Supermarine S.6B
A British racing seaplane designed by Reginald Mitchell and built by Supermarine for the 1931 Schneider Trophy contest. Refined from the S.6 around a more powerful Rolls-Royce R engine, it won the trophy outright for Britain in September 1931 and then set an absolute world air speed record of 407.5 mph. Only two were built; the race winner survives at the Science Museum in London.
Why It Mattered
The Supermarine S.6B was built for a single race: the 1931 Schneider Trophy, the seaplane contest that had become the premier international test of aircraft speed and technical development. Britain had won the two previous contests, and under the rules a third consecutive win would keep the trophy permanently; the S.6B delivered it. Weeks later, the type set an absolute world air speed record of 407.5 mph, the first time an aircraft had flown faster than 400 mph. The work fed what came next: its designer, Reginald Mitchell, went on to design the Spitfire, and the Rolls-Royce R engine was developed into the Griffon.
Design Notes
With only months available before the race, Mitchell refined the existing S.6 rather than attempting a clean-sheet design. The S.6B kept the Rolls-Royce R V-12, developed further for the 1931 contest; published figures for its output differ, with Museums Victoria reporting 2,783 horsepower for the developed engine and Vintage Aviation News about 2,350 horsepower in normal form. Mitchell improved the aerodynamics and redesigned the floats, which also served as additional radiator area to help cool the engine. Only two aircraft were built, serials S1595 and S1596, and they were flown by members of the RAF High Speed Flight.
Operational History
Britain's entry nearly did not happen: spending cuts during the Depression removed British government funding for the 1931 contest, and only Lady Houston's gift of £100,000 made a British team possible. Because France and Italy had pulled their teams out, the contest offered little real competition. On 13 September 1931, Flight Lieutenant John Boothman flew the Calshot course alone in S1595, averaging 340.08 mph over seven laps to keep the trophy in Britain, and set a world record speed of 379.05 mph the same day. On 29 September, Flight Lieutenant George Stainforth raised the absolute world air speed record to 407.5 mph, the first flight faster than 400 mph. Published sources disagree about which airframe Stainforth flew: Vintage Aviation News names S1595, while Wikipedia names S1596. With the trophy won outright, the contest was never held again, and both S.6Bs were retired after the record flights.
Afterlife
London's Science Museum received the winning aircraft, S1595, as a donation, and still exhibits it unrestored. The second aircraft, S1596, was tested briefly after the record flights and was written off following a non-fatal crash in 1931. Neither Mitchell nor Supermarine built another racing aircraft. The S.6B closed the line of Supermarine racing seaplanes that ran from the S.4 through the S.5 and S.6, and its engine and design experience fed into the Spitfire generation that followed.