USNBD, Bombs and Fuzes; Section III - Bomb Fuzes: M115, M116, M117

U.S.N.B.D. - UNITED STATES - BOMBS AND FUZES; PYROTECHNICS

SECTION III - BOMB FUZES

DATA:		U.S. ARMY TAIL FUZES
		M115, M116, M117
BOMBS USED IN
M115	AN-M30, 100 lb. G.P.
	AN-M57, 250 lb. G.P.
M116	AN-M43, 64, 500 lb. G.P.	(Service)
	AN-M58 500 lb. S.A.P.	MECHANICAL IMPACT
	M32, 600 lb. G.P.	PYROTECHNIC DELAY
M117	AN-M44, 65, 1000 lb. G.P.	(For Skip or Masthead bombing
	AN-M58, 1000 lb. S.A.P.	from land or carrier based)
	M33, 1100 lb. G.P.
	AN-M34, 66, 2000 lb. G.P.
	M103, 2000 lb. S.A.P.
FUNCTIONING	M16A1 primer detonators:
	4-5, 8-15 sec. delay.
	M16 primer detonators:
	4-5, 8-11 sec. delay.
	(Masthead, skip bombing)
ARMED CONDITION	When gear carrier stop protudes less than 1 in. below vane cup.
FUZES USED WITH	None
ARMING DATA	Same as AN-M100A2, AN-M101A2, AN-M102A2 respectively. See page 151.
VANE SPAN	5 in.
MAX. BODY DIAMETER	1.5 in.
OVERALL LENGTH	M115, 9.6 in.
	M116, 12.6 in.
	M117, 16.6 in.
MATERIAL	Cadmium plated steel.

GENERAL:

The only differences between these fuzes is in the length of the arming stem. Larger bombs require a longer arming stem so that the vanes can catch the air slip from the bomb. The only difference between these three fuzes and the M112A1 series is that this series employs the reduction gears as used in the AN-M100A2 series, consequently having a longer arming time. Actually, the M115 series is a composite of the M112 series body with the AN-M100A2 series vane and reduction gear assembly.

OPERATION:

As the vanes rotate, the pinion gear which is attached to the vane assembly revol-ves around the stationary gear. Since the movable gear has 30 teeth and the station-ary gear 29 teeth, the movable gear is rotated clockwise one tooth per revolution of the pinion gear. The arming stem is secured by a cotter pin to the movable gear sleeve and hence unthreads from the firing plunger as the movable gear is rotated. In un-threading, the arming stem lifts the movable gear, and since the stationary gear is held by a collar threading into the lower extension of the movable gear sleeve, the station-ary gear is lifted also. After 150-170 revolutions of the vanes, the arming stem will un-threaded from the firing plunger and the fuze will be armed. Further air travel will un-thread the arming stem from the fuze body and the entire arming assembly will fly off. On impact, the plunger compresses its creep spring and the spring-loaded firing pin for-ces the locking balls out into the enlarged part of the fuze cavity, freeing the firing pin. The cocked firing pin spring forces the firing pin against the primer, initiating the delay in the primer detonator.

REMARKS:

These fuzes will take either the M16 primer detonators with delay of 4-5 or 8-11 seconds, ot the M16A1 primer detonators with delay of 4-5 or 8-15 seconds. Actually the M16's are no longer being manufactured, though they are still to be found in the field. These fuzes can be used for skip or masthed bombing from land or carrier bases. These fuzes may have a groove around the top of the fuze (as in drawing) or the top may be staright as in the AN-M100 series (see page 151). The groove is a distinguish-ing mark used by manufactures making both fuzes and is not to be considered a posi-tive sign for fuze identification.

NEVER TURN THE VANES COUNTER-CLOCKWISE TO RENDER FUZE SAFE, AS THE ARMING STEM MAY DEPRESS PLUNGER INSTEAD OF ENGAGING IT.