The 'Usual Bomb Load' for British bombers, including of course the Lancaster, was worked out from tables published by the Command taking all operational factors into account. Most obviously the amount of fuel (and reserve) carried might affect the weight of ordnance carried.
It is quite true that 12,000lbs was a typical load for the Lancaster.
When actual operational bomb loads were examined in late 1943 all sorts of variations were discovered between Groups and these had to be explained. I'll give a few examples. The usable load for the Lancaster IIs of Nos. 3 and 6 Groups was 1500lbs less than for the Lancaster Is of Nos. 1 and 5 Groups because the empty weight of the Lancaster II was higher. The Mk II also had a higher fuel consumption, requiring more fuel against bomb load in the tables, and 6 Groups bases were further from Germany.
All Groups tried to maximise their efforts. The investigation revealed that 1 and 5 Groups' aircraft were 'occasionally' overloaded and that 6 Group's were 'often overloaded', notably on long range raids when the high fuel requirements might otherwise reduce the bomb lift of the Group.
An ongoing shortage of SBCs meant that many aircraft did take off with less than the maximum bomb loads. This led to the recommendation I have mentioned elsewhere that
"on the first night after a blank night [without operations] Lancasters should carry as many SBCs as are needed to make up the permitted weight and they should not be withheld to cover the possibility of another operation the following night, since the number of occasions on which operations occur on consecutive nights is not sufficiently high to justify any reduction in efficiency on the first night."
These and many other factors mean that the average bomb load carried by the Lancaster throughout the war was slightly less than a usual load of 12,000lbs. The average load, weighted by various factors, was 9,186lbs.
Cheers
Steve
It is quite true that 12,000lbs was a typical load for the Lancaster.
When actual operational bomb loads were examined in late 1943 all sorts of variations were discovered between Groups and these had to be explained. I'll give a few examples. The usable load for the Lancaster IIs of Nos. 3 and 6 Groups was 1500lbs less than for the Lancaster Is of Nos. 1 and 5 Groups because the empty weight of the Lancaster II was higher. The Mk II also had a higher fuel consumption, requiring more fuel against bomb load in the tables, and 6 Groups bases were further from Germany.
All Groups tried to maximise their efforts. The investigation revealed that 1 and 5 Groups' aircraft were 'occasionally' overloaded and that 6 Group's were 'often overloaded', notably on long range raids when the high fuel requirements might otherwise reduce the bomb lift of the Group.
An ongoing shortage of SBCs meant that many aircraft did take off with less than the maximum bomb loads. This led to the recommendation I have mentioned elsewhere that
"on the first night after a blank night [without operations] Lancasters should carry as many SBCs as are needed to make up the permitted weight and they should not be withheld to cover the possibility of another operation the following night, since the number of occasions on which operations occur on consecutive nights is not sufficiently high to justify any reduction in efficiency on the first night."
These and many other factors mean that the average bomb load carried by the Lancaster throughout the war was slightly less than a usual load of 12,000lbs. The average load, weighted by various factors, was 9,186lbs.
Cheers
Steve