Chapter X : Bomb-Throwing From Aircraft

During the piping times of peace the utility of aircraft asweapons of offence was discussed freely in an academic manner. It was urged that the usefulness of such vessels in thisparticular field would be restricted to bomb-throwing. So farthese contentions have been substantiated during the presentcampaign. At the same time it was averred that even as abomb-thrower the ship of the air would prove an uncertainquantity, and that the results achieved would be quite contraryto expectations. Here again theory has been supported bypractice, inasmuch as the damage wrought by bombs has beencomparatively insignificant.

The Zeppelin raids upon Antwerp and Britain were a fiasco in themilitary sense. The damage inflicted by the bombs was not at allin proportion to the quantity of explosive used. True, in thecase of Antwerp, it demoralised the civilian population somewhateffectively, which perhaps was the desired end, but the militaryresults were nil.

The Zeppelin, and indeed all dirigibles of large size, have oneadvantage over aeroplanes. They are able to throw bombs oflarger size and charged with greater quantities of high explosiveand shrapnel than those which can be hurled from heavier-than-airmachines. Thus it has been stated that the largest Zeppelins candrop single charges exceeding one ton in weight, but such astatement is not to be credited.

The shell generally used by the Zeppelin measures about 47 inchesin length by 8 1/2 inches in diameter, and varies in weight from200 to 242 pounds. Where destruction pure and simple is desired,the shell is charged with a high explosive such as picric acid orT.N.T., the colloquial abbreviation for the devastating agentscientifically known as "Trinitrotoluene," the base of which, incommon with all the high explosives used by the different powersand variously known as lyddite, melinite, cheddite, and so forth,is picric acid. Such a bomb, if it strikes the objective, abuilding, for instance, fairly and squarely, may inflictwidespread material damage.

On the other hand, where it is desired to scatter death, as wellas destruction, far and wide, an elaborate form of shrapnel shellis 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 piecesof the shell which is likewise broken up by the explosion, arehurled 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 themain charge. The detonator, comprising fulminate of mercury, isplaced in the head or tail of the missile. To secure perfectdetonation and to distribute the death-dealing contents evenly inall directions, it is essential that the bomb should strike theground almost at right angles: otherwise the contents are hurledirregularly and perhaps in one direction only. One greatobjection to the percussion system, as the method of impactdetonation is called, is that the damage may be localised. Abomb launched from a height of say 1,000 feet attains terrificvelocity, due to the force of gravity in conjunction with its ownweight, in consonance with the law concerning a falling body, bythe time it reaches the ground. It buries itself to a certaindepth before bursting so that the forces of the explosion becomesomewhat muffled as it were. A huge deep hole--a miniaturevolcano crater--is formed, while all the glass in the immediatevicinity of the explosion may be shattered by the concussion, andthe walls of adjacent buildings be bespattered with shrapnel.

Although it is stated that an airship is able to drop a singlemissile weighing one ton in weight, there has been no attempt toprove the contention by practice. In all probability theheaviest shell launched from a Zeppelin has not exceeded 300pounds. There is one cogent reason for such a belief. A bombweighing 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 flyupwards at a rapid speed. It is doubtful whether the planescontrolling movement in the vertical plane would ever be able tocounteract this enormous vertical thrust. Something would haveto submit to the strain. Even if the dirigible displaced say 20tons, and a bomb weighing one ton were discharged, the weight ofthe 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 readyfor firing, while others are discharged from a tube somewhatreminiscent of that used for firing torpedoes, with the exceptionthat little or no initial impetus is imparted to the missile; thevelocity it attains is essentially gravitational.

The French favour the tube-launching method since thereby it isstated to be possible to take more accurate aim. The objectiveis sighted and the bomb launched at the critical moment. In some instances the French employ an automatic detonator whichcorresponds in a certain measure to the time-fuse of a shrapnelshell fired from a gun.

The bomb-thrower reads the altitude of his airship as indicatedby his barometer or other recording instrument, and by means of atable at his command ascertains in a moment the time which willelapse before the bomb strikes the ground. The automaticdetonator is set in motion and the bomb released to explodeapproximately at the height to which it is set. When it burststhe full force of the explosion is distributed downwards andlaterally. Owing to the difficulty of ensuring the explosion ofthe bomb at the exact height desired, it is also made to explodeupon impact so as to make doubly sure of its efficacy.

Firing timed bombs from aloft, however, is not free fromexcitement and danger, as the experience of a French airmandemonstrates. His dirigible had been commanded to make anight-raid upon a railway station which was a strategicaljunction for the movement of the enemy's troops. Although thehostile searchlights were active, the airship contrived to slipbetween the spokes of light without being observed. Bydescending to a comparatively low altitude the pilot was able topick up the objective.

Three projectiles were discharged in rapid succession and thenthe searchlights, being concentrated, struck the airship,revealing its presence to the troops below. Instantly a spiritedfusillade broke out. The airmen, by throwing ballast and otherportable articles overboard pell-mell, rose rapidly, pursued bythe hostile shells.

In the upward travel the bomb-thrower decided to have a partingshot. The airship was steadied momentarily to enable the rangeto be taken, the automatic detonator was set going and the bombslipped into the launching tube. But for some reason or otherthe missile jambed.

The situation was desperate. In a few seconds the bomb wouldburst and shatter the airship. The bomb-thrower grabbed a tooland climbing into the rigging below hacked away at the bomb-throwing tube until the whole equipment was cut adrift and fellclear of the vessel. Almost instantly there was a terrificexplosion in mid-air. The blast of air caused the vessel to rolland pitch in a disconcerting manner, but as the airman permittedthe craft to continue its upward course unchecked, she soonsteadied herself and was brought under control once more.

The bomb carried by aeroplanes differs consider ably from thatused by dirigibles, is smaller and more convenient to handle,though considering its weight and size it is remarkablydestructive. In this instance complete reliance is placed upondetonation by impact. The latest types of British war-planebombs have been made particularly formidable, those employed inthe "raids in force" ranging up to 95 pounds in weight.

The type of bomb which has proved to be the most successful ispear-shaped. The tail spindle is given an arrow-head shape, thevanes being utilised to steady the downward flight of themissile. In falling the bomb spins round, the rotating speedincreasing as the projectile gathers velocity. The vanes act asa guide, keeping the projectile in as vertical a plane aspossible, and ensuring that the rounded head shall strike theground. The earlier types of bombs were not fitted with thesevanes, the result being that sometimes they turned over and overas they fell through the air, while more often than not theyfailed to explode upon striking the ground.

The method of launching the bomb also varies considerably,experience not having indicated the most efficient method ofconsummating this end. In some cases the bombs are carried in acradle placed beneath the aeroplane and launched merely bytilting them in a kind of sling, one by one, to enable them todrop to the ground, this action being controlled by means of alever. In another instance they are dropped over the side of thecar by the pilot, the tail of the bomb being fitted with a swiveland ring to facilitate the operation. Some of the Frenchaviators favour a still simpler method. The bomb is attached toa thread and lowered over the side. At the critical moment it isreleased 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 whilethe machine is aloft, an explosion is probable; while should theaero plane make an abrupt descent the missiles are likely to bedetonated.

A bomb which circumvents this menace and which in fact willexplode only when it strikes the ground is that devised by Mr.Marten-Hale. This projectile follows the usual pear-shape, andhas a rotating tail to preserve direction when in flight. Thedetonator is held away from the main charge by a collar andball-bearing which are held in place by the projecting end of ascrew-releasing spindle. When the bomb is dropped the rotatingtail causes the spindle to screw upwards until the projectionmoves away from the steel balls, thereby allowing them to fallinward when the collar and the detonator are released. In orderto bring about this action the bomb must have a fall of at least200 feet.

When the bomb strikes the ground the detonator falls down on thecharge, fires the latter, and thus brings about the bursting ofthe bomb. The projectile is of the shrapnel type. It weighs 20pounds complete, is charged with some four pounds of T.N.T., andcarries 340 steel balls, which represent a weight of 5 3/4pounds.

The firing mechanism is extremely sensitive and the bomb willburst upon impact with the hull of an airship, water, or softsoil. This projectile, when discharged, speedily assumes thevertical position, so that there is every probability that itwill strike the ground fairly and squarely, although at the sametime such an impact is not imperative, because it will explodeeven if the angle of incidence be only 5 degrees. It isremarkably steady in its flight, the balancing and the design ofthe tail frustrating completely any tendency to wobble or to turnturtle while falling.

Other types of missile may be used. For instance, incendiarybombs have been thrown with success in certain instances. Thesebombs are similar in shape to the shrapnel projectile, but arecharged with petrol or some other equally highly inflammablemixture, and fitted with a detonator. When they strike theobjective the bursting charge breaks up the shell, releasing thecontents, and simultaneously ignites the combustible.

Another shell is the smoke-bomb, which, up to the present, hasbeen used only upon a restricted scale. This missile is chargedwith a certain quantity of explosive to burst the shell, and asubstance which, when ignited, emits copious clouds of densesmoke. The scope of such a shell is somewhat restricted, it isused only for the purpose of obstructing hostile artillery fire. The shells are dropped in front of the artillery position and theclouds of smoke which are emitted naturally inter fere with theoperations of the gunners. These bombs have also been used withadvantage 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 toenable 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 tostrike the target, especially from a high altitude. So far asthe aeroplane is concerned it is somewhat at a disadvantage ascompared with the airship, as the latter is able to hover over aposition, and, if a spring-gun is employed to impart an initialvelocity to the missile, there is a greater probability of theprojectile striking the target provided it has been well-aimed. But even then other conditions are likely to arise, such asair-currents, which may swing the missile to one side of theobjective. Consequently adequate allowance has to be made forwindage, which is a very difficult factor to calculate fromaloft.

Bomb-dropping from an aeroplane is even more difficult. If forinstance the aeroplane is speeding along at 60 miles an hour, thebomb when released will have a speed in the horizontal plane of60 miles an hour, because momentarily it is travelling at thespeed of the aeroplane. Consequently the shell will describe acurved trajectory, somewhat similar to that shown in Fig. 7.

On the other hand, if the aeroplane is travelling slowly, say at20 miles an hour, the curve of the trajectory will be flatter,and if a head wind be prevailing it may even be swept backwardssomewhat after it has lost its forward momentum, and describe atrajectory 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 stationaryairship. Accordingly, the airman has to release the bomb beforehe reaches the target below. The determination of the criticalmoment for the release is not easy, inasmuch as the airman has totake into his calculations the speed of his machine, hisaltitude, and the direction and velocity of the air-currents.

The difficulty of aiming has been demonstrated upon severaloccasions 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 froman aeroplane. The target was a rectangular space marked out uponthe ground, measuring 170 feet long by 40 feet broad, and themissiles had to be dropped from a height of 2,400 feet. Theprize was won by the well-known American airman, Lieutenant RileyE. Scott, formerly of the United States Army. He dropped hisbombs in groups of three. The first round fell clear of thetarget, but eight of the remaining missiles fell within the area.

In the German competition which was held at Gotha in September ofthe same year the results were somewhat disappointing. Twotargets were provided. The one represented a military bivouacoccupying a superficies of 330 square feet, and the other acaptive balloon resembling a Zeppelin. The prizes offered wereL500, L200, and L80--$2,500, $1,000 and $400--respectively, andwere awarded to those who made the greatest number of hits. Theconditions were by no means so onerous as those imposed in theMichelin contest, inasmuch as the altitude limit was set at 660feet, while no machine was to descend within 165 feet. The firstcompetitor completely failed to hit the balloon. The secondcompetitor flying at 800 feet landed seven bombs within thesquare, but only one other competitor succeeded in placing onebomb within the space.

Bomb-dropping under the above conditions, however, is vastlydissimilar from such work under the grim realities of war. Theairman has to act quickly, take his enemy by surprise, availhimself of any protective covering which may exist, and incurgreat risks. The opposing forces are overwhelmingly against him. The modern rifle, if fired vertically into the air, will hurl thebullet to a height of about 5,000 feet, while the weapons whichhave been designed to combat aircraft have a range of 10,000 feetor more.

At the latter altitude aggressive tactics are useless. Theairman is unable to obtain a clear sharp view of the countrybeneath owing to the interference offered to vision byatmospheric haze, even in the dearest of weather. In order toobtain reasonable accuracy of aim the corsair of the sky must flyat about 400 feet. In this respect, however, the aeroplane is ata decided advantage, as compared with the dirigible. The machineoffers a considerably smaller target and moves with much greaterspeed. Experience of the war has shown that to attempt to hurlbombs from an extreme height is merely a waste of ammunition. True, they do a certain amount of damage, but this is due toluck, not judgment.

For success in aerial bomb operations the human element is mainlyresponsible. The daring airman is likely to achieve the greatestresults, as events have proved, especially when his raid issudden and takes the enemy by surprise. The raids carried out byMarix, Collet, Briggs, Babington, Sippe and many others haveestablished this fact incontrovertibly. In all these operationsthe airmen succeeded because of their intrepidity and theirdecision to take advantage of cover, otherwise a prevailing mistor low-lying clouds. Flight-Lieutenant Collet approached theZeppelin shed at Dusseldorf at an altitude of 6,000 feet. Therewas a bank of mist below, which he encountered at 1,500 feet. Hetraversed the depth of this layer and emerged therefrom at aheight of only 400 feet above the ground. His objective wasbarely a quarter of a mile ahead. Travelling at high speed helaunched his bombs with what proved to be deadly precision, anddisappeared into cover almost before the enemy had grasped hisintentions. Lieutenant-Commander, now Flight-Commander, Marixwas even more daring. Apparently he had no mist in which toconceal himself but trusted almost entirely to the speed of hismachine, which probably at times notched 90 miles per hour. Although his advent was detected and he was greeted with aspirited fusillade he clung to his determined idea. He headedstraight for the Zeppelin shed, launched two bombs and swung intothe higher reaches of the air without a moment's hesitation. Hisaim was deadly, since both bombs found their mark, and theZeppelin docked within was blown up. The intrepid airmanexperienced several narrow escapes, for his aeroplane was strucktwenty times, and one or two of the control wires were cut bypassing bullets.

The raid carried out by Commanders Briggs and Babington incompany with Lieutenant Sippe upon the Zeppelin workshops atFriedrichshafen was even more daring. Leaving the Allies' linesthey ascended to an altitude of 4,500 feet, and at this heightheld to the pre-arranged course until they encountered a mist,which while protecting them from the alert eyes of the enemybelow, was responsible for the separation of the raiders, so thateach was forced to act independently and to trust to the compassto bring him out of the ordeal successfully. Lieutenant Sippesighted Lake Constance, and taking advantage of the mist lyinglow upon the water, descended to such an extent that he foundhimself only a few feet above the roofs of the houses. Swingingroundto the Lake he descended still lower until at last he waspractically skimming the surface of the Lake, since he flew atthe amazingly low height of barely seven feet off the water. There is no doubt that the noise of his motor was heard plainlyby the enemy, but the mist completely enveloped him, and owing tothe strange pranks that fog plays with sound deceived hisantagonists.

At last, climbing above the bank of vapour, he found that he hadovershot the mark, so he turned quickly and sped backwards. Atthe same time he discovered that he had been preceded byCommander Briggs, who was bombarding the shed furiously, and whohimself was the object of a concentrated fire. Swooping downonce more, Lieutenant Sippe turned, rained his bombs upon theobjective beneath, drawing fire upon himself, but co-operatingwith Commander Babington, who had now reached the scene, hemanoeuvred above the works and continued the bombardment untiltheir ammunition was expended, when they sped home-wards underthe cover of the mist. Considering the intensity of the hostilefire, it is surprising that the aeroplanes were not smashed tofragments. Undoubtedly the high speed of the machines and thezigzagging courses which were followed nonplussed the enemy. Commander Briggs was not so fortunate as his colleagues; a bulletpierced his petrol tank, compelling a hurried descent.

The most amazing feature of these aerial raids has been theremarkably low height at which the airmen have ventured to fly. While such a procedure facilitates marksmanship it increases thehazards. The airmen have to trust implicitly to the fleetness oftheir craft and to their own nerve. Bearing in mind thevulnerability of the average aeroplane, and the general absenceof protective armouring against rifle fire at almost point-blankrange, it shows the important part which the human element iscompelled 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 ofmen, is the steel arrow, or "flechette" as it is called. It is afiendish projectile consisting in reality of a pencil of solidpolished steel, 4 3/4 inches in length. The lower end has asharp tapering point, 5/8ths of an inch in length. For adistance of 1 1/8th of an inch above this point the cylindricalform of the pencil is preserved, but for the succeeding threeinches to the upper end, the pencil is provided with four equallyspaced angle flanges or vanes. This flanging of the upper end ortail ensures the arrow spinning rapidly as it falls through theair, and at the same times preserves its vertical position duringits descent. The weight of the arrow is two-thirds of an ounce.

The method of launching this fearsome projectile is ingenious. Ahundred or even more are packed in a vertical position in aspecial receptacle, placed upon the floor of the aeroplane,preferably near the foot of the pilot or observer. Thisreceptacle is fitted with a bottom moving in the manner of atrap-door, and is opened by pressing a lever. The aviator hasmerely to depress this pedal with his foot, when the box isopened and the whole of the contents are released. The fall atfirst is somewhat erratic, but this is an advantage, as itenables the darts to scatter and to cover a wide area. As therotary motion of the arrows increases during the fall, the directline of flight becomes more pronounced until at last they assumea vertical direction free from all wobbling, so that when theyalight upon the target they are quite plumb.

When launched from a height they strike the objective withterrific force, and will readily penetrate a soldier's helmet andskull. Indeed, when released at a height of 4,000 feet they havebeen known to pierce a mounted soldier's head, and passvertically through his body and that of his horse also. Timeafter time German soldiers have found themselves pinned to theground through the arrow striking and penetrating their feet. Owing to the extremely light weight of the darts they can belaunched in batches of hundreds at a time, and in a promiscuousmanner when the objective is a massed body of infantry orcavalry, or a transport convoy. They are extremely effectivewhen thrown among horses even from a comparatively low altitude,not so much from the fatalities they produce, as from the factthat they precipitate a stampede among the animals, which isgenerally sufficiently serious and frantic to throw cavalry or atransport-train into wild confusion.

Although aerial craft, when skilfully handled, have proved highlysuccessful as weapons of offence, the possibilities of suchaggression as yet are scarcely realised; aerial tactics are intheir infancy. Developments are moving rapidly. Great effortsare being centred upon the evolution of more formidable missilesto be launched from the clouds. The airman is destined toinspire far greater awe than at present, to exercise a still moredemoralising influence, and to work infinitely more destruction.

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