placed orders for
172,800 of these cylinders, of which 89,225 had been delivered and were
in use. We developed a manifold filler which would take the gas from 12
to 24 cylinders at the same time and quickly inflate a kite balloon, a
speed of 23 minutes for a complete inflation having been reported from
one training camp.
In the production of portable hydrogen generators we had to produce
not only the machine but the chemicals required in the process. We
adopted the ferrosilicon and caustic soda process by which it was
possible to produce 10,000 cubic feet of hydrogen per hour in a field
generator. There was plenty of caustic soda to be had, but high grade
ferrosilicon, a production of large electrolytic furnaces, was scarce,
because of its heavy consumption in the steel industry. We procured,
however, 2,482 tons of it for our generators, of which over 2,360 tons
were supplied by the Electro-Metallurgical Sales Corporation alone.
An interesting feature of the gas supply in the field was the
use of "nurse balloons." The nurse balloon was simply a large
rubberized-fabric bag with a capacity of 5,000 cubic feet of gas. It
was used for storage of gas, and the observation balloons were fed
from it. We have not received the exact figures of the quantity of gas
used by the entire Balloon Service; but, as one item alone, private
manufacturers previous to the signing of the armistice produced and
delivered 17,634,353 cubic feet of hydrogen and were in position to
meet practically any demand for the gas. This figure is only a small
part of the total, since it does not include the hydrogen produced in
the permanent Government stations or by the field generators.
Hydrogen itself, while the lightest of cheap gases, and therefore
the one universally used in balloons, has the grave fault of being
dangerous to the balloonist. When mixed with the air it is highly
explosive, if touched off by a spark of fire or electricity. For years
balloonists have dreamed of a gas light enough to have great lifting
power, but which would not burn nor explode. There was such a gas known
to chemistry, and this was helium, discovered first in spectroscope
examinations of the corona of the sun, but later found by chemists
to exist rather freely in the atmospheric envelope of the earth.
Although one of every 100 parts of air is pure helium, it was not
until comparatively recent years that this light nonexplosive gas was
discovered in our atmosphere.
Now helium was rare and expensive, and until the United States
entered the war no one had considered its production as a commercial
possibility. Up to two years ago the total world production of helium
since its discovery had not been more than 100 cubic feet in all, and
the gas cost about $1,700 per cubic foot.
It had been discovered that certain natural gases issuing from the
ground in the United States contained limited quantities of helium.
The question was whether we could extract this helium in sufficient
quantities to make its use practical. The Signal Corps, the Navy,
and the Bureau of Mines combined in a cooperative plan to develop a
practical helium production. By adopting a method of obtaining the
helium from liquefied gas produced in the processes of the Linde Air
Products Co. and the Air Reduction Co., and also by the Norton process,
we attained astonishing success in this enterprise.
On the day the armistice was signed we had at the docks ready for
loading on board ships 147,000 cubic feet of helium. At its prewar
value this gas would have been worth about $250,000,000. On November
11, 1918, we were building plants which would produce helium at the
rate of 50,000 cubic feet per day, and the cost of obtaining it had
dropped from $1,700 per cubic foot to approximately 10 cents.
None of this gas was actually used in the war, but its production
by our chemists was hailed as the greatest step ever taken in the
development of ballooning. It now seems to have opened a new era in
lighter-than-air navigation. In war helium will nullify the incendiary
bullet which destroyed so many balloons and airships. In peace it
brings the possibilities of new types of construction of dirigible
airships, since its use eliminates entirely all of the frightful
dangers from lightning, static electricity, or sparks and flames from
gasoline engines or any other source.
The Army and Navy cooperated in the production of balloons. The
Army furnished the balloon cloth to the Navy. Navy balloons had two
automatic safety valves for the expanding gas, one on each side of
the balloon a third of the way back from the nose and just above the
equator; while the Army held to the French and British idea of a single
valve in the nose itself. The Navy adopted a Caquot-type balloon which
rides at an angle of about 25° to the horizontal and is somewhat
smaller than the Army model. The Navy used these balloons as spotters
for submarines and mines. They were towed on cables from the decks of
war ships, and were connected with the ships by telephone.
The use of parachutes with balloons is a comparatively recent
development, the man who first successfully descended to earth in a
parachute being not only still active and enthusiastic over aerial
development, but being in fact the chief inspector of all United States
Army balloons and parachutes. This is Maj. Thomas S. Baldwin, known the
world over as Capt. "Tom" Baldwin, hero of innumerable aerial exploits
of all kinds under all conditions and in all parts of the world, and at
present chief of the United States Army balloon inspection. The Yankee
balloon observer in France went up to his observation post in the
security of knowing that the equipment on which his life depended had
been O. K.'d by men who knew the business from beginning to end.
The parachute as it is known at the county fair and the parachute used
in the recent war were far apart in type, the latter embodying all the
improvements that the world's aeronautical experts could add to it. The
need for parachutes developed when hostile aviators began shooting down
the sausages. At first the one-man parachute was used exclusively, the
men in the basket leaping overboard the instant their balloon was fired
over their heads. Any delay on their part would be fatal, since the
entire bag would be consumed in 15 or 20 seconds and the observer would
then be unable to leap out of the falling basket. When the individual
parachutes were used, the maps and records in the balloon basket were
usually lost.
To overcome these difficulties, the designers invented the basket
parachute. This was considerably larger than the individual parachute,
and to operate it the balloonists pulled a cord which cut the basket
away from the balloon entirely. The spreading parachute overhead then
floated the basket, with the men themselves and all else it contained,
safely and quickly to the ground.
Although hundreds and even thousands of parachute jumps occurred during
the war, there were few fatalities from this cause. During all the
time our forces were at the front only one of our men was killed as
the direct result of a parachute drop. In that particular instance the
burning balloon fell on top of the open parachute, setting it on fire
and allowing the observer to fall unprotected the rest of the distance
to the ground. One of our observers was known to make four jumps from
his balloon on the same busy day, and another leaped thrice in four
hours. In the Argonne offensive 30 balloon jumps were made by our men.
As to the safety of our parachute equipment, the only complaint from
the Yankee balloonists at the front was that they were too safe. The
man who is escaping from a German airplane nose-diving at him with
a machine gun spitting fire is in a hurry and does not wish to be
detained by a parachute which floats him too slowly to the earth.
In the rigging of each kite balloon there are about 2,000 feet of rope
of different sorts. There was a shortage of proper cordage in the
United States at first, and the French thought they could furnish this
rigging to us. But this attempt proved to be unsuccessful, and we were
forced to develop a cordage manufacture in this country of high quality
and great quantity. We did this so swiftly that there was no serious
delay to the balloon production.
Up to November 11, 1918, we produced over 1,000 balloons of all kinds,
642 of these being of the final Caquot type which we adopted. This
production included many propaganda balloons for carrying printed
matter over the lines into the enemy's country. We supplied several
target balloons for gun practice on our aviation fields. We developed
new types of parachutes and built acres of canvas hangars for balloons.
We produced 1,221,582 feet of steel mooring cable. These are only the
major items in the balloon enterprise, and do not include hundreds of
others of less importance.
The balloon production was one of the most important and successful
of all our war projects. Although we had a limited knowledge of the
subject in the beginning, our balloons stood the hard test of actual
service and could bear comparison in every way with the best balloons
of Europe, where the art of balloon building had been in existence for
many years. Once our production actually started, we never had any
shortage of balloons for our own Army; and soon we would have been in
a position to produce the observation balloons for all of the armies
fighting Germany, if called upon to do so.
_Balloon production figures._
BALLOONS AND PARACHUTES.
----------------+--------------+--------------+---------------+------------
| Observation | Supply | Miscellaneous | Parachutes
| balloons | balloons | balloons |produced to--
|produced to-- |produced to-- | produced to-- |
Firm. +--------------+--------------+---------------+-------+-----
|Nov.11,|Mar.1,|Nov.11,|Mar.1,|Nov.11,|Mar.1, |Nov.11,|Mar.1,
| 1918. |1919. | 1918. |1919. | 1918. |1919. | 1918. |1919.
----------------+-------+------+-------+------+-------+-------+-------+-----
Goodyear Tire & | | | | | {[30]3| [30]3 |} |
Rubber Co., | 458 | 565 | 39 | 39| {[31]5| [31]7 |} 20 | 20
Akron, Ohio | | | | |{[32]53|[32]53 |} |
| | | | | | | |
B. F. Goodrich | | | | | | | |
Rubber Co., | | | | | {[30]3| [30]3 |} |
Akron, Ohio | 169 | 279 | 10 | 10 | {[31]1| [31]1 |} 15 | 15
| | | | | | | |
Connecticut | | | | | | | |
Aircraft | | | | | | | |
Corporation, | | | | | | | |
New Haven, Conn.| 22 | 37 | 72 | 72 | [31]1| [31]3 | |
| | | | | | | |
United States | | | | | | | |
Rubber Co., | | | | | | | |
East Cambridge, | | | | | | | |
Mass. | 23 | 37 | | | | | |
| | | | | | | |
Knabenshue Manu-| | | | | | | |
facturing Co., | | | | | | | |
East Northport, | | | | | | | |
Long Island | 3 | 25 | 1 | 1 | [31]1 | [31]1 | |
| | | | | | | |
French-American | | | | | | | |
Balloon Co., | | | | | | | |
St. Louis, Mo. | 1 | 1 | | | [31]2 | [31]2 | |
| | | | | | | |
Scott-Omaha Tent| | | | | | | |
& Awning Co., | | | | | | | |
Omaha, Nebr. | | | | |[32]161|[32]161| 53 | 228
| | | | | | | |
New York Tent & | | | | | | | |
Awning | | | | | | | |
Co., New York | | | | | | | 63 |
| | | | | | | |
Follemer-Clogg &| | | | | | | |
Co., Lancaster, | | | | | | | |
Pa. | | | | | | | 104 | 131
| | | | | | | |
Bickford Bros., | | | | | | | |
Rochester, N. Y.| | | | | | | 1 | 1
| | | | | | | |
Firestone Tire | | | | | | | |
& Rubber Co., | | | | | | | |
Akron, Ohio | | | 7 | 7 | | | |
| | | | | | | |
Columbia Mills | | | | | | | |
(Inc.), | | | | | | | |
Wilkes-Barre,Pa.| | | | | [32]1| [32]1 | |
--------+------+-------+------+-------+-------+-------+-----
| | | | | {[30]6| [30]6 |} |
Total | 676 | 944 | 129 | 129 |{[31]10| [31]14|} 256 | 458
manufactured | | | | |{[32]215|[32]215|} |
| | | | | | | |
Total shipped | | | | | | | |
to ports | 481 | | 6 | | | | 4 |
| | | | | | | |
Total shipped | | | | | | {[30]6|} |
to camps, etc. | | 463 | | 123 | |{[31]14|} |418
| | | | | |{[32]215|} |
----------------+-------+------+-------+------+-------+-------+-------+-----
[30] Target.
[31] Spherical.
[32] Propaganda.
WINDLASSES.