ROCKET USED IN

FUNCTIONING

IDENTIFICATION

ARMED CONDITION

None

7.2" (without booster).

GENERAL:

These two fuzes are identical, except that the Mk 136 has a shear wire through the setback collar. Both fuzes were to be replaced by the Mk 140; however, this fuze is being recalled from the field. The Mk 131 is being replaced by the Mk 156 fuze and the Mk 136 is being replaced by the Mk 158-0.

OPERATION:

The safety pin is removed when the rocket is loaded on the launcher, leaving the vanes secured by the setback collar, which has a leaf spring holding it up by pressure against the locking pins. On firing, the setback collar moves back (breaking the shear wire in the Mk 136), freeing the locking pins from the groove in the collar. On impact with water, the force on the vanes causes a torque sufficient to shear the vertical shear wire holding the vane cup to the neck of the fuze. The vanes are free to rotate, unthreading the spindle through the neck of the fuze body. As the spindle draws back from the inertia weight, the spring under the firing sleeve forces the sleeve and inertia weight up. Since the firing pin is locked to the firing sleeve by three locking balls, the firing pins and its spring (cocked against a collar on the firing pin) rise with the sleeve and inertia weight. As the sleeve clears the four spring-loaded detents in the fuze body just above the firing pin guide, the detents spring out under the sleeve. After approxi-mately four vane rotations, the firing pin will have been raised by the sleeve sufficiently to clear the shutter cavity, allowing the spring-loaded detonator shutter to move over into the armed position with the detonator lined up with the firing pin and booster lead-in. The spindle continues to rise until the  washer to which it is keyed engages a groove in the underside of the fuze neck. The inertia weight, sleeve, and firing pin cease rising when the sleeve engages the reatining ring after rising approximately 1/4". On contact with a submarine or other underwater obstruction, the three locking balls are forced inward, as inertia causes the weight to move forward on normal impact or laterally on oblique impact. As the weight moves clear, the locking balls are forced out-ward by the bevelled edge of the spring-loaded striker, which is then free to be driven into the detonator.

REMARKS:

The detents in the fuze body which spring out under the sleeve, are provided in or-der to allow the spindle to be screwed back down from the armed position without dan-ger of forcing the striker into the detonator. In view of the fact that the inertia piece may be insecurely lodged over the striker spindle, this procedure is not recommended on any rocket that has once been fired.

DO NOT REMOVE THESE FUZES FROM A PROJECTILE WITH ANY TOOL OTHER THAN THE SPANNER WHICH IS ISSUED WITH THE FUZE. SEPARATION OF THE TWO PARTS OF THE FUZE BODY ARMS THE FUZE.