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The Lancaster B.1 Special: The Gran Slam Bomb

Discussion in 'Allied Bomber Planes' started by Jim, Aug 19, 2007.

  1. Jim

    Jim New Member

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    Bielefeld, western Germany, 14th March 1945. The Lancaster B.1 (Special) heading towards its target had been unable to reach more than 14,000ft (4,250m). Beneath it bulked the outline of the largest and most destructive bomb ever used in war; the Grand Slam, weighing more than 22,000lb (10 tonnes). In the nose lay the bomb-aimer, holding the graticule of his sight on the target. The seconds ticked away interminably until at last the computer automatically released the huge bomb.
    The pilot, Squadron Leader Calder, felt the bomber lift as the weight came off, and the wings, which previously had taken on a distinct upward curve, resumed their normal shape.
    Lying prone in the nose, the bomb aimer watched as the huge weapon plunged downwards, dwindling in size as it did so, spinning as it went for greater accuracy. At first it appeared that it was going to fall short, but this was illusory. In the final seconds of its fall it seemed to sweep forward and hit about 90ft (30m) from the target.

    The Bielefeld Railway Bridge had survived previous attacks, but succumed to the first Grand Slam dropped.

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    The impact was not very spectacular; from that altitude there was just a tiny splash of mud as the Grand Slam, travelling faster than sound, penetrated something like 75ft (25m) into the earth. After an 11-second delay, however, a gigantic underground explosion erupted, flinging earth and mud some 500ft (150m) into the air, and forming an enormous cavity into which a large section of the target, a rail viaduct that was vital to German communications during the closing months of the war, collapsed.
    The Lancaster had not been flying alone; that would have been far too risky, even at this late stage in the war. It was accompanied by 14 others, each armed with a Tallboy, a smaller (12,000lb/ 5.4 tonnes) version of the Grand Slam. Even as the huge bomb went off, Tallboys were falling around the viaduct, their combined effect destroying several more arches of the now sadly battered target, and ensuring that it would never again be used to carry German reinforcements to where they were most needed.

    The Gran Slam, the largest bomb of all. Only 41 of these were dropped during WWII, all by Lancaster Specials of #617 Squadron.

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    The Lancaster had, in the space of three short years, become the backbone of RAF Bomber Command. A total of 7,366 were built, of which s almost half were lost on operations. They carried, out something like 156,000 operational sorties, an average of about 21 sorties each, which says much about the hazards they faced, and dropped more than 600,000 tons of bombs; an average of more than 81 tons each. They carried greater bomb loads farther than any other wartime bomber.


    1,000lb bombs n storage. Lancasters dropped no fewer than 217,640 of these between 1942 & 1945.

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    Lancaster’s formed the main equipment of the Pathfinder Force; they pioneered low-level marking and precision attacks, and, far more than any other heavy bomber type before or since, they proved amenable to modification to carry special weapons. With all this, the Lancaster retained its docile handling, even when badly damaged, which undoubtedly saved the lives of many crewmen. Long after the war, the Lancaster retains a mystique unequalled by any other bomber, and the affection of those that flew to war in it remains even now, over 50 years later.
     
  2. Spitfire XIV-E

    Spitfire XIV-E New Member

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    Lancaster B Mk III Special : Operation Chastise

    Before the later Tall Boy & Grandslam Bombs were developed, Barnes Wallace had devised another weapon in 1941 which he wanted to use against German Dams in the Ruhr Valley. The Air Ministry were at first sceptical but after many experiments and some persuasion, Wallace got his way and several prototypes of this weapon, which would become known as "Upkeep" or the Bouncing Bomb were made for testing. The first examples proved a bit of a disappointment and tended to break up when they hit the surface of the water. Wallace found that the weapon was being dropped too high at 150 feet. To resolve this issue he asked for it to be dropped at just 60 feet above the water. A new problem then arose as to how to keep the Aircraft at exactly 60 feet whilst on the Bomb Run. This was solved by fitting 2 Spotlights at each end of the Aircraft pointing down at Angles. When the 2 Lights came together in a figure 8 shape on the water, the Aircraft was at 60 feet. This was the answer to the problem and the Bomb now skipped across the water as he had envisaged although the aircraft had to pull up sharply because of the spray which was caused as it hit the surface. The bomb also needed to be back spun at 500 rpm so that it would hug the dam wall as it dropped down before exploding at a depth of 30 feet. This was achieved by fitting a special rotating motor on the Aircraft to spin the bomb before it was dropped. The final version of Upkeep would dispense with the outer casing that Wallace had put on in an effort to help it skip on the water. It weighed 9250 lbs which included 6600 lbs of "Torpex" High Explosive. Now all he needed was an Aircraft that could carry the new weapon. The Avro Lancaster was the only Aircraft capable of carrying Upkeep to Germany. Air Chief Marshall Sir Arthur Harris was asked to form a special squadron for the operation. He chose 5 Group Bomber Command. The new Squadron "X" later to be called 617 Squadron was to be based at RAF Scampton in Lincolnshire. Wing Commander Guy Gibson was chosen to command 617 Squadron a veteran of over 170 missions and he was given virtual Cart Blanche to select his own crews from existing Squadrons in 5 Group for No.617. Once everything was in place Gibson started to get his crews training for low level night attacks. He was told what the targets were for the operation (The Mohne, Eder, Sorpe & Ennepe Dams) so the crews used the reservoirs at Derwent Water in Derbyshire, Eyebrook in Leicestershire & The Fleet Lagoon at the rear of Chesil Beach near Weymouth in Dorset for practice. The crews were gradually getting the hang of flying low in the dark in small formations. Now the operation could be planned. The best time to hit the dams would be in the Spring when they were at their highest levels after the Winter run off. This was calculated to be around the middle of May 1943. Operation Chastise was therefore planned for 17th May 1943. The Aircraft were now being specially modified for the operation. They would be Lancaster B Mk III Specials with a modified Bomb Bay to accomodate the Upkeep bomb. 19 of these special Aircraft arrived in dribs & drabs at Scampton over the late winter & early spring of 1943. Gibson's aircraft was always "G" so he had AJ - G, other pilots then selected their aircraft. The Upkeep Bombs arrived on the 15th May after final testing on 29th April.


    The Mission

    On the evening of 17th May 1943 all was ready for the Attack on the Dams. 3 Waves of Aircraft would take off at different intervals. The Operations Room for the mission would be 5 Group HQ at Grantham. Code words had already been agreed - Goner for Bomb Dropped, Nigger for the Mohne Dam breached, after Gibson's Black Labrador which had been accidentally run over and killed that morning and Dinghy for the Eder Dam breached, this was Young's nickname after he had had to ditch in the sea twice whilst returning from previous missions. Gibson would lead the first wave in G-George along with M-Mother, P-Peter, A-Apple, J-Johnny, L-Leather, Z-Zebra, N-Nan & B-Baker. Take Off was at 21.25 hours. The outward route took them over the North Sea to Walcheren Island, Schouwen, then across Holland skirting around the Airbases at Eindhoven & Gilze-Rijen to curve around the Ruhr defences, then North to avoid Hamm before heading South to the Mohne. On arrival over Mohne Lake, Gibson made the first run. His bomb hit the Dam Wall and sank before a huge explosion and eruption of water in to the air. Next to have a go was Hopgood in M-Mother. As he was making his run the Flak became intense and his Aircraft was hit, he released his bomb which exploded but the blast caught the Aircraft and it was destroyed. Gibson then decided to fly parallel to Martin's Aircraft, P-Peter to draw the Flak away as he made his run. Again the Aircraft was hit but made it, the bomb was on target with the same result. Next to go was Young in A-Apple. Gibson & Martin flying parallel as he made his run, the bomb again hit square on but still no breach. Maltby in J-Johnny now made his run and after another successful hit the Dam finally gave way. A huge torrent of water now gushed through the gaping hole sweeping everything before it. Gibson now took the remaining Aircraft in the 1st Wave to the Eder. The valley was fogged in and the approach was extremely tricky because of steep terrain surrounding the Dam, it was however undefended. First to go was Shannon in L-Leather. After 6 attempts to make a run he decided to have a break. Maudsley in Z-Zebra made his run with the bomb hitting slightly off centre but exploded above the dam damaging the Aircraft. Shannon now made another run and this time the bomb hit square but there was no breach. Last to go in the first wave was Knight in N-Nan. His bomb hit dead centre and the wall gave way with yet another torrent of water pooring through the gap. 2 out of the 4 Dams had been successfully breached. The first wave now headed home minus Astell in B-Baker who was lost somewhere near Roosendaal in Holland after hitting power lines whilst inbound. A-Apple with Young's crew was shot down over the dutch coast outbound & Z-Zebra with Maudsley's Crew was shot down over Germany on the return leg.

    The 2nd & 3rd waves were tasked with striking the Sorpe & Ennepe Dams. The Sorpe was a different prospect all together. A large earthen wall tapering upwards at an angle on either side to a crest. It was decided to drop the Upkeep bomb across rather than head on to see if a breach could be obtained but the 2 bombs that were dropped this way made no visible impact on the structure. It was really a case of the wrong weapon for the wrong target. Only one bomb was released on the Ennepe Dam also with no effect. 2 Aircraft from each of the 2nd & 3rd waves were also lost - E-Easy with Barlow's Crew after hitting power lines outbound, K-King with Byers' Crew was shot down over the dutch coast outbound, S-Sugar with Burpee's Crew was shot down over Holland outbound & C-Charlie with Ottley's Crew was shot down over Germany also outbound. This made 8 out of the 19 Lancasters that took part in the raid that didn't return with a loss of 53 Aircrew. 3 actually making it out of Hopgood's Aircraft before it crashed.

    On hearing this news Wallace was beside himself with anguish. He had not expected that so many of the airmen would not return. He said to Gibson on his return that if he'd known that there would be so many losses that he wouldn't have started the thing in the first place. Gibson told him not to feel like that and that even if the crews had known they wouldn't be coming back they'd have still gone on the mission. This had left a profound mark on Wallace though and he vowed that any of his future projects would not involve risk to those who had to use them. Something on which he stuck to his word.

    Aftermath

    Although a spectacular feet of Airmanship, the Dams raid did not do the lasting damage that had been hoped for. Within 6 months both the Mohne & Eder had been repaired and the Ruhr was at full production capacity again within 3 months. It did however prove any doubters wrong that Great Britain was willing to take the fight to Germany at a time when some in the US & USSR were beginning to doubt this.

    Recognition

    Of the surviving Aircrew 33 were decorated on the 22nd June 1943 at Buckingham Palace with Guy Gibson receiving the Victoria Cross, 5 Distinguished Service Orders, 10 Distinguished Flying Crosses & 2 Conspicuous Gallantry Medals & various other awards given to the other aircrew. Unfortunately Gibson would not see out the war after his aircraft (A Mosquito) crashed in Holland in 1944 killing all on board.







    The Upkeep Bomb

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    The Mohne Dam the day after the attack.

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    Gibson with King George VI & Group Captain Whitworth discussing the Dam Busters Raid

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  3. brianw

    brianw Member

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    I don’t know whether this should be posted here with the story of the “Dams Raid” or in the thread for the film.

    The “Upkeep” mines; the original bouncing bomb were test dropped from a modified Wellington bomber; initial tests being not quite as successful as hoped, but by the time that the height, speed, removal of the wooden outer casing and the back-spin machinery had been sorted out, the result is now well documented.

    To those of you who have a bit of an eye for aircraft recognition might have noticed, at least one of the sequences in the film showing the tests drops involves a Mosquito dropping a spherical device, the “Upkeep” mines were barrel shaped once the wooden case was removed.

    The Mosquito shown in the film was actually testing another different bouncing bomb, “Highball”, intended to be used against the Tirpitz, such was the threat that this mighty warship posed to British shipping. The theory was that torpedoes weren’t usable because of the defensive nets around the ship.

    Ultimately the demise of Tirpitz was brought about by a combined effort from by Royal Navy submariners in their “X-Craft” causing such a level of damage to the ship requiring it to be brought south for repairs and into the range of the Lancasters of 44 and 617 squadrons flying from Scotland.

    Tirpitz was finally sunk during an attack by 617 squadron using “Tallboy” 12,000 pound bombs.

    Highball was never deployed and the only documented raid using the bouncing bomb technique was the “Dambusters raid”.
     
  4. brianw

    brianw Member

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    Oops! A slight mistake here.

    In the interest of historical accuracy, the sinking of the Tirpitz was carried out by 617 squadron and 9 squadron, not 44 sqdn.

    There were three attacks by 617 on Tirpitz, one from Yagodnik in Russia while the battleship was in Alten Fjord and twice from Scotland while undergoing extensive repairs in Tromso.

    Each time she was attacked using Tallboys and on the third attempt she finally capsized and sank. It was revealed after the war the the first attack in Alten Fjord did in fact cause "damage beyond repair" ... but nobody knew that at the time.
     

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