Spitfire Mk 21, serial DP851 on the ground
The Spitfire F.21, initially known as the Victor due to its significant departures from previous Spitfire designs, represented the zenith of the Spitfire’s evolution. This model introduced a range of advancements, particularly in its wing design and powerplant, which were aimed at harnessing the full potential of the Griffon 61 engine.
Development and Features
Prototypes and Early Development:
- The Spitfire PP139, considered the production prototype for the Spitfire 21, first flew on 24 July 1943.
- A second prototype fitted with a Griffon 61 and modified wing served as the interim standard Mk.21 prototype, flying in October 1942.
Design Characteristics:
- Engine: Equipped with the Griffon 61 engine featuring a two-speed/two-stage supercharger, delivering significantly more power than earlier Merlins.
- Propeller: A larger diameter five-bladed propeller, with some later models featuring contra-rotating propellers.
- Wing Design: The Spitfire 21 introduced a completely new wing, with a different aerofoil section and internal structure. This wing had a marginally increased span and area, featured wider span ailerons, and mounted a pair of 20mm cannon in each wing. The classic elliptical shape was altered.
- Fuselage and Tail: Combined elements of the Mk.VIII and XIV, including the broad chord fin and rudder, retractable tailwheel, and lengthened undercarriage struts for fully enclosed wheels when retracted.
- Electrical System: The last 15 production models were updated from a 12-volt to a 24-volt electrical system.
Operational History
Initial Production and Issues:
- The production prototype flew in July 1943, with the first production model following in January 1944.
- The RAF received its first Spitfire 21s in August 1944, but operational clearance was not granted until March 1945 due to prolonged development and handling issues.
- Handling problems, especially instability in the yawing plane, plagued the Spitfire 21. These issues led the Air Fighting Development Unit (AFDU) to recommend against its continued use, favoring the Hawker Tempests or Spitfire XIVs instead.
Final Verdict and Production:
- Despite its potential, only 120 production Spitfire 21s were built out of the 3,000 ordered.
- By the time it was cleared for service, the European war was nearly over, and the need for the aircraft had diminished. The last Spitfire F.21 was flown in December 1945.
Conclusion
The Spitfire F.21, though embodying advanced features and improvements, struggled to overcome its handling problems. The critical evaluation by the AFDU, combined with the war’s imminent end, curtailed its deployment. It marked the final chapter in the Spitfire’s storied history, embodying both the peak of its development and the conclusion of its frontline service.