Supermarine B.12/36

The Supermarine B.12/36 was a British prototype four-engine heavy bomber design that was destroyed by enemy action before completion during the Second World War.

Design and development

The Air Ministry issued a specification in 1936 for a four-engined heavy bomber to serve with the Royal Air Force.

Supermarine, among others, were invited to tender a design.

The Supermarine design, Type 316 was a single-spar, mid-wing aircraft; the leading edge was swept back but the trailing edge was straight. Bombs were carried in both the wings and fuselage. Defence armament was in three turrets. Of the different powerplants suggested for the Type 316, there were three of 1,000 + hp power: the Rolls-Royce Merlin inline liquid cooled engine, the Bristol Hercules radial engine and the Napier Dagger inline air-cooled. Estimated performance varied from 325 to 360 mph maximum speed (cruise around 260 mph), a maximum operating ceiling of around 30,000 ft and a range of 3,000 miles.

The designs were considered by the Air Ministry in late 1936. Initially low down in the list of preferred designs, by January 1937 it was selected as the preferred choice. Between the Air Ministry and Supermarine changes to the design were adopted giving a larger wing area and a twin tail unit. This revised design was the Type 317 and two prototypes with Hercules engines were ordered on 22 March 1937

The Short S.29 was considered as a backup but re-design work was requested and in June it was decided to order prototypes of that as well. The 316's designer Reginald Mitchell had died making the Supermarine design riskier.

To offer the greater use of possible engines, Supermarine continued with design work for a Merlin engined version – the Type 318. In July 1937 Supermarine were told to stop work on the 318 to concentrate on the 317.

While still under construction, the two prototypes and the construction plans were effectively lost when the Supermarine Works at Woolston was bombed by the Luftwaffe on 26 September 1940 and the Air Ministry order was formally cancelled in November.

The Short S.29 was accepted into service as the Short Stirling and was the principle British 4-engine heavy bomber until eclipsed by the Handley Page Halifax and Avro Lancaster. The latter two originated in a 1936 specification for a two-engined bomber/transport aircraft.

Notes and References

* [http://www.rjmitchell-spitfire.co.uk/otheraircraft/1932to1937.asp?sectionID=4 RJ Mitchell. A life in aviation] accessed 13 March 2008
*Buttler, Tony "British Secret Projects: Fighters & Bombers 1935-1950" Midland Publishing.

External links

* [http://freespace.virgin.net/john.dell/AArt2.htm artists impression of the Supermarine 318]
*http://www.csd.uwo.ca/Elevon/gustin_military/db/br/B1236SUP.html