Supermarine S4

Designed by RJ Mitchell for the 1925 Schneider Trophy contest.
Supermarine S4 seaplane on the slipway Supermarine S4 seaplane on the slipway


The Supermarine S4 (latterly Vickers-Supermarine) was the first of the three monoplane racing seaplanes built at Woolston (S4, S5 and S6 / S6B), all designed by Reginald J Mitchell as British entrants in the Schneider Trophy Competitions from 1925 to 1931.
The S4 used the Napier Lion engine, cleanly faired into the fuselage and featured a mid-set cantilever (unbraced) wing with Lamblin radiators of low frontal area, installed below the inner portion of the wings.
It was largely of wooden construction with the exception of the engine mount and the A-frames that supported the wooden floats. The cockpit was located well aft, with the pilot being seated well behind the wing trailing edge with the large floats being devoid of wire bracing.
The major challenges in the design of this 'family' of aircraft included engine development to very high powers (albeit at very short lives); engine cooling; the minimising frontal area and drag; control on take-off with very high torque and a fixed pitch propeller; water handling for both take-off and landing; and structural / control design to minimise the risks of flutter at the high speeds being achieved.
The S4 was first flown on 25th August 1925 and, before its departure to the United States for the 1925 competition, it set a world speed record for seaplanes at 226.75 mph.
In the United States, the aircraft suffered a disaster before it could compete in the competition proper when during a high speed pre-race test on 23rd October, the aircraft encountered high-speed flutter, causing loss of control and resulted in a high speed crash.  
Fortunately, the pilot Henri Biard survived albeit with some troublesome injuries (2 broken ribs)
Apart from the racing number ‘4’, the S4 was flown unmarked although it had been allocated the serial N197 and was British Registered as G-EBLP.
Despite its failure due to wing flutter, the S4 led directly to the development of the more successful Supermarine S5, S6 and S6B.


Powerplant One 680 hp Napier Lion VII engine
Span 30 ft 7.5 in
Maximum Weight 3,191 lb
Capacity  Pilot only
Maximum Speed 226.75 mph

Number built

1        Project aircraft


None       Destroyed in accident

Other information