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Supermarine B.12/36 (Type 316)

Heavy Bomber Prototype Aircraft

United Kingdom | 1937

"This Supermarine bomber project was, itself, ended by German bombs dropped on the production facility in September of 1940."

Authored By: Staff Writer | Last Edited: 05/05/2019 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.
Specification B.12/36 was issued by the British Air Ministry in 1936 to cover a new, all-modern, four-engined heavy bomber for use by the Royal Air Force (RAF). Three designs came from this initiative which was eventually fulfilled by the Short "Stirling" (detailed elsewhere on this site). The other two submissions were the ultimately-abandoned Armstrong Whitworth B.12/36 and the Supermarine B.12/36, the latter which produced the related Type 316, Type 317, and Type 318 forms.

Supermarine went down in World War 2 history as the makers of the classic "Spitfire" fighter series and added a navalized form through its "Seafire" development. However, large aircraft types were not out of its design, development and construction scope and proven by the many flying boats the company put out prior to the conflict. Against the details of their proposed "Type 316" to fulfill Specification B.12/36, Supermarine was contracted for two prototypes in 1937.

The Air Ministry sought a four-engined type with a maximum bomb load of 14,000lb and a range out to 2,000 miles. Conversely, engineers could opt for a longer-endurance design of 3,000 mile range with a reduced internal bomb load of 8,000lb. Cruising speeds would reach at least 230 miles per hour when flying at about 15,000 feet and turrets would be featured for local defense against enemy fighters. Beyond its service as a heavy bomber, the airframe should also prove suitable for service in the transport role. Drive power was also given some leeway for either Bristol (Hercules) or Rolls-Royce (Merlins) were under consideration for finalized bomber production forms. This produced the "Type 317" (Hercules-powered) and the "Type 318" (Merlin-powered) variants. In the end, the Merlin-powered variant was given up for good - no doubt those engines badly needed in other more important types like Spitfire fighters.

By mid-August of 1937, Supermarine had delivered a mockup model for official review and the design was becoming promising enough to continue pursuit - particularly in light of foreign air powers finding considerable successes with their own four-engined heavy bomber types - up to this point the Royal Air Force held an affinity for less-complex bomber workhorses usually driven by a pair of engines. The death of lead engineer R.J. Mitchell (1895-1937) from cancer in June of 1937 proved a devastating setback for the program which still hoped to garner complete support from the Air Ministry going forward and Supermarine's preoccupation with Spitfire production only served to push the Type 317 program back even further.

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Nevertheless, work on the prototypes continued but it was in a September 1940 Luftwaffe air raid that the future of the Type 317 was settled - German bombs landed squarely on the production facility which rendered the still-incomplete bomber prototypes a total loss. After a quick status review, the program was cancelled in full during November of 1940, bringing about an end to the promising venture and heavier reliance on the Short Stirling and other heavy bomber types that would soon join the RAF inventory.

As finalized, the Type 317 carried a large-area monoplane wing with rounded, tapered tips. The mainplanes were seated ahead of midships. The cockpit was added in stepped fashion, overlooking the nose, with excellent views of each engine pair found along the wing leading edges. The engines were housed in streamlined nacelles for maximum aerodynamic efficiency. The nose was slightly glazed to provide vision for the bombardier and a nose-mounted gun position. The fuselage then tapered rearwards and another gun position was located at the extreme end of the tail. The tail unit itself comprised a horizontal plane unit with rudders affixed at the edges, completing a "twin rudder" appearance common to many aircraft of the period. The undercarriage was of a conventional "tail dragger" arrangement with the main legs double-tired.

The Type 317 was designed to support a crew of six. Power was to be served from 4 x Bristol Hercules HE 1.5M series air-cooled radial piston engines developing 1,330 horsepower each. Dimensionally, the aircraft carried a wingspan of 97 feet and a length of 73.5 feet. Its service ceiling was estimated at 32,000 feet. Defensive armament amounted to 8 x 0.303in (7.7mm) machine guns located along various danger zones about the aircraft - at least two would be showcased at the nose and the tail. Internally, the bomb bay was cleared for carrying up to 7 x 2,000lb bombs or similar loads.

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Power & Performance
Those special qualities that separate one aircraft design from another. Performance specifications presented assume optimal operating conditions for the Supermarine B.12/36 (Type 316) Heavy Bomber Prototype Aircraft.
4 x Bristol Hercules HE 1.5M air-cooled radial piston engines developing 1,330 horsepower each.
329 mph
530 kph | 286 kts
Max Speed
31,972 ft
9,745 m | 6 miles
Service Ceiling
3,679 miles
5,920 km | 3,197 nm
Operational Range
800 ft/min
244 m/min
City-to-City Ranges
Operational range when compared to distances between major cities (in KM).
The nose-to-tail, wingtip-to-wingtip physical qualities of the Supermarine B.12/36 (Type 316) Heavy Bomber Prototype Aircraft.
73.5 ft
22.40 m
O/A Length
97.0 ft
(29.57 m)
O/A Width
22.0 ft
(6.70 m)
O/A Height
38,581 lb
(17,500 kg)
Empty Weight
59,007 lb
(26,765 kg)
Design Balance
The three qualities reflected below are altitude, speed, and range. The more full the box, the more balanced the design.
Available supported armament and special-mission equipment featured in the design of the Supermarine B.12/36 (Type 316) Heavy Bomber Prototype Aircraft .
8 x 0.303in (7.7mm) machine guns in multiple defensive positions including the nose and tail sections.

7 x 2,000lb conventional drop bombs (or similar) load.
Notable series variants as part of the Supermarine B.12/36 (Type 316) family line.
B.12/36 - Air Ministry Specification
Type 316 - Original proposed bomber form by Supermarine evolving to become the Type 317/Type 318 offerings.
Type 317 - Bristol Hercules-engined form eventually to serve as the production-quality model.
Type 318 - Rolls-Royce Merlin-engined form eventually dropped from consideration.
Global customers who have evaluated and/or operated the Supermarine B.12/36 (Type 316). Nations are displayed by flag, each linked to their respective national aircraft listing.

Total Production: 2 Units

Contractor(s): Supermarine - United Kingdom
National flag of the United Kingdom

[ United Kingdom (cancelled) ]
Relative Max Speed
Hi: 400mph
Lo: 200mph
Aircraft Max Listed Speed (329mph).

Graph Average of 300 MPH.
Era Crossover
Pie graph section
Pie graph section
Showcasing Aircraft Era Crossover (if any)
Max Alt Visualization
Small airplane graphic
Production Comparison
Entry compared against Ilyushin IL-2 (military) and Cessna 172 (civilian) total production.
MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030
Aviation Timeline
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Image of the Supermarine B.12/36 (Type 316)
Image copyright www.MilitaryFactory.com; No Reproduction Permitted.

Mission Roles
Some designs are single-minded in their approach while others offer a more versatile solution to airborne requirements.
Some designs stand the test of time while others are doomed to never advance beyond the drawing board; let history be their judge.
Going Further...
The Supermarine B.12/36 (Type 316) Heavy Bomber Prototype Aircraft appears in the following collections:
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