It has the distinction of being the first four-engined bomber to be introduced into service with the Royal Air Force (RAF). The Stirling was designed during the late 1930s by Short Brothers to conform with the requirements laid out in Air Ministry Specification B.12/36. Prior to this, the RAF had been primarily interested in developing increasingly capable twin-engined bombers but had been persuaded to investigate a prospective four-engined bomber as a result of promising foreign developments in the field. Out of the submissions made to the specification Supermarine proposed the Type 317, which was viewed as the favourite, whereas Short's submission, named the S.29, was selected as an alternative. When the preferred Type 317 had to be abandoned the S.29, which later received the name Stirling, proceeded to production. The Short Stirling was a four-engined monoplane heavy bomber designed to provide a previously unmatched level of strategic bombing capability to the Royal Air Force (RAF). It was powered by four Bristol Hercules radial engines which were spaced across its mid-mounted wing. The Stirling has the distinction of being the only British bomber of the period to see service that had been designed from the start with four engines - the Avro Lancaster was a re-engined, stretched-wingspan Avro Manchester while the Halifax was planned to be powered by twin Rolls-Royce Vulture engines but was similarly re-designed to use an arrangement of four Merlin engines in 1937. Although smaller than both of the pre-war American "XBLR"-designation designs (the 149-foot wingspan, 35-ton Boeing XB-15 and the 212-foot wingspan, 79-ton Douglas XB-19) and nearly as large Soviet experimental heavy bomber designs, the Stirling had considerably more power and far better payload/range than anything then flying from any British-based aviation firm. The massive 14,000 lb (6.25 long tons, 6,340 kg) bomb load put it in a class of its own, double that of any other bomber. It was longer and taller than the Handley Page Halifax and the Avro Lancaster which replaced it but both of these were originally designed to have twin engines. For more details of the development, design, operational history and six variants, click here.
