1941-Now Unused

The Stirling was a British heavy bomber of the Second world Warbuilt by Short Brothers. It was the first four engined British bomber and was surpassed by later designs. more...

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In the end it would be relegated to second-line duties, while four-engine conversions of earlier twin-engine designs took over its role.

Development

Through the 1930's the Royal Air Force was interested primarily in twin engine bombers. These designs put limited demands on engine production and maintenance, both of which were already stretched with the introduction of so many new types into service. However, the limitations in terms of power were so serious that they invested heavily in development of huge engines in the 2,000 horsepower (1,500 kW) class in order to improve performance. Meanwhile 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 decided to try their hand at the four engine bomber as well.

It seems the Air Ministry wasn't entirely clear what it wanted in the new design, and the resulting Specification B.12/36 was an odd mix of features. In addition to a 14,000 lb (6,350 kg) bombload carried to a range of 3,000 miles (4,800 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 "backcountry" 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. It is often said that the wingspan was limited to 100 ft (30 m) so the aircraft would fit into existing hangars, but this is not the case. The wingspan limit was imposed in an attempt, unsuccessful in the case of the Stirling, to ensure that weights were kept down.

Shorts was one of eleven designs returned in response to the requirements, but were likely to be the only company that could have realistically started production in a short time. They were already producing several four-engine flying boat designs of the needed size, and created their S.29 design by removing the lower deck and boat hull of their S.25 Sunderland. Their new S.29 design was largely identical otherwise; the wings and controls were the same, construction was identical, and it even retained the slight upward bend at the rear of the fuselage, originally intended to keep the Sunderland's tail clear of sea spray.

Shorts managed to persuade the RAF to dismiss most of its unrealistic design goals when they saw the S.29 would be an excellent bomber. On one point the RAF stood firm: the S.29 used the Sunderland's 114 ft (35 m) wing, and they demanded it be reduced to less than 100 ft (30 m), the same limit as imposed on the Handley Page Halifax and Avro Manchester. In order to get the needed lift from a shorter span and excess weight, the redesigned wing was thickened and reshaped.

Read more at Wikipedia.org