The Vickers Windsor was a Second World War British four-engine heavy bomber, designed by Barnes Wallis and Rex Pierson at the Vickers-Armstrongs factory at Brooklands.
As a possible replacement for the pre-war Vickers Wellington medium bomber, Vickers had proposed a series of designs.
The first, to meet the same specification as the Bristol Buckingham and Air Ministry Specification B.11/41, was for a high-speed twin-engined medium bomber, with remote controlled turrets in engine nacelles and guns in the nose.
This was considered to be neither fast enough to be a fast bomber nor well-armed enough to be a normal medium bomber.
A four-engined development of the same design was also drawn up.
The official position was that the Wellington was becoming obsolete but as the Vickers factories were set up only for geodetic construction any design would need to be based on that method.
Vickers were working on a Wellington with a pressurised cabin for high altitude work and the Ministry was interested in a pressurized version of the Warwick; this was supported by Lord Beaverbrook.
The proposed design changed the twin-engined Warwick wing for an elliptical wing with four Merlin engines.
The aircraft was expected to manage 43,000 ft (13,000 m) having delivered 8,000 lb (3,600 kg) of bombs.
The contract for two prototypes of the Warwick was covered by Specification B.5/41 and development and construction work proceeded until September 1942.
In mid-1942, the Wellington replacement and B.5/41 were merged as a result of a new specification, B.3/42 for a Lancaster replacement but without high altitude performance.
Vickers could take the work already done along and fit the four-engine wing to a new design of fuselage and a contract was raised for what would become the Windsor.
The wings of the first prototypes were built to the earlier specification and so had lower weight limits imposed.
The Windsor was designed to Air Ministry Specification B.5/41 (later modified to Spec. B.3/42) for a high-altitude heavy bomber with a pressurised crew compartment and an ability to fly at 345 miles per hour (555 km/h) at 31,000 feet (9,400 m).
Notable features of the Windsor included its pressurised crew compartment.
The main undercarriage consisted of four single-wheel oleo struts – one in each engine nacelle.
The defensive guns were mounted in barbettes at the rear of each outboard nacelle, which were to be remotely operated by a gunner in a pressurised compartment in the extreme tail.
The Windsor used Wallis’s geodetic body and wing structure that Vickers had previously used in the Wellesley, Wellington and Warwick bombers.
In these aircraft the wing structure flexural strength in bending and the torsional stiffness were calculated (and designed) as being controlled separately by a single spar and the geodetic lattice construction respectively.
However, testing of wings showed that the geodetic structure also contributed to the wing bending resistance so, for the Windsor, Wallis designed the wing so the geodetic structure would take all the torsional and bending loads.
This was achieved by gradually reducing the lattice angle (45 degrees relative to the span) at the wing tips to about 15 degrees at the root.
A spar was not needed so there was more room for fuel.
With no spar the wing was more flexible than before and there was concern that excessive deflections would occur in an emergency landing with wings full of fuel.
To limit the deflection at the wing tip Wallis added an extra landing gear leg in the outboard engine nacelles.
Instead of doped Irish linen covering used on the earlier geodetic aircraft, a stiff and light skin was used on the Windsor.
This was made from woven steel wires and very thin (1⁄1000-inch (0.025 mm) thickness) stainless steel ribbons, doped with PVC or other plastic, specially designed to avoid ballooning.
To properly fit the skin to the frame, a tuning fork had to be used.
Only three examples (the original plus successive prototypes known as Type 457 and Type 461) were built.
This was due to refinements in the existing Lancaster bomber, rendering it suitable for the role for which the Windsor had been designed.
The first prototype flew on 23 October 1943, the second on 15 February 1944, and the third on 11 July 1944.
All three were built at Vickers’ secret dispersed Foxwarren Experimental Department between Brooklands and nearby Cobham.
The two latter prototypes were tested until the end of the Second World War, when further development and production were cancelled.
First prototype, serial DW506, powered by four 1,315 horsepower (981 kW) Rolls-Royce Merlin 65 engines.
Second prototype, serial DW512, powered by four 1,635 horsepower (1,219 kW) Merlin 85 engines.
Third prototype, serial NK136, powered by four 1,635 horsepower (1,219 kW) Merlin 85 engines, armed with a pair of 20mm guns in each remote-controlled barbette in rear of outer engine nacelles, aimed from the unarmed tail position.