Supermarine S5 N220 on the slipway
After the failure of the British Entrants in the 1925 Schnieder Trophy competition, Air Ministry funding was provided to support a High-Speed Flight and the development of Entrants for the 1927 competition (There was no British entries in 1926 with the competition being won by the Italian Macchi MC39).
The designs that emerged were for the Short-Bristow Crusader, the attractive Gloster IV biplane and the Supermarine S5.
The S5, designed by RJ Mithchell, was of mixed construction with an all-metal fuselage with wooden wings and tail surfaces. Wire bracing was provided to both wing and floats which contributed to a lower structural weight fraction than had been achieved on the S4.
Three S5's were ordered (N219, N220 and N221) powered by the Napier Lion engine developed to deliver 900 hp at 3,300 rpm. Further design features introduced by the all-metal S5 included a very slim fuselage with fuel stored in the starboard float which helped to counteract the engine torque on take-off. Engine liquid cooling was achieved by wing surface radiators and additional longitudinal oil cooling surfaces running down the fuselage sides.
The pilot was seated further forward than was the case with the S4, being forward of the wing trailing edge.
Supermarine S5 N219 with handling party helping the pilot ashore
Engine developments to achieve sustained high power running included high compression operation with the use of tetra-ethyl lead to suppress premature detonation.
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.
The first S5 (N219) was first flown on 7th June 1927 and was powered by a direct drive engine.
This was followed by the second and third aircraft (N220 & N221) using a geared engine allowing a reduction in propeller rpm. Both took part in the race, which was held in Venice on 26th September 1927 and Flt Lt S.N. Webster was placed first at 281.65 mph flying N220, with N219 in second place at 273.01 mph.