Fuze M157; Igniters M15 and M16

Bombs

Type

Fuze

Burster

Cap

Functioning

Igniter used with

Armed condition

Arming time

18 - 30 vane revolutions;
150 - 220 feet of air travel

General: The igniters considered here use the Anemometer-Arming All-Ways Action Fuze M157. The Igniters M15 and M16 differ in that the M15 is designed to be attached to the outside of the bomb by means of a clamp, while the M16 has an adapter which allows the igniter to be installed in the filler-cap opening in the tank. Because of this dif-ference, the M15 is known as an external; the M16, as an internal igniter.

The Igniters M15 and M16 consists of either a sodium (Na) or a white phopshorus (W.P.) Hand Grenade M15 and a Burster C8R1 (DuPont C56 blasting cap and 2.5 grams of tetryl) fitted to the Fuze M157. If the bombs are to be dropped at sea, the Na grenade is used, while if the bombs are employed against land targets, the W.P. grenade is atta-ched. W.P.- and Na-filled Igniters M15 and M16 are available and are suitable for carrier use.

Operation: When the bomb is released, the arming wire is pulled, permitting the ane-mometer vanes to rotate. The rotation of the vanes threads the arming stem out of the fuze body; the fuze is armed when the stem clears the arming balls, allowing them to fall inward, freeing the striker for movement on impact. The arming assembly threads com-pletely out of the fuze and falls away. On impact, the striker pin and sleeve are forced together, igniting the Primer M26. Flash from the primer initiates the black powder boos-ter and, latterly, the Burster C8R1, which, in turn, breaks the grenade case, allowing the W.P. or Na to ignite the incendiary mixture scattering by the bursting tank.

Remarks: Even though the igniter is released safe and the fuze does not function, impact may break open the Grenade M15, scattering its white phosphorus or sodium filler. This will ignite the gasoline gel, just as though the burster had scattered the filler. For this reason, the igniter cannot be considered capable of "safe" dropping with absolute assurance of non-functioning.

The igniter M15 is designed to be clamped externally to the tank or fin assembly at any convenient point at which a suitable clamp has been provided or improvised. In ca-ses where no clamp has been provided, the local ordnance officer must ensure that the igniter is rigged in accordnance with the best ordnance practice. The clamp must be in-stalled so that the axis of the igniter is at 90° to the axis of the tank.

The supported cap is a cap specifically desinged for use with an igniter.

Figure 375. Igniters M15 and M15, and Cutaway Showing Fuze M157