*Divisions of Service*. In the army and navy, aeroplanes are used both
for offensive and defensive operations. They must carry out their own
work and intentions and prevent hostile craft from carrying out theirs.
In offensive operations the machines fly continuously over the enemy’s
country and attack every hostile craft sighted, thus creating a danger
zone within the enemy’s lines where no opposing machine can work without
being threatened with an overwhelming attack. The offensive also
includes bombing operations and the destruction of supply depots and
transportation centers. Defensive aerial operation consists in driving
out the enemy craft from our own lines, and in protecting working
machines when on photographing or observation trips. With a powerful
offensive there is of course little need for defense. The former method
is a costly one, and is productive of severe material and personal
losses.
At the present time there are eight principle functions performed by
military aeroplanes:
1. Offensive operations against enemy machines.
2. Reconnaissance, observation, special missions.
3. Bombing supply centers, railways, etc.
4. Photography.
5. Spotting for the artillery.
6. Signalling for infantry operations.
7. Submarine hunting.
8. Patrol and barrage.
[Illustration: Fig. 1. Curtiss "Baby". Biplane Speed Scout. Equipped
with 100 Horsepower Water Cooled Motor.]
Probably the most important service of all is performed by machines
under heading (1). If a successful offensive can be maintained over the
enemy’s lines he is unable to intelligently direct his artillery fire,
and can obtain no information regarding reinforcements, or troop
concentrations for an impending attack. With fighting aeroplanes
clearing the way for our own observation machines and artillery
spotters, the enemy is not only blinded, but is blocked in any attempt
to attack or concentrate his forces. The fact that the French aerial
offensive at Verdun was so efficiently and well maintained accounts for
the failure of the heavy German artillery. Driven far back over their
own lines, the German aviators were seldom able to observe the placing
of the shells, and as a result their gunners were practically trusting
to luck in reaching their target. An immediate and accurate bombardment
always followed one of the very infrequent German air raids over the
French lines. Whenever the French, partially abandoned their aerial
offensive in favor of a defensive campaign, they soon lost their mastery
of the air. As long as enemy machines can be kept back of their own
lines, new trench systems can be constructed, transportation lines can
be extended and ammunition dumps arranged, undertakings that would be
highly precarious with enemy observation machines continually passing
overhead.
[Illustration: Fig. 1. Italian "Pomilio" Two Seater Biplane. Courtesy
"_Flying_."]
To maintain an effective offensive places a tremendous strain on both
the men and the machines, for though the aeroplanes do not penetrate far
beyond the lines they usually meet with superior numbers, and in
addition are continually in range of the anti-aircraft guns. In an
attack over hostile country a slight mishap may cause the loss of a
’plane, for usually the distance from its base is so great as to prevent
a gliding return. Over its own lines an engine failure is usually only a
temporary inconvenience. Fighting aeroplanes, for the offensive, are
small high powered machines generally of the single seater type, and are
capable of high horizontal and climbing speeds. The armament consists of
a machine gun of the Lewis type, and occasionally a few light bombs may
be included in the equipment. As they do not carry out operations far to
the rear of the enemy’s lines they are provided with fuel for only two
or three hours, and this reduced fuel load is necessary for the high
speeds that must necessarily be attained. The area is limited to permit
of quick maneuvers in attack and escape, and at the same time to reduce
the head resistance and weight. The horizontal speed may run up to 150
miles per hour, with a climbing velocity that may exceed 1,000 feet per
minute. Such machines are variously known as "Speed Scouts," "Chasers,"
or "Pursuit Type" (French "DeChasse"). At the beginning of the war the
chasers were largely of the monoplane type, but at present the biplane
is in almost exclusive use.
[Illustration: Fig. 2. Machine Gun Mounting on Morane Monoplane. Gun
Fires Directly Through the Propeller Disc. The Deflecting Plate Attached
to the Root of the Propeller Blade Protects the Propeller When in Line
of Fire. Ammunition in This Gun Is Furnished in Straight Strips or
"Clips."]
The aeroplane employed for surveys of the enemy country and battle front
(2) are of an entirely different type and are much larger and slower.
These "Reconnaissance" machines are generally of the two-seater type,
the personnel consisting of an observer and the pilot, although in some
cases a third man is carried as an assistant to the observer, or to
handle a machine gun against an attack. Since their speed is
comparatively low, they are generally provided with an escort of
chasers, especially when employed on distant missions, this escort
repelling attacks while the observations are being made.
[Illustration: Fig. 2-a. Machine Gun Mounting on S. P. A. D. Biplane.
Gun Is Rigidly Attached to Fuselage Top in Front of Pilot.]
For accurate observation and mapping, the speed of an observation
machine must be necessarily low, and as they are additionally burdened
with a wireless set, an observer, a large fuel reserve, and other
impedimenta, they have a comparatively great area and are therefore
lacking in the maneuvering qualities of the chaser. The span will
average about 40 feet, and the weight carried per horsepower is greatly
in excess of that of the chaser. From a number of examples, the
reconnaissance type will average from 16 to 18 pounds per horsepower,
while the loading of the scout is from 8 to 12. This means that the
former has comparatively little reserve power for rapid climbing. The
present reconnaissance type is always armed, and must not be confused
with the early machine by that name, which, in fact, was merely an
enlarged training machine and had neither offensive nor defensive
powers. The Observer acts as gunner, and is located at a point where he
has the greatest possible range of vision, and where the angle of fire
is as little obstructed as possible.
The radius of action, or the distance traveled per tank of fuel, is
greater with the reconnaissance than with the chaser, present machines
having a capacity of from 10 to 12 hours on a single filling at normal
flight speed.
In bombing operations (3), the loading is very heavy and consequently a
"Bomber" must be a weight lifter to the exclusion of all other
qualities. Not only is the bomb load requirement severe, but the fuel
load is also of great importance, since bombing is usually carried out
at considerable distances from the base. Such machines may carry from
three to six men. All this calls for a tremendous area and a large power
plant. The Handley-Page "Giant," and the Caproni Triplane are examples
of Allied machines of this type while the German "Gotha," used in the
London air raids, is an equivalent enemy machine. As an example of the
weight carrying capacity of a typical bomber, the Handley-Page has
carried a test crew of 21 men, or a personnel load of 3,570 pounds. The
total weight, fully loaded, has been given as 11,500 pounds with a power
plant of 540 horsepower. The maximum speed is 90 miles per hour with a
climbing velocity of about 330 feet per minute. Duration is about 5%
hours at normal speed and full load.
[Illustration: Fig. 3. Handley-Page "Giant" Bombing Type Biplane.
Courtesy "_The Aeroplane_."]
[Illustration: Fig. 4. Curtiss Twin Motor Biplane-Type JN.]
Bombing is of great importance, not only because of the damage caused to
munition factories, transportation lines, store houses, etc., but also
because of the moral effect on both the enemy troops and the civil
population. A well-timed bombing raid will do more to disorganize an
army than almost any other form of attack, and this is attended with a
much less loss of life, and with less cost and equipment. Points in
enemy territory that could be reached in no other way are readily
attacked by bombing planes with all the disastrous effects of heavy
artillery fire. The aeroplane is better adapted for this service than
dirigibles of the Zeppelin type, for they require fewer men for their
operation, and in addition cost less to operate and build.
[Illustration: Fig. 4a. Curtiss "Wireless" Speed Scouts (S-2). By an
Ingenious Arrangement of the Interplane Struts There Is No Exposed Wire
or Cable.]
Bombing operations against well protected objectives are best made at
night since there is less chance of loss through anti-aircraft gun fire,
and also because of the difficulty that the defense machines have in
locating the raiders. Even when well equipped with searchlights and
listening stations, it is not the easiest thing in the world to pick out
and hold the location of an attacking squadron, for the searchlights
immediately betray themselves and can then be put out of action by fire
from the invaders. With the searchlights out of commission, it is almost
impossible for the defending chasers to locate and engage the raiders,
even before the bombs have been dropped. After the bomb dropping has
been accomplished (and with comparative accuracy because of the flares
dropped by the bombing party), the raiders are lightened of a
considerable portion of their load, and are correspondingly increased in
their ability to climb and to evade the enemy chasers.
[Illustration: Fig. 5. Sopwith Speed Scout or "Chaser."]
[Illustration: Fig. 6. Nieuport Biplane Scout with Machine Gun Pivoted
Above the Upper Wing. This Gun Fires Above the Propeller.]
Night flying in squadrons always introduces the danger of collision, and
to minimize this danger, by decreasing the number of machines, the size
and carrying capacity of the bombers has been continually increased.
Again, bombing requires the steady platform that only a large machine
can give, and for accuracy the span and area must be greater than that
of the reconnaissance type. In night flying a large machine is safer to
handle owing to its lower landing speed and ability to come to rest
quickly after landing, and this is of the greatest importance when
landing outside of the aerodrome. For daylight work at comparatively
short distances the smaller bomb carrier used at the beginning of the
war is probably preferable as it has better maneuvering qualities, and
as the bombs are divided among a greater number of machines they are not
so likely to be defeated before accomplishing their object. Because of
their great size, these bombing aeroplanes are nearly always of the
"twin motor" type with two, or even three, independent power plants. The
use of a twin power plant is an added insurance against forced landings
in hostile country, or over unsuitable ground, and even with one dead
engine the machine can be flown home at a fair speed.
[Illustration: Fig. 8. Fokker Synchronized Machine Gun. The Gun Is
Driven by the Motor in Such a Way That the Bullets Pass Between the
Propeller Blades. "_L’Aerophile_."]
"Spotting" for the guidance of the artillery is a duty usually performed
by the reconnaissance type, or small bombing type, and is usually done
under the escort of chasers. Their duty is to direct the battery as to
the placing of shots. The ideal machine for such a purpose would be the
direct lift type similar to a helicopter which could hover over one
particular spot until its object had been accomplished in making
measurements, and plotting enemy positions. Since no such machine is at
present available, the duty must be performed by a low speed aeroplane,
that is large enough to provide a fairly steady platform and at the same
time has sufficient speed for a quick getaway. A dirigible has the
necessary hovering qualities but lacks the speed necessary for avoiding
attack from even the slowest of aeroplanes, and in addition is a
magnificent target for anti-craft guns if kept at an altitude low enough
for accurate observation. A large speed range is a desirable
characteristic in such service.
Photography is of the greatest importance in reconnaissance, since the
camera distinctly records objects on the terrain, so small and obscure
that they may entirely escape the eye of the observer. Again, the
photograph is a permanent record that may be studied at leisure in
headquarters, or may be used in comparisons with photographs taken at an
earlier date in the same territory. Thus changes in the disposition of
enemy batteries, trenches, and troops can be quickly identified. With
modern aeroplane photographic equipment, a vast territory may be
investigated and mapped out by a single machine in a few hours.
Camouflage has but few terrors for the camera, and the photographs often
clearly reveal that which has been passed over time and time again by
the observers. When sent out on a specific mission, the aeroplane
returns the films in an amazingly short length of time, and within a few
minutes they are developed and are ready for the inspection of the
officers in charge. The analysis of these photographs has rapidly
developed into a science well worthy of a Sherlock Holmes. Changes in
the position of shadows, suspiciously sudden growths of underbrush,
changes in the direction of paths, and fresh mounds of earth all have a
definite meaning to the photographic expert.
[Illustration: Fig. 9. Types of Aeroplane Bombs. The Tail Surfaces Guide
the Bomb So That It Strikes on the Firing Pin and at the Same Time
"Safeties" the Bomb So That it Will Not Explode Until it Has Fallen for
Some Distance. In Falling, the Tail Blades Rotate and Release the Firing
Mechanism After the Bomb Has Fallen Clear of the Aeroplane. Courtesy of
"_Flying_."]
[Illustration: Fig. 9-a. Curtiss "JN" Twin Motor Biplane. Observer Is
Seated in Front.]
In the navy the aeroplane has proved of much value in scouting and
particularly in defense against the submarine. Because of its great
speed it has a daily radius of action many times that of a torpedo boat,
and because of its altitude the effective range of vision is still
further increased. At a fair height the observer can easily detect a
submarine even when submerged to a considerable depth, a feat impossible
when near the sea level. For disclosing the conditions existing in an
enemy harbor the aeroplane is fully the equal of the dirigible since it
can approach and retreat rapidly, and without much danger at
comparatively low altitudes. While the dirigible can float indefinitely
at one point, it must be done at an altitude that is safely out of range
of the enemy guns, and this is usually at a point where observation is a
difficult proposition. It does not take long to get the range of such a
target as a hovering dirigible, yet at a much lower altitude it is
difficult to handle naval anti-aircraft guns effectively against a
speeding aeroplane. The smaller scouting seaplanes can report the
position of a submarine to a torpedo boat or "sub-chaser," while the
larger machines are perfectly capable of dealing with the submarine at
first hand. On the large bombing type, a three-pounder gun and a number
of large bombs can be carried, either of which would be sufficient for
the purpose.
[Illustration: Fig. 10. Explosion of a German Aeroplane Bomb Near
Mesopotamia. Courtesy of "_Flying_."]
In land defense chasers and fighters are used for patrol, and to
maintain a barrage against the entrance of enemy machines into our
lines. The patrol machines work along the front line trenches, while the
machines maintaining the barrage are generally arranged in two parallel
lines back of the trenches, the first being about five miles, and the
second about ten miles from the front. All three lines are generally
placed between the enemy and the principal stations and railroad centers
to insure protection from enemy bombers and reconnaissance machines.
Should the first line patrol fail to keep raiders from crossing the
first line trenches, they will have to pass through at least two more
zones of organized fighting squadrons before reaching a vulnerable spot
in our lines. The machines used for patrol and barrage are of the high
speed and fast climbing chaser type. The response to an attack involves
rapid climbing, and a high degree of maneuvering.
[Illustration: Fig. 11. Caproni Triplane with Three Independent Power
Plants. The Motor in the Central Body Drives a Pusher Propeller, While
the Other Power Plants Are Mounted in the Two Outer Bodies and Drive
Tractor Screws. This is an Example of the Larger Bombing Aeroplanes. The
Gun Is Mounted in the Front of the Center Body. Courtesy "_The
Aeroplane_."]
Except for the bombers and battle planes, the machine gun or
"Mitraleuse" has been the only form of arm in common use on aeroplanes.
These use ammunition approximating service rifle caliber and are
furnished in bands, strips or drums according to the type of gun. With
larger guns, the weight of the ammunition has been found excessive with
all but the largest bombing machines, and the recoil of a large caliber
gun has also been difficult to overcome. In a modern American aeroplane
gun of large caliber the recoil has been reduced to almost a negligible
degree, even up to the four-pounder size, by a system of balanced
projectile reactions. This gun has met successful tests, but whether it
has met with general adoption would be difficult to say at the present
time. In Europe, large caliber aeroplane guns have been used on large
"battle planes" or "gun planes" for shelling dirigibles, or in
destroying searchlight stations in bombing raids. The battle planes are
nearly always of the "Twin" type with the gun mounted in the front end
of the fuselage.
*Summary of Types*. To sum up the types required in military operations,
we have: (1) High speed "Chaser" or "Scout" (Single seater), (2) High
speed "Chaser" (Two-seat type), (3) Reconnaissance type, (4) Bombing
type, (5) Gun or Battle Planes. This does not include the training
machines of the two place and "Penguin" types, but as these are simply
unarmed modifications of the two place reconnaissance and single seat
machine, respectively, we will not go into further details at this point
regarding their construction.
*The Chaser or Pursuit Type*. The most important factors in the design
of a chaser are speed and maneuvering ability. The speed must be at a
maximum in both the horizontal and vertical directions, for climbing
ability is fully of as much importance as horizontal speed. Second in
importance is the maximum altitude or "Height of ceiling" to which the
machine can ascend. This maximum "Ceiling" generally goes hand in hand
with the climbing speed, since a fast climber generally has a
correspondingly high maximum altitude. The combination of weight and
head resistance must be such that the climb interferes as little as
possible with the forward velocity.
[Illustration: De Havilland. V. Single Seat "Chaser" or "Speed Scout"
with a Single Rigidly Mounted Machine Gun on Top of Hood (To Left). It
will Be Noted That the Top Wing is Staggered Back Instead of Forward as
in the Usual Type, Thus Allowing the Pilot to Look Directly Up and in
Front of the Top Wing. Dimensions Are in Millimeters.]
Great climbing ability means a large power reserve, hence the weight
carried per horsepower is reduced to from 8 to 12 pounds on the fastest
machines, against the 16 to 18 pounds carried on the larger and slower
reconnaissance types. Strength must be sacrificed to meet these
conditions, so that instead of having a safety factor of from 8 to 12 as
in the larger machines, it is cut to about 5.5, or in other words, the
strength is relatively only half that of the usual type of aeroplane.
This great reduction in strength calls for careful handling, especially
in landing, and also painstaking care in the design and choice of
materials.
High speeds and maneuvering ability both call for small wing areas and
short spans, the areas being so adjusted that the resistance is at a
minimum at the highest speeds. The short spans have a minimum of exposed
interplane bracing and thus indirectly reduce both the head resistance
and the weight. Unfortunately, the most favorable areas at high speeds
are too small for safe landing speeds. With a fixed area, the minimum
landing speed is only a little less than one-half of the maximum flying
speed, hence with a maximum of 150 miles per hour the minimum will
probably be little less than 70 miles per hour. The most efficient wing
sections, and the greatest refinement in the body design, bracing, and
chassis are necessary at speeds of over 100 miles per hour. All other
conditions being equal, the resistance varies as the square of the
velocity, hence at 150 miles per hour, the resistance is 2.25 times that
at 100 miles per hour.
The following table gives approximately the apportionment of the head
resistance producing items in a typical speed scout or chaser.
─────────────────────────────────────────────────────────────────
Body (Fuselage) 68 per cent
─────────────────────────────────────────────────────────────────
Chassis, wheels, struts, etc. 15 per cent
─────────────────────────────────────────────────────────────────
Tail, rudder, fin, elevator 5 per cent
─────────────────────────────────────────────────────────────────
Wing structure, struts, wire, fittings. 12 per cent
─────────────────────────────────────────────────────────────────
The aerodynamic drag due to the lift of the wings is not included in the
above, the useless or parasitic resistance alone being considered. It
will be noted that the body causes by far the greater part of the
resistance, and as a result, the body of the speed scout requires the
most careful attention in regard to streamline form. Fortunately this is
possible with the short stumpy body of the chaser, since a true
streamline form approximates the average body dimensions of the scout.
In the larger machines, the body resistance is not as great in
proportion to the other items since there are more struts and stay
wires, the chassis is larger, and the tail surfaces are of greater area.
The chassis is the next largest item and is one of the most difficult
items to reduce. It has been suggested by several people that the
chassis could be stored away in the body while in flight, but this adds
additional mechanism and weight, and any automatic mechanism for folding
up the chassis members would likely prove unreliable.
*Chaser Armament*. A single seat chaser is provided with one or two
machine guns mounted on top of the fuselage, and directly in front of
the pilot, the length of the barrel being parallel with the fore and aft
center line. They may either be fixed rigidly to the fuselage top, or so
that they can be pointed up, and over the top of the upper wing. With
the machine guns fixed rigidly to the body, as in the early chaser
monoplanes used by Garros and Vedrines, it was necessary at all times to
fire directly through the disc area swept out by the propeller.
Two plans were tried for preventing the propeller from being broken by
the bullets. The first consisted of a device operated by the motor that
stopped the gun whenever the propeller blade came within the path of the
bullets. This early mechanism proved unreliable, since the frequent
stopping, with the propellers running 1200 revolutions per minute, soon
put the apparatus out of order. Soon after the failure of this method,
designers mounted curved protective steel plates on the inner portions
of the propeller blades at points where they were likely to be struck
with bullets. According to calculations in probability and chance, only
one bullet out of every eighteen will strike the protective plate on the
propeller blade, and hence only one out of eighteen bullets will be
wasted. This, however, was a makeshift, and on modern machines the gun
is driven, or "Synchronized" with the motor so that the bullets pass
between the blades.
[Illustration: Curtiss Biplane in Flight. Taken from Another Machine.
Courtesy "_Aerial Age_."]
Many modern single seat chasers have the gun pivoted to the top of the
fuselage so that the pilot can fire above the top plane and to either
side of the body. This does away with the difficulty of keeping the
machine headed directly at the enemy when in action, a method that is
imperative with the fixed type of gun. Two seater chasers are generally
arranged so that the gunner is seated back of the pilot, and the gun is
so pivoted and supported that it can be swung through a wide radius both
toward the front and on either side. This freedom of gun action at least
partly compensates for the slower maneuvering qualities of the two
seater type, since the gun may be swung with the target through quite a
range of field, and without changing the flight direction of the
machine. A gun of this type is provided with stops which prevent the
gunner from shooting into the outlying parts of his own machine. The gun
mounting in many cases of two seater construction consists of a light
circular track that runs around the edge of the cockpit opening. The gun
standard runs on this track, and the gun is pivoted at the upper end of
the standard so that the muzzle can be raised or lowered. The gun turns
in a horizontal plane by sliding on the track, and can be followed
around by the gunner who is seated in the center on a pivoted seat. With
this mounting it is possible to guard against a rear attack, to shoot
straight up, or nearly straight down over the sides of the fuselage.
In a few machines of the two seater type, two machine guns are provided,
one pivoted gun in the rear, and one gun rigidly fastened to the
fuselage in front of the pilot. It is very seldom that both guns can be
brought into action at once unless engaged with a number of enemy
machines, although the front gun is handy in pursuit, and at a time when
the rear gun is ineffective because of the pilot in front of him. Even
with the double equipment, the superior maneuvering qualities of the
single seater makes matters more even than would commonly be supposed.
An added advantage of the single seater is that it is smaller and
therefore more difficult to hit.
English speed scouts have largely adopted the American Lewis gun. The
cartridges in this gun are arranged radially in a circular drum, and are
fed to the gun as the drum revolves. The drum is mounted on the barrel
near the breech and is operated automatically by the successive
explosions. This feeds the cartridges and rejects the empty shells
without the attention of the pilot. It fires about 600 shots per minute.
When one drum is exhausted, another drum of new cartridges can be
quickly and easily inserted. The French use the belt system to a large
extent. In this system the cartridges are attached side by side on a
cotton web belt as in the older types of army machine guns. As in the
Lewis gun, the cartridges are fed automatically by the recoil of the
explosions, and the belt moves through the breech with a step by step
movement until the ammunition is exhausted. This is not nearly as
compact an arrangement as the Lewis gun, and is more difficult to pivot
on account of the dangling belts.
On the right hand side of the Nieuport body there is a drum on which the
belt with the loaded cartridges is wound. The empty end of the belt is
wound on a drum at the left, this drum being provided with a spring to
keep the belt taut. The empty cartridges are discharged through a tube
that passes through the side of the body. On the 1916 Fokker the gun is
of the Maxim type, and is immovably fastened above the engine cowl and
slightly to the right. To fire the gun, the pilot presses down a small
lever fastened to the control column, and from this lever the connecting
Bowden wire closes the motor clutch and starts the gun. A cam is fixed
to the motor shaft in relation to the propeller blades. When firing, the
elevator control is locked fore and aft, while the lateral control
movement is operated by the pilot’s knees. Steering is by the action of
his feet on the rudder bar. Thus the pilot can balance laterally, and
steer with his hands free for the manipulation of the gun, but he cannot
change his elevation.
[Illustration: Aeromarine Training Seaplane]
*Power Plant of the Chaser*. In the smaller speed scouts, the motor is
of the rotary air cooled type, the output ranging from 80 to 110
horsepower, but as the power demands increased the water-cooled motor
came into use, and at the present time has found favor with a large
number of builders. When the power exceeds about 120 horsepower it is
difficult to thoroughly cool the rotary engine, and although the Gnome,
Clerget and Le Rhone are extremely desirable on a chaser because of
their light weight, they cannot be used profitably on the larger scouts.
Up to the present time, the Nieuport and Sopwith use the Clerget and Le
Rhone rotary motors, but the S. P. A. D. and several others have adopted
the water-cooled type. Nearly all of the German chasers, such as the
Roland and Albatros, are water-cooled. Such motors must weigh well below
3 pounds per horsepower if there is to be sufficient power reserve for
fast climbing. The Curtiss scouts are also water-cooled, although the
rating is only 100 horsepower. The French and German machines are very
heavily powered, motors of 175 horsepower being very common, even on
single seaters. The fuel capacity is very limited, probably not
exceeding 2.5 to 3 hours in any case.
*General Dimensions of Scouts*. The following table will give a better
idea of the principal characteristics of these machines. It gives the
overall dimensions, power, speed, climb, etc. It will be noted that the
Nieuport biplane scouts have a smaller lower chord (*). The speeds given
are the sea level speeds since a great change in altitude affects the
performance to a marked degree.
*Reconnaissance Type Arrangement*. These machines are almost invariably
of the two seater type, and are equipped either with one machine gun for
the observer, or with a rigidly fixed gun for the pilot and a pivoted
gun at the rear for the observer. In the majority of cases the observer
is seated in the rear cockpit (Tractor types), and at a point where he
has a greater visual radius and field of fire. With the pusher type, the
observer is, of course, seated in the extreme front of the body, where
he has an extremely wide angle of vision. The pilot in the rear seat of
the pusher is effectually screened from any gun action, either from the
front, side or rear, as the propeller cuts off the field at the back and
the observer and interplane bracing blocks the way at the front and
sides. The observer’s cock-pit is equipped with the signalling
apparatus, photographic equipment, map boards, etc., as well as the
ammunition for the gun. The pilot’s compartment contains the navigating
instruments and controls.
*Armament*. At the beginning of the war nearly all of the French two
seaters were of the pusher type, this arrangement, of course, resulted
in almost a completely dead angle of fire in the rear, and a front
horizontal angle that was practically restricted to 160 degrees. Owing
to the forward position of the gun the vertical angle was quite good,
230 degrees or even better. In the tractor two seater, with a single
movable gun mounted "En barbette" at the rear, the horizontal angle is
about 180 degrees, but the vertical angle is less than with the pusher
type. When the rear gun is supplemented with a front rigidly mounted
gun, there is some protection at the front, but the rigid gun is far
from being as effective as the pivoted rear gun. The front gun of course
fires through the propeller. This armament is used by the German
machines "Aviatic," "Rumpler," "Albatros," and "L. V. G." The forward
rigid gun is usually of the infantry type, while the movable rear gun is
lighter. The latter is fed by drums, or rolled bands on spools, so that
reloading can be performed in the wind stream.
With the two seater type used in reconnaissance, artillery spotting, or
photography, the power is generally in the neighborhood of 220-260
horsepower, and the speed varies from 85 to 100 miles per hour. The area
is approximately 400 to 480 square feet. A single engine is generally
used.
*General Dimensions and Speeds*. Reconnaissance machines of various
types and makes are listed in the following table. A pusher is indicated
by (P) and a tractor by (T). The German aeroplanes (G), and the Allied
aeroplanes (A), are both listed for comparison: It will be noted that
several types of machines have been made by the same firms, and that in
some cases the same machines have different power plants. The Albatros
C-III has been furnished with both the 170 and 220 Mercedes motor. The
Ago biplane has a tapering wing, and the chord width (*) given is taken
at the body. While very recent machines cannot be described, because of
certain restrictions, the horsepower of the latest two seaters will
average about 240 horsepower. If the dates and power items are noted, it
will be seen that the machines used in 1917 have much larger motors
than those built in 1916. The weight per square foot of surface will
average about 6.5 pounds. The loading per horsepower rarely exceeds 17.0
pounds.
*Bombing Type Aeroplanes*. These large aeroplanes are fitted with either
two or three independent power plants. The German bombers are
represented by the Gotha, A. E. G., Friedrichshafen, and Rumpler G,
while the Allied bombers are the Caproni, Handley-Page, Farman, Voisin,
etc. The speed is about that of the reconnaissance type, and will seat
three or more men. The motors average 500 560 horsepower per power
plant, and the wing area is usually well over 1,000 square feet. The
small two seaters are generally equipped with two pivoted machine guns,
while the three seaters have a third machine gun arranged so that it can
be lowered and fired through a trap door in the bottom of the body.
Defense may thus be had from the rear, or below. In some of the pusher
types, a rapid fire gun of comparatively heavy caliber is mounted at the
front of the body in place of the usual machine gun. This is usually the
case with the sea planes used for submarine chasing.
In addition to bombing operations, these large machines are also used
for the protection of "spotting" aeroplanes, or for the direct
protection of the lines against land attacks. These heavily armed
bombers are very difficult to attack, even for the smaller and more
agile "Chasers," as they can fire from below as well as from the front,
top, or sides. In the bombers which have only a single gun in the rear,
the gunner is working at a disadvantage if his adversary forces him to
continually raise and lower his gun from the top of the body to the
lower trap door. This is very tiring to the rear gunner, and if the
chaser’s tactics are carried out for a sufficient length of time, it can
wear out the gunner by continually rising and dropping at the tail of
the bombing plane. In regard to the front gun, the twin motor type
offers many of the advantages of the pusher, and as a whole, the twin
arrangement will nearly double the field of fire of either the tractor
or pusher.
The bombing planes must have a very large radius of action, particularly
those that are used in night bombing operations. The Gothas in bombing
London fly several hundred miles from their base, and recently a
Handley-Page bombing plane flew from London to Constantinople, Turkey,
making only a few stops on the way. Starting out from Hendon, England,
the Handley-Page machine flew to Paris, down the Rhone valley to Lyons
and Marseilles, and then to Pisa, and Rome (Italy), where they landed.
From Rome the machine passed over Naples, over Oranto and then over the
Albanian Alps to the base at Salonica. Making preparations at this base
they flew the final stage of the trip to Constantinople, a distance of
250 miles over hostile country. The bombing of the Turkish capital was
done at night after a flight of 2 1/2 hours from Salonica. When over the
sea of Marmora, the ship "Goeben" was bombed, and in addition a hit was
scored on the two submarines lying at her side. Four bombs struck the
"Goeben" directly, from an altitude of 800 feet. Two more bombs were
dropped on the German ship, "General," which was the headquarters of the
German staff. Finally, after 30 minutes over the city of Constantinople,
the Turkish War Office was the recipient of two more bombs. In the words
of the Turkish communiqué this "Was not entirely destroyed." On its
return to Salonica it was found that the machine had been struck by 26
shrapnel bullets. This disabled one of the power plants so that the
greater part of the return journey was made on a single motor.
From London to Salonica five men were carried. In addition was their
luggage, bedding, two tool boxes, spare parts equivalent in weight to
one engine, and two 11’-6" spare propellers. Complete, the machine
weighed over 6 tons, with a useful load of about 6,000 pounds. In
crossing the Albanian Alps the machine frequently was at an altitude of
10,000 feet. The power plant consisted of two 275 horsepower Rolls-Royce
motors, and even at this high altitude, and with the heavy loading, no
trouble was experienced. During the bombing, only three men were
carried, the remainder of the useful weight being made up of bombs and
other ammunition. While this record will probably be beaten before this
book goes to press, it will at least give an idea as to the requirements
and capabilities of the bombing type aeroplane.
*Military Training Machines*. The military training machines used in the
United States are generally of the two seater tractor type, similar in
external appearance to the reconnaissance type machines already
described. They are low powered, 90 to 125 horsepower, and will have an
average span of 40’-0". The controls are in duplicate so that the
student’s controls move in unison with the instructor’s.