The following U.S. military report covers two types of Japanese high-explosive incendiary bombs designed for aerial bursts. The report was originally published in Tactical and Technical Trends, No. 47, June 1, 1944. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

JAPANESE AERIAL BURST BOMBS A British source states that as of the latter part of January 1944 there were two types of Japanese high explosive, incendiary bombs known to be intended to give aerial bursts. *          *          * a. 32-Kg Bomb The most commonly used type appears to be the 32 kilogram (70 pound) Model 99 high explosive incendiary bomb. This bomb is equipped with an impact nose fuze and a mechanical time tail fuze. The tail contains 3-1/2 pounds of high explosive, and the body contains 198 incendiary pellets of steel filled with phosphorus. The angled tail fins causes the bomb to spin in the air. On explosion, the incendiary pellets are shot down in the form of a cone with an estimated danger radius of 50 to 75 yards. The fragmentation effect will probably not extend beyond 75 yards, but the incendiary effect will continue below the point of bursts, depending on the time required for the pellets to burn. b. 250-Kg Bomb This bomb (see Tactical and Technical Trends No. 36, p. 39) is a 550 pound high explosive incendiary bomb. It is equipped with impact nose fuze and a time fuze in the tail. This bomb contains 75 pounds of high explosive and 756 incendiary fragments. The angled tail fins cause the bomb to spin in the air, and on explosion, the fragments are sprayed conically downwards. The fragments are scattered over a 175-yard radius when the air burst occurs 100 ft above the ground and the incendiary action continues for 20 seconds. c. Time Fuze The aerial burst fuzes are all mechanical time fuzes. Settings can be made in the airplane. These fuzes are not armed until the bomb attains a speed of 1,000 rpm. This requires a drop of 3,000 feet for the 250-kg bomb, and this bomb must therefore be dropped at least that distance before it will burst. The 32-kg bomb probably requires a similar drop. They may be set to drop much greater distances before bursting. d. Bomb Clusters Japanese sources indicate that cluster bombs may be used against either airborne or grounded aircraft. There are two types. A two pound bomb is packed 40 to a cluster, and the more common 2/3 pound is packed 76 to a cluster. The cluster opens shortly after leaving the releasing plane, which, it is believed, makes the drop a few hundred feet above the target. The individual bombs scatter. Explosions occur only as separate bombs hit targets. They are a hollow-charge type. A penetration of several inches of steel is possible for such bomb blast in the limited area directly in front of the bomb nose. A further effect is described as similar to the explosion of a 40-mm AA shell, excluding fragmentation.

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