Spitfire Mk XII MB878, trials with 500lb bomb in 1943
Griffon-Engined Spitfires
The pursuit of enhanced performance for the Spitfire led to the incorporation of the more powerful Rolls-Royce Griffon engine. With a capacity one-third greater than the Merlin, the Griffon promised significantly higher power outputs.
Early Development
- Initial Prototypes: Supermarine began developing the Spitfire with the Griffon engine in early 1940. Two prototypes were ordered, designated as Mk.IV initially but later changed to Mk.XX to avoid confusion with the PR.IV.
- First Flight: The first Mk.XX, powered by a 1,735 hp Griffon IIB with a two-speed/single-stage supercharger and a four-bladed propeller, flew on 27 November 1941. An order for 750 Mk.XXs was placed, but circumstances led to the development of a different version for production.
Production Version: Spitfire F.XII
- Development and Role: The need for a high-performance fighter at low altitude to counter Fw 190 ‘hit and run’ raids on England’s south coast led to the development of the F.XII. This version used the low-rated Griffon III or IV engine. The first prototype F.XII, converted from the first Mk.XX, flew on 24 August 1942, with the first production aircraft flying in October 1942.
- Design Features:
- Engine Cowling: The Spitfire XII featured a restyled engine cowling to accommodate the larger Griffon engine, which had a lower thrust line and rotated in the opposite direction compared to the Merlin.
- Wings and Rudder: It had clipped ‘C’ wings and a pointed rudder. Early aircraft were based on the Mk.V airframe with a fixed tailwheel, while later examples used the Mk.VIII airframe with a retractable tailwheel.
- Fuel Capacity: The internal fuel capacity was the same as the earlier Spitfire I/II/V models, resulting in a poor range. A 30 imperial gallon (136-liter) drop tank slightly extended the range, but this was not a major issue given the aircraft’s short-range interception role.
Operational Use
- Entry into Service: The Spitfire XII entered service in February 1943, serving with two RAF home defense squadrons until 1944.
- Performance and Missions: The Spitfire XII was very fast at low altitudes and excelled in its intended role. It worked effectively alongside Typhoon squadrons. Notably, on one occasion in May 1943, Spitfire XIIs of 91 Squadron claimed five Fw 190s in a single day. The aircraft also participated in shipping reconnaissance missions and fighter sweeps into France.
The incorporation of the Griffon engine marked a significant enhancement in the Spitfire’s performance, particularly at low altitudes, fulfilling critical defense needs during World War II.