Position and method of fixing in bomb: The fuze is screwed into the nose of the bomb and tightened with a spanner wrench.

Components of explosive train: A primer sets off a delay element which fires a gaine which in turn sets off the booster.

Fuzes likely to be found with: Probably B-4 (a).

Delay times: Not known (short delay only).

Threads: 1 5/8 inches diameter, 8 threads per inch.

Description: The upper portion of the fuze body houses the arming vane assembly. The lower portion of the fuze body houses the firing pin which is attached to a plug, and the two safety plungers which protrude beyound the point of the firing pin. The vanes are riveted to a sleeve which is screwed to the arming spindle. The vanes are free to rotate, but two grub screws prevent their falling off. A spring keeps the firing pin away from the primer, after the fuze is armed, until impact with the target. A selector unit permits a de-lay to be set. The standard Army gaine is sourrounded by a booster. Spanner holes are prevent. A U-shaped safety wire is also probably used.

Operation: Upon release from the plane, an arming wire is withdrawn from the holes in the vanes and the vanes rotate, but do not fall free. The arming spindle is screwed up-ward by the vanes, raising the two safety plungers with it. This allow the firing pin point protrude below the plungers. On impact, the primer carrier moves against the spring and hits the firing pin to set off the firing train.

Figure 96 – A-4 (a) Bomb Fuze.