| The Stirling was the first four-engined British heavy bomber of the Second World War. Built by Short Brothers, it was to have a relatively short operational career. Throughout the 1930s, the Royal Air Force was interested primarily in twin-engine bombers and invested heavily in development of huge engines in the 2000 horsepower (1500 kW) class in order to improve performance. In the US and USSR were developing bombers with four smaller engines, which proved to have excellent range and fair lifting capacity, so in 1936 the RAF also decided to investigate the feasibility of the four-engined bomber. The Air Ministry Specification B.12/36 had a mixture of requirements.[citation needed] In addition to a 14000 lb (6350 kg) bombload carried to a range of 3000 miles (4800 km) (incredibly demanding for the era), the aircraft should also be able to be used as a troop transport for 24 soldiers. The idea was that it would fly troops to far corners of the British Empire and then support them with bombing. To help with this task as well as ease production, it needed to be able to be broken down into parts for transport by train. Since it could be operating from limited "back country" airfields, it needed to lift off from a 500 ft (150 m) runway and able to clear 50 ft (15 m) trees at the end, a specification most small aircraft would have a problem with today. The wingspan was limited to 100 ft (30 m) so the aircraft would fit into existing hangars. The wingspan limit was also imposed ... |