British Bomb, 250 lb TI, No. 11 Mk 1, No. 12 Mk 1, No. 13 Mk 1, No. 13 Mk 2
The Bombs No. 13 Mk I and Mk II have bodies, base plates, and burster containers identical to those of the corresponding marks of the T.I. Bombs No. 1.
The ejector plate is perforated and has a wooden block attached to it by screws. This block houses the photoflash igniter. The photoflash unit has a thin metal body, and a central burster tube filled with black powder.
The candles are arranged in two layers around the central flash unit. A primed cambric washer is located between the primed ends of the two layers.
Tail Construction: Same as for the No. 1 T.I. bomb tails.
The bomb is suspended by a single lug, which is welded to the body.
Both the 250 lb. T.I. Bombs No. 11 and No. 12 were manufactured in limited numbers, and have been superseded by the Bomb No. 13. Both bombs were similar to the No. 13, but the No. 12 was filled with 40 Type B1 candles packed around the photoflash unit, while the No. 11 contained no candles, the space being packed with sand to act as ballast.