ALLIED BOMBS AND FUZES

DESIGNATION

PRINCIPAL MARKING

Fuze No. 860

CLASSIFICATION

Nose, Fuze, Aerial Burst

Mk I & II

TYPE OF MISSILE

Target Identification Flares

MARKINGS:

BOMBS USED IN:

12 inch T.I. Flares

LEGEND

1

9

2

10

3

11

4

12

5

13

6

14

7

15

8

16

COLOR

Aluminum.

OVERALL LENGTH

6.0 inches (about 5.2 inches are visible).

OVERALL WIDTH

2.5 inches.

MATERIAL OF CONSTRUCTION

Aluminum.

DESCRIPTION

This fuze is designated to function at a predetermind altitude, (usually 3000 feet), and is operated by atmospheric pressure. In general, the fuze consists of an arming vane cap (1), arming vane assembly (2), an altitude setting screw (3) and arming screw (4). Inside a brass cylinder (5) is a vacuum capsule (6) containing an inside spring (7) and an arming pin (8). Atmos-pheric pressure tends to keep the vacuum capsule compressed against the action of the inside spring (7). The arming pin (8) normally is at rest in the striker housing (9) which contains three symmetrically located balls (10) and three more symmetri-cally located balls (12). These balls are held in place by a sleeve (11). The spring-loaded striker (13) is continually bearing against the lower set of balls (12) under the action of striker spring (13). A spring (14) is pressing the brass cylinder (5) up- wards against the arming screw (4). A screw type safety pin (15) blocks the path of the striker and must be unscrewed by hand in the Mk I fuze. In the Mk II fuze, the safety pin is pulled out when the flare is dropped.

Operation

On the ground, the arming pin (8) prevents the balls (10) from moving inwards and allowing the sleeve (11) to move upwards. (See fig. 3.) As the aircraft rises, air pressure decreases and the vacuum capsule (6) expands, causing the point of the arm-ing pin (8) to move into the hole in the striker (16). This is shown in Fig. 3. When the flare is dropped, the arming vane cap (1) is pulled off and the arming vanes (2) rotate and fall free, carrying with them, the ar- ming screw (4) which is attached to the vanes. This allows the brass cylinder (5) to move up under action of the arming spring (14) until it is stopped by the alti-tude setting screw (3). The fuze then is in the condition as shown in Fig. 4. As the flare drops through the air, the air pres-sure increases, causing the vacuum capsule (6) to be compres- sed and, thereby, withdrawn the arming pin (8) from the striker housing (9). This allows the balls (10) to move in, and the slee-ve (11) to move upwards under pressure from the balls (12) which are being forced outwards by the striker spring (13) which bears down on the striker (16). As the balls (12) move out, the striker (16) is free to move down, piercing the primer and setting of the explosive train.

POSITION & METHOD OF FIXING IN BOMB

Screwed into the nose of the flare.

COMPONENTS OF EXPLOSIVE TRAIN

Primer and bursting charge.

DELAY TIMES

None. Functions at 3000 feet.

REMARKS

The 860 Mk I & II are identical in all respects except shape. See Tail Fuze No. 867 for additional drawings.