The Super Stirling

In the early part of 1941, inside the corridors of power of Royal Air Force (RAF) Bomber Command, there was a growing concern regarding the Halifax and Lancaster bomber force in contrast to the Sterling platform. The perceived disadvantages of the Sterling had many in the Command clamoring for an upgrade to the existing aircraft. This lead to the RAF to send a formal request for an enhanced Sterling, in the form of Specification B.8/41. The result of this was the project called “Super Stirling” which was based on the new Centaurus CE3Sm radial engine.

The new blue print for the Short Super Stirling, tagged project S36, began with the introduction of the Centaurus CE3Sm radial engine early in the summer of 1941. With the power plant in hand, it was time for the engineering team at Short Brothers (from 1943 forward, the company was named Short Brothers and Harland) to start developing the S36 concept. The first thing they did was redesign the whole wing structure. The baseline Stirling fuselage was extended for the installation of a larger central bomb bay intended to carry the huge and still in the developmental stages 8,000lb free fall bomb. This alone represented a major upgrade over the original Stirling bomber. In addition, six more wing-based cells were installed. Each cell could carry up to 1,000lb of ordinance.

In the autumn of 1941, the RAF’s Controller of Research and Development (CDR) Department issued a paper covering, among other things, the expected operational characteristics of the S36 design. The CRD viewed the new bomber as a “typical night bomber having high useful load at a comparatively slow, economical cruising speed (214mph at 15,000′) just six miles per hour faster than the Stirling”. Despite the uninspired report, the CDR still recommended that the project go to full production mode.

The first, true outline of the project now known as the Stirling III, which was revealed to the RAF’s top brass in July 15th 1941, offered an insight into the Short engineers’ vision. The “III” design had a powerful defensive armament system. Two .5 inch machine guns were placed in the nose of the aircraft, four additional ones in both mid upper and tail turrets. Another machine gun, a .303 inch caliber, was installed under the fuselage in an under turret mechanism. Maximum takeoff weight for the new bomber was estimated at 103,100lb. Top operational speed was 311 mph at a 20,000 service ceiling. Maximum operational ceiling was determined to be 29,300′. In August a further revision of the S36’s profile was made. But the outlines of it were the same, a similar airframe to the original bomber with an increase bomb load and extended longer fuselage. The S36 was conceived to be able to carry a powerful 23,500lb total bomb load, compare to the original Stirling’s 14,000lb capacity, for 2,300 miles.

On the 19th of November 1941, the Air Ministry issued Specification Order B.8/41 to cover the program costs and allocation of resources. Nevertheless, questions were raised regarding the new aircraft’s feasibility. The Controller General Office was skeptical of the Stirling III production success. In a report made public in the fall of 1941-42, the CRD issued some reservations about the development of the S36 as it compared with the Halifax and Lancaster platforms. Or even the much anticipated Avro Super Bomber design, still years away from presentation. Still, the CDR endorsed the project with an order of two sample aircraft on 9th of January 1942. The CRD assigned serials JR540 and JR543 to the two units. One, without a certain operational requirement, the other ready to fly once completed.

It was estimated that the first unit would take to the air in the autumn of 1943. Shorts were also encouraged to prepare a production blue print for an Initial Production Order of twenty aircraft with a possible extension of 130 units. On May 11th, the Commander in Chief of the RAF’s Bomber Command, Air Chief Marshall Sir Arthur Harris wrote that “the B.8/41 was expected to eradicate the weakness of the present Stirling force and with much bigger span wings should be a better aircraft. But the new potential given does not justify the change over, the switch will cost at least 126 Stirlings at Rochester plus a ratio of two B.8/41s for three Stirlings. The best course is to concentrate on the Hercules VI Stirling which will go a long way to improve the really weak feature, its operational ceiling at weak mixture. The Hercules VI should push this up to 19,000′ from 16,000′ which is superior to the B.8/41”. Coming from Harris, these words were gospel to the Air Ministry.

A fortnight later, Short brothers were told to cease all work on the S36 project. The Ministry estimated that by the time the S36 achieved operational status, and taking into the equation the expected increases in additional weight that usually goes into a new aircraft, the new profile of the bomb load would be insufficient to justify the losses of standard production Stirling. The decision stunned Shorts who, for a while, entertained the idea of privately continuing with the program. But on August 5th they decided to abandon the whole program. The valuable data gained during the program’s life was used on another air platform concept; the Vickers Long Range High Altitude Super Bomber.

– Raul Colon

References:
Air Power: The men, machines, and ideas that revolutionized war; from Kitty Hawk to Gulf War II, Stephen Budiansky, Penguin Books 2004
International Air Power Review, AIR Time Publishing, Volume 22, 2007

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