During the piping times of peace the utility of aircraft as weapons of
offence was discussed freely in an academic manner. It was urged
that the usefulness of such vessels in this particular field would
be restricted to bomb-throwing. So far these contentions have been
substantiated during the present campaign. At the same time it was
averred that even as a bomb-thrower the ship of the air would prove
an uncertain quantity, and that the results achieved would be quite
contrary to expectations. Here again theory has been supported by
practice, inasmuch as the damage wrought by bombs has been comparatively
insignificant.
The Zeppelin raids upon Antwerp and Britain were a fiasco in the
military sense. The damage inflicted by the bombs was not at all in
proportion to the quantity of explosive used. True, in the case of
Antwerp, it demoralised the civilian population somewhat effectively,
which perhaps was the desired end, but the military results were nil.
The Zeppelin, and indeed all dirigibles of large size, have one
advantage over aeroplanes. They are able to throw bombs of larger size
and charged with greater quantities of high explosive and shrapnel than
those which can be hurled from heavier-than-air machines. Thus it has
been stated that the largest Zeppelins can drop single charges exceeding
one ton in weight, but such a statement is not to be credited.
The shell generally used by the Zeppelin measures about 47 inches in
length by 8 1/2 inches in diameter, and varies in weight from 200 to
242 pounds. Where destruction pure and simple is desired, the shell
is charged with a high explosive such as picric acid or T.N.T., the
colloquial abbreviation for the devastating agent scientifically known
as "Trinitrotoluene," the base of which, in common with all the high
explosives used by the different powers and variously known as lyddite,
melinite, cheddite, and so forth, is picric acid. Such a bomb, if it
strikes the objective, a building, for instance, fairly and squarely,
may inflict widespread material damage.
On the other hand, where it is desired to scatter death, as well as
destruction, far and wide, an elaborate form of shrapnel shell is
utilised. The shell in addition to a bursting charge, contains bullets,
pieces of iron, and other metallic fragments. When the shell bursts,
their contents, together with the pieces of the shell which is likewise
broken up by the explosion, are hurled in all directions over a radius
of some 50 yards or more, according to the bursting charge.
These shells are fired upon impact, a detonator exploding the main
charge. The detonator, comprising fulminate of mercury, is placed in
the head or tail of the missile. To secure perfect detonation and to
distribute the death-dealing contents evenly in all directions, it is
essential that the bomb should strike the ground almost at right
angles: otherwise the contents are hurled irregularly and perhaps in
one direction only. One great objection to the percussion system, as
the method of impact detonation is called, is that the damage may be
localised. A bomb launched from a height of say 1,000 feet attains
terrific velocity, due to the force of gravity in conjunction with its
own weight, in consonance with the law concerning a falling body, by the
time it reaches the ground. It buries itself to a certain depth before
bursting so that the forces of the explosion become somewhat muffled as
it were. A huge deep hole--a miniature volcano crater--is formed,
while all the glass in the immediate vicinity of the explosion may be
shattered by the concussion, and the walls of adjacent buildings be
bespattered with shrapnel.
Although it is stated that an airship is able to drop a single missile
weighing one ton in weight, there has been no attempt to prove the
contention by practice. In all probability the heaviest shell launched
from a Zeppelin has not exceeded 300 pounds. There is one cogent reason
for such a belief. A bomb weighing one ton is equivalent to a similar
weight of ballast. If this were discarded suddenly the equilibrium of
the dirigible would be seriously disturbed--it would exert a tendency
to fly upwards at a rapid speed. It is doubtful whether the planes
controlling movement in the vertical plane would ever be able to
counteract this enormous vertical thrust. Something would have to submit
to the strain. Even if the dirigible displaced say 20 tons, and a bomb
weighing one ton were discharged, the weight of the balloon would be
decreased suddenly by approximately five per cent, so that it would
shoot upwards at an alarming speed, and some seconds would elapse before
control was regained.
The method of launching bombs from airships varies considerably. Some
are released from a cradle, being tilted into position ready for firing,
while others are discharged from a tube somewhat reminiscent of that
used for firing torpedoes, with the exception that little or no
initial impetus is imparted to the missile; the velocity it attains is
essentially gravitational.
The French favour the tube-launching method since thereby it is stated
to be possible to take more accurate aim. The objective is sighted and
the bomb launched at the critical moment. In some instances the French
employ an automatic detonator which corresponds in a certain measure to
the time-fuse of a shrapnel shell fired from a gun.
The bomb-thrower reads the altitude of his airship as indicated by his
barometer or other recording instrument, and by means of a table at his
command ascertains in a moment the time which will elapse before the
bomb strikes the ground. The automatic detonator is set in motion and
the bomb released to explode approximately at the height to which it
is set. When it bursts the full force of the explosion is distributed
downwards and laterally. Owing to the difficulty of ensuring the
explosion of the bomb at the exact height desired, it is also made to
explode upon impact so as to make doubly sure of its efficacy.
Firing timed bombs from aloft, however, is not free from excitement and
danger, as the experience of a French airman demonstrates. His dirigible
had been commanded to make a night-raid upon a railway station which was
a strategical junction for the movement of the enemy's troops. Although
the hostile searchlights were active, the airship contrived to slip
between the spokes of light without being observed. By descending to a
comparatively low altitude the pilot was able to pick up the objective.
Three projectiles were discharged in rapid succession and then the
searchlights, being concentrated, struck the airship, revealing its
presence to the troops below. Instantly a spirited fusillade broke out.
The airmen, by throwing ballast and other portable articles overboard
pell-mell, rose rapidly, pursued by the hostile shells.
In the upward travel the bomb-thrower decided to have a parting shot.
The airship was steadied momentarily to enable the range to be taken,
the automatic detonator was set going and the bomb slipped into the
launching tube. But for some reason or other the missile jambed.
The situation was desperate. In a few seconds the bomb would burst and
shatter the airship. The bomb-thrower grabbed a tool and climbing into
the rigging below hacked away at the bomb-throwing tube until the whole
equipment was cut adrift and fell clear of the vessel. Almost instantly
there was a terrific explosion in mid-air. The blast of air caused the
vessel to roll and pitch in a disconcerting manner, but as the airman
permitted the craft to continue its upward course unchecked, she soon
steadied herself and was brought under control once more.
The bomb carried by aeroplanes differs consider ably from that used by
dirigibles, is smaller and more convenient to handle, though considering
its weight and size it is remarkably destructive. In this instance
complete reliance is placed upon detonation by impact. The latest types
of British war-plane bombs have been made particularly formidable, those
employed in the "raids in force" ranging up to 95 pounds in weight.
The type of bomb which has proved to be the most successful is
pear-shaped. The tail spindle is given an arrow-head shape, the vanes
being utilised to steady the downward flight of the missile. In falling
the bomb spins round, the rotating speed increasing as the projectile
gathers velocity. The vanes act as a guide, keeping the projectile in as
vertical a plane as possible, and ensuring that the rounded head shall
strike the ground. The earlier types of bombs were not fitted with these
vanes, the result being that sometimes they turned over and over as they
fell through the air, while more often than not they failed to explode
upon striking the ground.
The method of launching the bomb also varies considerably, experience
not having indicated the most efficient method of consummating this
end. In some cases the bombs are carried in a cradle placed beneath the
aeroplane and launched merely by tilting them in a kind of sling, one by
one, to enable them to drop to the ground, this action being controlled
by means of a lever. In another instance they are dropped over the side
of the car by the pilot, the tail of the bomb being fitted with a swivel
and ring to facilitate the operation. Some of the French aviators favour
a still simpler method. The bomb is attached to a thread and lowered
over the side. At the critical moment it is released simply by severing
the thread. Such aeroplane bombs, however, constitute a menace to the
machine and to the pilot. Should the bomb be struck by hostile rifle or
shell fire while the machine is aloft, an explosion is probable; while
should the aero plane make an abrupt descent the missiles are likely to
be detonated.
A bomb which circumvents this menace and which in fact will explode
only when it strikes the ground is that devised by Mr. Marten-Hale.
This projectile follows the usual pear-shape, and has a rotating tail to
preserve direction when in flight. The detonator is held away from the
main charge by a collar and ball-bearing which are held in place by the
projecting end of a screw-releasing spindle. When the bomb is dropped
the rotating tail causes the spindle to screw upwards until the
projection moves away from the steel balls, thereby allowing them to
fall inward when the collar and the detonator are released. In order to
bring about this action the bomb must have a fall of at least 200 feet.
When the bomb strikes the ground the detonator falls down on the charge,
fires the latter, and thus brings about the bursting of the bomb. The
projectile is of the shrapnel type. It weighs 20 pounds complete, is
charged with some four pounds of T.N.T., and carries 340 steel balls,
which represent a weight of 5 3/4 pounds.
The firing mechanism is extremely sensitive and the bomb will burst
upon impact with the hull of an airship, water, or soft soil. This
projectile, when discharged, speedily assumes the vertical position, so
that there is every probability that it will strike the ground
fairly and squarely, although at the same time such an impact is not
imperative, because it will explode even if the angle of incidence be
only 5 degrees. It is remarkably steady in its flight, the balancing and
the design of the tail frustrating completely any tendency to wobble or
to turn turtle while falling.
Other types of missile may be used. For instance, incendiary bombs have
been thrown with success in certain instances. These bombs are similar
in shape to the shrapnel projectile, but are charged with petrol or some
other equally highly inflammable mixture, and fitted with a detonator.
When they strike the objective the bursting charge breaks up the shell,
releasing the contents, and simultaneously ignites the combustible.
Another shell is the smoke-bomb, which, up to the present, has been used
only upon a restricted scale. This missile is charged with a certain
quantity of explosive to burst the shell, and a substance which, when
ignited, emits copious clouds of dense smoke. The scope of such a shell
is somewhat restricted, it is used only for the purpose of obstructing
hostile artillery fire. The shells are dropped in front of the artillery
position and the clouds of smoke which are emitted naturally inter fere
with the operations of the gunners. These bombs have also been used
with advantage to denote the position of concealed hostile artillery,
although their utility in this connection is somewhat uncertain, owing
to the difficulty of dropping the bomb so accurately as to enable the
range-finders to pick up the range.
Dropping bombs from aloft appears to be a very simple operation, but
as a matter of fact it is an extremely difficult matter to strike the
target, especially from a high altitude. So far as the aeroplane is
concerned it is somewhat at a disadvantage as compared with the airship,
as the latter is able to hover over a position, and, if a spring-gun
is employed to impart an initial velocity to the missile, there is a
greater probability of the projectile striking the target provided it
has been well-aimed. But even then other conditions are likely to arise,
such as air-currents, which may swing the missile to one side of the
objective. Consequently adequate allowance has to be made for windage,
which is a very difficult factor to calculate from aloft.
Bomb-dropping from an aeroplane is even more difficult. If for instance
the aeroplane is speeding along at 60 miles an hour, the bomb when
released will have a speed in the horizontal plane of 60 miles an hour,
because momentarily it is travelling at the speed of the aeroplane.
Consequently the shell will describe a curved trajectory, somewhat
similar to that shown in Fig. 7.
On the other hand, if the aeroplane is travelling slowly, say at 20
miles an hour, the curve of the trajectory will be flatter, and if a
head wind be prevailing it may even be swept backwards somewhat after it
has lost its forward momentum, and describe a trajectory similar to that
in Fig. 8.
A bomb released from an altitude of 1000 feet seldom, if ever, makes
a bee-line for the earth, even if dropped from a stationary airship.
Accordingly, the airman has to release the bomb before he reaches the
target below. The determination of the critical moment for the release
is not easy, inasmuch as the airman has to take into his calculations
the speed of his machine, his altitude, and the direction and velocity
of the air-currents.
The difficulty of aiming has been demonstrated upon several occasions at
aviation meetings and other similar gatherings. Monsieur Michelin,
who has done so much for aviation in France, offered a prize of
L1,00--$5,000--in 1912 for bomb-dropping from an aeroplane. The target
was a rectangular space marked out upon the ground, measuring 170 feet
long by 40 feet broad, and the missiles had to be dropped from a height
of 2,400 feet. The prize was won by the well-known American airman,
Lieutenant Riley E. Scott, formerly of the United States Army. He
dropped his bombs in groups of three. The first round fell clear of the
target, but eight of the remaining missiles fell within the area.
In the German competition which was held at Gotha in September of the
same year the results were somewhat disappointing. Two targets were
provided. The one represented a military bivouac occupying a superficies
of 330 square feet, and the other a captive balloon resembling a
Zeppelin. The prizes offered were L500, L200, and L80--$2,500, $1,000
and $400--respectively, and were awarded to those who made the greatest
number of hits. The conditions were by no means so onerous as those
imposed in the Michelin contest, inasmuch as the altitude limit was set
at 660 feet, while no machine was to descend within 165 feet. The first
competitor completely failed to hit the balloon. The second competitor
flying at 800 feet landed seven bombs within the square, but only one
other competitor succeeded in placing one bomb within the space.
Bomb-dropping under the above conditions, however, is vastly dissimilar
from such work under the grim realities of war. The airman has to act
quickly, take his enemy by surprise, avail himself of any protective
covering which may exist, and incur great risks. The opposing forces are
overwhelmingly against him. The modern rifle, if fired vertically into
the air, will hurl the bullet to a height of about 5,000 feet, while
the weapons which have been designed to combat aircraft have a range of
10,000 feet or more.
At the latter altitude aggressive tactics are useless. The airman is
unable to obtain a clear sharp view of the country beneath owing to the
interference offered to vision by atmospheric haze, even in the dearest
of weather. In order to obtain reasonable accuracy of aim the corsair
of the sky must fly at about 400 feet. In this respect, however, the
aeroplane is at a decided advantage, as compared with the dirigible. The
machine offers a considerably smaller target and moves with much greater
speed. Experience of the war has shown that to attempt to hurl bombs
from an extreme height is merely a waste of ammunition. True, they do a
certain amount of damage, but this is due to luck, not judgment.
For success in aerial bomb operations the human element is mainly
responsible. The daring airman is likely to achieve the greatest
results, as events have proved, especially when his raid is sudden and
takes the enemy by surprise. The raids carried out by Marix, Collet,
Briggs, Babington, Sippe and many others have established this fact
incontrovertibly. In all these operations the airmen succeeded because
of their intrepidity and their decision to take advantage of cover,
otherwise a prevailing mist or low-lying clouds. Flight-Lieutenant
Collet approached the Zeppelin shed at Dusseldorf at an altitude of
6,000 feet. There was a bank of mist below, which he encountered at
1,500 feet. He traversed the depth of this layer and emerged therefrom
at a height of only 400 feet above the ground. His objective was barely
a quarter of a mile ahead. Travelling at high speed he launched his
bombs with what proved to be deadly precision, and disappeared
into cover almost before the enemy had grasped his intentions.
Lieutenant-Commander, now Flight-Commander, Marix was even more daring.
Apparently he had no mist in which to conceal himself but trusted almost
entirely to the speed of his machine, which probably at times notched 90
miles per hour. Although his advent was detected and he was greeted with
a spirited fusillade he clung to his determined idea. He headed straight
for the Zeppelin shed, launched two bombs and swung into the higher
reaches of the air without a moment's hesitation. His aim was deadly,
since both bombs found their mark, and the Zeppelin docked within was
blown up. The intrepid airman experienced several narrow escapes, for
his aeroplane was struck twenty times, and one or two of the control
wires were cut by passing bullets.
The raid carried out by Commanders Briggs and Babington in company with
Lieutenant Sippe upon the Zeppelin workshops at Friedrichshafen was even
more daring. Leaving the Allies' lines they ascended to an altitude of
4,500 feet, and at this height held to the pre-arranged course until
they encountered a mist, which while protecting them from the alert eyes
of the enemy below, was responsible for the separation of the raiders,
so that each was forced to act independently and to trust to the compass
to bring him out of the ordeal successfully. Lieutenant Sippe sighted
Lake Constance, and taking advantage of the mist lying low upon the
water, descended to such an extent that he found himself only a few feet
above the roofs of the houses. Swinging round to the Lake he descended
still lower until at last he was practically skimming the surface of the
Lake, since he flew at the amazingly low height of barely seven feet
off the water. There is no doubt that the noise of his motor was heard
plainly by the enemy, but the mist completely enveloped him, and
owing to the strange pranks that fog plays with sound deceived his
antagonists.
At last, climbing above the bank of vapour, he found that he had
overshot the mark, so he turned quickly and sped backwards. At the same
time he discovered that he had been preceded by Commander Briggs, who
was bombarding the shed furiously, and who himself was the object of
a concentrated fire. Swooping down once more, Lieutenant Sippe turned,
rained his bombs upon the objective beneath, drawing fire upon himself,
but co-operating with Commander Babington, who had now reached the
scene, he manoeuvred above the works and continued the bombardment until
their ammunition was expended, when they sped home-wards under the
cover of the mist. Considering the intensity of the hostile fire, it
is surprising that the aeroplanes were not smashed to fragments.
Undoubtedly the high speed of the machines and the zigzagging courses
which were followed nonplussed the enemy. Commander Briggs was not
so fortunate as his colleagues; a bullet pierced his petrol tank,
compelling a hurried descent.
The most amazing feature of these aerial raids has been the remarkably
low height at which the airmen have ventured to fly. While such a
procedure facilitates marksmanship it increases the hazards. The airmen
have to trust implicitly to the fleetness of their craft and to their
own nerve. Bearing in mind the vulnerability of the average aeroplane,
and the general absence of protective armouring against rifle fire at
almost point-blank range, it shows the important part which the human
element is compelled to play in bomb-dropping operations.
Another missile which has been introduced by the French airmen, and
which is extremely deadly when hurled against dense masses of men,
is the steel arrow, or "flechette" as it is called. It is a fiendish
projectile consisting in reality of a pencil of solid polished steel, 4
3/4 inches in length. The lower end has a sharp tapering point, 5/8ths
of an inch in length. For a distance of 1 1/8th of an inch above this
point the cylindrical form of the pencil is preserved, but for the
succeeding three inches to the upper end, the pencil is provided with
four equally spaced angle flanges or vanes. This flanging of the upper
end or tail ensures the arrow spinning rapidly as it falls through the
air, and at the same times preserves its vertical position during its
descent. The weight of the arrow is two-thirds of an ounce.
The method of launching this fearsome projectile is ingenious. A hundred
or even more are packed in a vertical position in a special receptacle,
placed upon the floor of the aeroplane, preferably near the foot of the
pilot or observer. This receptacle is fitted with a bottom moving in the
manner of a trap-door, and is opened by pressing a lever. The aviator
has merely to depress this pedal with his foot, when the box is opened
and the whole of the contents are released. The fall at first is
somewhat erratic, but this is an advantage, as it enables the darts to
scatter and to cover a wide area. As the rotary motion of the arrows
increases during the fall, the direct line of flight becomes more
pronounced until at last they assume a vertical direction free from all
wobbling, so that when they alight upon the target they are quite plumb.
When launched from a height they strike the objective with terrific
force, and will readily penetrate a soldier's helmet and skull. Indeed,
when released at a height of 4,000 feet they have been known to pierce a
mounted soldier's head, and pass vertically through his body and that
of his horse also. Time after time German soldiers have found themselves
pinned to the ground through the arrow striking and penetrating their
feet. Owing to the extremely light weight of the darts they can be
launched in batches of hundreds at a time, and in a promiscuous manner
when the objective is a massed body of infantry or cavalry, or a
transport convoy. They are extremely effective when thrown among horses
even from a comparatively low altitude, not so much from the fatalities
they produce, as from the fact that they precipitate a stampede among
the animals, which is generally sufficiently serious and frantic to
throw cavalry or a transport-train into wild confusion.
Although aerial craft, when skilfully handled, have proved highly
successful as weapons of offence, the possibilities of such aggression
as yet are scarcely realised; aerial tactics are in their infancy.
Developments are moving rapidly. Great efforts are being centred upon
the evolution of more formidable missiles to be launched from the
clouds. The airman is destined to inspire far greater awe than at
present, to exercise a still more demoralising influence, and to work
infinitely more destruction.