12000lb High Capacity Bomb Print
Written by David Boyd   
Thursday, 01 January 2009 20:43

12000lb High Capacity Bomb

In July 1942 the Static Detonation Committee was asked about the efficiency of a 12000lb blast bomb - a 8000lb high capacity bomb with an additional 4000lb section, the Committee's reply was that a 12000lb high capacity bomb would have a greater damage effect than just a 8000lb and a 4000lb and so the Air Staff decided to proceed with the development of the 12000lb High Capacity bomb.

The Committee requested three bomb cases so that various exploding systems could be compared. Initial loading tests were carried out and were successful. It was found that Lancasters modified to carry the 8000lb high capacity would require the tail of the bomb to be reduced by 5 inches but Lancasters of the final design could accommodate the full length.

By January 1943 detonation trials had been completed, by May transporting, loading and dropping trials had also been completed. It took four men over two hours to load the trolley and bolt the two sections together, loading of the aircraft took 35 minutes. Ballistic trails were also completed but results were not satisfactory and the tail was redesigned.

At the end of October 1943 the bomb was approved for service, although some doubts had been raised about both sections of the bomb detonating simultaneously and the Air Staff were not satisfied that the bomb was reliable enough for production. By this time 30 bombs had been released by Bomber Command and so a provisional order for 50 bombs was requested until trials had been fully completed.

In late 1944 it was suggested that the bombs could be used to attack Japanese harbours with a short delay fuze, trials were completed in October 1944 with a 0.05 second and 0.14 second delay but it was found that the bombs may break up giving an incomplete detonation so the bomb was found to be unsuitable.

12000lb High Capacity bomb specifications

Bomb 12,000-lb HC Mk I-II
Construction Cast Steel
Usual weight 11,936lb (5425.45kg)
Charge/weight ratio 80%
Total length 196in (497.84cm)
Body length 142.5in (361.95cm)
Body diameter 38in (96.52cm)
Wall thickness 0.5in (1.27cm)
Tail length 36.5in (92.71cm) or 64in (162.56cm) 
Tail width 38in (96.52cm)
Filling Amatex 9, Torpex 2

Number of 12000lb High Capacity bombs released per year








12000lb HC







Sources - AVIA 46 285, AVIA 46 163