Spitfire PR Mk X fitted with pressure cockpit
The development of the Spitfire into photo-reconnaissance (PR) variants continued with the PR.X and PR.XI, representing the second generation of these specialized aircraft. These models were powered by advanced 60 or 70 series Merlin engines and incorporated airframe characteristics from the fighter versions Mk.IX, Mk.VII, and Mk.VIII.
Spitfire PR.XI
- Development and Service Entry: The unpressurised PR.XI was the first to appear, with its maiden flight in November 1942, quickly entering service due to the urgent demand for effective PR Spitfires. Initial conversions of Mk.IX fighters into PR.IXs by the Photographic Reconnaissance Unit (PRU) at Benson involved fitting two cameras in the rear fuselage, although these lacked the wing tanks of later PR.XI models.
- Variants:
- Early PR.XI (Type 374): These were converted from Mk.IX airframes and featured Merlin 61 or 63 engines, a fixed tailwheel, and the original Mk.IX fin and rudder.
- Definitive PR.XI (Type 365): These incorporated Merlin 70 engines, a retractable tailwheel, and a pointed fin and rudder. Some later models even had Merlin 77 engines.
- Wing Configuration: All PR.XIs had standard span wings.
- Camera Equipment: Standard camera setups included options similar to the earlier PR.IV, with configurations such as two vertical and one oblique F.24 camera, or two vertical F.24s or F.52s. Later aircraft featured a universal mounting system, allowing for quick changes in camera configuration.
- Production and Service Duration: The PR.XI became the main photo-reconnaissance Spitfire variant from 1943, with a total of 471 units built. The last PR.XI was delivered in February 1945.
Spitfire PR.X
- Development and Service Entry: The pressurised PR.X entered service significantly later, in 1944, due to its low priority status. Only 16 units were produced. The PR.X featured the pressure cabin characteristics of the Spitfire Mk.VII but was otherwise similar to the PR.XI.
- Operational Challenges:
- The PR.X was not popular with pilots and was operational with only two squadrons for a brief period of just over a year.
- It was realized that pressurisation was unnecessary for most reconnaissance sorties.
- The thick canopy of the PR.X reduced visibility, which was a crucial factor for reconnaissance missions.
- The added complexity of maintaining the pressure cabin systems also proved to be a disadvantage.
The Spitfire PR.XI and PR.X played essential roles in aerial reconnaissance during World War II. The PR.XI, with its versatility and robust performance, became the predominant PR variant, while the PR.X, despite its advanced pressurization system, was less favored due to operational inefficiencies and limited need for high-altitude reconnaissance. These aircraft highlighted the adaptability of the Spitfire platform to meet diverse mission requirements, contributing significantly to the Allies’ intelligence-gathering efforts.