Two major problems now remained before any attack could be mounted. The first was how to transport Upkeep to the target, whilst the second, was how to train a squadron sufficiently to give the best possible chance of success.


The first was easily solved. The RAF's champion in shear bomb lifting capacity, the Avro Lancaster - which had only twelve months earlier entered active service - was the obvious, indeed the only choice.


However, even though the Lancaster would have little trouble with the weight of Upkeep; modifications were required to the aircraft to allow the weapon to be carried. These were devised by Mr. Roy Chadwick, designer of the Lancaster, and resulted in the removal of both the bomb bay doors and mid upper turret. In addition, special fairings were installed at each end of the bomb bay to maintain smooth air flow over the aircraft. The changes to the standard Lancaster resulted in a new variant of the aircraft: the Lancaster Mk. BI Special or type 464 Provisioning Lancaster.


Side View Of Mk. BI Special Lancaster

View #1 Of Lancaster With Upkeep Bomb Loaded

View #2 Of Lancaster With Upkeep Bomb Loaded


The second problem, was not as easily resolved. Upon being requested that he release an entire Lancaster Squadron for special training. Air Chief Marshall Harris, Commander of Bomber Command, claiming that his Lancaster Squadron's were far to valuable to be wasted on such unimportant targets as Dams, flatly refused.

Instead on March 21, 1943, the Air Ministry authorized that a new unit, initially known as "X" Squadron, but soon after renumbered No. 617 Squadron was to be formed at Scampton, Lincolnshire and be attached to No. 5 Group. The new squadron it was decided would be lead by Wing Commander Guy Gibson, DSO and Bar, DFC and Bar.


With only the knowledge that their target would require low level flying over water at night. Gibson and his hand picked and much decorated crews, began low flying four engine aircraft like never before. Training continued even during the hours of daylight; with moonlight conditions being simulated by means of coloured cockpit windows and special goggles.


The crews soon had little difficulty flying at the required 220 mph; but the critical height of sixty feet became a growing concern amongst them. The normal pressure altimeter lacked the accuracy; whilst the radio altimeter, although better, also failed to give sufficiently accurate readings to be relied upon. The problem was eventually solved by fitting two Adlis lamps to the underside of the aircraft; one the nose and the other in the rear section of the bomb bay. It was then a fairly simple process to align each beam in such a way that they would converge on the water at exactly sixty feet below the aircraft.

UPKEEP Mine Installed Into Modified Lancaster Bomb Bay

Dam's Raid

16/17 May 1943


"The Final Problems"

Lancaster ED932 "AJ-G" With UPKEEP Loaded

(click image to see larger view)

Spotlight Postion Diagram