Rolls-Royce Limited increase its own production rates. By the late 1920s, aero engines made up most of Rolls-Royce's business. Henry Royce's last design was the Merlin aero engine, which was first flown in prototype form in 1935, although he had died in 1933. This was developed from the R engine, which had powered a record-breaking Supermarine S.6B seaplane to almost in the 1931 Schneider Trophy. The Merlin was a powerful supercharged V12 engine and was fitted into many World War II aircraft: the British Hawker Hurricane, Supermarine Spitfire, de Havilland Mosquito (twin-engine), Avro Lancaster (four-engine) (a development of the Avro Manchester with
Rolls-Royce 25/30 Rolls-Royce 25/30 The Rolls-Royce 25/30 built between 1936 and 1938 is an updated version of the 20/25 with larger engine to provide more power, as often, over-large bodies had been fitted to the earlier model leading to complaints about its performance. The in-line 6-cylinder, overhead-valve 25/30 hp engine is similar to that used in the 20/25 but increased in capacity to by increasing the bore from to , with the stroke remaining at . The compression ratio is 6:1. A single proprietary Stromberg downdraught carburettor replaced the Rolls-Royce one, and magneto ignition was no longer fitted, but a standby coil