USNBD, Bombs and Fuzes; Section III - Bomb Fuzes: T50E4, T50E1, T89, T90

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

SECTION III - BOMB FUZES

DATA:		U.S. ARMY - NAVY FUZE
		T50E1, T89 T50E4, T90
T50E1, T89	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 Nose Fuze
T50E4, T90	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,
	10-40 ft. above ground.
ARMED CONDITION	If vanes are free to rotate,
	assumed to be armed
	(Unless safety pin can be inserted as in T89 and T90)
ARMING TIME	3600 ft. min. SAT (some lots of T50E4 3100 ft.)
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. They are designed to detonate the bomb at a point above the earth which will give effective fragmantation. These ring type fuzes are specially sensitive to "passing objects" and therefore are useful in defoliating by blast and in getting roof top bursts in city areas.

At the present stage of development approximately 80% of the fuzes will operate properly upon approach to the target; up to 15% may function spontaneously after arming but before approaching the target; and 5% will be inoperative.

OPERATION:

When the bomb is dropped the arming wire is pulled, releasing the spring-loaded vane locking pin which jumps out, freeing the vane for rotation. The vanes rotate and drive the electric generator and the worm and spur gear reduction train. After the re-quired 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 a hole in the rotor housing, locking the detonator in the armed position and at the same time withdrawing from the keyway in the arming stem. The vanes continue to rotate at high speed, driving the generator which in the meantime has 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 nose fuze but are not tactically interchangeable with impact fuzes or with each other. If the T50E1 or T89 fuze are used in bomb sizes for which the T50E4 or T90 fuzes are specified, very low air bursts will result. The same is true for the reverse transporsition.

Some lots of the T50E4 cannot accommodate the M1 (T2E1) Air Travel Arming Delay because of a much heavier steel ring around the vanes. No delayed arming can be ac-complished on these lots of fuzes.

The T89 and T90 have a safety pin running alongside the booster to secure the de-tonator rotor in the unarmed position. Before installation in a bomb, the safety pin should be removed and reinserted. If it cannot be reinserted, the fuze is armed partially armed and should be destroyed.

The T50E1 and T50E4 do not have the booster safety pin so if a fuze is found with the vane locking pin gone and the vanes free to rotate, it must be considered armed and should not be used.

Vanes may be either 10 bladed steel vanes or three bladed plastic vanes, interchan-geably.