Vickers-Armstrongs 447 Windsor

Designed to provide better performance than the Lancaster in the long-range bomber role, the Vickers Windsor had many interesting features, but suffered from protracted development and was cancelled in 1945.

The B. 3/42 resulted from the merger of the B. 5/41 and the twin-engine Wellington replacement project. Vickers declared that it could not do the four-engine job at the required weight, so the weight limitations were dropped and it then became possible to combine the two designs. It was also possible to ‘lift’ most of Vickers’ work on the 8.5/41 into the B. 3/42 since the new design had the same engines and wings but a different fuselage (for example a great deal of the calculations could be applied); however, all of the work on the pressure cabin was wasted. Vickers called the project its Type 447 and, for stressing purposes, B. 3/42 requested a maximum speed of 350mph (563km/h) EAS.

The two prototypes, which retained the original serials, were to be joined by two more, MP829 and MP832 ordered on 4th July 1942 (in fact these were never built). The B. 3/42 Mock-Up Conference took place on 29th and 30th October, another prototype, NK136, was ordered on 10th December and on 1st January 1943 J E Serby notified Vickers of the extension of the contract to include the prototypes plus two pre-production aircraft (NN670 and NN673). This was followed on 21st April by a production order for 300 aeroplanes to be built at Weybridge and in the autumn the new bomber was called the Windsor B Mk. l. The first prototype DW506 made its maiden flight on 23rd October 1943 but the first two machines had to be limited to 55,000lb (24,948kg) all-up-weight because they had been too far advanced in construction for the additional strengthening to be incorporated that would take them up to B. 3/42 standards.

The bomber’s defensive armament was the subject of extensive investigation and controversy. In August 1942 a combination was established of two fixed 0.303in (7.7mm) machine guns in the nose plus two 20mm cannon in a turret at the extreme rear of the fuselage but, in due course, the tail turret was dispensed with and the vacant position used as a sighting and control station for two barbettes, one at the rear of each outer engine nacelle, which each contained two rearward-firing 20mm guns. This later arrangement was officially adopted on 15th February 1943 and in 1944 the second Warwick prototype, L9704, was used to test it, but with 0.5in (12.7mm) machine guns fitted in lieu of the 20mm. In April 1944 it was also decided to provide stations for amidships beam guns as supplementary armament.

Initially the barbettes were to be fitted to the fourth Windsor but these were brought forward to go on K136, which had now become the third prototype. This aircraft, known as the Type 461 and powered by Merlin 65s, was to be the only other Windsor to fly after DW406 and DW412 (on 11th July 1944) and it was much closer to the production standard; the remotely-controlled guns were not fitted until 1945 but they were used in firing tests until 1946. The weight of the barbettes raised problems over the aeroplane’s CofG and the favoured solution was an extended nose. The single pilot cockpit also caused controversy because, in an emergency, access to the pilot’s station by another crew member was near impossible. As a result on 16th August 1944 a drawing was produced showing the Windsor with a new nose based on an RAE ‘Lancaster’ design; here a seated bomb aimer controlled a twin 0.5in (12.7mm) turret behind which came the pilot’ cockpit with side-by-side seating. AlI-up-weight was now 80,000lb (36,288kg).

It was expected that the Windsor, starting at some 75,000lb (34,020kg) all-up-weight, would be capable of development to something approaching 84,000lb (38,102kg), when the Mk. IV Lancaster would probably reach the limit of its development at 75,000Ib. The Windsor was 10mph to 20mph (16km/h to 32km/h) faster than the Lancaster IV and, with a maximum 12,000Ib (5,443kg) load, had a 490 mile (788km) range excess. To meet the long-range requirements of the Pacific War, in spring 1944 Vickers submitted a proposal to extend the Windsor’s still air range with 4,000Ib (1,814kg) of bombs to 4,000 miles (6,436km), which involved sacrificing most of the armour protection and some of the self-sealing material from the fuel tanks; the company stated that this version could be delivered from the start of Windsor production.

In April 1944 it was expected that Windsor production should begin in mid-1945 and during 1946 work up to a peak of forty per month. It was hoped that by mid-1947 thirty squadrons would be equipped with the type, mostly for operations in the Japanese theatre, but VCAS doubted, with its present armament, that the bomber would be suitable for that arena. The Windsor ever-increasing weight brought proposals to fit Griffon engines, but these would require considerable redesign and were not adopted. Pierson’s first brochure for a Griffon Windsor was completed in December 1944. Four 2,070bhp (1 ,544kW) Griffons (with the barbette guns) offered a maximum 382mph (615km/h) at 23,000ft (7,010m), sea level rate of climb at maximum loaded weight (79,000lb [35,834kg]) was 1,380ft/min (421m/min), service ceiling 30,000ft (9,144m) and the maximum bomb load was 12,000lb (5,443kg). An alternative Bristol Centaurus installation took the weight to 81 ,400lb (36,923kg) but reduced the ceiling to 27,000ft (8,230m).

The defensive armament problem, together with several other delays, meant that by the end of the war the type was not offering a sufficient advance for production to proceed. In November 1944 the order for 300 machines was cut to 100, and later to just 40. Then on 17th November 1945, at a Ministry production meeting, the surviving B Mk. ls were cancelled. On 23rd November Vickers was told that ‘the manufacture of Windsor aircraft should cease immediately’. At this point NN670 was almost complete and NN673 well advanced and both were eventually reduced to produce.

The Windsor was originally designed as a replacement for the obsolescent Wellington and was to be an aircraft that could take its place in the first line alongside the Lancaster and Halifax; its development life would also extend well beyond either of these types. As originally conceived the Windsor was a fast, lightly-armed and comparatively heavily armoured night bomber which was to carry a moderate load of 4,000Ib (1,814kg) at a maximum cruise speed of 330mph (531 km/h) but, when it became clear that it would be needed for the Pacific, the debate centred on just how suitable it might be. In its initial stages the type was found to be not sufficiently in advance of the Lancaster IV in range or general performance to justify the Ministry’s plans to employ it actively in the war against Japan; it was also thought undesirable to introduce a new type in this theatre until it had been fully tried out in the UK.

Interest in the Windsor had gradually waned, Vickers became increasingly involved in the commercial aviation field and it was to be the Lincoln which entered production to serve the post-war RAF. The RAF also evaluated two American bombers, the Boeing B-29 Superfortress and the Consolidated B-32 Dominator, and at one point it was keen to have the B-29. In fact there were proposals to build the B-29 in Britain but this never happened. The RAF had to settle with the Lincoln as its main post-war heavy bomber until examples of the B-29 were loaned [87 loaned from the USAF] as the Washington B.1 were acquired in 1951.

Vickers Windsor Development

In January 1945 Rex Pierson completed a brochure for a Windsor powered by four Rolls-Royce Clyde RCI. I. AC turboprop engines and fitted with four main undercarriage legs of a six-wheel bogie type then in the course of development. Visibly the airframe was unchanged, with a Windsor prototype nose, and only the engine nacelles had been altered; the rear nacelle guns were also retained. Cruise speed was estimated to be 390mph (628km/h) at 20,000ft (6,096m), sea level rate of climb 3,050ft/min (930m/min), time to 30,000ft (9,144m) 17.0 minutes and service ceiling 37,000ft (11,278m). A maximum 3,580gal (16,278Iit) of internal fuel would have been carried and the range was 2,415 miles (3,886km). The Clyde turboprop, an example of a new concept of a jet engine and a propeller joined together, offered a combined 3,020bhp (2,252kW) and 1,225lb (5.4kN) thrust at sea level and 3,310bhp (2,468kW) and 738ib (3.3k ) for maximum speed and climb. Contra-rotating propellers would have been fitted if they were available.

The extra power from the Clyde would have been very beneficial to the bomber, which was designated Type 601 Windsor B Mk. 2. In view of the attractive performance offered by the engine MAP informed Vickers on 27th February 1945 that it had been decided to fit NN673 with the new powerplants and asked that design work should proceed as soon as possible. Two more production Windsors were to be similarly converted (the same letter also stated that the idea of fitting the Griffon had been abandoned). Pierson replied that NN673 should be flying with Merlins by January 1946, but added that Rolls-Royce had reported that Clyde units would not be available until April 1946. By June 1945 this version had been given the revised ‘ideal’ nose with the twin 0.5in (12.7mm) turret, but the conversion and the whole project was cancelled on 16th January 1946.


Type 447

    First prototype, serialled DW506, powered by four 1,315 horsepower (981 kW) Rolls-Royce Merlin 65 engines.

Type 457

    Second prototype, serialled DW512, powered by four 1,635 horsepower (1,219 kW) Merlin 85 engines.

Type 461

    Third prototype, serialled NK136, powered by four 1,635 horsepower (1,219 kW) Merlin 85 engines, armed with four 20mm guns in remote-controlled barbettes in rear of outer engine nacelles (a pair in each) aimed from the unarmed tail position.

Specifications (Vickers Windsor Type 447)

General characteristics

  • Crew: six to seven[
  • Length: 76 ft 10 in (23.43 m)
  • Wingspan: 117 ft 2 in (35.71 m)
  • Height: 23 ft (7.01 m)
  • Wing area: 1,248 ft² (116 m²)
  • Empty weight: 38,606 lb (17,548 kg)
  • Loaded weight: 54,000 lb (24,545 kg)
  • Powerplant: 4 × Rolls-Royce Merlin 65 liquid-cooled V12 engine, 1,635 hp (1,220 kW) each


  • Maximum speed: 317 mph (276 knots, 510 km/h) at 23,000 ft (7,010 m)
  • Range: 2,890 mi (2,513 nmi, 4,653 km) with 8,000 lb (3,600 kg) bombs
  • Service ceiling: 27,250 ft (8,300 m)
  • Rate of climb: 1,250 ft/min (6.4 m/s)


  • Guns: 4 × 20 mm cannon in remote controlled barbettes firing to rear[
  • Bombs: about 15,000 lb (6,800 kg) of bombs[

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