and redesigning the engine cowling. The Air Ministry ordered two S.6 seaplanes, both of which were built by August 1929. Modifications to the seaplanes were made by Mitchell so the engines could be used at maximum power, as issues were discovered: the radiators were found to be inadequate; high engine torque made the S.6 move in a circle; and the centre of gravity was incorrectly positioned. The 1929 race at Calshot was won by Supermarine with the S.6 attaining an average speed of . Three of the four new aircraft were entered by the UK. The older Italian Macchi M.52R came second and Supermarine's backup, an S.5, took third place. Supermarine S.6B (1931) Britain's final entry in the series, the Supermarine S.6B, marked the culmination of Mitchell's quest to "perfect the design of the racing seaplane". It was sponsored by a wealthy philanthropist, Lady Houston, who donated after the British Government decided not to enter an RAF team for the 1931 contest. Mitchell opted to design an improved version of the S.6, whilst making as few changes as possible. The improvements that were made included a more powerful engine, and provision was made for such effects as the increase in engine-produced heat and extra torque, and the greater quantities of cooling oil and fuel required. The S.6B was a larger seaplane than the S.6, and had to be given a more efficient cooling system, and a stronger frame. The S.6B competed the course successfully, and won the 1931 race. As the Schneider Trophy rules included the stipulation that the contest would end when any one country managed to win the trophy three times in five years, the S.6B's victory won the contest outright for Britain. The aircraft went on to break the world air speed record when it reached a speed of that year. Mitchell was awarded the Commander of the Most Excellent Order of the British Empire (CBE) on 29 December 1931 for services in connection with the Schneider Trophy contest. Type 224 In 1930, specification F7/30 was issued for a fighter aircraft able to be used by both day and night squadrons. Mitchell's proposed design, the Type 224, was one of three monoplane designs made into prototypes for the Air Ministry. The final design incorporated an open cockpit, four Vickers machine guns, and a Rolls-Royce Goshawk engine, along with a fixed undercarriage. Also included was an inverted gull