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Supermarine S.4/S.5/S.6


The Supermarine S.4 was a 1920s British single-engined single seat monoplane racing seaplane built by Supermarine to compete in the 1925 Schneider Trophy.

It crashed and was destroyed before the competition started.

Allocated the civil registration G-EBLP and the Air Ministry serial number N197,  the S.4 first flew on 24 August 1925.

On 13 September 1925 on Southampton Water, it raised the world’s seaplane speed record (and the British speed record) to 226.752 mph (365.071 km/h). 

With high hopes of a British victory, the S.4, together with two Gloster III biplanes, was shipped to the United States of America for the 1925 race.

During trials at Bay Shore Park, Baltimore on 23 October 1925, piloted by H. C. Biard, it was seen to sideslip into the water from 200 ft (61 m) and was wrecked. 

Biard, who survived with two broken ribs, stated that he lost control following violent wing vibration.

The race was won two days later by Lieutenant James Doolittle, flying a Curtiss R3C at an average speed of 232.573 mph (374.443 km/h), faster than the S.4’s world record of a month before.

Most sources have suggested the accident was due to flutter.


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.

The first aircraft flew for the first time on 7 June 1927.

The S.5s came 1st and 2nd in the 1927 race held at Venice, the winning aircraft (Serial number N220) was flown by Flight Lieutenant Sidney Webster at an average speed of 281.66 mph (453.28 km/h).

One S.5, N221, crashed on 12 March 1928 during an attempt on the world air speed record, killing the pilot Flight Lieutenant Samuel Kinkead, who had flown the Gloster IV in the 1927 Schneider Trophy Race.

Concern over the unreliability of the supercharged Lion powering the Gloster VI led to the High Speed Flight entering one S.5 (N219, fitted with a geared Lion engine for the event) along with the two S.6s for the 1931 Schneider contest.

The S.5, flown by Flight Lieutenant D’Arcy Greig finished third in 46 minutes 15 seconds at a speed of 282.11 mph (454.20 km/h), behind the winning S.6 flown by Flying Officer H. Richard Waghorn and a Macchi M.52.


The Supermarine S.6 is a 1920s British single engine single seat racing seaplane built by Supermarine.

The S.6 continued the line of Supermarine seaplane racers that were designed for Schneider Trophy contests of the late 1920 and 1930s.

The two S.6 racers were entered into the 1929 Schneider Trophy at Calshot, England. 

N247 came first piloted by Flying Officer H.R.D. Waghorn at a speed of 328.63 mph (528.88 km/h). 

N248 was disqualified when it turned inside one of the marker poles, but nonetheless, set World closed circuit records for 50 and 100 km during its run.


The two existing S.6s were re-designated as S.6As with new floats, added cooling areas and statically balanced control surfaces.

S.6A N247 won at Calshot in 1929 and S.6A N248 was disqualified.


The Supermarine S.6B is a British racing seaplane developed by R.J. Mitchell for the Supermarine company to take part in the Schneider Trophy competition of 1931.

The S.6B marked the culmination of Mitchell’s quest to “perfect the design of the racing seaplane” and represented the cutting edge of aerodynamic technology for the era.

Flown by members of RAF High Speed Flight, the type competed successfully, winning the Schneider Trophy for Britain.

Shortly after the race, S.6B S1596, flown by Flt Lt. George Stainforth, broke the world air speed record, attaining a peak speed of 407.5 mph (655.67 km/h).






28 ft 10 in (8.79 m) including floats

25 ft 3 in (8 m) fuselage only


30 ft 0 in (9.14 m)


12 ft 3 in (3.73 m)

Wing area

145 sq ft (13.5 m2)


RAF 27

Empty weight

4,590 lb (2,082 kg)

Gross weight

6,086 lb (2,761 kg)


1 × Rolls-Royce R, 

V-12 liquid cooled piston engine,

2,350 hp (1,750 kW) at 3,200 rpm


2 bladed fixed pitch metal propeller


Maximum speed

407.5 mph (655.8 km/h, 354.1 kn)

(World speed record)

390 mph (340 kn; 630 km/h)

Normal, in level flight

Alighting speed

95 mph (83 kn; 153 km/h)

Wing loading

42 lb/sq ft (210 kg/m2)


0.386 hp/lb (0.635 kW/kg)

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