Tail Fuzes No. 895 Mk I and No. 875 Mk I (Service)

Description: Around the sided of the No. 895 fuze body are water entry ports, pro-tected by small spring-loaded valves, which serve as anti-counter-mining devices. The water ports lead into a rubber bellows, which rests on a shoulder of the fuze body and also under the spring housing. Inside, and resting on the upper lip of the spring housing, is a striker sleeve with two holes drilled in it to accommodate two retaining balls. The balls rest in a groove of the spring-loaded striker and hold it back.

Around the striker sleeve is a stationary sleeve having a cut-away top into which the retaining balls can move. On the upper end of the striker is a lock sleeve, which is held down by a spring and which holds retaining balls in a fixed housing. This device functions to prevent the action of the fuze when the bomb lands on its tail. Through the top of the fuze is drilled a hole into which is fitted a safety plunger, through which the safety and transit wire are fitted. Below this is a rubber disc, which seals the fuze body. In the unarmed position the striker fits down into the detonator shutter and prevents it from moving into line. The detonator shutter is of the rotary type and is attached by a rod to the moving sleeve. Below the detonator is the magazine, which is screwed into the lower part of the fuze.

Operation: When the bomb is put in the plane, the transit wire is removed and a safety wire inserted. On release, this wire is pulled, and the fuze is armed. Upon entering the water, water enters the fuze through the entry ports and fills the bellows. As the bellows fill, the spring housing is moved up, carrying the striker sleeve with it. This moves the striker up out of the detonator shutter and compress the striker spring. It also moves the shutter into line, as it is attached to it by means of a small rod. When the bellows have expanded sufficiently to move the striker sleeve to the cut-away portion of the stationary sleeve, the striker cams the retaining balls out and the striker hits the deto-nator and fires the fuze.

Remarks: Two issues of the No. 895 Mk I type of fuze are at present in service use. The Fuze No. 895A Mk I, with a setting of 18 ft., is used in the A.S. 100-lb. Bomb Mk VI. The Fuze No. 895/30 Mk I, with a setting of 30 ft., is used in the A.S. 600-lb. Bomb Mk I. The designation of the later issues of the No. 895 Mk I type was altered to include the normal depth setting. Changes in depth setting are accomplished by the insertion of an additional between the top cap of the fuze and the spring housing.

The Fuze No. 875 is similar to the No. 895, except that more positive detonator-shut-ter action has been provieded in the latter. The depth setting of the No. 875 are set by the manufacturer and are designed for different uses. The Fuze No. 875A, whose red color indicates an 18-ft. depth setting, is used with A.S. 100-lb. Bomb Mk IV. The Fuze No. 875B, whose blue color indicates a 22-ft. depth, is used in the A.S. 25-lb. Bomb Type A Mk I. The Fuze No. 875C, whose green color indicates a 30-ft. depth setting, is used in the A.S. 600-lb. Bomb Mk I.

The fuzes will not fire in a normal hard-surface impact, as such an impact causes no movement of the operating mechanism. If the bomb should strike tail-first, firing is pre-vented by the lightly spring-loaded lock sleeve.

Countermining, i.e. firing due to a sudden increase in hydrostatic pressure resulting from the nearby explosion of another bomb, is prevented by small spring-loaded valves fitted over the water entry ports.

Figure 176 - Tail Fuze No. 895 Mk I