Blackburn B.20: Doing the Splits

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Introduction: The Blackburn B.20 is a highly peculiar aircraft from the 1930’s that had an incredibly interesting layout, which never really caught on. Despite its uniqueness, many researchers often forget about it when discussing British flying boats. This is despite the fact that the aircraft was a highly advanced design, with the research it undertook being classified for the entirety of the Second World War.


Description: When designing seaplanes, there are certain sacrifices which must be made during the design process. For instance, with flying boats, the engines need to be kept out of the way of sea spray. The hull must also give good seakeeping qualities. These all have consequences on aerodynamics, and thus, performance. Floatplanes can have smaller and narrower floats, since the body of the aircraft is raised, but this still has a huge impact on performance. The designers at Blackburn, however, decided to combine the best of both systems into a single aircraft. The idea was that a smaller, shallower hull similar to that of a floatplane would save some weight compared to a flying boat, but that it could utilise the better aerodynamic qualities of the latter. This was done by creating a split in the body of the aircraft, with a float at the bottom and the fuselage on top. The float could then by lowered for landing, taxiing and take-off, and raised shortly after to become flush with the fuselage. When lowered, the float raised the fuselage in such a way that it gave the ideal angle of incidence required for take-off.


The Air Staff saw that the idea had some merit, and ordered a single prototype, in order to test the idea. The aircraft was also put forward for a patrol aircraft requirement, but this was awarded to the SARO Lerwick. The B.20 took to the skies on March 27th, 1940. The aircraft was powered by two Rolls-Royce Vultures, which, though less than reliable in service, provided an immense amount of power, giving a speed of 306mph (492km/h) at 15,000ft (4,572m), which was very close to the performance of the Hawker Hurricane at the same altitude, being only 1mph faster than the B.20, though there are accounts of it flying even faster (up to 345mph!). The aircraft did suffer from some issues, which were not related to the hull system. These issues were more to do with flutter, which would ultimately cause the loss of the aircraft on 7th April, 1940, taking most of the crew with it. This spelt the end for the program, but not the concept, with Blackburn designing a whole family of aircraft based on this configuration, including the B.40 (a potential Sunderland replacement), and the B.44 (a fighter aircraft), though none of these designs came to fruition.




Span: Floats retracted: 82ft 2in (25.04m)
Floats extended: 76ft 0in (23.16m)
Length: 69ft 7.5in (21.22m)
Wing Area: 1,066sq ft (99.14sq m) (including floats)
Normal-Loaded-Weight: 35,000lb (15,876kg)
Powerplant: 2x 1,720hp (1,283kW) Rolls-Royce Vulture
Max. Speed/Height: 306mph (492km/h) at 15,000ft (4,572m) (estimated)
Armament 8x 250lb (113kg) bombs
8x 0.303in (7.7mm) machine guns

Conclusion: I believe that this aircraft would make for an extremely unique addition to the UK tree. There is simply no other aircraft like it.



“British Secret Projects 4: Bombers 1935 to 1950” by Tony Buttler
Blackburn B.20 | Secret Projects Forum
Blackburn B20: The Unique Flying Boat - PlaneHistoria
Blackburn B-20 Experimental Flying Boat | Old Machine Press
The Blackburn B-20
Neither Fish nor Fowl; The Blackburn B20, B40 and B44 Retracting Hull Flying Boats - Forgotten Aircraft - Military Matters


+1, Blackburn gonna Blackburn

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