Supermarine Spitfire Mk XX
The Supermarine Spitfire Mk IV, later redesignated Mk XX, was an experimental British fighter developed during the Second World War. It became the first Spitfire powered by the Rolls-Royce Griffon engine, marking an important stage in the aircraft’s development.
By 1940, Supermarine recognised that the Rolls-Royce Merlin engine would eventually limit further improvements in performance. Therefore, designers investigated fitting the larger and more powerful Griffon engine into the existing Spitfire airframe.
The prototype, serial number DP845, first flew on 27 November 1941, piloted by Supermarine test pilot Jeffrey Quill. It featured a Rolls-Royce Griffon IIB engine producing approximately 1,735 horsepower. This offered considerably more power than earlier Merlin engines.
However, installing the Griffon required several modifications. These included strengthened engine mountings, a redesigned engine cowling, enlarged cooling equipment and a four-bladed propeller. The engine also rotated in the opposite direction to the Merlin, changing the aircraft’s handling characteristics during takeoff.
During development, engineers experimented with several improvements, including braking flaps and a proposed armament of six 20 mm Hispano cannons. Although a mock-up of this armament was fitted, the six-cannon arrangement never entered production.
In early 1942, the aircraft received the designation Mk XX to avoid confusion with the Spitfire PR Mk IV reconnaissance aircraft. Subsequently, DP845 became a development prototype for the Griffon-powered Spitfire Mk XII.
Although the Mk IV / XX never entered production, its development helped establish the foundation for later Griffon-powered Spitfires, including the successful Mk XII, Mk XIV and subsequent variants.
