Bombsight

Bombsight, apparatus combining optical and calculating devices for aiming and releasing bombs from aircraft. The first bombsights, used during World War I, were simple devices similar to the aiming sight on a rifle. Later in the war the simple sight was replaced by a telescope with cross hairs. To correct for drift and airspeed and to aid the bombardier in making ballistic calculations, various mechanisms were gradually added.

The bombsights used by the U.S. early in World War II (the Sperry and the Norden bombsights) consisted essentially of a telescope with cross hairs, a complex calculating machine, and a group of gyroscopes. With these bombsights a conspicuous aiming point on the target area is located in the telescope and centered on the cross hairs; the necessary information (such as the size of the bomb, altitude and speed of the plane, speed and direction of the wind, target motion, and atmospheric conditions) is entered in the calculating machine; the gyroscopes stabilize the bombing approach; and control of the plane is turned over to an automatic pilot coordinated with the bombsight. The bombs are then automatically released at the proper instant.

Although the accuracy of such a bombsight is high, operations under combat conditions may introduce bombing errors of considerable magnitude. Of all bombs dropped during World War II, about 20 percent fell within 305 m (1000 ft) of the aiming point.

Radar bombsights came into use as regular combat equipment in 1943, making successful bombing possible on moonless nights and through heavy overcast. After the war further improvements were made so that high-speed, high-altitude bombing could be done with much greater accuracy than was formerly attained at much lower speeds and altitudes.

The greatest advances in bombsight technology have occurred in the systems used for dive-bombing by modern fighter-bombers. Using high-speed digital-computer calculations, accurate radar-ranging inputs, improved pilot displays, and automatic release systems, the bombing accuracy of modern jet fighters has been greatly improved.