Rolls-Royce Mustang Mk.X

Overview

The North American Mustang Mk.X, also known as the "Rolls-Royce Mustang" or Mustang X, was an experimental variant of the North American Mustang I, (factory designation Model NA-73) where the Allison engine was replaced by a Rolls Royce Merlin. The improvements in performance led to the adoption of the Merlin, in the form of the licence-built Packard V-1650 version of the Merlin, in following production of the P-51 Mustang. The Mustang, had been designed and developed by North American Aviation in 1940 to a requirement by the British Purchasing Commission for fighters to equip the Royal Air Force. However while the airframe was sound, the engine did not perform well at the high altitudes characteristic of air to air combat over Europe. Rolls Royce took up a recommendation that the Mustang be tested with a Merlin engine and five aircraft were converted. The aircraft were tested by the British and then the US Army Air Forces. It is distinct from the Merlin-powered P-51B/C that later followed. The development proceeded incorporating a Rolls-Royce Merlin 65 medium-high altitude engine along with numerous modifications, in an experimental programme undertaken by Rolls-Royce in 1942.