Short S.29 Stirling

Specification B.12/36 and the Stirling

In this and the following pages I intend to explore some of the design features of the Short Stirling, and more interestingly relate them to the environmental and political context. This (some say) ugly plane, was designed for a reason- with features that are a clever solution to a complex brief.

Shorts Stirling hold many records- the first 4-engined monoplane bomber of W.W.II, the the first designed from the outset with 4 engines and the first to be withdrawn from service. The design provided good service during the first part of the war - especially after Britain had proven its will to fight after the Battle of Britain. After paving the way for the Halifax & Lancaster it became a victim of the latter's success. Once the Halifax& Lancaster were online, the Stirling's problems became more apparent. Mainly it's altitude ceiling and top speed were limited, as was its ability to carry the latest ordinance. The losses sustained to Flak were higher than the latter rivals, so missions were tailored to suit - mining ("Gardening") and glider towing became its final role before retirement.
Given numerous design shortcomings it is well worth considering the circumstances surrounding the design of this aircraft. Designed around the B12/36 specification, which demanded an aircraft capable of lifting off a 500ft runway and able to clear 50ft trees at the end, the wingspan should not exceed 100ft - specifications which must seem absurd in the light of latter designs - and more especially those of the US 8th Air Force.
It is important however to consider the nations circumstances before dismissing the specification as unrealistic. Britain was still in serious debt (from the Great War), a country expecting to be able to negotiate a peace with the Nazis without a war lasting passed Christmas. By the end of the Battle of Britain - the British economy way just about spent- with only £6 million left in gold reserves, the nation was incapable of continuing the fight without external aid. This aid was to come - just in the nick of time from the USA.

Through political uncertainty in '39- nobody could have really known how monumental the threat would become. The specification was further hamstrung in other ways- the plane should be capable of carrying 100 soldiers, could be transported by train - in pieces that can be readily reassembled.

The solution to the various conflicting requirements of the specification was sought by Shorts - an experienced flying boat designer- who used the basic wing design of the Sunderland Flying boat, (which itself was an extremely hardy and capable submarine hunter- with long the long range essential for the role. The resulting machine is immediately striking - mainly due to it's height standing on it's wheels - the pilot sat 22ft 9in from the ground! In flight it looks long and lanky in the fuselage with relatively stubby wings. On first seeing the posture of the plane on the ground the nose high pitch must look rather odd- there is plenty of propellor clearance (few ground crews were killed by walking into the spinning props as with other planes- especially the Liberator)- so why those very long& fragile legs?

To meet the requirement for a short takeoff the plane had to be able to jerk its nose upward at the end of the run to clear the runway end, it had to be able to do this without stalling - so the short wing's aerofoil was very thick, and the flaps very long in chord. The first factors limited the maximum altitude- to a level that suited the Flak gunners.

References
British Warplanes of WWII, ed. Daniel J. March
Pilots & Flight Engineers notes- Stirling I, III, IV. Air Data publications © 1973
The Stirling Bomber - Michael J.F. Bowyer