T.I. 250-lb.

{No. 1 Mks I, IC, II, and III; No. 2 Mks I, II, and III; No. 3 Mks I, IC, II, and III; No. 4 Mks I, IC, II, and III; No. 5 Mk I; No. 6 Mk I; No. 9 Mk I; No. 10 Mk I; No. 15 Mk I; No. 16 Mks I, IC, II, and III; No. 17 Mks I and III; No. 23 Mks IC, and III; No. 24 Mks IC and III; No. 25 Mks IC and III; No. 26 Mk III; No. 27 Mk III; and No. 28 Mk III (Serive)}

Body Construction: The corresponding marks of the numbered bombs listed in this section are identical in construction and operation. They differ only in the types of cand-les they contain. Bombs Mk I and Mk II are nose-fuzed only, while Mks IC and III have provisions for both nose and tail fuzing.

Mk I Body – The Mk I bomb body consists of a heavy gauge steel tube, to one end of which is welded a steel nose. The after end of the body is closed by a tail plate held in place by six brass rivets. The tail plate has two bayonet slots and a hole to be engaged by a transit base or the tail unit.

In the nose of the bomb is located the burster container, which houses a 3-ounce black-powder ejection charge in a cambric byg or celluloid conatiner.

Immediately abaft the burster container is the ejection plate, slightly smaller than the internal diameter of the bomb body, to which the central flash tube is welded. The divisi-on disc, which separates the two layers of candles, is located at the opposite end of the flash tube. The inside of the tube and both sides of the division disc are covered with primed cambric. The igniter ends of both layers of candles rest against one end of the primed discs.

The candles are held in position in the bomb body by felt or corrugated paper strip lin-ing the inside of the body, a number of notched packing discs located beneath the tail plate, and a notched washer located against the ejection plate. Three equispaced wood-en battens, which pass through notches in the division plate, extend between the ejec-tor plate and tail plate in order to force off the tail plate when the bomb functions.

Mk II Body – The Mk II bomb body is identical to the Mk I except for the use of a dif-ferent type suspension lug, and a light-gauge steel body which necessitates the use of a cast-iron weight welded inside the nose.

Mk III Body – The body of the Bomb Mk III consists of a light-gauge steel tube which has a steel nose welded to one end. A cast-iron weight is welded inside the nose secti-on. The after end of the body is closed by a tail plate held in position by three locating studs, which engage three slots in the after end of the body, and is secured in position by three brass rivets.

The tail plate has two bayonet slots and a hole to be engaged by pins on a transit base, or the securing screws of the Tail Unit No. 75 Mk I or Mk II. A V-slot in the skirt of the tail plate, aligned with one end of the locating studs and diametrically opposite the hole, receives the locating pin on the Tail No. 75 to assure that the tail slot for the tail fuze lanyward is aligned with the suspension lug of the bomb. The suspension lug is of the same type used on the Mk II body.

The burster container is similar to that of the Bomb Mk I, but is welded to the ejector plate and internally threaded to receive the forward end of the central flash tube. The after end of this tube therads into the tail-fuze adapter, which is locked in place, and the whole assembly is secured to the tail plate by a locking ring.

The two layers of candles are separated by a division disc, and a priming system, si-milar to the one end used in the Bomb Mk I, is used to ignitie them. The candle are posi-tioned as in the Bomb Mk I, but the wooden battens are not used, as the central flash tube serves to force off the tail plate when the bomb functions.

Mk IC Body – This bomb is very similar to the Mk III, but as it employs a Mk I body converted for tail fuzing, its body is of thick-gauge steel, and consequently the nose weight is dispensed with. The central tube is welded to the inner end of the burster con-tainer and is also welded to the ejector plate.

Functioning

Mks I and II – When the bomb is dropped, the fuze is set in operation and the bomb falls freely until the fuze explodes, igniting the burster charge of the bomb. The flash from the burster charge passes through the flash hole in the burster container, and is conveyed to the primed cambric discs on the division disc by the primed cambric in the central flash tube. These division discs ignite the candles.

Simultaneously, the gases from the burster charge expand and force the ejector plate toward the tail of the bomb. The wooden battens force the tail plate and tail off the bomb, and the ignited candles are ejected and function in the normal manner.

Mks III and IC – If the bomb is tail-fuzed only, the functioning of the fuze produces a flash which ignites the primed cambric in the central flash tube. This primed cambric con-veys the flash to the burster charge, which it ignites, and also passes through holes in the central tube to ignite the primed cambric discs on either side of the division disc. These in turn ignite the candle.

Simultaneously the explosion of the burster charge shatters the burster container at a weakened point, and the gases formed force the ejector plate toward the tail of the bomb. The central tube forces off the tail plate and tail unit, and the candles are ejected to function in the normal manner.

If the bomb is nose-fuzed only, it will function in a similar manner except, that the burster charge is ignited directly by the flash from the fuze magazine and the primed cambric tube is ingited by the burster charge.

Tail Construction

The Tail Units No. 1 Mk II, and No. 35 Mk I consist of a tail cone to which a cylindrical strut is attached by four fins. Three screws secure the tail to the tail plate of the bomb.

The Tail Assembly No. 75 Mk I consists of a tail cone to which cylindrical strut is atta-ched by four fins. Three screws attach the cone to the tail plate of the bomb, and a lo-cating pin engages a V-slot in the tail plate to position the tail. An arming assembly, consisting of an arming spindle, arming vanes, and an arming-spindle fork, is also present. The Tail Mk II has cut-away fins to allow the arming vanes to be recessed for protec-tion. Both the Tails Mk I and Mk II have inspection windows in the tail cone.

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

Filling

No. 1 Mk I – 60 Type A, or 62 Type K candles

No. 1 Mks IC and III – 60 Type K candles

No. 1 Mk II – 60 Type A candles

No. 2 Mk I – 56 Type A and 4 Type D candles, or 56 Type K and 4 Type L candles

No. 2 Mk II and III – 56 Type A and 4 Type D candles

No. 3 Mks I, IC, II, and III – 20 Type A and 40 Type B1 candles

No. 4 Mks I, IC, II, and III – 16 Type A, 40 Type B1, and 4 Type D candles

No. 5 Mk I – 30 Type A and 30 Type B1 candles

No. 6 Mk I – 26 Type A, 30 Type B1, and 4 Type D candles

No. 9 Mk I – 60 Type C candles

No. 10 Mk I – 60 Type B1 candles

No. 15 Mk I – 30 Type A and 30 Type D candles

No. 16 Mks I, IC, II, and III – 9 Type A, 46 Type B2, and 4 Type F candles

No. 17 Mks I and III – 60 Type M candles

No. 23 Mks IC and III – 9 Type A and 39 Type B2 candles

No. 24 Mks IC and III – 11 Type A, 45 Type C, 1 Type D, and 3 Type F candles

No. 25 Mks IC and III – 23 Type B2, 19 Type B3, 1 Type D, 1 Type E and 2 Type F candles

No. 26 Mk III – 11 Type A, 27 Type B2, 18 Type C, 1 Type D, 1 Type F, and 2 Type P candles

No. 27 Mk III – 39 Type Q and 1 Type R candle

No. 28 Mk III – 16 Type A, 40 Type C, and 4 Type D candles

Figure 74 – T.I. 250-lb Bomb No. 1 Mk I

Figure 75 – T.I. 250-lb. Bomb No. 1 Mk III