The Short Stirling was developed in response to Air Ministry Specification B12/36 which called for an aircraft capable of carrying a bomb load of 14,000lb over a range of 2,000 miles – a hugely impressive requirement for the day. Based on the 4-engined Sunderland flying boat with the lower deck and hull removed, it was otherwise largely identical. The prototype first flew on 14 May 1939 and by early 1940 the aircraft was in full production.
The Stirling Mk I was powered by 4 x Bristol Hercules XI radial engines, each of 1,500 hp, whilst the definitive Mk III version was equipped with Hercules XVIs rated at 1,650 hp. The aircrew comprised two pilots, a navigator/bomb-aimer, flight engineer, and three air gunners, whilst defensive armament consisted of 2 x .303 Browning machine guns in each of the nose and dorsal turrets with 4 x .303 Brownings in the tail. Unfortunately, the maximum bomb load could be carried for only some 600 miles and thus a typical load for missions to Italy or deep into Germany was in the order of 3,500 lb.
Entering RAF service with No 7 Squadron in January 1941, the Stirling soon proved popular with its aircrew; it handled well and could out-turn both the Ju88 and Me110 night fighters. It possessed a low ceiling, however, which necessitated many missions being flown as low as 12,000 ft; raids against Italy necessitated flying through, rather than over, the Alps and on combined missions against Germany it proved a favoured Luftwaffe target. An additional shortcoming was the unfortunate design of its bomb bay which precluded carriage of the 4,000lb ‘cookie’. The Halifax, and more particularly Lancaster, offered significantly better performance and when these machines became available in larger numbers from early 1943 it was decided to relegate the Stirling to secondary roles. By the end of 1943, the aircraft was being used for mine-laying and a considerable number were built and modified for glider-towing.
The Stirling equipped 28 RAF squadrons at one time or another and, post-war, six machines were acquired by Egypt for use in the 1948 Arab/Israeli War. A total of 2,383 aircraft were built of which there are no known survivors.