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"Japanese 50-kg HE Bomb, Type 97" from Tactical and Technical Trends

The following U.S. military report was originally published in Tactical and Technical Trends, No. 42, January 13, 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.]


The information given in the following article is based on a report from India. The first specimen of this incendiary bomb was recovered in April 1943. The accompanying sketch illustrates the details of this bomb.

*          *          *

a. Description

The four 1/16-inch sheet steel tail fins (1) are spot welded to the tail cone and are braced by two sets of 5/16-inch tubular struts (2).

[Japanese 50-kg HE Incendiary Bomb, Type 97]

To the 1/8 inch steel bomb body (5) the tail cone is welded at one end (3) and at the other end, the steel bulkhead (11) to which the steel bomb nose (12) is secured by the three grub screws (9).

The bulkhead (11) is drilled centrally and tapped to take the long burster tube (7) filled with HE, reported to be picric acid.

The bomb nose (12) houses the picric acid booster pellet (15) embedded in the 2 1/2 kg HE ejection charge (14) which is separated from the steel-turned bulkhead (11) by the cardboard disk (13).

The nose fuze employed is A.2 (b) although fuze A.2 (a) could also be utilized: two grub screws (10) secure the nose fuze.

The normal army type suspension band (6) and rectangular-hinged suspension lug (8) are attached centrally to the bomb body.

The main filling (4) consists of 400 to 450 tightly packed cylindrical rubber pellets 1 inch long by 1 inch in diameter, impregnated with yellow phosphorus and carbon disulphide (approximately 8 kgs in weight) in a 64.5 per cent solution of white phosphorus in carbon disulphide - a heavy, clear, golden liquid approximately 6 quarts in quantity.

b. Functioning

On impact the fuze functions to initiate the detonation of the picric acid booster pellet (15) to detonate the HE charge in the nose of the bomb which in turn detonates the HE in the central bursting tube (7).

Fragmentation of the nose unit up to 80 yards radius results from the first explosion, and widespread scattering of the incendiary liquid and rubber pellets follows the simultaneous detonation of the burster tube.

These incendiary pellets have been located within a radius of 50 yards from the point of impact of the bomb, and when dry will ignite spontaneously on exposure to the air: they burn at a low temperature and with a small flame for about five minutes.

When first expelled from the bomb they are in a sticky condition and will even adhere to vertical surfaces.

c. Characteristics

Maximum diameter of body     7 3/4 in
Width of tail 6.75 in
Length of tail1 ft 8 1/2 in
Overall length, including fittings3 ft 9 in
Length of missile excluding fittings2 ft 7 in
Thickness of casing at side 1/8 in
Thickness of casing at nose 1.0 in (approx)
Thickness of casing at base 1/8 in
Weight of main fillingHE in nose 2 1/2 kg
Total weight46 kg
Span of tail vanes9 1/2 in
Color and typical markings of bodyBlue-gray with 1 inch bands of yellow and white
Color and typical markings of nose Blue-gray
Color and typical markings of tail or vanesBlue-gray


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