BOMB-AIMING DEVICE.

Taihape Daily Times, 20 February 1918, Page 6

BOMB-AIMING DEVICE.

INGENIOUS CONTRIVANCE.

CORRECTING AEROPLANE- WORK-

I, a bomb be dropped from an nero- , t „ it is sav ten thousand plane, when it is, s j, feet up, and is travelling at a speed ot one hundred miles an hour the oin will strike the ground at a consi e able distance ahead of the point ver ically beneath that at which it is released, the exact spot varying with the shape of the bomb, its relative weight compared with its size and the direction and force of the wind. In view of the long distances travllcd by bombs dropped from fast aeroplanes when at great heights, it is easy to understand how difficulty is the problem of hitting any particular object, assuming that the airman simply throws out bombs to the best of his judgment. Up to the time of writing the German airraiders have flown at great heights, and it was a foregone conclusion that they would use some form of instrument to tell them when a bomb should be released w T ith a view to hitting a railwmy station or other important building. One of the Gotha aeroplanes was recently captured by the French, and in interesting description of this machine is given in a recent number of La Nature.

The aiming instrument carried is a very ingenious contrivance, the main feature of which is a telescope hung on gimbals and pointing downwards through the floor of the bomber’s compartment. '• HELP OF A SPIRIT LEVEL. It is most important that this instrument should be truly vertical during sighting, and this object is attained by a form of spirit level, in which a bubble comes into a centre ofYT|?fass disc when the telescope is correctly set. An image of this bubble can bo, seen by the bomber when he is looking through the telescope, and this enables him to keep it correctly pointed regardless of the irregular motion of the aeroplane. Such an instrument by itself would, of course, be useless for the purpose in view, as the observer would see only objects exactly under the machine. Just below the telescope, therefore, is fixed a prism, which acts on the principle of the prismatic field-glass, ■ but, instead of deflecting the image at right angles it can be set to show an object at any desired angle ahead of the aeroplane. Now, certain angles correspond with certain distances at certain heights. We will suppose, for instance that the aeroplane is flying at a height of ten thousand feet, and that the bomb must be released half a mile in rear of Jhe object in order to hit it. The angle corersponding to this distanc'd at such a height is, roughly, fifteen degrees. The bomber, therefore, sets his prism at this angle, and the pilot keeps his machine at the correct height’ and points it towards the object being aimed at. When this object comes into the centre of the view seen through the telescope the bomber releases his bomb, which should then score ar hit, provided the weather is calm. Naturally the flight of a bomb is affected by wind to some extent, and as its force in all probability does not remain constant, but varies in the different layers of air through which the bomb passes, the correction necessary Tor this factor can only be roughly estimated. Hence bombs can’only be aimed with anything like absolute accuracy in still weather.