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24th of August 1925

As a purpose built raceaircraft the Supermarine S.4, a single engine and single seat seaplane, it took off for the first time on this day in 1925.

Designed by the Chief Engineer and the Technical Director of the aircraft manufacturer Supermarine, R.J. Mitchel (1895 - 1937) it was a purpose built race aircraft for the Schneider Trophy Air Race.

The aircraft was for a large part made of wood, although metal was also used in the monocoque fuselage and the cantilever wing, which was unbraced.

As powerplant a Napier Lion VII engine was installed, a 12 cylinder petrol engine with the cylinders in a "W" configuration delivering 700 bhp, it first ran in 1917. 14 versions of the engine were produced until the 30s of the last century. The Napior Liion enginewas used in more then 30 aircraft. in the first half of the 20th century Napier Lion engine Only one Supermarine S.4 was built, registered G-EBLP. After its first flight in 1925 the aircraft set a British and World speed record for seaplanes of 122.436 knost (226.752 mph / 365.071 kph) on the 13th of September 1925.

The Supermarine S.4 in on the water in front of the Supermarine factory in Woolston, UK

After setting this record the aircraft was shipped to the United States, together with two Gloster III biplanes in preparation of the Schneider Trophy.

On the 23rd of October 1925, two days before the 1925 race, during a trial flight in Blatimore the aircraft sideslipped in to the water'. Observer stated that the sideslip occurred at a height of 200 ft (61 meters) and as the aircraft contacted the water it broke up. According to the pilot, who survived the landing with two broken ribs, he lost control of the aircraft as result of a strong wing vibration.

The world record set on the 13th of September 1925 by the Supermarine S.4 was broken in the 1925 Schneider Trophy Race by Lt. James Doolittle (who would later plan and lead the Doolittle raid with B25 bombers flown of aircraft carriers). In a Curtiss R3C he reached a speed of 125.579 knots (232.573 mph / 374.443 kph), winning the 1925 Schneider Trophy. Lt. James Doolittle on the Curtiss R3C in 1928

Specifications for the Supermarine S.4 General characteristics

  • Crew: 1

  • Length: 26 ft 7+3⁄4 in (8.122 m)

  • Wingspan: 30 ft 7.5 in (9.335 m)

  • Height: 11 ft 8.75 in (3.5751 m)

  • Wing area: 139 sq ft (12.9 m2)

  • Empty weight: 2,600 lb (1,179 kg)

  • Gross weight: 3,191 lb (1,447 kg)

  • Powerplant: 1 × Napier Lion VII W-12 liquid-cooled piston engine, 700 hp at 2,000 rpm

  • Propellers: 2-bladed fixed-pitch propeller


  • Maximum speed: 239 mph (385 km/h, 208 kn) [2]

  • Wing loading: 23 lb/sq ft (110 kg/m2)

  • Power/mass: 0.21 hp/lb (0.35 kW/kg)

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