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Supermarine: S.5

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1927. Racing seaplane. (N219).
Sept 1940.

Note: This is a sub-section of Supermarine.

The Supermarine S.5 was a 1920s British single-engined single-seat racing seaplane built by Supermarine. Designed specifically for the Schneider Trophy competition, the S.5 was the progenitor of a line of racing aircraft that ultimately led to the Supermarine: Spitfire.

After the failure of the British Entrants in the 1925 competition, Air Ministry funding was provided to support a High-Speed Flight and the development of entrants for the 1927 competition. The designs that emerged were for the Short-Bristow Crusader, the Gloster IV biplane and the Supermarine S.5.

The Supermarine S.5 was designed by Reginald Joseph Mitchell for the 1927 competition. Following the earlier loss of the S.4 before the 1925 Schneider Trophy event Mitchell designed a new all-metal monoplane racer. Unlike the S.4's all-wood structure, the S.5 featured composite construction with the semi-monocoque fuselage mainly duralumin including the engine cowlings. The S.5 had a low, braced wing with spruce spars and spuce-ply ribs and a plywood skin. The S.5 had a very slim fuselage with fuel stored in the starboard float to help counteract the engine torque on take-off. The pilot was seated further forward than was the case with the S4, being forward of the wing trailing edge.

Three aircraft were built, one (N219) with a direct drive 900 hp (671 kW) Napier Lion VIIA engine, and the other two with a geared 875 hp (652 kW) Napier Lion VIIB engine. Engine liquid cooling was achieved by wing surface radiators and additional longitudinal oil cooling surfaces running down the fuselage sides. The wing surface radiators were made of corrugated copper sheets instead of the Lamblin type radiators of the S.4.

The major contribution of Schneider racing was arguably in engine development including advanced fuels and fuel additives, supercharging, valve cooling and low drag installation of liquid cooled engines and their radiator systems. Engine developments for the S.5 included the achievement of sustained high power running through use of high compression operation aided by use of tetra-ethyl lead to suppress premature detonation.

The first aircraft flew for the first time on 7 June 1927. The second and third aircraft (N220 & N221) using a geared engine allowing a reduction in propeller rpm. Two aircraft took part in the race, which was held in Venice on 26th September 1927; Flt Lt S.N. Webster was placed first at 281.65 mph flying N220, with N219 in second place at 273.01 mph.

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