按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
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；005；000in 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。