OP 1665 - British Ordnance; Part1 - Aircraft Bombs and Pyrotechnics; Chapter 18 - Target Identification Bombs: T.I. 250-lb., Spot Fire, No. 8 Mk I, IC, II, and III (Service)

BRITISH EXPLOSIVE ORDNANCE

Part 1 - Chapter 18

Target Identification Bombs

T.I. 250-lb., Spot Fire, No. 8 Mk I, IC, II, and III (Service)

Data

Fuzing	Nose Fuze No. 860 Mk II, No. 848, or No. 896 Mk I; Tail Fuze No. 867 Mk I
Color markings	The bomb is painted black over-all with a ½-in. red filling band located 8 in. from the nose. SPOT FIRE in red, green, or yellow letters, according to the filling, is stencilled on the nose; and SPOT FIRE, preceded by the appropriate color, is stencilled on the body in white
Tail No.	No. 1 Mk II, No. 35 Mk I, or No. 75 Mk II
Over-all length	67.75 in.
Body diameter	12 in.
Tail length	27.2 in.
Tail width	11.7 in.
Total weight	Mk I and IC, 205 lb.; Mk II and III, 215 lb.
Burning time	Red, 20 min. (approx.);
	green and yellow, 1 hr. (approx.)

Body Construction:

Mk I Body – The bomb body, tail plate, and burster are the same as those used in the T.I. Bomb No. 1 Mk I. However, the burster container has a crossed slit on its inner end, filled with solder, to pass the flash from the burster charge to an igniter located in the impregnated bale.

The ejector plate is held by screws against a steel ring welded to the inside edge of the nose. The ejector plate has a central flashhole covered by a thin copper disc, which has two crossed slits filled with solder. Three loacting pins are welded to the ejector plate, and locate the bale igniter centrally over the flash hole.

The filling bale consists of rolled cotton wool enclosed in cheesecloth, and held toget-her by wire and steel bands. Six wooden battens extend from the ejector plate to the tail plate and serve to force off the tail plate when the bomb functions.

The igniter at the nose end of the bale consist of an igniter base into which a tube filled with incendiary composition is screwed. A central hole in the igniter base is located above the flash hole in the ejector plate, and has a similar closing disc of copper with a solder-filled cross slit.

A diaphragm, soldered to the bomb body under the tail plate, holds the bale in place.

Mark II Body – The Bomb Mk II differs from the Mark I only in general body construc-tion, as the T.I. Bomb No. 1 Mk II differs from the No. 1 Mk I.

Mk III Body – The Bomb Mk III is similar in body and tail plate construction to the T.I. Bomb No. 1 Mk III. The internal arrangement of the filling is similar to that in the Bomb No. 8 Mk I. However, as this bomb is arranged for tail fuzing, a length of instantaneous fuse leads from the tail fuze pocket, through a steel tube located along the inside of the bomb body, and into the forward end of the burster container. A burster capsule is atta-ched to each end of the fuze.

Mk IC Body – The Mk IC bomb differs from the Mk III as the T.I. Bomb No. 1 Mk IC dif-fers from the No. 1 Mk III.

Functioning

Mk I and II – The functioning of the fuze ignites the burster charge, which simultane-ously ruptures the three soldered cross slits, to initiate the incendiary charge in the igni-ter, and forces the ejector plate toward the rear, causing the wooden battens to push off the tail plate and eject the bale. The incendiary charge in the igniter heats its tube until the impregnated cotton wool in the bale catches fire.

Mk III and IC – The operation, when nose-fuzed, is the same as for the Mks I and II, and, when tail-fuzed, differs only in that the flash from the tail-fuze magazine is trans-mitted to the burster container by the instantaneous fuze, where the burster charge is ignited by the burster capsule.

Tail Construction: Same as for the T.I. Bomb Tails No. 1.

Suspension: The bomb is suspended by a single lug, which is welded to the body.

Filling: The filling consists of a bale of color-impragnated cotton wool.

Figure 77 – T.I. 250-lb., Spot Fire, Bomb No. 8 Mk I