- Yes
- No
Introduction: The Supermarine Type 317 is an interesting aircraft project from a well-renowned aircraft company that has been lost to time, simply being regarded as a footnote in British bomber aircraft development.
Background: In the mid-1930’s, the Air Staff believed that the heavy bomber would be the most effective weapon for both offensive and defensive operations. This was the time where it was believed that the “bomber would always get through”, which made it an unstoppable strike weapon that could solve many issues. This was also a time of rapid technological advance, with engines increasing in both size and power, and airframe manufacturing techniques making leaps and bounds from design to design. It was thus found necessary to design a new generation of bomber which would carry heavier loads than existing types over longer distances. The Air Staff had also sent fact finding missions to the US, and they were impressed by the projects going on at that point, with aircraft such as the B-17 and B-18 being drawn up and prepared for testing at this point. The UK issued two requirements: B.12/36 and P.13/36 were both issued in order to provide a wide-ranging modernisation to the British bomber fleet. For B.12/36, Shorts and Supermarine were chosen to produce aircraft, their designs becoming the Stirling and the Type 317 respectively.
Description: The initial design was the Type 316, a four-engined monoplane of full metal construction, except for the control surfaces, which were fabric covered. The 316 made use of a distributed bomb storage system, as it used a single spar. This reduced wing bending, and allowed for a thinner fuselage. The leading edge was also swept back to a noticeable degree, with the trailing edge being straight and perpendicular to the fuselage. Armament consisted of 29x 250lb (113kg) or 500lb (227kg) or 7x 2000lb (907kg) bombs, or 8x .303in (7.7mm) machine guns. The Type 316 would quickly evolved into the Type 317, essentially becoming a new aircraft design. The wing was changed to one with a linear taper, with the tips and ailerons having an elliptical curvature. The aircraft was designed to be as aerodynamically clean as possible, apart from the rear turret, which did not match up to the fuselage all that well. Additionally, the tail was changed to a twin fin type, as found on other heavy bombers of the time, such as the Halifax. The Type 317 was powered by Bristol Hercules piston engines, with the Type 318 being the Rolls-Royce Merlin-powered variant. Two prototypes were ordered in March 1937. In July, it was decided that the 318 was to be cancelled in order to reduce workload on Supermarine (already busy with the Spitfire) and to help speed up the program. A mock-up was built, which was examined on the 12th of August, and the prototypes began construction. However, they were never completed, as Supermarine prioritised their Spitfire work over the bomber project, with the Air Staff also introducing new types in the meantime. The project’s fate was sealed on the 26th of September, 1940, when the partially completed fuselages were destroyed in an air raid by the Luftwaffe on the Supermarine Itchin factory. The order for the Type 317 was cancelled shortly after.
Performance:
Spoiler
| Span: | 97ft (29.57m) |
|---|---|
| Length: | 73ft 6in (22.40m) |
| Wing Area: | 1,358sq.ft (126.16sq.m) |
| All-Up-Weight | 55,000lb (24,948kg) |
| Powerplant: | 4x 1,315hp (981kW) Bristol Hercules HE.1.SM |
| Max Speed/Heigh | 360mph (579km/h) at 14,500ft (4,420m) |
| Armament: | 29x 250lb (113kg) 0r 500lb (227kg) or 7x 2,000lb (907kg) bombs, |
8x 0.303in (7.7mm) machine guns|
Conclusion: The Supermarine Type 317 remains as an interesting project in British bomber development, remaining an interesting “what-if” aircraft for those who have researched it. Though a promising aircraft, Supermarine’s concentration on the Spitfire meant that it was overstretched as a company, and thus had to give the 317 a lower priority. This may have ultimately been the right decision with the benefit of hindsight, with the bomber gap left behind by the cancellation of the type quickly being filled by other aircraft. Still though, one must ponder how a Supermarine heavy bomber would have really turned out.
Sources:
Spoiler
“British Secret Projects 4: Bombers 1935 to 1950” by Tony Buttler
Supermarine Type B12/36, 317 | Key Aero
Supermarine B12/36 (Type 316 - 318) | Secret Projects Forum
R J Mitchell and Supermarine: R. J. Mitchell’s Bomber and his death.