Description
Brass except steel arming vanes and firing pin.
The fuze consists of three parts: the fuze body, the striker spindle, and the nose cap arming assembly.
The fuze body contains the striker spindle which is held in place by a shear wire and a brass locating pin. The lower end of the body is internally threaded to take a standard Navy gaine or magazine. A safety fork fits into the upper side of the fuze body, one prong of the fork extending up through eyelets in the vane assembly to prevent premature rotation. The upper part of the brass striker spindle is externally threaded for the arming sleeve and has a stop screw threaded into the top end. The steel firing pin is screwed into the lower end of the spindle. The nose cap arming assembly consists of the arming vanes, brass nose cap, and arming sleeve. The arming sleeve, internally threaded, screws onto the striker spindle and its length of travel is limited by the stop screw at the top end of the spindle. The nose cap and arming vanes are secured to the arming sleeve by four small screws.
A heavy wire eyelet is attached to the side of the fuze body and serves as a guide for the starting wire which is soldered to the nose cap at two points and gives an initial turn to the arming assembly.
Screwed clockwise into nose; there are spanner wrench flats on side of body. No anti-withdrawal or locking device used.
The threads on the striker spindle are 25 threads per inch.
Two different types of arming vanes have been used on this fuze, the vanes varying as to size, shape, and pitch; each type has six blades.
The A-3(b) differs from the A-3(a) as follows:
The nose cap is .87 Inches larger in the A-3(b) and the arming assembly is correspondingly larger.
The striker spindle threads are 28 per inch as compared to 8 per inch in the A-3(a).
The body portion is more heavily constructed than that of the A-3(a).
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. The arming vane assembly rotates up on the striker spindle and locks against the stop screw, thereby arming the fuze. On impact, the striker spindle is forced inward, shearing the shear wire, and the firing pin pierces the primer.
Hazardous Components
Navy gaine or magazine.
Physical Data
Length, overall - 6.38 in (162 mm)
Width, overall - 2.25 in (57 mm)
Vane span - 3.5 in (89 mm) or 4.38 in (111 mm)
See Also
Nose, A-3(a), Type 97 Mk 2 Model 2
Tail, B-2(a), for Type 99 No. 25 Ordinary
Source(s)
OP 1667, Japanese Explosive Ordnance, Volume 1 (1946)
USNBD - Japanese Bombs & Fuzes (1944)
TM-E9-1984, Enemy Bombs and Fuzes, Section VII, Japanese Fuzes (1942)
