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Supermarine B.12/36 (Type 316)

1937 WORLD WAR 2 X-PLANE

History of Supermarine B. 12/36 (Type 316)

Specification B.12/36 was published by the Air Department in 1936 and covered the new, state-of-the-art four-engine heavy bomber for the Royal Air Force (RAF). This initiative resulted in three designs culminating in the short film "Sterling" (detailed elsewhere on this page).

The other two submissions were the eventually discontinued Armstrong Whitworth B. 12/36 and Supermarine B. 12/36, the latter producing the related 316, 317 and 318 forms.

Supermarine goes into World War II history as the manufacturer of the classic Spitfire family of fighter jets, with the addition of a navalized form through the development of the Seafire. However, large aircraft types are not beyond the scope of design, development and construction, as evidenced by the many airships the company released before the conflict.

Contrary to their proposed details of a "Type 316" conforming to the B. 12/36 specification, Supermarine was commissioned for two prototypes in 1937.

The Department of the Air Force is looking for a four-engine type with a maximum bomb load of 14,000 pounds and a range of up to 2,000 miles. Instead, engineers could opt for a more durable design with a range of 3,000 miles and an 8,000-pound reduction in internal bomb load.

When flying at an altitude of about 15,000 feet, the cruise speed will be at least 230 mph, and the turret will be used to locally defend against enemy fighter jets. In addition to being used as a heavy bomber, the airframe should also prove suitable for transport missions.

There was also some freedom in propulsion, with Bristol (Hercules) or Rolls-Royce (Merlins) being considered for the final bomber production form. This resulted in the "Type 317" (Hercules powered) and "Type 318" (Merlin powered) variants.

In the end, the Merlin-powered variants were jettisoned for good - no doubt the much-needed engines in other, more important types like the Spitfire.

By mid-August 1937, Supermarine had delivered a mock-up for official review, and the design became promising enough to be pursued - especially considering foreign air forces on their own four-engine heavy aircraft Considerable success with bomber types - so far the RAF has developed an affinity for the less sophisticated workhorse of bombers, which are often twin-engine powered. The death of chief engineer R. J. Mitchell (1895-1937) of cancer in June 1937 was a devastating setback for the program, which still wanted the full support of the Air Department and served the Supermarine focused on Spitfire Type 317 production is just to push the Type 317 program earlier.

Still, work on the prototype continued, but it wasn't until a Luftwaffe raid in September 1940 that the future of the Type 317 was decided - German bombs landed directly on the production site, making the still incomplete bomber prototype a overall loss. After a quick status check, the program was completely phased out in November 1940, ending a promising venture and increasing reliance on short Stirlings and other heavy bomber types that would soon be added to the RAF in stock.

When completed, the Type 317 had a large area monoplane wing with a rounded tapered tip. The main aircraft is located midship forward. The cockpit is added in a layered, nose-facing fashion with excellent views of each pair of engines along the leading edge of the wing. The engine is housed in a streamlined cabin for maximum aerodynamic efficiency. The nose is lightly glazed to provide bombardier visibility and nose-mounted gun pockets.

The hull then tapers aft, and another gun emplacement is located at the very end of the stern. The tail itself consisted of a horizontal aircraft unit with rudders attached to its edges, completing the "dual rudder" look common to many aircraft of the era.

The undercarriage is in a traditional "trail" arrangement with twin tire main legs.

The Type 317 is designed to support a crew of six. Power is provided by four Bristol Hercules HE 1.5M series air-cooled radial piston engines, each rated at 1,330 hp. Dimensionally, the aircraft has a wingspan of 97 feet and a length of 73.5 feet. Service ceiling is estimated at 32,000 feet. Defensive armament consists of 8 x .303 in (7.7 mm) machine guns located in various hazardous areas around the aircraft - at least two of which can be seen in the nose and tail.

Inside, the bomb bay has been cleared and can hold up to 7 x 2,000 lb bombs or similar.