USNBD, Bombs and Fuzes; Section III

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

SECTION III - BOMB FUZES

DATA:		U.S. ARMY - NAVY FUZE
		T91, T92
T91	AN-M30 100 lb. G.P.
	AN-M57 250 lb. G.P.
	AN-M66 2000 lb. G.P.
	AN-M88 220 lb. Frag.
	M81 260 lb. Frag.	Aerial Burst, VT Type Nose Fuze
T92	AN-M64 500 lb. G.P.
	AN-M65 1000 lb. G.P.
	AN-M78 500 lb. Chem.
	AN-M79 1000 lb. Chem.
FUNCTIONING	Automatic serial burst,
	30-60 ft. above ground
	when released below
	10,000 ft.
ARMED CONDITION	If vanes are free to rotate,
	assumed to be armed unless safety pin can be inserted.
ARMING TIME
T91	2000 ft. Min. SAT.
T92	2600 ft. Min. SAT.
FUZES USED WITH	AN-M100A2 series normally; M160 series
OVERALL LENGTH	10.4 in.
MAX. BODY DIAMETER	3.4 in.
MATERIAL	Steel body, plastic top, metal ring, steel or plastic vanes.

GENERAL:

These are VT fuzes of the ring type, similar to the T50E1 series. They are designed to detonate the bomb at a point above the earth which will effective fragmentation. The 91 and T92 differ from the T50E1 group in that ther have greater sensitivity and are specially designed to be used for low level, medium level, and dive bombing. These ring type fuzes are especially sensitive to "passing" objects and therefore are useful in defoliating by blast and in getting roof top bursts in city areas.

At presen, about 80% will operate properly upon approach to the target; 15% may function spontaneously after arming, and 5% will be inoperative. These fuzes have Min. SAT reduced to 2000 or 2600 ft. for use in low, medium and dive bombing. SAT can be extended by use of the M1 (T2E1) Air Travel Arming Delay.

OPERATION:

When the bomb is dropped, the arming wire is pulled releasing the spring-loaded vane locking pin which jumps out, freeing the vanes for rotation and drive the electric generator and the worm and spur gear reduction train. After the required number of vane revolutions, the detonator lines up with the booster lead-in and at the same time becomes electrically connected to the firing circuit. The rotor detent in the detonator rotor snaps into the socket in the rotor housing, locking the detonator in the armed po-sition and at the same time withdrawing from the keyway in the arming stem. The vanes continue ti rotate, driving the generator which has in the meantime activated the VT element and charged the firing condenser. The fuze is now armed.

Upon approach to the target under the proper conditions, the VT element activates the firing circuit which discharges the firing condenser, through the electric detonator, initiating the explosive train.

REMARKS:

These fuzes are mechanically interchangeable with the AN-M103 series nose fuzes but are not tactically interchangeable with impact fuzes or with each other. If the T91 fuze is used in bomb sizes for which the T92 is specified, very low air bursts will result. The same is true for receive transposition.

These fuzes are not the be used for horizontal bomb runs because the Min. SAT is such that the fuzes may be completely armed when only 250 ft. below the carrying air-craft and early bursts in this position would cause damage to the plane.

The following fuzes have been issued: T91, T91E1, T92, T92E1, T92E2, T92E3. They differs in that the T91, T92, and T92E2 have a booster safety pin, making them identi-cal in appearance to the T89 and T90. The 92E2 and T92E3 are modified electrically to give slightly better operating efficiency. Vanes may be either 10 bladed steel vanes or three bladed plastic vanes.