Specialist High Explosive Bombs

• "Upkeep"

  Designed by Dr. Barnes Wallis for use against the German Ruhr Valley Dams it was successfully deployed by 617 Squadron on the night of 16/17 May 1943. Upkeep was technically speaking more a mine than a bomb, contained 9,150 lb.. Of Torpex explosive and was denoted using a hydrostatic fuse preset to exploded at a preset depth. The weapon was delivered to the target underneath the aircraft, prior to dropping the weapon was rotated at a pre-calculated revolution which allowed the weapon to skip across the surface of the water; upon hitting the face of the dam Upkeep would then sink and explode at a preset depth.

• 12,000 lb.."Tallboy" MC

  Designed by Dr. Barnes Wallis, "Tallboy" and "Grandslam" marked a major advance in bomb design and ballistics. Where as traditional bombs exploded on impact with a surface. Dr. Wallis' so called "earthquake" bombs were designed to penetrate into the earth before exploding and relied entirely on destroying the target by shock wave rather than blast. Are often a near miss rather than a direct hit proved sufficient to totally destroy a target.

  Tallboy's were constructed using high quality steel and each hard a specially hardened nose cone to allow the bomb to penetrate the earth. Each was stabilized in decent by four tail fins which were inclined by five degrees which caused the bomb to rotate around its vertical axis as it fell, and allowed for the bomb to stabilize itself as it fell..

  Dropped, from specially modified Avro Lancaster's the only aircraft capable of lifting the bomb, at an optimum height of 18,000 feet, a Tallboy filled with 5,200 lb.. Of Torpex explosive took 37 seconds to reach the ground. At impact a terminal speed of 750 mph was reached and resulted in the bomb penetrating approximately 25 feet before exploding. The first of its type was dropped by Lancaster's of 617 Squadron on 8/9 June 1944 against the railway tunnel near Saumur France. 854 Tallboys were dropped before the end of hostilities against targets that included shipping, submarine and U-boat pens, viaducts, canals and V-Weapon sites. In the event that a target was unidentified or was obscured for any reason, crews were instructed to bring their weapon home and land!

• 22,000 lb.."Grandslam" MC

  Similarly designed by Dr. Barns Wallis, the 22,000 lb.."Grandslam," which contained 11,000 lb.. Of Torpex explosive was the largest of all bombs to enter the Command's inventory during World War Two. Deployed and acting in basically the same way as the 12,000 lb.."Tallboy", Grandslam was used against heavily reinforced targets such as U-boat Pens. Only 40 of the type were dropped during the war and like its smaller brother could only be delivered by heavily modified Avro Lancaster.

• "Johnnie Walker"

  Designed and made available to the Command in 1943, the 500 lb.. Oscillating mine was not used until 15 September 1944 when the German battleship Tirpitiz was attack at Kaa Fjord, Norway.