Description
The fuze consists of the fuze body, arming vane assembly, striker spindle and detonator holder.
The fuze body is of one-piece construction. It houses the striker spindle which is held in position by a locating screw and a brass shear wire. The upper portion of the spindle is threaded and a steel firing pin is screwed into the lower end. The arming vane assembly consists of a nose cap, arming vanes and arming sleeve. The arming sleeve is internally threaded and screws onto the spindle. Its length of travel is limited by a stop screw threaded into the top of the spindle. The nose cap and four arming vanes are attached to this sleeve by four short screws.
The lower end of the fuze body is grooved circumferentially. The cup-like detonator holder is secured to the fuze body by two screws which fit into this groove.
A heavy wire eyelet is attached to the side of the fuze body and serves as a guide for the starting wire. The starting wire is soldered to the nose cap in two places and gives an initial turn to the arming assembly when the bomb is dropped. A safety fork fits into the upper portion of the fuze body, one prong of which extends up through eyelets of arming vane assembly to prevent premature vane rotation.
The upper portion of the fuze body down to the external threads is exactly the same as the A-3(a) as regards construction and dimensions, except that there is no projecting collar on the shoulder just above the external threads.
Used in Type 99 No. 6 Smoke and 32 kg. Incendiary.
Functioning
On release of bomb, the arming wire pulls the starting wire through the eyelet, breaking it loose at the soldered points and simultaneously imparting an initial rotation to the arming vane assembly. In seven revolutions, the arming sleeve rises up the striker spindle to lock against the stop screw and arm the fuze. On impact, the entire assembly (vanes, nose cap, sleeve, and spindle) is driven inward, shearing the shear wire and the firing pin pierces the detonator.
Hazardous Components
Detonator.
Physical Data
Length, overall - 5.31 in (134.9 mm)
Width, overall - 2.19 in (55.6 mm)
See Also
Nose, A-3(a), Type 97 Mk 2 Model 2
Source(s)
OP 1667, Japanese Explosive Ordnance, Volume 1 (1946)
TM-E9-1984, Enemy Bombs and Fuzes, Section VII, Japanese Fuzes (1942)
