Westland Welkin

The Welkin was a twin-engine heavy fighter from the Westland Aircraft company, designed to fight at extremely high altitudes in the stratosphere. It was created in response to the arrival of modified Junkers Ju 86[?] bombers flying reconnaissance missions which suggested the Luftwaffe might attempt to re-open bombing of England at high altitudes. In the end this threat never materialized, and the Welkin was produced only in small numbers.

The Welkin was essentially a modified Whirlwind, fitted with a much larger wing, new engines in the form of Rolls Royce Merlin 76/77's, and a pressurized cockpit. The last item required the majority of the effort in designing the Welkin. After extensive development a new cockpit was developed that was built out of heavy-gauge duraluminum bolted directly to the front of the main spar. The cockpit hood used an internal layer of thick perspex to hold the pressure, and an outer thin layer to form a smooth line. Heated air was blown between the two to keep the canopy clear of frost.

When the pressurization system was driven by a Rotol supercharger attached to the left-hand engine, providing a constant pressure of 3.5 lbs/sq in over the exterior pressure. This resulted in an apparent altitude of 24,000 ft when the plane was operating at its design altitude of 45,000 ft. This apparent altitude is still too high for normal breathing, the the pilot still had to wear an oxygen mask during flight. A rubber gasket filled with the pressurized air sealed the canopy when the system was turned on, and a valve ensured the pressure was controlled automatically.

Other than that, changes were minor. The wings were so large that the Fowler flaps used on the Whirlwind weren't needed, and were replaced by a simple split-flap. The extra wing area also required more stability, so the tail was lengthened to provide more arm.

By the time the plane was complete and rolling off the line, it was apparent that the Germans had lost interest in the high-altitude mission, and in the end only 75 Welkins were produced. A two seat version known as the Welkin Mk. II was produced in only two examples.

Links:

Westland Welkin (http://www.military.cz/british/air/war/fighter/welkin/welkin_en.htm)