16–17 May 1943

Wing Commander Guy Penrose Gibson, VC, DSO and Bar, DFC and Bar. (Imperial War Museum)
Wing Commander Guy Penrose Gibson, V.C., D.S.O. and Bar, D.F.C. and Bar. © IWM (CH 11047)

16–17 May 1943: Nineteen modified Avro Lancaster B.III Special long-range heavy bombers of No. 617 Squadron, Royal Air Force, carried out Operation Chastise, a low-level night attack against four hydroelectric dams in the Ruhr Valley.

The purpose of the attack was to disrupt German steel production. It was estimated that 8 tons of water were required to produce 1 ton of steel. Breaching the dams would reduce the available water and hydroelectric power, disrupt transportation of materials on the rivers, and flood iron ore and coal mines and power plants. If the dams were destroyed, it was believed that the effects would be the same as attacks against 26 categories of industrial targets further down the Ruhr Valley.

Led by 24-year-old Wing Commander Guy Penrose Gibson, D.S.O. and Bar, D.F.C. and Bar, a veteran of 172 combat missions, the aircrews of No. 617 Squadron dropped a spinning cylindrical bomb, code-named “Upkeep”, from a height of just 60 feet (18.3 meters) over the reservoirs behind the dams, while flying at precisely 240 miles per hour (386.2 kilometers per hour).

The 9,250-pound (4,195.8 kilogram) Vickers Type 464 bomb was designed to skip along the surface and to strike the dam, and then sink to the bottom. There, a pressure detonator exploded the 6,600 pound (2,994 kilogram) Torpex charge directly against the wall with the water pressure directing the energy through the wall.

Guy Gibson's Avro Lancaster B.III Special, ED932/G, AJ-G, "bombed up" with an Upkeep bomb. © IWM (HU 69915)
Guy Gibson’s Avro Lancaster B.III Special, ED932/G, AJ-G, “bombed up” with a Vickers Type 464 bomb. © IWM (HU 69915)

Nineteen Lancasters took off from RAF Scampton beginning at 9:28 p.m. on the 16th, and flew across the North Sea at only 100 feet (30.5 meters) to avoid being detected by enemy radar. The bombers succeeded in destroying the Möhne and Eder dams and damaging the Sorpe. A fourth dam was attacked but not damaged. The last surviving bomber returned to base at 6:15 a.m. on the 17th.

Of the nineteen Lancasters launched, two were damaged and turned back before reaching the targets. Six were shot down and two more collided with power lines during the low-level night flight. Of 133 airmen participating in the attack, 53 were killed.

GIBSON, Guy, with PO Frederick M. Spafford, FL Robert E.G. Hutchinson, PO Andrew Deering and FO Torger H. Taerum
Wing Commander Guy Penrose Gibson, V.C., D.S.O. and Bar, D.F.C. and Bar, Commander No. 617 Squadron, with the crew of “G George”: Pilot Officer Frederick Mchael Spafford, D.F.C., bomb aimer; Flight Lieutenant Robert Edward George Hutchinson, D.F.C. and Bar, wireless operator; Pilot Officer Andrew Deering, D.F.C., gunner; Flying Officer Torger Harlo Taerum, D.F.C., navigator. Flight engineer Sergeant John Pulford and tail gunner Flight Lieutenant Richard A.D. Trevor-Roper are not present.  © IWM (TR 1127) 

Guy Gibson was awarded the Victoria Cross by King George VI. An additional 33 survivors were also decorated. 617 Squadron became known as “The Dambusters.” A book, The Dam Busters, was written about the raid by Paul Brickhill, who also wrote The Great Escape. A 1955 movie starred Richard Todd, O.B.E., as Wing Commander Gibson. There have been reports that a new movie is planned.

An Avro Lancaster B.III Special drops an "Upkeep" bomb during tests, April 1943. (Imperial War Museum)
An Avro Lancaster B.III Special drops an “Upkeep” bomb during tests at Reculver, April 1943. Imperial War Museum, still from film, IWM (FLM 2340)
After being dropped from an Avro Lancaster, the “special mine” bounces across the water. (Imperial War Museum)
Post-strike reconnaissance photograph shows the breach of the Mohne Dam in the Ruhr Valley, 16 May 1943. (Imperial War Museum)
Post-strike reconnaissance photograph shows the breach of the Möhne Dam in the Ruhr Valley, 17 May 1943. The gap is 250 feet (76 meters) wide and 292 feet (22 meters) deep. © IWM (CH 9687)

The Avro Lancaster B.III Special was a four-engine long range heavy bomber modified to carry the Type 464 bomb. It was operated by a crew of seven: Pilot, flight engineer, navigator, radio operator, bomb aimer, nose gunner and tail gunner. The “Lanc” was 69 feet, 6 inches (21.184 meters) long with a wingspan of 102 feet (31.090 meters) and overall height of 20 feet (6.096 meters). The modified bomber had an empty weight of 35,240 pounds (15,984.6 kilograms and a maximum takeoff weight (MTOW) of 60,000 pounds (27,215.5 kilograms).

The Lancaster B.III Special was powered by the Packard Motor Car Company’s license-built version of the Rolls-Royce Merlin 24, the Packard V-1650-1 Merlin 224. These were liquid-cooled, supercharged, 1,648.96-cubic-inch-displacement (27.022-liter) single overhead cam (SOHC) 60° V-12 engines with four valves per cylinder and a compression ratio of 6.0:1. The Merlin 224 used a two-speed, single-stage supercharger. 100/130-octane aviation gasoline was required. The engine had a Normal Power rating of 1,080 horsepower at 2,650 r.p.m. and 9,500 feet (2,896 meters); Military Power, 1,240 horsepower at 3,000 r.p.m. at 11,000 feet (3,353 meters); and 1,300 horsepower at 3,000 horsepower with 54.3 inches of manifold pressure (1.84 Bar) for Takeoff. The Merlins drove three-bladed de Havilland Hydromatic quick-feathering, constant-speed propellers which had a diameter of 13 feet (3.962 meters). The propeller gear reduction ratio was 0.477:1. The V-1650-1 was 6 feet, 7.7 inches (2.024 meters) long, 2 feet, 6.0 inches (0.762 meters) wide and 3 feet, 6.6 inches (1.082 meters) high. It weighed 1,512 pounds (685.8 kilograms).

These engines gave the Lancaster a cruising speed of 200 miles per hour (321.9 kilometers per hour) and maximum speed of 272 miles per hour (437.7 kilometers per hour). The service ceiling was 24,700 feet (7,528.6 meters) and maximum range was 2,530 miles (4,071.6 kilometers).

Defensive armament for a standard Lancaster consisted of eight air-cooled Browning .303-caliber Mark II machine guns in three power turrets, nose, dorsal and tail. The Lancasters assigned to Operation Chastise had the dorsal turret deleted to reduce weight and aerodynamic drag. The gunner normally operating that turret was moved to the front turret, relieving the bomb aimer to deal with the operation of the specialized mission equipment.

7,377 Avro Lancasters were built. Only two remain in airworthy condition.

The first two modified Avro Lancaster B.III Specials assigned to No. 617 Squadron, RAF Scampton, April 1943. (Royal Air force)
The first two modified Avro Lancaster B.III Specials assigned to No. 617 Squadron, RAF Scampton, April 1943. In the foreground is ED825/G, AJ T. (Royal Air Force)
One of the two flyable Lancasters remaining, “City of London,” the Battle of Britain Memorial Flight Vickers-Armstrongs Ltd.-built Lancaster B.I, PA474. The airplane is marked as “Mickey the Moocher,” EE176, QR M. (Crown Copyright)
Victory Aircraft Ltd.-built Avro Lancaster B Mk.X FM213, marked as KB726, VR A.

Highly Recommended: The Dam Busters, by Paul Brickhill. Evans Brothers, London, 1951

© 2018, Bryan R. Swopes

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11 thoughts on “16–17 May 1943

  1. very proud to know that a young guy gibson at the young age of only 24 led the raid .
    what a heavy burden to carry god bless him and all the young men who took part .

    1. Thank you, David. I agree with you. So hard to believe that men so young had to carry such a heavy burden of responsibility. I feel that it is so important that we remember their sacrifice. How can we know who we are, and where we are going, if we don’t remember where we have been as a civilization? And thank you, very much, for looking at my blog! — Bryan

  2. Such an important mission during WW2 which despite only being partially successful was such a boost for the war effort . Thank you for the blog which I check every day to see what has happened I the aviation world on that date.

  3. Two missing from the photo of Gibson and his crew: Flight Lieutenant Trevor-Roper, the tail gunner, and Sergeant Pulford, the flight engineer.
    Engage nit-pick mode…
    Gibson was 25 when he formed 617 Squadron.
    The story is told about when Gibson was touring America after the dams raid and, during one of his addresses, the subject of tours of duty came up and how American airmen were rotated Stateside after 25 missions.
    Gibson was asked how many missions he had flown and when he answered “One hundred and seventy-five”, there was stunned silence…

    1. Thank you, Bruce. About those nits: Wing Commander Guy Penrose Gibson,VC, DSO and Bar, DFC and Bar, was born at Simla, India, 18 August 1918. He was interviewed by Air Vice Marshal Ralph Cochrane for the assignment to “Squadron X” on 18 March 1943. He arrived at RAF Scampton to take command of No. 617 Squadron on 21 March. When Operation Chastise was flown 16–17 May, Guy Gibson was 24 years, 9 months, 10 days old—2 months, 28 days before his 25th birthday.

  4. Bryan

    I rely heavily on your detailed research and wonderfully informative articles to help keep my Wings of Freedom Aviation Museum’s Website current and compelling!

    Your work is much appreciated and highly respected!

    1. Thank you very much, David. That is very kind of you. I try to find the most accurate information possible, and sometimes that’s a judgement call. I prefer original, or at least contemporaneous sources. With modern information, I try to find corroboration elsewhere. It is not uncommon to find what I consider to be “better” info, and I try to go back and update previous articles. I still find it amusing, though, when I find myself listed as a source. David, you are one of my most loyal readers, and I appreciate it very much.

  5. More “nit pick” of an otherwise good article:
    1. The Flight Engineer was left out of the list of crew; he sat beside the pilot in a folding ‘jump seat’, handled the various engine and other controls as an extra pair of hands; he also was trained to fly the aircraft should the pilot need a break, or become wounded; and,
    2. The colour photo of VR-A is not “Just Jane”, which is still not airworthy; VR-A is from the Cdn Warplane Heritage Museum in Hamilton, Ontario, and actually flew to the UK in 2014 to spend 7 weeks flying to various UK air displays accompanying the BBMF Lancaster (a superb DVD is available from the CWHM, detailing this ‘operation’)

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