Japanese Aerial-Burst Bombs

Further intelligence reports on Japanese aerial-bombs used against Allied bombers:

JAPANESE AERIAL-BURST BOMBS

This article briefly outlines information received from the South Pacific regarding Japanese aerial-burst incendiary bombs.

At the present time two types of Japanese bombs are known which are designed to give aerial bursts. These bombs correspond with descriptions by pilots of bombs dropped on flights of our planes.

32 KILOGRAM BOMB

The 32-kilogram (70-pound) Model 99 high-explosive incendiary bomb appears to be the most commonly used type. This bomb is equipped with an impact nose fuse and a mechanical time tail fuse. The body of the bomb contains 198 incendiary pellets of steel filled with phosphorus and the tail contains 3J pounds of high explosive. On explosion the incendiary pellets shoot downwards in the form of a cone with an estimated danger radius of 50 to 75 yards. In addition to the incendiary effect of these pellets the bomb case supplies a fragmentation effect though probably not extending beyond 75 yards.

The bomb has angled tail fins which cause it to spin in the air.

250 KILOGRAM BOMB

The 250-kilogram (550-pound) high-explosive incendiary bomb is Type 2, Mark 3, Model 1. It is equipped with an impact nose fuse and mechanical time tail fuse. The bomb contains 73 pounds of high explosive and 756 incendiary fragments. On explosion fragments are sprayed conically downwards with great force to a range of 200 yards. Due to its angled tail fins this bomb also spins in the air.

TIME FUSE

The aerial-burst fuses used by the Japanese are all mechanical time fuses. Settings cannot be made in the airplane. The fuses do not arm until the bomb spins at the rate of 1,000 revolutions a minute. To attain this rate of spin the 250-kilogram bomb requires a drop of 3,000 feet and, therefore, must be released at this altitude or higher to insure a burst. The 32-kilogram bomb requires a similar drop. They may be set, however, to drop much greater distances before bursting.

BOMB CLUSTERS

Captured documents indicate that bomb clusters may be used against aircraft in flight. One type contains 76 bombs each weighing two-thirds of a pound while another variety contains 40 two-pound bombs. These bombs detonate on impact and are of the hollow charge variety.