Vickers 447 / 457 / 480 Winsor

The Barnes Wallis geodetic construction, introduced on the Vickers Wellesley and used later on the Vickers Wellington and Vickers Warwick, was highly successful. To exploit its physical characteristics fully, however, a very big aeroplane was desirable.
Vickers' designer, Rex Pierson, used geodetics in evolving a four-engined bomber to meet Specification B.13/36, but the Short Stirling was awarded the contract. Another opportunity came with Specification B.1/39, but this was again unsuccessful, and it was not until the submission to Specification B.5/41 that the Vickers tender was accepted.
The requirement was for a high-altitude heavy bomber with pressurized crew compartment, and an ability to fly at 555km/h at 9450m. Two prototypes of the new bomber were ordered, but changes resulted in a new specification, B.3/42, being drawn up. Vickers designated their design the Type 447, and the name Windsor was given to the aircraft. Various armament trials were carried out on a Warwick prototype, and the first Windsor flew from Farnborough, where it had been assembled, on 23 October 1943. It attained a speed of 486km/h at 7620m, and had completed almost 34 hours of flight testing before being written off in a forced landing, caused by problems with a propeller constant-speed unit. The second prototype, Type 457, contained armour plating and other modifications, and flew from Wisley on 15 February 1944, demonstrating similar performance to the first aircraft. This aircraft was grounded in June 1946, and broken up.
A third Windsor, Type 480, was flown on 11 July 1944, with some further changes incorporated. This aircraft was fitted later with defensive barbettes in the outboard engine nacelles, each barbette having two remotely-controlled rear-firing 20mm cannon.
Trials for these were carried out by a Lancaster, but although further tests continued for some 10 months, the Windsor programme was cancelled on 15 March 1946, with the third aircraft finishing its days as an instructional airframe. A fourth Windsor, originally Type 471 but later changed to Type 483, was almost complete when the programme finished.

Engines: 4 x Rolls Royce Merlin 65, 1613 hp
Max take-off weight: 24500 kg / 54014 lb
Empty weight: 17500 kg / 38581 lb
Wingspan: 35.71 m / 117 ft 2 in
Length: 23.42 m / 76 ft 10 in
Height: 7.01 m / 23 ft 0 in
Wing area: 115.94 sq.m / 1247.97 sq ft
Max. speed: 275 kts / 510 km/h / 317 mph
Ceiling: 8305 m / 27250 ft
Range: 2511 nm / 4650 km / 2889 miles
Armament: 2 x 7.7mm machine-guns, 2 x 20mm cannon
Bombload: 5500kg