Silhouette challenge

[Mechta]

Blackburn B40 ?

The Blackburn B40 retracting-bottom flying-boat was a follow-on design to the Blackburn B20. The B20 had been designed with a shorter range (1,500 miles) than the mighty four-engined Sunderland Flying Boat (2,500 miles), But by 1940 the American PBY Catalina had shown that a two engined design could achieve the same endurance as the Sunderland and operate more economically. So in April 1940 ( a few weeks after the loss of the B20 prototype) a new specification (R13/40) was issued for a Sunderland replacement based around using the same principles as the B20, to be powered by either two Napier Sabre or Bristol Centaurus. It was anticipated that the new design would have the same range as the Sunderland but with increased speed and more effective defensive armament. Armament was to include a 20 mm cannon amongst the other defensive armament and perhaps a Vickers 40mm mounted in the nose for offensive use. The B40 was anticipated to be complimentary to the R14/40 project for a large flying boat with increased range (which led to the Short Shetland). The B40 design looked essentially similar to the B20, but had twin fins instead of the B20s single fin.

At the time the B40 specification was written the need to be able to patrol in the middle of the Atlantic was not anticipated, since the hunting grounds of the U boats were then in the Atlantic approaches, but with the success of radar equipped aircraft by Coastal Command the U-boats were forced to operate at greater ranges. Thus in early1941 it was felt desirable to increase the range of the B40 to at least 3,000 miles. Design work continued and two prototypes were ordered (the serial numbers ES966 and ES979 being allocated) but it was just not possible to achieve the range required with two engines while still retaining armament, a decent bomb-load and an acceptable single-engine performance, so the project was wound-down in late 1941 with formal cancellation in January 1942.