Lancaster "Thumper"

Lancaster Thumper Mk III

The RAF BBMF Lancaster, PA474, is currently painted to represent an aircraft which served with No 617 Squadron after the Dams Raid. This is the story of the original aircraft and its wartime pilot and crew.

Some of the specially-modified Type 464 Lancasters, which survived the Dams Raid, remained in service with No 617 Squadron afterwards. However, these aircraft were not suitable for all operations and the Squadron needed replacement, standard Lancasters, as well as replacement crews to make up losses. One of the brand-new aircraft delivered to the unit to meet this need was Lancaster B1 DV385.

Lancaster DV385

Lancaster DV385 was built by Metropolitan-Vickers Ltd at Trafford Park, Manchester, at a stage of the war when the average build time for a Lancaster was 8 weeks. DV385 rolled off the production line in October 1943. It was delivered to No 617 Squadron at RAF Coningsby (by a quirk of fate now the home to the RAF BBMF Lancaster PA474) in November 1943 and given the squadron codes ‘KC-A’. The aircraft was retro-fitted with bulged bomb-bay doors enabling it to carry one of the huge 12,000-lb HC ‘thin-case’ ‘blockbuster’ blast bombs or a 12,000-lb ‘Tallboy’ bomb internally. DV385’s first bombing mission was flown on 16th December 1943; this was the first of four ‘ops’ it flew from Coningsby, three of them captained by Flight Lieutenant Tom O’Shaughnessy to drop 12,000-lb HC bombs against V-weapon sites in France. On 9th January 1944, 617 Squadron moved the few miles north to Woodhall Spa, taking DV385 with them.

Bob Knights and his Crew

Bob Knights Another Lancaster squadron, No 619, was already based at Woodhall Spa and moved to Coningsby to make way for 617 Squadron. One of the 619 Squadron crews, led by pilot Bob Knights, was coming towards the end of their tour at the close of 1943. Some of the crew were going to reach the ‘magic’ end-of-tour figure of 30 ‘ops’ slightly before the others and they did not want to be split up, reasoning that they were safer together. So they had decided to volunteer for a second operational tour with No 617 Squadron. Knights and his crew were about to become very familiar with Lancaster DV385.

Robert (‘Bob’) Edgar Knights was born in January 1921, in London. He volunteered for service as a pilot with the RAF and was eventually called up in March 1941, aged 20. He completed his flying training in America under the ‘Arnold Scheme’, flying Stearman PT17s, Vultee BT13s and AT6A ‘Texans’. In May 1942, after returning to England to complete his training, he crashed an Airspeed Oxford twin-engine aircraft. Bob badly injured his hand in the accident and this kept him off flying for 6 months. In June 1943, with 474 hours flying under his belt, Pilot Officer Bob Knights and his crew – Sergeants Rhude (navigator), Bell (bomb aimer), Twells (flight engineer), Rowan (wireless operator), Hobbs (mid-upper gunner) and Derham (rear gunner) – joined No 619 Squadron to fly Lancasters on bombing operations.

Before he could fly operationally with his own crew, Bob Knights had to complete the traditional ‘second dickey’ ‘op’ with an experienced crew to ‘learn the ropes’. He flew with Flt Lt ‘Ted’ Dampier-Crossley DFC, a New Zealander in the Royal Australian Air Force, who was flying with the RAF on 619 Squadron. Dampier-Crossley’s aircraft was Lancaster EE112, it wore the code letters ‘PG-T’ (normally ‘T’ for ‘Tommy’) and the crew had named it ’T’ for “Thumper” and painted the Walt Disney rabbit character, from the 1942 Walt Disney film Bambi, on the nose. Dampier-Crossley was an experienced operational bomber pilot and he taught Bob Knights some useful tricks and tactics, such as never flying straight and level but weaving constantly, which Bob’s crew subsequently credited with helping to keep them alive. Sadly, a couple of months later, on the night of 10/11th August 1943, Dampier-Crossley and his entire crew were killed during a raid on Nuremburg. A replacement Lancaster coded ‘PG-T’ arrived on the squadron and was allocated to Knights and his crew, who decided to name it “Thumper Mk II” in honour of Ted Dampier-Crossley and his crew. The so-called ‘Battle of Berlin’ began shortly afterwards and the Bob Knights crew made eight attacks against the "Big City", raids in which Bomber Command's losses were particularly high. On another occasion the crew was en route to bomb Hamburg when one of the engines failed shortly after reaching the Dutch coast. They would have been justified in turning back, but pressed on and bombed the target successfully from only 10,000 feet.

Wg Cdr John Bell As a Lancaster had only a single pilot, Bob Knights decided that he would train his bomb-aimer, John Bell, to fly the aircraft in case he was killed or incapacitated. He felt that the bomb-aimer could most easily be spared from his other duties in such an eventuality. John Bell, who is the only surviving member of the crew, told the editor, during a visit to the BBMF at Coningsby in September 2012, that he spent several hours in all at the controls of a Lancaster with Bob standing beside him advising him. It is unlikely that such a novice Lancaster pilot, with no other piloting experience, would ever have been able to land the aircraft if his pilot was rendered ‘hors de combat’, but at least he might have been able to fly it back over friendly territory before the crew took to their ‘chutes’. John also said that he always seemed to over-control the aircraft, finding it difficult to keep it steady. When he was flying it, he said, “The rest of the crew were not best pleased!”

617 Squadron

By the end of 1943 the crew was approaching the required 30 ‘ops’ of a full operational tour with 619 squadron; they were due for a well-earned rest tour, but, instead, they volunteered for a second operational tour with No 617 Squadron. After they had been interviewed by 617’s Commanding Officer, Wing Commander Leonard Cheshire, the crew was posted to the elite unit in January 1944.

On the night of 20th January 1944, Flight Lieutenant Tom O’Shaughnessy, who had so far been the regular pilot of DV385, was killed in a training accident at Snettisham, Norfolk, along with his navigator Flying Officer Holding. He was flying one of the original Type 464 ‘Dams Raid’ Lancasters (ED918) and crashed into the sand dunes at the Wash bombing ranges, whilst practising for a proposed raid on an Italian dam that did not, in fact, go ahead. After Tom O’Shaughnessy’s tragic death, DV385 needed a new crew and it was allocated to Bob Knights. He and his crew immediately decided that their new aircraft should be named “Thumper Mk III” and the artwork – the cartoon rabbit holding a foaming pint of beer – was duly painted on the nose.

Lanc Thumper III nose art on 617 Sqn DV385 KC-A They also started the ‘bomb log’ under the cockpit with a bomb symbol for each ‘op’ successfully completed by “Thumper Mk III”. The aircraft eventually flew 36 successful operations before it was retired from service in March 1945 (35 bomb symbols are painted on PA474 replicating a wartime photograph). It also flew an additional 13 sorties on which it reached the target, but circumstances prevented the bombs being dropped and they were brought back, as the Squadron’s precision role sometimes demanded.

Bob Knights and his crew first flew “Thumper Mk III” operationally on the night of 8th February 1944, as part of a force of 12 Lancasters which carried out an outstandingly accurate and successful night bombing raid against the Gnome-Rhone aero engine factory at Limoges. Four nights later the crew took part in a long-range attack on the Antheor viaduct, on the railway line between Toulon & Cannes, in an attempt to destroy the strategically important coastal rail link between France and Italy. The target was heavily defended and opposing ground fire was intense as the crew dropped their first 12,000-lb HC bomb. During February, March and April 1944, mostly flown by Bob Knights, “Thumper” was used to attack factories and industrial sites producing vital war materials and equipment for the Germans. In April 1944, having completed more than 30 operations Bob Knights was awarded the DFC.

D-Day – Operation ‘Taxable’

On the eve of D-Day, 5-6th June 1944, Knights and his crew flew “Thumper Mk III” on the highly-secret, deception raid, Operation ‘Taxable’ (the ‘op’ being recorded with a letter ‘D’ on the bomb symbol on the aircraft’s mission tally). The object of this operation was to convince the Germans that the main invasion fleet was heading for the Pas de Calais. Creating this illusion required the precise flying of elongated circuits, whilst bundles of radar-reflective, aluminium-foil strips of pre-determined and varying lengths – ‘window’ – were dropped through the flare chute every 5 seconds. Another, similar, spoof operation, codenamed ‘Glimmer’, was conducted by Short Stirlings of No 218 Squadron in the Boulogne area. Both were successful and, by daybreak on 6th June, the German High Command was trying to react across an unnecessarily broad front. Many of the best German troops were kept on the wrong side of the Seine and the confusion caused by these operations undoubtedly helped the Allies to gain a vital foothold in Normandy on D-Day.


TallBoy On 15 occasions, 10 of them with Bob Knights at the controls, “Thumper Mk III” was used to drop the 12,000-lb ‘Tallboy’ deep-penetration, ‘earthquake’ bombs against high value targets. Designed by Barnes Wallis, the ‘Tallboy’ was a remarkable weapon, combining the explosive force of a large, high-capacity bomb and the penetrating power of armour-piercing munitions. When it was introduced it was the only weapon in the Royal Air Force’s inventory capable of breaking through the thick concrete structures of the German U-boat shelters, E-boat pens and V-weapon sites. ‘Tallboy’ measured 21 feet (6 metres) long and contained 5,200 lbs of Torpex explosive. With a streamlined (ogival) shape, it was fitted with a long, light-alloy, conical tail with 4 small square fins. These fins were offset by 5 degrees, causing the bomb to spin during its fall, aiding stability and improving its accuracy. To increase its penetrative power, the nose of the bomb contained a specially-hardened and precisely-machined, steel plug. ‘Tallboy’ was ballistically perfect and in consequence had a very high terminal velocity. Released from an altitude of 18,000 feet, a ‘Tallboy’ took only 37 seconds to fall to ground; when it hit, it was supersonic and still accelerating. It could penetrate 16 feet (5 m) of concrete and made a crater 80 feet (24 m) deep and 100 feet (30 m) across, which would have taken 5,000 tons of earth to fill. The bomb was designed to detonate below ground, transferring all of its energy into the target structure. This 'earthquake' effect caused more damage than a direct hit, as it shook the whole target structure, causing major damage to all parts of it and making repair impossible or uneconomic. The fuses in the rear of the bomb could be set to give it sufficient time to penetrate before exploding. The time delay could be set to between 11 seconds and 30 minutes after impact.

Saumur Rail Tunnel

The first time that the Bob Knights crew dropped a ‘Tallboy’ from “Thumper Mk III” was the operational debut for the new bomb on the night of 8/9th June 1944 (D-Day+2). The target for the new weapon was the Saumur railway tunnel in France, some 125 miles to the south of the Normandy battle area. This raid was prepared in great haste, as intelligence indicated that a German Panzer unit was expected to move by train through the tunnel. The aim was to prevent these and any other German reinforcements reaching Normandy from the south. The target area was illuminated with flares by four Lancasters of 83 Squadron and then marked at low level by two Mosquitos of 617 Squadron. Twenty-five Lancasters of 617 Squadron, 19 carrying ‘Tallboys’, dropped their bombs with great accuracy. One ‘Tallboy’ actually pierced the roof of the tunnel and brought down a huge quantity of rock and soil. The tunnel was blocked for a considerable period and the Panzer unit was badly delayed. No aircraft were lost on this raid.

Special Bomb Sight (SABS)

To achieve accuracy with these large single bombs, 617 Squadron used a special bombsight – the Stabilising Automatic Bomb Sight (SABS) Mk IIA – which, for the first time in the RAF’s history, permitted true precision bombing from medium altitude. These special bomb sights were hand-made, precision instruments, produced in small numbers and used only in specialist roles. With a well-trained and practiced bomb-aimer, able to keep the SABS aiming graticule exactly over the aiming point during the approach to the target, the sight automatically calculated the aircraft’s ground speed and wind drift. These were the principal factors which led to inaccuracies with earlier bomb sights, like the Mk XIV in use with the rest of Bomber Command. The SABS fed information to a Bombing Direction Indicator mounted in front of the pilot, which showed him whether any course correction, left or right, was required. It also calculated the bomb release point and released the bomb automatically at the correct moment. Given optimum conditions, a well-trained crew could reliably place a bomb within 80 yards of the target from 18,000 feet. Achieving this level of precision required extremely accurate flying. Unfortunately, it also required a long straight run-up to the target of between 5 and 10 minutes, during which no evasive action was possible, making the Lancaster a sitting target for the defences, especially radar-directed ‘predicted’ flak. The combination of SABS and ‘Tallboy’ was effective only if the aiming point could be clearly identified and tracked visually by the bomb aimer. Some missions were aborted or unsuccessful because this was not possible and, due to the cost and complexity of their manufacture, ‘Tallboy’ bombs which were not dropped were brought back to base.

“Thumper Mk III” bomb aimer, John Bell, said that the first time that they dropped practice bombs using the SABS, he scored direct hits on the aiming triangle on the bombing range in the Wash with the first two bombs. On the third run, John felt that things were not quite going right and he took over manually, missing the target by 75 yards. “I learned from that,” he said, “the automatics were better than me”. He went on to say, “When everything was going right, there was no need for communication between the bomb aimer and the pilot, as the Bomb Direction Indicator mounted in front of the pilot gave him all the steering information needed. It was only if it drifted off that the bomb aimer needed to give the pilot heading corrections to make the pilot’s indication live again.”

“Thumper” Fights On

During a daylight raid against E-boat pens at Le Havre on 14th June 1944 “Thumper Mk III” was hit by flak but only lightly damaged. It was flying again the next day, dropping a ‘Tallboy’ against the E-boat pens at Boulogne.

Lanc Thumper MkIII

Most of the aircraft’s ‘ops’ over the next few weeks were ‘Tallboy’ raids against various V-weapon sites, including a V1 bomb store, various V2 rocket sites and the V3 long-range-gun construction site at Mimoyecques. John Bell remembers the direct hit with ‘his’ Tallboy on the north-west edge of the concrete dome at the V2 rocket site at Wizerne on 17th Jul 44. He watched the bomb all the way down to impact. This attack caused severe damage to the site, which was still under construction. Three Tallboys, including the one dropped from “Thumper”, exploded next to the tunnels, one burst just under the dome, and another burst in the mouth of one tunnel. The whole hillside collapsed, undermining the dome support, and burying the entrances to the V2 launch tunnels. Although the concrete dome was unscathed, the buttresses supporting it were dislodged and the dome tilted, jeopardising the bunker from underneath. The site was abandoned a few weeks later. (The site is now the ‘La Coupole’ museum.)

The last ‘op’ that Bob Knights flew in “Thumper” was on 5th August 1944, dropping a ‘Tallboy’ on the U-boat submarine pens at Brest. On 7th August he delivered the aircraft to Coningsby for servicing and modifications to be carried out; subsequently Lancaster LM482 ‘KC-Q’ became his aircraft. This was the point at which bomb aimer John Bell DFC left the crew and the squadron for a ground job. By this time he had flown 50 ‘ops’ and decided enough was enough; his luck had held, but now was the time to stop. He became an Admin (Accounts) Officer for 6 years and then he subsequently served as a Photographic Interpreter for the rest of his career, leaving the RAF on retirement in 1977 as a Wing Commander MBE DFC and with two Korean War medals.

Tirpitz and After

“Thumper Mk III” (now coded ‘KC-V’) returned to operations on 3rd October, piloted by Flying Officer James Castagnola (later Flight Lieutenant Castagnola DSO DFC). On 28th October and 12th November 1944 he captained “Thumper” on the final raids against the powerful German battleship Tirpitz, mooredat Tromso. In common with all the Lancasters used on these missions “Thumper” was modified for long-range flying. The mid-upper turret was removed along with many other internal fittings, and ex-Vickers Wellington overload fuel tanks were fitted, along with a Mosquito long-range tank, increasing the fuel capacity from 2,154 to 2,406 gallons, giving a range of 2,250 miles. On the last of these missions, the Castagnola crew reported a direct hit with their ‘Tallboy’ against the battleship’s superstructure and the mighty ship capsized. For “Thumper Mk III” the war was almost but not quite over, and a swastika on the 32nd bomb symbol on the mission log indicated a German fighter shot down by its gunners – its luck was still holding. The heavy-hitting bomber flew its last successful ‘op’ dropping a ‘Tallboy’ against the Bielefeld viaduct on 22nd February 1945 and then, in March 1945, as the war approached its end, “Thumper” was retired. DV385 ended its life at No 46 Maintenance Unit, where it was eventually struck off charge and scrapped after the war had ended.

Bob Knights DSO DFC

Bob Knights & Crew Bob Knights flew 41 ‘ops’ with 617 Squadron, 29 of them in “Thumper Mk III”, and many of them amongst the unit’s most challenging precision bombing operations. He also took part in all three Lancaster raids against the Tirpitz. In December 1944, after flying an official total of 67 bombing operations,Bob was rested. In January 1945, he was awarded the DSO. During his 10 months with 617 Squadron, 8 of the unit’s Lancasters had failed to return from ‘ops’ and another had been lost in an accident. Thirty-two of his fellow squadron aircrew had been killed and more had been injured or become prisoners of war. In April 1945 Bob was seconded to BOAC; he stayed with the airline for 32 years, retiring in 1976 as a Boeing 747 training captain. Bob Knights DSO DFC died in December 2004, aged 83.

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