shipment in a warehouse built for the purpose at the plant of the
Standard Aero Corporation at Elizabeth, N. J. The Standard Aero
Corporation was engaged under contract to set up 10 per cent of the
Handley-Page machines complete in this country. These were to be used
at our training fields.
Again, in the case of the Handley-Page, the engineering details proved
to be a serious cause of delay. We found it difficult to install the
Liberty engines in this foreign plane. When the armistice cut short
operations, 100 complete sets of parts had been shipped to England, and
seven complete machines had been assembled in this country.
None of the American-built Handley-Page machines saw service in France.
There had been great delay in the construction of the assembling
plant in England, and the work of setting up the machines had only
started when the armistice was signed. The performance table of the
Handley-Page shows its characteristics as follows:
Speed at ground level, 97 miles per hour.
Climb to 7,000 feet, 18 minutes 10 seconds.
Climb to 10,000 feet, 29 minutes.
Ceiling 14,000 feet, 60 minutes.
On its tests 390 gallons of gasoline, 20 gallons of oil, and 7 men were
carried, but no guns, ammunition, nor bombs.
After a long delay, about January 1, 1918, tentative arrangements had
been made with the Caproni interests looking toward the production of
Caproni biplanes in this country. These machines had a higher ceiling
and a greater speed than the Handley-Page. Capt. d'Annunzio with 14
expert Italian workmen, bringing with him designs and samples, came to
this country and initiated the redesigning of the Caproni machine to
accommodate three Liberty engines. The actual production of Caproni
planes in this country was limited to a few samples which were being
tested when the armistice was signed. The factories had tooled up for
the production, however, and in a few months Capronis would doubtless
have been produced in liberal quantities.
The performance of the sample planes in two tests is shown by the
following figures:
----------------------+-----------------------+-----------------------
| Test 1. | Test 2.
----------------------+-----------------------+-----------------------
Speed at ground level | 100 miles per hour | 103.2 miles per hour.
Climb to 6,500 feet | 16 minutes 18 seconds | 14 minutes 12 seconds.
Climb to 10,000 feet | 33 minutes 18 seconds | 28 minutes 42 seconds.
Climb to 11,200 feet | 49 minutes |
Climb to 13,000 feet | | 46 minutes 30 seconds.
----------------------+-----------------------+-----------------------
[Illustration: ONE OF THE SMALL THOMAS-MORSE SCOUTS BESIDE A GIANT
HANDLEY-PAGE MACHINE.]
[Illustration: ARMORED GERMAN AIRPLANE SHOT DOWN ON THE WESTERN FRONT.]
[Illustration: NIEUPORT SCOUT BESIDE A LOENING MONOPLANE.]
As we had produced fighting planes built around the Liberty motor,
so, too, in the night-bombing class American invention, with the
experience of several months of actual production behind it, was able
to bring out an American bombing plane that promised to supersede all
other types in existence. This machine was designed by Glen L. Martin
in the fall of 1918. It was a night-bomber equipped with two Liberty
12-cylinder engines. The Martin spread of 75 feet gave it a carrying
capacity comparable with that of the Handley-Page. Its speed of 118
miles an hour at ground level far exceeded that of either the Caproni
or Handley-Page, and it was evident that its ceiling would be higher
than that of the Caproni, the estimated ceiling of the Martin being
18,000 feet. The machine never reached the state of actual quantity
production, but several experimental models were built and tested.
Being built around its engine it reflected clean-cut principles of
design, and its performances in the air were truly remarkable for a
machine of its type. The following table shows the results of the
preliminary tests of the Martin bomber:
----------------------+-----------------------+-----------------------
| Test 1. | Test 2.
----------------------+-----------------------+-----------------------
Speed at ground level | 113.3 miles per hour | 118.8 miles per hour.
Climb to 6,500 feet | 10 minutes 45 seconds | 7 minutes.
Climb to 10,000 feet | 21 minutes 20 seconds | 14 minutes.
Climb to 15,000 feet | | 30 minutes 30 seconds.
Total weight | 9,663 pounds | 8,137 pounds.
----------------------+-----------------------+-----------------------
The total delivery of airplanes to the United States during the period
of the war was 16,952. These came from the following sources: United
States contractors, 11,754; France, 4,881; England, 258; Italy, 59.
[Illustration:
FIGURE 12.
U. S. SQUADRONS AT THE FRONT.
A squadron is equipped with from 15 to 25 planes.
Apr. 30, 1918. 3 ===
May 31, 1918. 12 ============
June 30, 1918. 13 =============
July 31, 1918. 14 ==============
Aug. 31, 1918. 26 ==========================
Sept. 30, 1918. 32 ================================
Oct. 31, 1918. 43 ===========================================
Nov. 11, 1918. 45 =============================================]
Estimates of aircraft strength on the front were always uncertain, due
to variations in the estimates of the number of planes in a squadron.
The standing of the United States in aeroplanes at the front is
indicated in the estimate of the American Air Service as of November
11, 1918. The figures of this estimate are as follows:
France 3,000
Great Britain 2,100
United States 860
Italy 600
-----
Total 6,560
These figures represent fighting planes equipped ready for service,
but do not include replacement machines at the front or in depots or
training machines in France.
[Illustration:
FIGURE 13.
COMPARISON ENEMY PLANES BROUGHT DOWN BY U. S. FORCES AND U. S.
PLANES BROUGHT DOWN BY THE ENEMY.
U. S. planes lost to enemy. ============== 271
Enemy planes lost to U. S. forces[29] ======================== 491
[29] Confirmed losses; in addition there were 354 unconfirmed.]
The actual strength of the central powers in the air is at this time
not definitely known to us. Such figures as we have are viewed with
suspicion because of the two methods of observation in reporting an
enemy squadron. This may be 24 planes to a squadron, that number
representing the planes in active service in the air. But each squadron
had a complement of replacement planes equalling the number of active
planes, so that the squadron could be listed with 48 planes.
However, as some indication of the relative air strengths of the
central powers we have a report from the chief of the Air Service
of the American Expeditionary Forces showing that on July 30, 1918,
Germany had 2,592 planes on the front and Austria 717.
[Illustration: THE GLENN MARTIN BOMBER.
The gross weight of this machine is 9,663 pounds. It can be equipped
with five Lewis machine guns. Its ground speed is 113 miles an hour and
its service ceiling is 12,800 feet. It climbs to a height of 6,500 feet
in 10 minutes 45 seconds and to 10,000 feet in 21 minutes 20 seconds.]
[Illustration: THE CAPRONI, EQUIPPED WITH THREE LIBERTY 12-CYLINDER
ENGINES.]
CHAPTER III.
THE LIBERTY ENGINE.
The Liberty engine was America's distinctive contribution to the war
in the air, and her chief one. The engine was developed in those first
chaotic weeks of preparation of 1917, when our knowledge of planes,
instruments, and armament as then known in Europe was still a thing of
the future. The manufacture of engines for any aeronautical purpose
was one which we might approach with confidence. We possessed in the
United States motor engineering talent at least as great as any in
Europe, while in facilities for manufacture--in plants which had built
our millions of automobile engines--no other part of the world could
compare with us. Therefore, while waiting word from Europe as to the
best type of wings, fuselages, instruments and the like, we went ahead
to produce for ourselves a new, typically American engine which would
uphold the prestige of America in actual battle.
Many Americans have doubtless wondered why we built our own engine
instead of adopting one or more of the highly developed European
engines then at hand; and no doubt our course in this vital matter
has sometimes been set down to mere pride in our ability and to an
unwillingness to follow the lead of other nations in a science in
which we ourselves were preeminent--the science of building light
internal-combustion engines. But national pride, aside from giving us
confidence that our efforts in this direction would be successful, had
little other weight in the decision. There were other reasons, and
paramount ones, reasons leading directly from the necessity for the
United States to arrive at her maximum aerial effort in a minimum of
time, that irresistibly compelled the aircraft production organization
to design a standard American engine. Let us examine some of these
considerations.
If there was anything to be observed from this side of the Atlantic
with respect to the tendencies of aircraft evolution in Europe it was
that the horsepowers of the engines were continually increasing, these
expansions coming almost from month to month as newer and newer types
and sizes of engines were brought out by the European inventors. It
was evident to us that there was not a single foreign engine then in
use on the western front that was likely to survive the test of time.
Each might be expected to have its brief day of supremacy, only to be
superseded by something more modern and more powerful.
Yet time was an element to which in this country we must give grave
consideration. To produce in quantities such as we were capable of
producing would ordinarily require a year of maximum industrial effort
to equip our manufacturing plants with the machines, tools, and skilled
workmen necessary for the production of parts. The finished articles
would under normal circumstances begin coming in quantity during the
second year of our program. It would have been fatal to "tool up" our
plants for the manufacture of equipment that would be out of date by
the time we began producing it a year later.
The obvious course for the United States to adopt, not only with
engines but with all sorts of aeronautical equipment, was to come into
the manufacturing competition not abreast with European progress but
several strides ahead of it, so that when we appeared on the field it
would be with equipment a little in advance in type and efficiency of
anything the rest of the world had to offer.
This factor of time was a strong element in the decision to produce
a standard American engine, since with the possible exception of the
Rolls-Royce there was no engine in Europe of sufficient horsepower and
proved reliability to guarantee that it would retain its serviceability
for the necessary two years upon which we must reckon. There was no
other course that we could safely adopt.
But there were other conditions that influenced our conclusion. We
believed that we could design and produce an engine much more quickly
and with much better results than we could copy and produce any
approved foreign model. This proved to be true in actual experience.
Along with the production of Liberty engines we went into the quantity
manufacture of a number of European engines in this country; and the
experience of our engineers and factory executives in this work was
anything but pleasant. Among others we produced in American factories
the Gnome, the Hispano-Suiza, Le Rhone, and the Bugatti engines.
Now European manufacture of mechanical appliances differs from ours
largely in the degree to which the human equation is allowed to
enter the shop. In continental practice much of the metallurgical
specifications and also of the details of mechanical measurements,
limits of requisite accuracy, variations which can be allowed, etc.,
are not put on paper in detail for the guidance of operators, but are
confided to the recollections of the individual workmen. A machine
comes in its parts to the assembly room of a foreign factory, and
after that it is subject to adjustments on the part of the skilled
workmen before its operation is successful. It must be tinkered with
before it will go, so to speak. Nothing of the sort is known in an
American factory. When standard parts come together for assembly the
calibrations must have been so exact that the machine will function
perfectly when it is brought together; and assembling becomes mere
routine. Thus when we came to adopt foreign plans and attempt to adapt
them to our practices, we encountered trouble and delay.
Thirteen months were required to adapt the Hispano-Suiza 150-horsepower
engine to our factory methods and to get the first engine from
production tools, while eight months were similarly spent in producing
the Le Rhone 80-horsepower engines. Both of these engines had been
in production in European factories for a long time, and we had the
advantage of all the assistance which the foreign manufacturers could
give us.
These experiences merely confirmed the opinions of American
manufacturers that the preparations for the production of any aviation
engine of foreign design--if any such suitable and adequate engine
could be found--would require at least as much time as to design
and tool up for the production of an American engine. When to this
was added the necessity of waiting for several weeks or months for
a decision on the part of our aviation authorities, either in the
United States or in Europe, as to which of the many types of engines
then in use by the allies should be put into production here,
procuring and shipping to this country suitable samples, drawings,
and specifications, negotiating with foreign owners for rights to
manufacture, etc., there was but one answer to be made on this score,
and that was to design and build an all-American engine.
Another factor in the decision was that of our distance from France,
a fact making it necessary for us to simplify as much as possible
the problem of furnishing repair parts. At the time we entered the
war the British air service was using or developing 37 different
makes of engines, while France had 46. Should we be lured into any
such situation it might have disastrous results, if only because of
the difficulties of ocean transportation. Germany was practically
concentrating upon not more than 8 engines. The obvious thing for us
to do was to produce as few types of engines as possible, thus making
simpler the problem of manufacturing repair parts and shipping them to
the front.
With these considerations in mind, the Equipment Division of the
Signal Corps in May of 1917 determined to go ahead with the design and
production of a standard engine for the fighting forces of the aviation
branch of the Army. In the engineering field two men stood out who
combined in themselves experience in designing internal-combustion
engines which approached nearest to combat engines, with experience
also in large quantity production.
J. G. Vincent, with the engineering staff of the Packard Motor
Car Co., had for approximately two years been engaged in research
work, developing several types of 12-cylinder aviation engines of
approximately 125 to 225 horsepower, which, however, were not suitable
for military purposes because of their weight per horsepower. This
work had resulted in the acquirement of a large amount of data and
information which would be invaluable in the design of such an engine
as the one proposed; and also had resulted in the upbuilding of an
efficient experimental organization. He had also had wide experience in
designing internal-combustion motors for quantity production.
E. J. Hall, of the Hall-Scott Motor Car Co., for eight years had
been developing and latterly producing several types of aeronautical
engines, which he had delivered into the service of several foreign
governments, including Russia, Norway, China, Japan, Australia, Canada,
and England. He had also completed and tested a 12-cylinder engine of
300 horsepower, which, however, was of too great weight per horsepower
to be suitable in its form at that time for military purposes. He had
thus acquired a large experience and fund of information covering
the proper areas and materials for engine parts, and proper methods
of tests to be applied to such engines, and in addition he had
general experience in quantity production. All of this information
and experience was of invaluable assistance not only in designing
the new engine, but in determining its essential metallurgical and
manufacturing specifications.
These two men were thus qualified in talent and in practice to lay down
on paper the lines and dimensions of the proposed engine, an engine
that would meet the Army's requirements and still be readily capable
of prompt quantity production. They had in their hands the power to
draw freely upon the past experience and achievement of practically the
entire world for any features they might decide to install in the model
power plant to be produced. And this applied not only to the patented
features of American motors, but also of foreign engines; for each man
had exhaustively studied the leading European engines, including the
Mercedes upon which Germany largely pinned her faith up to the end of
the war.
With respect to American motor patents, an interesting situation had
arisen in the automobile industry. The leading producers of motor cars
were in an association which had adopted an arrangement known as the
cross-licensing agreement. Under this agreement all patents taken out
by the various producers (with a few exceptions) were thrown into a
pool upon which any producer at will was permitted to draw without
payment of royalties.
A similar arrangement was adopted with respect to the Liberty engine,
except that the Government pledged itself to pay an agreed royalty for
the use of patents. Thus the engineers designing the engine might reach
out and take what they pleased regardless of patent rights. The result
was likely to be a composite type embracing the best features of the
best engines ever built. Theoretically, at least, a super-engine ought
to result from such an effort.
The ideal aviation engine should produce a maximum of power with a
minimum of weight; it must run at its maximum power during a large
proportion of its operating time, a thing that an automobile motor
seldom, if ever, does for more than a few minutes at a time; and it
should consume oil and fuel economically to conserve space and weight
on the airplane.
Such was the problem, the design of an engine to meet these
requirements, that confronted these two engineers when they were called
to Washington and asked to undertake the work.
There have been so many versions of the story of how the Liberty engine
was designed and produced in its experimental models that it is fitting
that the exact history of those memorable weeks should be set down here.
The engine was put on paper in the rooms occupied by Col. E. A. Deeds
at the Willard Hotel in Washington. Col. Deeds had been the man of
broad vision who, by taking into consideration the elements of the
problems enumerated above, determined that America could best make her
contribution to the aviation program by producing her typically own
engine. He had proposed the plan to his associate, Col. S. D. Waldon,
who had thereupon studied the matter and agreed entirely with the plan.
The two officers persuaded Messrs. Hall and Vincent to forego further
efforts on their individual developments and to devote their combined
skill and experience to the creation of an all-American engine.
The project was further taken up with the European authorities in
Washington, and it was supported unanimously.
In these conferences it was decided to design two lines of combat
engines. Each should have a cylinder diameter of 5 inches and a piston
stroke 7 inches long; but one type should have 8 cylinders and the
other 12. The 8-cylinder engine should develop 225 horsepower, as
all the experts believed then, in May, 1917, that such a motor would
anticipate the power requirements as of the spring of 1918, while the
12-cylinder engine should develop 330 horsepower, as it was believed
that this would be the equal of any other engine developed through 1919
and 1920. Every foreign representative in Washington with aeronautical
experience agreed that the 8-cylinder 225-horsepower engine would be
the peer of anything in use in the spring of 1918; yet, so rapidly
was aviation history moving that inside of 90 days it became equally
clear that it was the 12-cylinder engine of 330 horsepower, and not the
8-cylinder engine, upon which we should concentrate for the spring of
1918.
With these considerations in mind Messrs. Hall and Vincent set to work
to lay out the designs on paper. With them were Col. Deeds and Col.
Waldon, the officers to insist that nothing untried or experimental be
incorporated in the engines, the engineers to direct their technical
knowledge by this sine qua non. The size of the cylinders, 5 by 7
inches, was adopted not only because the Curtiss and the Hall-Scott
Companies, the largest producers of aviation engines in the United
States, had had experience with engines of this size, but also because
a new and promising French engine, the Lorraine-Dietrich, had just made
its appearance in experimental form, and it was an engine approximately
of that size.
On May 29, 1917, Messrs. Vincent and Hall set to work. Within two or
three days they had outlined the important characteristics of the
engine sufficiently to secure--on June 4--the approval of the Aircraft
Production Board and of the Joint Army and Navy Technical Board to
build five experimental models each of the 8 cylinder and the 12
cylinder sizes.
The detail and manufacturing drawings of the two engines were made
partly by the staff of the Packard Motor Car Co., under Mr. O. E.
Hunt, and partly by an organization recruited from various automobile
factories and put to work under Mr. Vincent at the Bureau of Standards
at Washington. Due credit must here be given to Dr. S. W. Stratton, the
director of that important governmental scientific bureau. The Liberty
engine pioneers woke him up at midnight and told him of their needs.
He promptly tendered all the facilities of the Bureau of Standards,
turning over to the work an entire building for use the following
morning. Thereafter Dr. Stratton gave the closest cooperation of
himself and his assistants to the work.
While the detail drawings were being made, the parts for the 10 engines
were at once started through the tool rooms and experimental shops of
various motor car companies. This work centered in the plant of the
Packard Co., which gave to it its entire energy and wonderful faculties.
Every feature in the design of these engines was based on thoroughly
proven practice of the past. That the engine was a composite is shown
by the origin of its various parts:
Cylinders: The Liberty engine derived its type of cylinders from the
German Mercedes, the English Rolls-Royce, the French Lorraine-Dietrich,
and others produced both before and during the war. The cylinders were
steel inner shells surrounded by pressed-steel water jackets. The
Packard Co. had developed a practical production method of welding
together the several parts of a steel cylinder.
Cam shafts and valve mechanism above cylinder heads: The design
of these was based on the general arrangement of the Mercedes and
Rolls-Royce, and improved by the Packard Motor Car Co. for automatic
lubrication without wasting oil.
Cam-shaft drive: The general type as used on the Hall-Scott, Mercedes,
Hispano-Suiza, Rolls-Royce, Renault, Fiat, and others.
[Illustration: WELDING JACKET ON CYLINDER FOR LIBERTY ENGINE. CADILLAC
MOTOR CAR CO., DETROIT, MICH.]
[Illustration: DRILLING CYLINDER FLANGES WITH MULTIPLE DRILL. PACKARD
MOTOR CAR CO.]
[Illustration: MACHINING THE CONNECTING RODS FOR THE LIBERTY ENGINE.
CADILLAC MOTOR CO.]
[Illustration: GAUGING VALVES AND PISTONS FOR THE LIBERTY ENGINE.
LINCOLN MOTOR CO.]
Angle between cylinders: In the Liberty the included angle between
the cylinders is 45°. This angle was adopted to save head resistance,
to give greater strength to the crank case, and to reduce periodic
vibration. This decision was based on the experience of the Renault and
Packard engines.
Electric generator and ignition: The Delco system was adopted, but
specially designed for the Liberty to provide a reliable double
ignition.
Pistons: The die-cast aluminum-alloy pistons of the Liberty were based
on development work by the Hall-Scott Co. under service conditions.
Connecting rods: These were of the forked or straddle type as used on
the DeDion and Cadillac automobile motors and also on the Hispano-Suiza
and other aviation engines.
Crank shaft: A design of standard practice, every crank pin operating
between two main bearings, as in the Mercedes, Rolls-Royce, Hall-Scott,
Curtiss, and Renault.
Crank case: A box section carrying the shaft in bearings clamped
between the top and bottom halves by means of long through bolts, as in
the Mercedes and Hispano-Suiza.
Lubrication: The system of lubrication was changed, this being the only
change of design made in the Liberty after it was first put down on
paper. The original system combined the features of a dry crank case,
such as in the Rolls-Royce, with pressure feed to the main crank-shaft
bearings and scupper feed to the crank-pin bearings, as in the
Hall-Scott and certain foreign engines. The system subsequently adopted
added pressure-feed to the crank-pin bearings, as in the Rolls-Royce,
Hispano-Suiza, and other engines.
Propeller hub: Designed after the practice followed by such well-known
engines as the Hispano-Suiza and Mercedes.
Water pump: The conventional centrifugal type was adapted to the
Liberty.
Carburetor: The Zenith type was adapted to the engine.
As the detailed and manufacturing drawings were completed in Washington
and Detroit they were taken to various factories where the parts for
the first engine were built.
The General Aluminum & Brass Manufacturing Co., of Detroit, made the
bronze-back, babbitt-lined bearings.
The Cadillac Motor Car Co., of Detroit, made the connecting rods, the
connecting-rod upper-end bushings, the connecting-rod bolts, and the
rocker-arm assemblies.
The L. O. Gordon Manufacturing Co., of Muskegon, Mich., made the cam
shafts.
The Park Drop Forge Co., of Cleveland, made the crank-shaft forgings.
These forgings, completely heat treated, were turned out in three
days, because Mr. Hall gave the Cleveland concern permission to use the
Hall-Scott dies.
The Packard Motor Car Co. machined the crank shafts and all parts not
furnished or finished elsewhere.
The Hall-Scott Motor Car Co., of Berkeley, Calif., made all the bevel
gears.
The Hess-Bright Manufacturing Co., of Philadelphia, made the ball
bearings.
The Burd High-Compression Ring Co., of Rockford, Ill., made the piston
rings.
The Aluminum Castings Co., of Cleveland, made the die-cast alloy
pistons and machined them up to grinding.
The Rich Tool Co., of Chicago, made the valves.
The Gibson Co., of Muskegon, Mich., made the springs.
The Packard Co. made all the patterns for the aluminum castings, which
were produced by the General Aluminum & Brass Manufacturing Co., of
Detroit.
The Packard Motor Car Co. used many of its own dies in order to obtain
suitable drop forgings speedily, and also made all necessary new dies
not made elsewhere.
As these various parts were turned out they were hurried to the tool
room of the Packard Co., where the assembling of the model engines was
in progress.
Before the models were built, however, extraordinary precautions had
been taken to insure that the mechanism would be as perfect as American
engineering skill could make it. The plans as developed were submitted
to H. M. Crane, the engineer of the Simplex Motor Car Co. and of the
Wright-Martin Aircraft Corporation, who had made a special study of
aviation engines in Europe, and who for upward of a year had been
working on the production of the Hispano-Suiza 150-horsepower engine
in this country. He looked the plans over, and so did David Fergusson,
chief engineer of the Pierce-Arrow Motor Car Co. Many other of the best
experts in the country in the production of internal-combustion motors
constructively criticized the plans, these including such men as Henry
M. Leland and George H. Layng, of the Cadillac Motor Car Co., and F. F.
Beall and Edward Roberts, of the Packard Car Co.
When the engineers were through, the practical production men were
given their turn. The plane and engine builders examined the plans
to make sure that each minute part was so designed as to make it
most adaptable to quantity production. The scrutiny of the Liberty
plans went back in the production scale even farther than this; for
the actual builders of machine tools were called in to examine the
specifications and to suggest modifications, if necessary, that would
make the production of parts most feasible in machine tools either of
existing types or of easiest manufacture.
Thus scrutinized and criticized, the plans of the engine were the
best from every point of view which American industrial genius could
produce in the time which was available. It was due to this exhaustive
preliminary study that no radical changes were ever made in the
original design. The Liberty engine was not the materialization of
magic nor the product of any single individual or company, but it was a
well-considered and carefully prepared design based on large practical
aviation-engine experience.
On July 4, 1917, the first 8-cylinder liberty engine was delivered in
Washington. This was less than six weeks after Messrs. Hall and Vincent
drew the first line of their plans. The same procedure was even then
being repeated in the case of the 12-cylinder engine. By the 25th day
of August the model 12-cylinder liberty had successfully passed its
50-hour test. In this test its power ranged from 301 to 320 horsepower.
As an achievement in speed in the development of a successful new
engine this performance has never been equaled in the motor history of
any country. No successful American automobile motor was ever put in
production in anything under a year of trial and experimentation. We
may well believe that in the third year of war the European aviation
designers were working at top speed to improve the motive power of
airplanes; yet in 1917 the British war cabinet report contains the
following language:
Experience shows that as a rule, from the date of the
conception and design of an aero engine, to the delivery of the
first engine in series by the manufacturer, more than a year
elapses.
But America designed and produced experimentally a good engine in six
weeks and a great one in three months, and began delivering it in
series in five months. This was due to the fact that we could employ
our best engineering talent without stint, to the further fact that
there were no restrictions upon our use of designs and patents proved
successful by actual experience, and to the fact that the original
engine design produced under such conditions stood every expert
criticism and test that could be put upon it and emerged from the trial
without substantial modification.
As soon as the first Liberty models had passed their official tests
plans were at once made to put them in manufacture.
The members of the Aircraft Production Board chose for the chief of
the engine production department Harold H. Emmons, an attorney and
manufacturer of Detroit, Mich., who, as a lieutenant in the Naval
Reserve Force, was just being called by the Navy Department into active
service.
The production of all aviation engines, for both Army and Navy, was
in his hands throughout the rest of the war. He placed orders for
100,993 aviation engines of all types, which involved the expenditure
of $450,000,000 and more of Government funds. Of these 31,814 were
delivered ready for service before the signing of the armistice. The
United States reached a daily engine production greater than that of
England and France combined.
In August, 1917, it was intended to manufacture both engines, the
8-cylinder and the 12-cylinder, and an agreement was reached with the
Ford Motor Co. of Detroit to produce 8-cylinder Liberty engines to
the number of 10,000. But before this contract could be signed the
increasing powers of the newest European air engines indicated to our
commission abroad that we should concentrate our manufacturing efforts
upon the 12 alone, that being the engine of a power then distinctly
in advance in the rapid evolution of aviation engines. The engine
production department, therefore, entered into contracts for the
construction of 22,500 of the 12-cylinder Liberties, and the first of
these contracts was signed in August, a few days after the endurance
tests had demonstrated that the 12-cylinder engine was a success.
Of this number of Liberty engines the Packard Motor Car Co. contracted
to build 6,000; the Lincoln Motor Co., 6,000; the Ford Motor Co.,
5,000; Nordyke & Marmon, 3,000; the General Motors Corporation (Buick
and Cadillac plants), 2,000; while an additional contract of 500
engines was let to the Trego Motors Corporation.
Early in the liberty engine project it became apparent that one of
the great stumbling blocks to volume production would be the steel
cylinder, if it were necessary to machine it out of a solid or
partially pierced forging such as is used for shell making. This
problem was laid before Henry Ford and the engineering organization of
the Ford Motor Co., at Detroit, and they developed the unique method
of making the cylinders out of steel tubing. One end of the tube was
cut obliquely, heated, and in successive operations closed over and
then expanded into the shape of the combustion chamber, with all bosses
in place on the dome. The lower end was then heated and upset in a
bulldozer until the holding-down flange had been extruded from the
barrel at the right place. By this method a production of 2,000 rough
cylinders a day was reached.
The final forging was so near to the shape desired that millions of
pounds of scrap were saved over other methods, to say nothing of an
enormous amount of labor thus done away with. The development of this
cylinder-making method was one of the important contributions to the
quantity production of Liberty engines.
[Illustration: EXPERIMENTAL WORK ON NEW IDEAS FOR LIBERTY ENGINE.]
[Illustration: TEST CYLINDERS FOR THE LIBERTY ENGINE AT THE PLANT OF
NORDYKE & MARMON, INDIANAPOLIS, IND.]
[Illustration: CRANK-SHAFT DIE FOR THE LIBERTY ENGINE. BUICK ENGINE
CO., DETROIT.]
[Illustration: ACCEPTED LIBERTY ENGINES BEING BOXED FOR SHIPMENT.]
It was evident that in the actual production of the Liberty engine
there would continually arise practical questions of manufacturing
policy that might entail modifications of the manufacturing methods,
while our aviation authorities in Europe could be expected to advance
suggestions from time to time that might need to be embodied in
the mechanism. Consequently it was necessary to create a permanent
development and standardization administration for the Liberty engine.
Nor could this supervision be located in Washington, because of the
extreme need for haste, but it must exist in the vicinity of the plants
doing the manufacturing.
For this reason the production of the Liberty engine was centered
in the Detroit manufacturing district, since in this district was
located the principal motor manufacturing plant capacity of the United
States. James G. Heaslet, formerly general manager of the Studebaker
Corporation and an engineer and manufacturer of wide experience, was
installed as district manager. The problems incident to the inspection
and production of the Liberty engine were placed in charge of a
committee consisting of Maj. Heaslet (chairman); Lieut. Col. Hall, one
of the designers of the engine; Henry M. Leland; C. Harold Wills, of
the Ford Motor Co.; and Messrs F. F. Beall and Edward Roberts, of the
Packard Motor Car Co. With them were also associated D. McCall White,
the engineer of the Cadillac Motor Co., and Walter Chrysler, of the
Buick Co.
The creation of this committee virtually made a single manufacturing
concern of the several, previously rival, motor companies engaged in
producing the Liberty engine. To these meetings the experts without
reservation brought the trade secrets and shop processes developed in
their own establishments during the preceding years of competition.
Such cooperation was without parallel in the history of American
industry, and only a great emergency such as the war with Germany could
have brought it about. But the circumstance aided wonderfully in the
development and production of the Liberty engine.
Moreover, the Government drew heavily upon the talent of these great
manufacturing organizations for meeting the special problems presented
by the necessity of filling in the briefest possible time the largest
aviation engine order ever known. Short-cuts that these firms might
have applied effectively to their own private advantage were devised
for the Liberty engine and freely turned over to the Government. The
Packard Co. gave a great share of its equipment and personnel to the
development. The most conspicuous success in the science of quantity
production in the world was the Ford Motor Co., which devoted its
organization to the task of speeding up the output of Liberty engines.
In addition to the unique and wonderfully efficient method of making
rough engine cylinders out of steel tubing, the Ford organization also
perfected for the Liberty a new method of producing more durable and
satisfactory bearings. Messrs. H. M. and W. C. Leland, whose names
were indissolubly linked with the Cadillac automobile, organized and
erected the enormous plant of the Lincoln Motor Co. and equipped it
for the production of the Liberty, at a total expense of approximately
$8,000,000.
Balanced against these advantages brought by highly trained technical
skill and unselfish cooperation were handicaps such as perhaps no
other great American industrial venture had ever known. In the first
place, an internal-combustion engine with cylinders of a 5-inch bore
and pistons of a 7-inch stroke--the Liberty measurements--was larger
than the automobile engines then in use in this country. This meant
that while we apparently had an enormous plant--the combined American
automobile factories--ready for the production of Liberty engines,
actually the machinery in these plants was not large enough for the
new work, so that new machinery therefore must be built to handle this
particular work. In some cases machinery had to be designed anew for
the special purpose.
To produce every part of one Liberty engine something between 2,500
and 3,000 small jigs, tools, and fixtures are employed. For large
outputs much of this equipment must be duplicated over and over again.
To provide the whole joint workshop with this equipment was one of the
unseen jobs incidental to the construction of Liberty engines--unseen
by the general public, that is--yet it required the United States
to commandeer the capacity of all available tool shops east of the
Mississippi River and devote it to the production of jigs and tools for
the Liberty engine factories.
Then there was the question of mechanical skill in the factories.
It soon developed that an automobile motor is a simple mechanism
compared with an intricate aviation engine. The machinists in ordinary
automobile plants did not have the skill to produce the Liberty engine
parts successfully. Consequently it became necessary to educate
thousands of mechanics, men and women alike, to do this new work.
It was surprising to what extent unfriendly influence in the United
States, much of it probably of a pro-German character, cut a figure
in the situation. This was particularly true in the supply factories
furnishing tools to the Liberty engine plants. Approximately 85 per
cent of the tools first delivered for this work were found to be
inaccurate and incorrect. These had to be remade before they could
be used. Such tools as were delivered to the Liberty plants would
mysteriously disappear, or vital equipment would be injured in unusual
ways; in several instances cans of explosives were found in the coal
at power plants; fire-extinguishing apparatus was discovered to be
rendered useless by acts of depredation; and from numerous other
evidences the builders of Liberty engines were aware that the enemy had
his agents in their plants.
Difficulty was also experienced in the production of metals for the new
engines. The materials demanded were frequently of a much higher grade
than the corresponding materials used in ordinary automobile motors.
Here was another unseen phase of development which had to be worked out
patiently by the producers of raw materials.
[Illustration: LIBERTY ENGINE READY FOR TEST AT THE LINCOLN MOTOR CO.,
DETROIT, MICH.]
[Illustration: LIBERTY ENGINE ON INSTRUCTION STAND, WILBUR WRIGHT
FIELD.]
[Illustration: VIEW SHOWING LIBERTY ENGINE WITH PROPELLER HUB ATTACHED.]
[Illustration: TEST SHED AND STAND WITH LIBERTY ENGINE MOUNTED WITH
TEST PROPELLER. PACKARD MOTOR CAR CO.]
Difficulties in transportation during the winter of 1917-18 added their
share to the perplexing problems of the engine builders, while at times
the scarcity of coal threatened the complete shutdown of some of the
plants.
Under such obstacles the engine-production department forced the
manufacture of the Liberty engine at a speed never before known in
the automotive industry. In December, 1917, the Government received
the first 22 Liberty engines of the 12-cylinder type, durable and
dependable, a standardized, concrete product, only seven months after
the Liberty engine existed merely as an idea in the brains of two
engineers. These first engines developed a strength of approximately
330 horsepower, and this was true also of the first 300 Liberty engines
delivered, these deliveries being completed in the early spring of 1918.
When the Liberty engine was designed our aviation experts believed that
330 horsepower was so far in advance of the development of aero engines
in Europe that we could safely go ahead with the production of this
type on a quantity basis. But again we reckoned without an accurate
prophetic knowledge of the course of engine development abroad. We
were building the first 300 Liberty engines at 330 horsepower when
our aviation reports informed us from overseas that an even higher
horsepower would be desirable. Therefore our engineers "stepped up"
the power of the Liberty 12-cylinder engine to 375 horsepower. Several
hundred motors of this power were in process of completion when again
our observers in France advised us that we could add another 25
horsepower to the Liberty, making it 400 horsepower in strength, and
be sure of leading all of the combatant nations in size and power of
aviation engines during 1918 and 1919. This last step, we were assured,
was the final, definite one. But to anticipate possible extraordinary
development of engines by other nations, our engineers went even
further than the mark advised by our overseas observers and raised the
power of the Liberty engine to something in excess of 400 horsepower.
This enormous increase over the original power of the Liberty engine
required changes in the construction, notably in increasing the
strength of practically all of the working parts, including the crank
shaft, the connecting rods, and the bearings. The change also resulted
in making scrap iron of a large quantity of the jigs and special tools
employed in making the lighter engines. A still further change had to
come in the character of some of the steel used in some of the parts,
and this went back to the smelting plants, where new and better methods
of producing steel and aluminum for the Liberty engine had to be
developed.
Thus while there were no fundamental changes in the design of the
engine, the increase of its power required a considerable readjustment
in the engine plants. Yet so rapidly were these changes made that on
the first anniversary of the day when the design of the Liberty engine
was begun--May 29, 1918--the Signal Corps had received 1,243 Liberty
engines. In this achievement motor history was written in this country
as it had never been written before.
From a popular standpoint it may seem that the Liberty engine was
radically changed after its inception, but such an assertion is
entirely unwarranted; for in the fundamental thing, the design, there
was but one change made after the engine was laid down on paper in May,
1917, namely, in the oiling system. The original Liberty engine was
partially fed with oil by the so-called scupper system, whereas this
later was changed to a forced feed under compression. The scupper feed
worked successfully, but the forced feed is foolproof and was therefore
installed upon the advice of the preponderance of expert criticism.
It is also true that in working out certain practical manufacturing
processes some of the original measurements were altered. But this is a
common experience in the manufacture of any internal-combustion engine,
and alterations made for factory expediency are not regarded as design
changes, nor are they important.
The delivery of 22 motors in December of 1917 was followed by the
completion of 40 in January, 1918. In February the delivery was 70. In
March this jumped to 122; then a leap in April to 415; while in May
deliveries amounted to 620.
The quantity production of Liberties may be said to have started in
June, 1918, one year after the engine's conception in Washington. In
that month 1,102 motors of the most powerful type were delivered to the
service. In July the figure was 1,589; in August, 2,297; in September,
2,362. Then in October came an enormous increase to the total of 3,878
Liberty engines. During the month before the armistice was signed the
engine factories were producing 150 engines a day.
In all, up to November 29, 1918, 15,572 Liberty engines were produced
in the United States. In the disposal of them the American Navy
received 3,742 for its seaplanes; the plants manufacturing airplanes
in this country took 5,323 of them; 907 were sent to various aviation
fields for training purposes; to the American Expeditionary Forces in
France, in addition to the engines which went over installed in their
planes, we sent 4,511 Liberty engines; while 1,089 went to the British,
French, and Italian air services.
Some of the earliest Liberties were sent to Europe. In January, 1918,
we shipped 3 to our own forces in France. In March we sent 10 to the
British, 6 to the French, and 5 to the Italians. By June 7 the English
tests had convinced the British air minister that the Liberty engine
was in the first line of high powered aviation engines and a most
valuable contribution to the allied aviation program. The British
air minister so cabled to Lord Reading, the British ambassador in
Washington. Again on September 26 the British air ministry reported
that in identical airplanes the Liberty engine performed at least
as well as the Rolls-Royce engine. Birkight, who designed the
Hispano-Suiza engine in France, declared that the Liberty engine was
superior to any high-powered aviation engine then developed on the
Continent of Europe.
[Illustration: INSTALLING LIBERTY ENGINE IN THE LEPERE FUSELAGE AT
PACKARD PLANT, SHOWING PROGRESSIVE ASSEMBLY.]
[Illustration:
FIGURE 14.
LIBERTY ENGINES PRODUCED EACH MONTH DURING 1918.
Jan. 40 =
Feb. 70 =
Mar. 122 ==
Apr. 415 ======
May. 620 =========
June. 1102 =================
July. 1589 ========================
Aug. 2297 ==================================
Sept. 2362 ===================================
Oct. 3878 ==========================================================
Nov. 3056 ==============================================
Dec. 2437 =====================================]
A more concrete evidence of the esteem in which this American creation
was held by the European expert lies in the size of the orders which
the various allied Governments placed with the United States for
Liberty engines. The British took 1,000 of them immediately and
declared that they wished to increase this order to 5,500 to be
delivered by December 31, 1918. The French directed inquiries as to
the possibility of taking one-fifth of our complete output of Liberty
engines. The Italians also indicated their intention of purchasing
heavily for immediate delivery.
This increased demand for the engine had not been anticipated in our
original plans, as we had no idea that the allied Governments would
turn from their own highly developed engines to ask for Liberty engines
in such quantities. The original program of 22,500 engines was only
sufficient for our own Army and Navy requirements. As soon as the
foreign Governments, however, came in with their demands we immediately
increased the orders placed with all the existing Liberty engine
builders, and in addition contracted to take the entire manufacturing
facilities of the Willys-Overland Co. at its plants in Toledo and
Elyria, Ohio, and Elmira, N. Y. We also engaged the entire capacity of
the Olds Motor plant at Lansing, Mich. In addition we had subsequently
contracted for the production of 8,000 of the 8-cylinder engines. Thus
the number of engines which would have been delivered under contract,
if peace had not cut short the production, would have been 56,100
engines of the 12-cylinder type and 8,000 of the 8's.
The foreign Governments associated with us in the war against Germany
showered their demands upon us for great numbers of the American
engines, not only altogether because of the excellence of the Liberty,
but because partially their plane production exceeded their output of
engines. Mr. John D. Ryan, Director of Aircraft Production, verbally
agreed to deliver to the French 1,500 Liberty engines by December 31,
and further agreed to deliver motors to the French at the rate of 750
per month during the first six months of 1919. The British had already
received 1,000 Liberty motors, and this order was increased with Mr.
Ryan personally by several thousand additional engines to be delivered
in the early part of 1919. When the armistice was signed the Liberty
engine was being produced at a rate which promised to make it the
dominant motive power of the war in the air before many months had
passed.
The engine was originally named the "United States Standard 12-cylinder
Aviation Engine." In view of the service which it promised to render to
the cause of civilization, Admiral D. W. Taylor, the chief construction
officer of the Navy, suggested during the early part of the period of
production that the original prosaic name be discarded and that the
engine be rechristened the "Liberty." Under this name the engine has
taken its place in the history of the war as one of the most efficient
agencies which was developed and employed by this country.
CHAPTER IV.
OTHER AIRPLANE ENGINES.
The production of the Liberty engine so captured popular attention
that the public never fairly understood nor appreciated the extent of
another production enterprise on the part of those providing motive
power for our war airplanes. This was the supplementary manufacture
of aero engines other than those which bore the proud appellation of
"Liberty."
Let the production figures speak for themselves. In those 19 months,
starting with nothing, we turned out complete and ready for service
32,420 aero engines. Of these thousands of engines less than
one-half--the exact figure being 15,572--were Liberty engines. The rest
were Hispano-Suizas, Le Rhones, Gnomes, Curtisses, Hall-Scotts, and
some others, a total of 16,848 in all--built largely for the training
of our army of the air.
This production would have been even more notable had the war
continued, for at the date of the signing of the armistice the United
States had contracted for the construction of 100,993 aircraft engines.
Of these 64,100 were to be Liberty engines, so that the total plan of
construction of engines other than the Liberty would have produced
about 37,000 of them. The total cost of carrying through the combined
engine project would have been in the neighborhood of $450,000,000.
While at the outbreak of the war American knowledge of military
aviation may have been meager, still it was evident from the start that
we would be able to go ahead with certain phases of production on a
huge scale without waiting for the precise knowledge of requirements
that would come only from an exhaustive study of the subject in
Europe. In the first place we knew that we must train our aviators.
For this purpose there was at the start no particular need of the
highly-developed machinery then in use on the western front. The
first aircraft requirement of the early training program was for safe
planes, regardless of their type, and motive power to drive them. Later
on, when we were better prepared, would come the training that would
afford our aviators experience with the fighting equipment. So at the
start there was no reason why we should not proceed at once with the
construction of such training machines as we knew how to build.
An aviation program for war falls into these two divisions--the
equipment required for training and that required for combat. While
our organization, particularly through the Bolling commission which we
had sent to Europe, was making a study of our combat requirements and
while we were pushing forward the design and production of the Liberty
engine, we forthwith developed on an ambitious scale the manufacture of
training planes and engines in this country.
The training of battle aviators, on the other hand, also separates
into two parts, the elementary training and the advanced training. The
elementary training merely teaches the cadet the new art of maintaining
himself in the air. Later, when he has mastered the rudiments of
mechanical flight, he goes into the advanced training, the training in
his fighting plane, where he requires equipment more nearly of the type
used at the front.
For the elementary training we had some good native material to start
with. The Curtiss Airplane Co. had been building training planes and
engines both for the English and Canadian air authorities. This was
evidently the most available American airplane for our first needs.
The Curtiss plane was known as the "JN-4" and it was driven by a
90-horsepower engine called the Curtiss "OX." In the production of this
equipment on the scale planned by the Signal Corps, the embarrassing
feature, the choke point, was evidently to be the manufacture of the
engine. The Curtiss plant at Buffalo for the manufacture of planes
could be quickly expanded to meet the Government demands; but the
Curtiss engine plant at Hammondsport, N. Y., could not develop the
production of "OX" engines up to our needs and at the same time
complete the orders which it was filling for the English and Canadian
air services.
Consequently, contracts were awarded to the Curtiss Co. for its
capacity in the production of "OX" engines, and then the American
aviation authorities came to an agreement with the Willys-Morrow plant
at Elmira, N. Y., for an additional 5,000 of these motors. Ordinarily
it would require from five to six months to equip a plant with the
large machine tools and the smaller mechanical appliances necessary for
such a contract as this. But the Willys-Morrow plant tooled up in three
months and was ready to start on the "OX" manufacturing job.
[Illustration: CURTISS ENGINE, MODEL OX-5.]
[Illustration: HALL-SCOTT ENGINES BEING INSTALLED IN AIRPLANE
FUSELAGES.]
[Illustration: TWO VIEWS OF LE RHONE 80-HORSEPOWER ENGINE.
This is one of the successful rotary engines.]
If speed in production was required at any point in the aviation
development it was here in the manufacture of the elementary training
planes and engines. Without training material, no matter how many
aviation fields we set in order nor how many student aviators we
enlisted, the movement of our flying forces toward the front could not
even begin. And here entered an interesting engineering and executive
problem that had to be worked out quickly by those in charge of our
aircraft construction. If it were plotted on paper, the curve of
requirements for aircraft training material would climb swiftly to
its peak during the first six or eight months of the war and then
decline with almost equal swiftness until it reached a low level. In
other words, we must produce the great number of training machines in
the shortest time possible in order to put our thousands of student
aviators into the air at once over the training fields; but when
this training equipment had been brought up to initial requirements,
thereafter our needs in this direction could be met by only a small
production, since the rate of wastage of such material is relatively
low. Once our fields were fully equipped, the same apparatus could be
used over and over again as the war went on, with little regard to
the improvements of the type of battle planes, so that the ultimate
manufacture need be large enough only to keep this equipment in
condition.
It soon became evident that the production of Curtiss planes and
engines, even under the heavy contracts immediately placed, would
not be sufficient to take care of our elementary training needs; and
the aviation administration began looking around for other types of
aircraft that would fit into our plans. The experts in all branches
of war flying which the principal allied nations had sent to the
United States, warned us against the temptation to adopt many types
of material in order to secure a quick early production. If the
training equipment were not closely standardized in types, it would
result in confusion and delay, both in training the aviator to fly and
in preparing him for actual combat. Such had been the experience in
Europe; and we were now given the benefit of this experience, so that
we might avoid the mistakes which others had made. We were advised to
adopt a single type of equipment for each class of training; but if
that were not consistent with the demands for speed in getting our
service in the air, then at the most we should not have more than two
types either of planes or engines.
In the elementary training program it was evident that we could not
equip ourselves with a single type of plane, except at considerable
expense in time. Consequently we went ahead to develop another.
We found a training airplane being produced by the Standard Aero
Corporation and known as the "Standard-J." The company had been
developing this machine for approximately a year, and its plant could
be expanded readily to meet a large contract. For the engine to drive
this plane we adopted the Hall-Scott "A7A." This was a four-cylinder
engine. It had the fault of vibration common to any four-cylinder
engine, but it was regarded otherwise by experts as a rugged and
dependable piece of machinery. The Hall-Scott Co. was equipped to
produce this motor on an extensive scale, since at the time this
concern was probably the largest manufacturer of aviation engines
in the United States, with the possible exception of the Curtiss Co.
The engine had been used in airplanes built by the Standard Aero
Corporation, the Aero Marine Co., and the Dayton-Wright Co. Therefore
the Joint Army and Navy Technical Board recommended the Standard-J
plane and the Hall-Scott A7A engine as the elementary training
equipment to alternate with the Curtiss plane and engine.
The Government placed contracts with the Hall-Scott Co. for 1,250
engines, its capacity. But, since a large additional number would be
required, a supplementary contract for 1,000 A7A's was given to the
Nordyke & Marmon Co. The Hall-Scott Co. cooperated with this latter
concern by furnishing complete drawings, tools, and other production
necessities.
When it came to the advanced training for our aviators, more highly
developed mechanical equipment was required. There must be two sorts
of this equipment. The advanced student must become acquainted with
rotary engines such as were used by the French and others to drive the
small, speedy chassé planes, while he must also come to be familiar
with the operation of fixed cylinder engines, possessing upwards of
100 horsepower. These latter were the engines in commonest use on
observation and bombing planes. For each type, the rotary and fixed, we
were permitted by our policy to have two sorts of engines in order to
get into production as quickly as possible, but not more than two.
Here again we had to survey the field of engine manufacture and select
closely, at the same time making in point of speed approximately as
good a showing as if we had adopted every engine with claims for our
consideration and had told manufacturers of them to produce as many as
they could.
In this case of rotary engines, our aviation representatives in Europe
advised the production here of Gnome and Le Rhone motors. There were
two models of the Gnome engine, one developing 110 horsepower and the
other 150. The Le Rhone engine produced 80 horsepower. The Bolling
commission had recommended that the Gnome 150 be used in some of our
combat planes.
In the spring of 1917 we were producing a few Gnome 110 horsepower
engines in this country. The General Vehicle Co. at some time
previously had taken a foreign order for these engines. But neither
the Gnome 150 nor the Le Rhone 80 had been built in the United States,
both of these having been developed and used exclusively in France.
The first recommendations from our observers in France advised us to
produce 5,000 of the more powerful Gnome 150's and 2,500 Le Rhone 80's.
The production of Gnome engines in this country forms a good
illustration of the manner in which aircraft requirements at the front
were constantly shifting, due to the rapid evolution of the science
of mechanical flight. Our officers did not hesitate to overrule their
previous decisions, if such a course seemed to be justified, even at
the cost of rendering useless great quantities of work already done
and material already produced. This has been shown in the case of the
Liberty engine. At the start we set out to build Liberty 8-cylinder
engines on a large scale, only to discontinue this work before it was
fairly started; but later on we again took up a Liberty 8-cylinder
project on almost as great a scale as had been planned originally.
So with the production of the heavy 150-horsepower Gnome engine. Our
European advisors were first of the opinion that we should go heavily
into this production. Consequently the equipment end of the Signal
Corps projected a program of 5,000 of the large Gnome engines. Such
a contract was entirely beyond the capacity of the General Vehicle
Co., which had been building the lighter Gnomes. So the Government
entered into negotiations with the General Motors Co. to assume the
greater burden of this undertaking. Under the pilotage of the aircraft
authorities, an agreement was reached for the industrial combination
of the General Motors Co. and the General Vehicle Co. The former
concern brought its vast resources and numerous factories into the
consolidation; while the latter furnished the only skilled knowledge
and experience there was in the United States in the art of making
rotary engines. This seemed to be a great step in our progress and an
achievement in itself; but just as the undertaking of the construction
of large Gnome engines was about to be started, events in Europe had
caused our observers there to revise their first judgment, and we
received cabled instructions recommending that we discontinue the
development of the Gnome 150.
The entire program for Gnome 150's was canceled, and thereafter the
General Vehicle Co., with its relatively small capacity, was called
upon to produce as many of the small Gnome 110's as it could. As a
matter of record the production of these engines amounted to 280 in
number.
The Signal Corps found it difficult to induce manufacturers in this
country to undertake the construction of foreign designed engines at
all. The plans and specifications of mechanical appliances furnished
by foreign engineers and manufacturers are so different from ours
that trouble is invariably experienced in attempts to use them here.
Successful concerns in this country naturally hesitated to pick up
contracts on which they might fail and thus tarnish their reputations.
Our advisors in Europe were insistent that we should produce Le Rhone
engines in quantity in the United States, yet it was hard to find
any manufacturing concern willing to undertake such a development.
Nevertheless, the production of Le Rhone engines proved to be one of
the most successful phases of the whole aircraft program. Its story
illustrates the obstacles encountered in adapting a foreign device to
American manufacture, and it also shows how American production genius
can overcome these handicaps.
It was only after strenuous efforts on our part that the Union Switch
& Signal Co., of Swissvale, Pa., a member of the Westinghouse chain of
factories, was induced to take up the Le Rhone contract. This project
called for the production of 2,500 rotary Le Rhones of 80 horsepower
each. Let us see how the manufacturers took this totally unfamiliar
machine and went about it to reproduce it in this country.
One might think that it would be necessary only to take the French
drawings, change the metric system measurements to our own scale of
feet and inches, and proceed to turn out the mechanism. But it was not
so simple as that. We did receive the drawings, the specifications,
the metallurgical instructions and the like, but these we found to be
unreliable and unsatisfactory from our point of view. For instance,
according to the French instructions the metallurgical requirements
for the engine crank-shaft called for mild steel. This was obviously
incorrect; and if an error had crept into this part of the plans there
was no telling how faulty the rest of them might be. So from the
metallurgical standpoint alone this became a laboratory job of analysis
and investigation. A sample engine had been sent to us from France.
Every piece of metal in this engine was examined by the chemists to
determine its proper constituents, and from this original investigation
new specifications were made for the steel producers.
The drawings of the engine were quite unsatisfactory from the point
of view of American mechanics. They were found to be incorrect, and
there were not enough of them. Consequently this required another
study on the part of engineers and a new set of drawings to be made
up. All of this fundamental work monopolized the time of a large force
of draughtsmen and engineers for several months, working under the
direction of E. J. Hall and Frank M. Hawley. The engine could not be
successfully built without this preliminary study, yet this is a part
of manufacture of which the uninitiated have little knowledge.
[Illustration: THREE VIEWS OF BUGATTI 410-HORSEPOWER ENGINE.]
[Illustration: THREE VIEWS OF THE HISPANO-SUIZA ENGINE.]
The production of the Le Rhone engine might have been materially
delayed by these difficulties, except for the organizing ability of
the executives handling the contract. While the metallurgists were
specifying the steel of the engine parts and the engineers were
drafting correct plans, the factory officials, with the assistance
of the engine production division of the Air Service, were procuring
machinery and tooling up the plant for the forthcoming effort. By the
time this equipment was installed the plans were ready, the steel mills
were producing the proper qualities of metal, and all was ready for the
effort. The Gnome-Le Rhone factories in France sent one of their best
engineers, M. Georges Guillot, and he assisted in the work at the Union
Switch & Signal Co. So rapidly was the whole development carried out
that the first American Le Rhones were delivered to the Government in
May, 1918, considerably less than a year after the project was assumed
by the Union Switch & Signal Co., which concern had not received the
plans of the engine until September, 1917. By the time the armistice
was signed the company had delivered 1,057 Le Rhone engines. Subsequent
contracts had increased the original order to 3,900 Le Rhones, all of
which would have been delivered before the summer of 1919, had the
coming of peace not terminated the manufacture. Although France is
the home of the rotary aviation engine, M. Guillot has certified to
the Aircraft Board that these American Le Rhones were the best rotary
engines ever built.
When it came to the selection of fixed cylinder engines for our
advanced training program, all of the indications pointed to a single
one, the Hispano-Suiza engine of 150 horsepower. This was a tried
and true engine of the war, tested by a wealth of experience and
found dependable. France had used the engine extensively in both its
training and combat planes. In 1916 it had been brought to the United
States for production for the allies, and when we entered the war the
Wright-Martin Aircraft Corporation was producing Hispano-Suizas in
small quantity. By the early summer of 1917, however, the motor had
fallen behind in the development of combat engines because of the
increasing horsepowers demanded by the fighting aces on the front, but
it was still a desirable training engine and could, if necessary, be
used to a limited extent in planes at the front.
The plane adopted by the American aircraft authorities for this
type of advanced training was known as the Curtiss "JN 4H." It was
readily adapted for the use of the Hispano-Suiza 150-horsepower
engine. Contracts for several thousand of these engines were placed
with the Wright-Martin Aircraft Corporation, and up to the signing
of the armistice 3,435 engines were delivered. Before we could start
the production of this engine it was necessary for the Government to
arrange with the Hispano-Suiza Co. for the American rights to build it,
this arrangement including the payment of royalties. Incidentally it
is interesting to note that royalty was the chief beneficiary of the
royalties paid by the American Government, King Alfonso of Spain being
the heaviest stockholder of the Hispano-Suiza Co.
Although our policy permitted us to produce a second training engine
of the fixed cylinder type, no engine other than the Hispano-Suiza was
taken up by us. A number presented their claims for consideration, but
they were one and all rejected. Among these were the Curtiss engines
"OXX" and "V." A few of both of these had been used by the Navy, but
neither one seemed to the Signal Corps to meet the requirements. The
Sturtevant Co. had developed a 135-horsepower engine and built a few of
them, while Thomas Bros., at Ithaca, N. Y., had taken the Sturtevant
engine and modified it in a way that they claimed improved it, although
the changes had not substantially increased the horsepower. This engine
was rejected on the ground that it was too low in horsepower to endure
as a useful machine through any considerable period of manufacture, and
also because it was too heavy per horsepower to accomplish the best
results.
To sum it up, our training program was built around the above named
engines--the Curtiss "OX" and the Hall-Scott "A7A" for the elementary
training machines; the Gnome and Le Rhone, for the rotary engine
types of planes in the advanced training; and the Hispano-Suiza
150-horsepower, for the advanced training in fixed-cylinder-engine
machines. Between the dates of September 1, 1917, and December 19,
1918, we sent to 27 fields 13,250 cadets and 9,075 students for
advanced training. They flew a total of 888,405 hours and suffered
304 fatalities, or an average of 1 fatality for every 2,922.38 flying
hours. At one field the training fliers were in the air 19,484 hours
before there was 1 fatality; another field increased this record to
20,269 hours; while a third made the extraordinary record of 1 casualty
in 30,982 flying hours.
Although we do not possess the actual statistics, the best unofficial
figures show that the British averaged 1 fatality for each 1,000
flying hours at their training camps, the French 1 for each 900 flying
hours, while the Italian training killed 1 student for each 700 flying
hours. These figures are significant, although varying conditions in
the types of training programs may account to some extent for the wide
differences in numbers of casualties at American as compared with
allied training camps.
But while we were producing engines for the training airplanes, both
elementary and advanced, we were not staking our whole combat program
on the Liberty engine alone, although we expected that engine to be our
main reliance in our battle machines. Our organization, both at home
and abroad, was on the alert continually for other engines that might
be produced in Europe or the United States and which would be so far in
advance of anything in use by the air fighters in Europe in 1917 as to
justify our production of them on a considerable scale. One of these
motors which seemed to promise great results for the future was the
Rolls-Royce, which had even then, in 1917, taken its place at the head
of the British airplane engines.
Considerable difficulty was experienced in reaching a satisfactory
arrangement with the Rolls-Royce Co. We expected to duplicate this
engine at the plant of the Pierce-Arrow Motor Car Co., at Buffalo, N.
Y., but the British concern objected to this arrangement on the ground
that the Pierce-Arrow people were commercial competitors.
It was several months before we could agree on a factory and arrive at
a contract satisfactory to both sides. Meanwhile the Liberty engine
had scored its great success, and the expected enormous production of
Liberties tended to cool the enthusiasm of our aircraft authorities for
the Rolls-Royce, as it was evident that the Liberty itself would be as
serviceable and as advanced in type as the British product.
The Rolls-Royce Co. wished to manufacture here its "190," an engine
developing from 250 to 270 horsepower; and for this effort it was
prepared to send to the United States at once a complete set of jigs,
gauges, and all other necessary tooling of a Rolls-Royce plant. With
this equipment ready at hand the company expected to produce about 500
American-built Rolls-Royce engines before the 1st of July, 1918.
But so rapidly was the evolution of aircraft engines going ahead that
even during the time of these negotiations it became evident that
something more than 250 horsepower would soon be needed in the fighting
planes on the Western front. We therefore abandoned the Rolls-Royce
model 190 and started negotiations for the 270-horsepower engine, the
latest and most powerful one produced by the Rolls-Royce Co. But for
this engine the British concern could not furnish the tooling, which
would have to be made new in this country, and this would reduce the
schedule of deliveries. As a result no American-built Rolls-Royce
engine was ever made.
Another disappointing experience in attempting to produce a foreign
designed motor in this country was the project to bring the manufacture
of Bugatti engines to the United States. When our European aircraft
commission arrived in France, the first experimental Bugatti engine
had just made its appearance. It was apparently a long step in advance
of any other motor that had been produced. This French mechanism was
a geared 16-cylinder engine. It weighed approximately 1,100 pounds
and was expected to develop 510 horsepower. It seemed to be the motor
to supplement our own Liberty engine construction. Although heavier
than a Liberty, it was much more powerful. The first Bugatti engine
built in France was purchased by the Bolling commission and hurried to
the United States with the urgent recommendation that we put it into
production immediately and push its manufacture as energetically as we
were pushing that of the Liberty engine.
The Signal Corps acted immediately upon this advice and prepared
to proceed with the Bugatti on a scale that promised to make its
development as spectacular as that of the Liberty. The Duesenberg
Motor Corporation, of Elizabeth, N. J., was even then tooling up for
the production of Liberty engines. We took this concern from its
Liberty work and directed it to assume leadership in the production
of Bugattis. The Liberty engine construction had been centered in the
Detroit district. We now prepared to establish a new aviation engine
district in the East, associating in it such concerns as the Fiat Plant
at Schenectady, N. Y., the Herschell-Spillman Co., of North Tonawanda,
N. Y., and several others. For a time the expectation for the Bugatti
production ran almost as high as the enthusiasm for the Liberty engine,
but the whole undertaking ended virtually in failure, a failure again
due to the tremendous difficulty in adapting foreign engineering plans
to American factory production.
This was the story of it. In due time the sample Bugatti engine
arrived, and with it were several French engineers and expert
mechanics. But, once set up, the Bugatti motor would not function,
nor was it in condition to run; for, as we discovered, during its
test in France a soldier had been struck by its flying propeller. His
body had been thrown twice to the roof of the testing shed, and the
shocks had bent the engine's crank shaft. Then, too, we learned for
the first time that the design and development of this engine had not
been carried through to completion and that a great deal of work would
be required before the device could be put into manufacture. The tests
in France had developed that such a fundamental feature as the oiling
system needed complete readjustment, and this was only indicative
of the amount of work yet to be done on the engineering side of the
production. We did our best with this engine; but to redesign it and
develop it so that it could pass the severe 50-hour test demanded
by our Joint Army and Navy Technical Board was the work of months,
and after that the tooling up of plants had to be accomplished. The
American Bugatti was just getting into production when the armistice
was signed, a total of only 11 having been delivered.
As we have seen, we were already building several hundred Hispano-Suiza
150-horsepower engines for our training planes. Soon after the arrival
of our aircraft commission in France we were advised to go into the
additional manufacture of the latest Hispano-Suiza geared engine of
220-horsepower. Consequently the Washington office at once arranged
with the Wright-Martin Aircraft Corporation, which was building the
smaller Hispano-Suizas, to undertake the production of this newer
model also. The preparations for this manufacture had gone on in the
Wright-Martin plant for a considerable period of time when further
advice from Europe informed us that the Hispano-Suiza 220 was not
performing successfully on account of trouble with the gearing. This
fact, of course, canceled the new contract with the Wright-Martin
Co., the incident being another of those ups and downs with which the
undertaking was replete.
Along in the summer of 1918 the Hispano-Suiza designers in Europe
brought out a 300-horsepower engine. By this date the development
of military flying had made it apparent that engines of such great
horsepower could be used advantageously on the smaller planes. However,
the engine plants of the allied countries were already taxed to their
capacities by their existing contracts, and the demands of these
countries for high-powered engines could not be supplied unless we in
America could increase our manufacturing facilities even further.
In following out this ambition, we placed contracts for the production
of 10,000 Hispano-Suiza 300-horsepower engines. Of these, 5,000 were
to be built by the Wright-Martin Aircraft Corporation. To enable this
company to fulfill the new contract we leased to it the plant owned by
the Government in Long Island City which had formerly been owned by
the General Vehicle Co. The other 5,000 of these engines were to be
built by the Pierce-Arrow Motor Car Co. at Buffalo. We also contracted
for the entire manufacturing facilities of the H. H. Franklin Co., of
Syracuse, N. Y., to aid both the Wright-Martin Corporation and the
Pierce-Arrow Co., in this contract. The first of these high-powered
Hispano-Suiza engines were expected to be delivered in January, 1919,
but this project, of course, was interrupted by the armistice.
To summarize the complete engine program of the aviation development,
the total contracts for engines provided for the delivery of 100,993
engines. These were divided as follows:
OX 9,450
A7A 2,250
Gnome 342
Le Rhone 3,900
Lawrence 451
Hispano-Suiza: 180-horsepower 4,500
Hispano-Suiza: 150-horsepower 4,000
Hispano-Suiza: 300-horsepower 10,000
Bugatti 2,000
Liberty-12 56,100
Liberty-8 8,000
The delivery of aviation engines of all types to the United States
Government, engines produced as part of our war program, were as
follows, by months:
July, 1917 66
August, 1917 139
September, 1917 190
October, 1917 276
November, 1917 638
December, 1917 596
January, 1918 704
February, 1918 1,024
March, 1918 1,666
April, 1918 2,214
May, 1918 2,517
June, 1918 2,604
July, 1918 3,151
August, 1918 3,625
September, 1918 3,802
October, 1918 5,297
------
Total 28,509
The production by types was as follows to November 29, 1918:
OX 8,458
Hispano-Suiza 4,100
Le Rhone 1,298
Lawrence 451
Gnome 280
A7A 2,250
Bugatti 11
Liberty 15,572
At the signing of the armistice the United States had produced about
one-third of the engines projected in its complete aviation program.
Of the output of training engines to November 29, 1918, the various
airplane plants took 9,069 for installation in planes, 325 (all of
these being Le Rhone rotaries) went to the American Expeditionary
Forces in France, 515 (all of which were Hispano-Suizas) were taken by
the Navy, a single A7A model was sent to one of the allied countries,
while 6,376 engines were sent directly to the training fields.
Of the combat engines produced to November 29, 1918 (which
classification includes all of the Liberties, the two more powerful
types of the Hispano-Suiza, and the Bugatti engine), 5,327 went to the
various airplane plants for installation in planes, 5,030 of them were
sent directly to the American Expeditionary Forces, 3,746 were turned
over to the Navy, 1,090 went to the several allied nations, and 941
were taken by the training fields.
The shipment of aviation engines to Europe, however, does not imply the
immediate use of them by our airplane squadrons at the front. In this
report shipment to the American Expeditionary Forces means the shipment
of engines from the American factories producing them. As a matter of
fact several months usually elapsed from the dispatch of an engine from
an American shop until it actually reached the Air Service in France,
and even then another month might be required to put the engine into
actual service. As a result, of the 5,000 and more aviation engines
sent to France by the American engine producers, outside of those
installed in their planes, less than 3,000 are recorded in the annals
of the American Expeditionary Forces as having been received by them up
to the end of December, 1918, the missing 2,000 being in that period
either somewhere in transit or in warehouses on the route to their
destination.
It is of interest to note what makes of foreign engines were used
by our airmen in the war operations. An appended table shows the
list of those received, their names, their rated powers, the numbers
received month by month, and the totals. The records of the American
Expeditionary Forces show that the squadrons in all received from all
sources 4,715 aviation engines up to the end of the year 1918, but
it should be borne in mind that this figure does not include more
than 2,000 engines, principally Liberties, recorded on this side of
the Atlantic as having been shipped to the Army abroad. Of the 4,715
engines noted as received, 2,710 were Liberties.
None of the foreign engines used by our pilots even approached
the Liberty in power. The nearest in power were a Renault and an
Hispano-Suiza, both rated at 300 horsepower.
_Table of engines received from foreign sources in American
Expeditionary Forces monthly._
Legend for Name and horsepower:
A Hispano-Suiza 180
B Hispano-Suiza 220
C Hispano-Suiza 300
D Renault 190
E Renault 300
F Le Rhone 80
G Le Rhone 120
H Clerget 120
I Clerget 140
J Salmson 230
K Fiat 300
L Gnome 150
M Peugeot 230
N Beardmore 160
------+----+----+----+----+----+----+----+----+----+----+----+----+------
Name | | | | | | | | | | | | |
and |Jan.| |Mar.| |May.| |July. |Sept. |Nov.| |Total.
horse-| |Feb.| |Apr.| |June. |Aug.| |Oct.| |Dec.|
power.| | | | | | | | | | | | |
------+----+----+----+----+----+----+----+----+----+----+----+----+------
A | | | | | | | | | 8 | | 11 | | 19
B | | | | 3 | | | 17 |164 |134 | 66 | 15 | | 399
C | | | | | | | | | 1 | | | | 1
D | | | 4 | | 4 | | 18 | | | | | | 26
E | | | | | | 4 | 10 | 14 | 3 | 32 | 20 | | 83
F | | | | | | | | | 10 | 19 | 85 | | 114
G | | | | 6 | | 8 | 14 | 43 | | 43 | | | 114
H | | | | 3 | | 6 | 12 | 8 | | 14 | 29 | | 72
I | | | | | | | | | | | 10 | | 10
J | | | | 4 | 6 | 2 | 23 | 95 | 92 | 92 | 8 | | 322
K | | | | | | | | | 23 | 10 |150 | | 183
L | | | 12 | | 20 | | 66 | | 86 | 22 |200 | | 406
M | | | | | | 2 | | | | | | | 2
N | | | | | | | | | | 14 | | | 14
------+----+----+----+----+----+----+----+----+----+----+----+----+------
Total | | | 16 | 16 | 30 | 22 |160 |324 |357 |312 |528 | | 1,765
------+----+----+----+----+----+----+----+----+----+----+----+----+------
CHAPTER V.
AVIATION EQUIPMENT AND ARMAMENT.
On one of the early days in the great war a Russian aviator, aloft in
one of the primitive airplanes of that time, was engaged in locating
the positions of the enemy when he chanced upon a German birdman
engaged in a similar mission.
In those ancient times--for they seem ancient to us now, although less
than five years have elapsed--actual fighting in the air was unknown.
The aviators had no equipment for battle; indeed, it was doubtful
if the thought had occurred to either side to keep down the enemy's
aircraft by the use of armed force borne upon wings. In the first
months of aviation in the great war the fliers of both sides recognized
a sort of _noblesse oblige_ of the air, which, if it did not make for
actual friendship or fraternizing between the rival air services,
at least amounted to a respect for each other often evidenced by an
innocuous waving of hands as hostile flying machines passed each other.
But now the wounds of war had begun to smart; and when the Russian saw
the German flier going unhindered upon a work that might bring death
to thousands of soldiers in the Czar's army, a sudden rage filled his
heart, and he determined to bring down his adversary, even at the
cost of his own life. Maneuvering his craft, presently he was flying
directly beneath the German and in the same direction and was but
a short distance below his enemy's plane. Then, with a pull on his
control lever, the Russian shot his machine sharply upward, hoping
to upset the German and to escape himself. The result was that the
machines collided, and both crashed to the ground. This was probably
the first aerial combat of the war.
It seems strange to us to-day that the highly complicated and
standardized art of fighting with airplanes was developed entirely
during the great war and, indeed, was only started after the war had
been in progress for several months. Yet such was the case. At the
beginning of the war there was no such thing as armament in aircraft,
either of the offensive or defensive sort. It is true that a small
amount of experimentation in this direction had occurred prior to the
war and also in the early months of fighting, but it was not until the
summer of 1915 that air fighting, as it is so well known to the entire
world to-day, was begun.
In this country we had successfully fired a machine gun from an
airplane in 1912, while at the beginning of the war the French had a
few heavy airplanes equipped to carry machine guns. Yet in August,
1915, Maj. Eric T. Bradley, of the United States Air Service, but then
a flight sublieutenant in the Royal Flying Corps, frequently flew over
the lines hunting for Germans; and his offensive armament consisted of
a Lee-Enfield rifle or sometimes a 12-gauge double-barreled shotgun.
The aviators in those pioneer days usually carried automatic pistols,
but the danger to one side or the other from such weapons was slight,
owing to the great difficulty of hitting an object moving as swiftly as
an airplane travels. The earlier planes also packed a supply of trench
grenades for dropping upon bodies of troops. Another pioneer offensive
weapon for the airplane was the steel dart, which was dropped in
quantities upon the enemy's trenches. Great numbers of these darts were
manufactured in the United States for the allies, but the weapon proved
to be so ineffective that it had but a brief existence.
It is said that before the pilots carried any weapons at all the first
war aviators used to shoot at each other with Very pistols, which
projected Roman candle balls. The start of air fighting may be said to
have come when the Lewis machine guns were brought out for use in the
trenches. Presently these ground guns were taken into the planes and
fired from the observers' shoulders. Then for the first time war flying
began to be a hazardous occupation so far as the enemy's attentions
were concerned.
It was soon discovered that the machine gun was the most effective
weapon of all for use on an airplane, because only with rapid firers
could one hope to hunt successfully such swiftly moving prey as
airplanes. It had become patent to the strategists that it was of
supreme importance to keep the enemy's aircraft on the ground. Hence
invention began adapting the machine gun to airplane use.
The swiftest planes of all were those of the single-seater pursuit
type. It was obviously impossible for the lone pilot of one of these
to drop his controls and fire a machine gun from his shoulder. This
necessitated a fixed gun that could be operated while the pilot
maintained complete control of his machine, and such necessity was the
mother of the invention known as the synchronizing gear.
This ingenious contrivance, however, did not come at once. Most of the
war planes were of the tractor type; that is, that they had the engine
and propeller in front, this arrangement giving them better maneuvering
and defensive powers in the air than those possessed by planes with the
rear, pushing propellers. The first fixed machine gun was carried on
the upper plane of the biplane so as to shoot over the arc described
by the propeller. With the gun thus attached parallel to the line of
flight, the pilot needed only to point the airplane itself directly
at the target to have the gun trained on its objective. But such an
arrangement proved to be unsatisfactory. A single belt or magazine of
cartridges could, indeed, be fired from the gun, but there was no more
firing on that trip, because the pilot could not reach up to the upper
plane to reload the weapon.
So the fixed gun was brought down into the fuselage and made to fire
through the whirling propeller. At first the aviators took their
chances of hitting the propeller blades, and sometimes the blades
were armored at the point of fire, being sheathed in steel of a shape
calculated to cause the bullets to glance off. This system was not
satisfactory. Then, since a single bullet striking an unprotected
propeller blade would often shatter it to fragments, attempts were
made to wrap the butts of the blades in linen fabric to prevent this
splintering, and this protection actually allowed several shots to
pierce the propeller without breaking it.
This was the state of affairs on both sides early in 1915. The
French Nieuports had their fixed guns literally shooting through the
propellers, the bullets perforating the blades, if they did not wreck
them. As late as February, 1917, Maj. Bradley, who was by that time
a flight commander in the British service, worked a Lewis gun over
the Bulgarian lines with the plane propellers protected only by cloth
wrappings.
All of this makeshift operation of fixed machine guns was changed by
the invention of the synchronizing device. This is an appliance for
controlling the fire of the fixed gun so that the bullets miss the
blades of the flying propeller and pass on in the infinitesimal spaces
of time when the line of fire ahead of the gun is clear of obstruction.
The term "synchronizing" is not accurate, since that word implies
that the gun fires after each passage of a propeller blade across the
trajectory. Such is not the truth. The propeller revolves much more
rapidly than the gun fires. The device is also called an "interrupter,"
another inexact term, since the fire of the gun is not interrupted, but
only caused at the proper moments. Technicians prefer the name "gun
control" for this mechanism.
Who first invented the synchronizer is a matter of dispute, but all
observers agree that the Germans in the Fokker monoplanes of 1915 were
the first to use it extensively. Not until some time after this did
the allies generally install similar devices. Some have attributed the
original invention to the famous French flier, Roland Garros.
Two types of synchronizers were developed, one known as the hydraulic
type and the other as the mechanical. In operation they are somewhat
similar. In each case there is a cam mounted on the engine shaft so
that each impulse of the piston actuates a plunger. The plunger passes
on the impulses to the rest of the mechanism. In the mechanical control
the impulse is carried through a series of rods to the gun, causing
the latter to fire at the proper moments. In the hydraulic control the
impulse is transmitted through oil held at a pressure in a system of
copper tubes. The hydraulic synchronizer is known as the Constantinisco
control, commonly called the "C. C." after the military fashion of
using initials. This was the device copied for American planes in the
war.
In April, 1917, we knew practically nothing about the use or
manufacture of aircraft guns. We had used airplanes at the Mexican
border, but not one of them carried a machine gun. The Lewis gun, which
is a flexible type of aircraft weapon pointed on a universal pivot by
the observer in a two-place plane, was being manufactured by the Savage
Arms Corporation for the British Government; but we had never made a
gun of the fixed type in this country, nor did we know anything about
the construction or manufacture of synchronizers.
One special requirement of the aircraft machine gun is that it must
be reliable in the extreme. It is bad enough to have a gun jam on the
ground, but in the air it may be fatal, for little can be done there
to repair the weapon. A jam leaves the gunner to the mercy of his
adversary, so in the production of aircraft armament there must be not
only special care in the manufacture of the guns, but the ammunition,
too, must be as perfect as human accuracy can make it. The cartridges
must be either hand-picked and specially selected from the run of
service ammunition, or else manufactured slowly and expressly for the
purpose, with minute gauging from start to finish of the process.
Another requirement for the aircraft gun is that it must function
perfectly in any position. On the ground a machine gun is fired
essentially in a horizontal position, but the airman dives and leaps in
his maneuvering and must be able to shoot at any instant.
Aircraft guns are subject to extreme variations of temperature, and so
they must be certain to function perfectly in the zero cold of the high
altitudes, regardless of the contraction of their metal parts.
Then, too, such guns must be able to fire at a much greater rate than
those of the ground service. Five hundred shots per minute is regarded
as sufficient for a ground gun, but aircraft guns have been brought
up to a rate of fire as high as 950 to 1,000 shots per minute. The
Browning aircraft gun, never used by us, but in process of development
when the armistice was signed, had been speeded up to 1,300 shots per
minute, with all shots synchronized to miss the blades of the propeller.
The rate of fire in the air can not be made too swift. Suppose an
airplane were flying past a long, stationary target, such as a
billboard, at the relatively slow speed of 100 miles an hour. Assume
on this plane a flexible machine gun aimed at the billboard at right
angles to the line of flight. If this is a fast machine gun, it may
shoot 880 times a minute, at which rate the shots will come so fast
that the explosions will merge into a continuous roar. Yet the bullets
fired at such a rate from a machine moving at even such low speed will
be spaced out along the billboard at intervals of 10 feet. But most
of the fighting planes traveled much faster than 100 miles per hour.
Thus it is entirely possible for two antagonists in the air to aim with
complete accuracy at each other and both to pass unscathed through
the lines of fire. The faster, therefore, the aircraft gun fired, the
better the chances of bringing down the enemy plane.
The Lewis gun, invented by Col. Lewis, of the United States Army, was
the weapon most generally used by the allies as the flexible gun for
their airplanes, operated on a universal mount which permitted it to
be pointed in any direction. The Lewis aircraft gun was the ground gun
modified principally by stripping it of the cooling radiator and by the
addition of a gas check to reduce the recoil. The Lewis was fed by a
drum magazine, a more desirable feed for flexible guns than any belt
system. The German flexible gun, the Parabellum, had the unsatisfactory
belt feed.
The Vickers gun was the only successful weapon of the fixed type
developed in the war before we became a belligerent. We were
manufacturing Vickers guns in the United States prior to April, 1917;
but when the Signal Corps faced the machine-gun problem, in September,
1917, it found that the Infantry branches of the Army had contracted
for the entire Vickers production in this country.
Accordingly, the equipment division of the Signal Corps, in the face
of marked opposition, took up the development of the Marlin gun as
an aircraft gun of the fixed type. This gun, however, proved to be
extraordinarily successful and was regarded by our Flying Service
and by the aviators of the allies to be the equal of the Vickers in
efficiency. Because of this development, when there came the need of
tank guns, in June, 1918, the Aircraft Board, which had succeeded the
Signal Corps as the director of aerial activities, was able to supply
7,220 Marlin machine guns within two weeks for this purpose.
The first order for Marlin guns was placed on September 25, 1917;
and over 37,500 of them had been produced before December, 1918.
The Marlin-Rockwell factory began producing 2,000 guns per month in
January, 1918, and increased this rapidly until as many as 7,000 guns
were built in one month. The Marlin gun shoots at the rate of 600
to 650 shots per minute and is fed by a belt of the disintegrating
metal-link type.
As to Lewis guns, which we adopted as our flexible weapon, more than
35,000 of them were delivered to the Air Service up to December, 1918.
In February, 1918, the Savage Arms Corporation built 1,500 of them,
increasing their monthly deliveries until in the month of October,
1918, they turned out 5,448 of these weapons. The Lewis gun which the
British had been using carried 47 cartridges in its magazine. A notable
accomplishment of the manufacture of Lewis guns for our use was to
increase the capacity of the magazine to hold 97 cartridges.
In our De Haviland-4 planes we installed two Marlin fixed guns, each
firing at the rate of 650 shots per minute, equipping the weapons with
Constantinisco controls to give the plane a maximum fire of 1,300 shots
per minute through the blades of a propeller whirling at a rate as
high as 1,600 revolutions per minute. Four fixed guns have also been
successfully fitted to one plane and timed so that none of the bullets
struck the propeller blades.
At the time the armistice was signed the rate of production of special
aircraft ammunition, a classification including tracer bullets,
incendiary bullets, and armor-piercing bullets, exceeded 10,000,000
rounds per month.
The original estimate for the quantity of ammunition our Flying Service
should have was later greatly increased because the squadrons at the
front began installing as many as four guns on a single observation
plane.
Although different aviators had their own notions about the loading of
ammunition belts, certain sequences in the use of the three types of
special ammunition were usually observed. First usually came the tracer
cartridge, which assists the gunner in directing his aim; then two or
three armor-piercing cartridges, relied upon to injure the hostile
engine or tap the gasoline tank; and finally one or two incendiary
cartridges to ignite the enemy's gasoline as it escaped, sending him
down in flames. Such a sequence would be repeated throughout the
ammunition belt or magazine container.
The belts for the fixed guns carry a maximum of 500 rounds of
cartridges. The belt which we furnished to our fliers at the front
was made of small metallic links fastened together by the cartridges
themselves. As the gun was fired and the cartridges ejected, the links
fell apart and cleared the machine through special chutes. The total
production of such belting in this country amounted to 59,044,755
links. Although the links are extremely simple in design, the great
accuracy required in their finish made production of them a difficult
manufacturing undertaking. The production and inspection of each link
involved over 36 separate operations. It actually cost more to inspect
belt links than to manufacture them.
We produced 12,621 British unit sights for airplane guns and sent 1,550
of them overseas. We also bought an adequate number of small electric
heaters to keep the gun oil from congealing in the cold of high
altitudes.
A novel undertaking for our photographic manufacturers was the
production of the so-called gun cameras which are used to train
airplane gunners in accuracy of fire. Target practice with a machine
gun in an airplane is dangerous to the innocent bystander; and it
was found to be impracticable, moreover, to tow suitable targets for
actual machine-gun fire. Consequently, quite early in the war, the air
services of the allies adopted the practice of substituting cameras for
the machine guns on the practice planes.
One of these gun cameras, invented by Thornton Pickard, of Altringham,
England, imitated in design a Marlin aircraft machine gun; and in
order to make a picture with it, the gunner must go through the same
movements that he would employ in firing a Marlin gun. Thus, if the gun
were pointed directly on the target, the target would appear squarely
in the center of the picture taken; and this showed the gunner's
accuracy as well as if he had fired cartridges from the actual weapon.
These gun cameras were of two sorts. One type took a single picture
each time the trigger was pulled. Those of the other sort took a number
of pictures automatically at a speed approximately that of the firing
of a machine gun. This latter type was much the same as a moving
picture camera, the resulting film being a string of silhouettes of the
target, each exposure showing whether the aim of the gunner was exact
at the instant the picture was taken.
In September, 1917, the Eastman Kodak Co. began the development of a
camera gun of the "burst" or automatic moving-picture type. After our
authorities had seen the model, the Navy ordered a number of them,
while the Air Service placed increasing orders for these instruments
until 1,057 had been produced and delivered to the Government by
November, 1918. This camera was not used in the fixed airplane guns,
but was designed to train the operators of the flexible Lewis gun. The
camera exactly replaced the ammunition magazine on a Lewis gun.
Of the single-shot gun cameras 150 were delivered during the
hostilities. This design was obtained from Canada and duplicated here.
The use of the so-called Bromotype paper in gun cameras was one of
the interesting phases of this development. As everyone acquainted
with photography knows, a picture is made ordinarily by exposing a
sensitized plate or film, developing the latter to make a negative,
then exposing sensitive print paper to the light that comes through the
negative, thus reversing the lights and shadows and creating a positive
in the exact semblance of the subject photographed. A concern in
Cleveland, Ohio, the Positype Co., produced Bromotype paper which could
be exposed directly in the camera, coming out of the developing process
as a positive without the intervention of a film or plate negative.
Bromotype paper is much more highly sensitized than ordinary print
paper, so that it may be adequately exposed in an instantaneous,
high-speed snapshot. The exposure is then developed in the ordinary way
in the dark room, the familiar negative image appearing on the surface
in the ruby light of the lantern. At this point the special developing
process enters. The paper negative, without being fixed, is immersed
in a bath of chemicals that dissolves away the sensitized surface that
has been oxidized by the light from the camera lens--that is, the
image--leaving on the paper only the unoxidized, or unexposed, parts of
the sensitization. The paper now presents an unbroken white surface.
It is then redeveloped by a special solution, and the picture in its
true values of light and shade thus comes into existence. The entire
development and finishing of this paper requires only 2½ to 3 minutes.
Under this system, of course, only one finished print of each exposure
can be made; but the airplane gunners needed only one print to show
their aim. Positype paper was thus admirably adapted for use in the
airplane gun cameras; and because of its cheapness and the simplicity
and rapidity of its use, it was rapidly supplanting film at the
training camps in this country when the armistice was signed.
AIRPLANE BOMBS.
The American production of bombs to be dropped from airplanes was not
started so soon as production in some of the other branches of ordnance
development, due to numerous difficulties encountered in working up
the design of this new matériel. Although aerial bombing was steadily
increasing in effectiveness and magnitude when hostilities ended, yet
this kind of fighting was a development that came relatively late in
the war; and the lack of perfected standards at the time this country
became a belligerent helped to impede our program.
Some of the bombs first designed and put into production were later
rejected by our forces in France, as they had become obsolete before
being shipped overseas. We managed to manufacture a great quantity of
unloaded bombs by the time the armistice was signed, enough, in fact,
to provide for the Army's needs during another year of warfare. These
had to be loaded with explosives before they were ready for use. We
lacked adequate facilities for loading bombs with explosives, although
these facilities were being provided rapidly when the war ended. The
result was that the thousands of completed American bombs remained
unloaded, while practically all the bombs used by our fliers in France
were of foreign manufacture.
Military science had had some small experience with aerial bombing
prior to the great war. Italian aviators had dropped bombs of an
ineffective sort during Italy's war in Africa. When Mexico was having
a civil war in 1914 American air-sailors of fortune on one side or the
other dropped bombs on troops from their planes.
In the great war the first nation to attempt bombing on any systematic
scale was Germany, who sent her Zeppelins over London and Paris
early in the conflict and released bombs upon the heads of the
helpless civilians. Yet this early and impressive effort was, in its
difficulties, out of all proportion to the actual damage done to the
city of London, largely due to the fact that Germany had not yet
produced effective aerial bombs. The frightful scenes and noises of a
bomb raid probably did more to reduce the morale in these early days
than the destruction caused by the exploding missiles.
It is an exceedingly difficult trick to drop a bomb from any
considerable altitude and hit what you are aiming at. The speed of the
airplane, its height above the ground, the shape of the bomb itself,
and the currents of air acting on the falling missile influence its
line of flight. The aviator approaching an enemy target drops the bomb
long before his airplane is directly above the object aimed at.
The line of the bomb's flight is a parabolic curve. The speed at which
the airplane travels at first propels the bomb forward, almost as if it
had been shot from a stationary gun. As the downward velocity of the
bomb increases very rapidly, it soon becomes so great in proportion to
velocity forward that the course of the missile bends sharply downward
until, as it nears the ground, it is falling nearly in a vertical
line. Hence, it becomes evident that accurate bomb dropping is an art
attained only by much practice on the part of the aviator.
The latest bombing machines were equipped with sights which enabled the
birdman to drop these deadly objects with greater accuracy than had
been possible earlier in the war. While some of the expert European
bombers scorned the new inventions in sights and preferred to continue
the use of makeshift sights which they themselves had invented and
installed on their planes, the average accuracy of bomb dropping was
considerably greater after bomb sights came into general use.
These sights were adjusted to height, air speed, and strength of wind.
When these adjustments had been made, the two sighting points were in
such position that, if the bomb were dropped when the target was in
line with them, an accurate hit would be registered.
We adopted a British sight, tested and found satisfactory by the
Royal Flying Corps, and known as the High Altitude Wimperis, and in
the United States as the Bomb Sight Mark I-A. On November 11, 1918,
American factories, working on contracts placed by the Ordnance
Department, had produced 8,500 of them. The job of turning out this
intricate mechanism was turned over to Frederick Pearce & Co.,
of New York City, in January, 1918. Later in the year additional
contracts were given to the Edison Phonograph Works and to the Gorham
Manufacturing Co. These contracts called for 15,000 sights. By
December 12, 1918, these concerns had completed a total of 12,700 of
them.
[Illustration: A 250-POUND DEMOLITION BOMB CARRYING 125 POUNDS OF
EXPLOSIVE AND HAVING HEAVY CAST-STEEL NOSE AND PRESSED SHEET STEEL REAR
BODY.]
[Illustration: A 25-POUND FRAGMENTATION BOMB CARRYING 3 POUNDS OF
EXPLOSIVES, DESIGNED FOR USE AGAINST TROOPS.]
[Illustration: A 40-POUND INCENDIARY BOMB OF THE INTENSIVE TYPE, WITH
STEEL NOSE AND FUSIBLE ZINC REAR CASING.]
[Illustration: AIRPLANE FLARE.]
[Illustration: MARK I, HIGH CAPACITY DROP BOMB. A 105-POUND DEMOLITION
BOMB, CARRYING 55 POUNDS OF EXPLOSIVE.]
[Illustration: MARK II, HIGH CAPACITY DROP BOMB, NOW OBSOLETE, HAVING
BEEN FOUND TOO SMALL FOR DEMOLITION PURPOSES.]
[Illustration: MARK II--A FRAGMENTATION DROP BOMB.
A 20-pound fragmentation bomb, made from a converted 3-inch
artillery shell, carries 1½ pounds of explosives to be used
against troops. Projection at nose causes burst to take place
above ground.]
[Illustration: DROP BOMB, MARK III.]