It was RJ Mitchell’s revolutionary design for the Supermarine S4, an all-wooden, racing monoplane seaplane intended for the 1925 Schneider Trophy air-race, that evolved into Britain’s most famous and iconic Second World War fighter aircraft, the Spitfire.
Supermarine aircraft won the prestigious air-race five times, but it was the three successive victories between 1927 and 1931 that enabled Britain to win the cup outright and to retain the trophy.
The Supermarine S4 first flew on 24 August 1925. The aircraft, along with two Gloster III biplanes, were shipped to Baltimore in the United States of America for the race, but during trials at Bay Shore Park 23 October 1925 the S4, piloted by HC Biard, crashed and was wrecked.
Undaunted by the loss Mitchell created the S5, an all-metal monoplane racer. Supermarine built three S5s, one powered by a direct drive 900hp Napier Lion VIIA engine and the other two by a geared 875hp Napier Lion VIIB engine.
The 1927 Schneider Trophy air race was held on Monday 26 September at Venice. The Italian team entered three Macchi M52s, while the British, the only other nation to enter, put up two Supermarine S5s and a Gloster IVB. Flight Lieutenant Sydney Webster, flying an S5 roared into the lead and took the race with an average speed of 281.66mph, breaking the world speed records for both seaplanes and landplanes.
It was while working on the development of the Supermarine S6 that Mitchell decided that the Napier engines had reached the limit of their performance capabilities and approached Sir Henry Royce to see if he could create a new, more powerful, engine. Sir Henry agreed to develop an engine that could produce 1,500hp, with the potential to go to 1,900hp. In just six months Rolls-Royce delivered their first R engine. The design of the S6 was based upon the S5, with fuel tanks fitted in the floats to allow for the extra fuel required by the thirsty R engine. The additional heat generated by the engine was dissipated across the surfaces of the wings and floats, which were used as radiators.
The next race was held on 7 September 1929 and consisted of seven laps of a 50km circuit over the Solent near Southampton. The superior S6 and Flight Lieutenant Henry Waghorn finished first, having set an average speed of 328.65mph.
By 1930 the great Depression was taking its toll around the world and the British government, which had previously funded Britain’s Schneider Trophy entry, decided that the expected £100,000 cost could not be justified. Supermarine gave up hope of entering the race, which was made worse in the knowledge that Britain, along with the Americans and Italians, had won the trophy twice before and all three nations were in a position to win it outright if they could secure a third victory.
Assistance came from quite an unusual quarter. In early 1931 the colourful Lady Lucy Houston, widow of Sir Robert Houston, her third husband, gave £100,000 to Supermarine in order to allow them to compete. This left Mitchell barely enough time to prepare a suitable aircraft for the race. Rather than develop a new S7 he chose to improve the existing aircraft and created the S6B. The main difference with the S6 was a more powerful Rolls-Royce R engine that produced a much superior 2,350hp, an increase of 450hp compared with the 1929 version. In total two S6Bs were built for the race, along with two S6s fitted with the new floats and designated S6As.
The 1931 Schneider Trophy race was set to be run on 12 September; however by the time race day had come along all of the other competing nations had pulled out, leaving Britain to compete alone. Nine days before the race the Royal Aero Club refused a request from the Italian and French teams for a postponement. Flight Lieutenant John Boothman was declared the winner with an average speed of 340.09mph and as a result the British team had won the Schneider Trophy outright, in perpetuity.
Later on race day Flight Lieutenant George Stainforth set a new world speed record of 379mph in a Supermarine S6B. Over the coming days the S6B went on to break the world speed record twice more, and on 29 September 1931 Mitchell’s aircraft became the first to break the 400mph barrier with an average speed of 407.5mph.
The book is published by Pen and Sword Books (Aviation) and is currently available in hardback. The ISBN reference number is 9781848843073. Click here to order your copy.
The book is published by Pen and Sword Books (Aviation) and is currently available in hardback. The ISBN reference number is 9781848846456. Click here to order your copy.