Supermarine Spitfire (Griffon-powered variants)
| Spitfire | |
|---|---|
|
|
| Spitfire F Mk 22 of 607 (County of Durham) Sqn, Royal Auxiliary Air Force. | |
| Role | Fighter/ Fighter reconnaissance/ Photo reconnaissance. |
| Manufacturer | Supermarine |
| Designer | Joseph Smith. |
| First flight | 27 November 1941 (Mk IV) |
| Introduction | October 1942 (Mk XII) |
| Retired | 1955, RAF |
| Primary user | Royal Air Force |
| Produced | 1942–48 |
| Variants | Seafire, Spiteful, Seafang |
The Rolls-Royce Griffon engine was designed in answer to Royal Navy specifications for an engine capable of generating good power at low altitudes. Concepts for adapting the Spitfire to take the new engine had begun as far back as October 1939; Joseph Smith felt that "The good big 'un will eventually beat the good little 'un." and Ernest Hives of Rolls-Royce thought that the Griffon would be "a second power string for the Spitfire". The first of the Griffon-engined Spitfires flew on 27 November 1941.
Although the Griffon-engined Spitfires were never produced in the large numbers of the Merlin-engined variants they were an important part of the Spitfire family, and in their later versions kept the Spitfire at the forefront of piston-engined fighter development. This article describes the Griffon-powered Spitfire variants.
Wing types
The majority of Spitfires from the Mk VIII used C, D and E wing types. Unless otherwise noted, all Griffon-engined Spitfire variants used the strengthened Dunlop AH10019 "four spoke" pattern mainwheels. With the increasing use of hard-surfaced runways in the post-war years, many Spitfires were either manufactured or re-fitted with, larger mainwheels which were of a "three spoke" pattern. These were used on modified undercarriage legs which had reduced "toe-in" for the axles, which reduced tyre scrub.
C type
Also known as the "Universal wing" the new design was standard on the majority of Spitfires built from mid-1942. This wing was structurally modified to reduce labour and manufacturing time plus it was designed to allow mixed armament options, A type, B type or four 20 mm Hispano cannon.
The undercarriage mountings were redesigned and the undercarriage doors were bowed in cross section allowing the legs to sit lower in the wells, eliminating the upper-wing blisters over the wheel wells and landing gear pivot points. Stronger undercarriage legs were raked 2 inches (5.08 cm) forward, making the Spitfire more stable on the ground and reducing the likelihood of the aircraft tipping onto its nose. During production of the Mk VIII and Mk IX, a new undercarriage leg was introduced which had external v-shaped "scissor-links" fitted to the front of the leg; this also led to small changes in the shape of the undercarriage bay and leg fairings. Several versions of the Spitfire, including Mk XIV and Mk XVIII had extra 13 gallon integral fuel tanks in the wing leading edges, between the wing-root and the inboard cannon bay.
The Hispano Mk.II cannons were now belt fed from box magazines allowing for 120 rpg (the Châtellerault system). The fairings over the Hispano barrels were shorter and there was usually a short rubber stub covering the outer cannon port. Redesigned upper wing gun bay doors incorporated "teardrop" shaped blisters to clear the cannon feed motors and the lower wings no longer had the gun bay heating vents outboard of the gunbays. To provide room for the belt feed system of the cannon, the inner machine gun bays were moved outboard between ribs 13 and 14. As the Spitfire was no longer to be used as a night fighter, the retractable landing lights were no longer fitted.
D Type
These were specifically made for the Photo-Reconnaissance Spitfires, including the PR XIX; no armament was fitted and the D-shaped leading edges of the wings ahead of the main spar, were converted into integral fuel tanks, each carrying 66 gallons. To avoid the expansion of fuel in hot weather damaging the wing, pressure relief valves, incorporating small external vent pipes, were fitted near the wing tips.
E type
Structurally unchanged from the C wing, the outer machine gun ports were eliminated, although the outer machine gun bays were retained and their access doors were devoid of empty cartridge case ports and cartridge case deflectors. The inner gun bays allowed for two weapon fits;
- 2 × 20 mm Hispano Mk II cannon with 120 rounds-per-gun (rpg) in the outer bays combined with 2 × .50 cal Browning M2 machine guns, with 250 rpg in the inner bays. With the relocation of the Hispano to the outer gun bay the blisters covering the feed motors were moved outboard on the gun bay doors.
or
- 4 × 20 mm Hispano cannon with 120 rpg (this configuration was rarely fitted.)
The 20 mm Hispano cannon were moved outboard and a more effective .50 calibre Browning .50 cal M2/AN heavy machine gun with 250 rpg was added to the inner gun-bay replacing the outer Browning .303s. The first trial installation of the installation (modification 1029) was made in BS118, a Mark XI in November 1943. This armament later became standard for all Spitfire Mk XIVs used by 2 TAF as fighters. The improved armament was more effective for both air-to-air engagements and air-to-ground attacks.
The Mk XII flew operationally with their rounded wingtips replaced by shorter, squared off fairings; the single-stage supercharger of the Griffon II or IV used in the Mk XIIs meant that it was rated and used as a low altitude fighter and the LF prefix used by Merlin-powered Spitfires was never applied. Starting in early 1945 most Spitfire Mk XIVs also used clipped wing tips, mainly to reduce wrinkling of the wing's skin; again the LF prefix was not applied to these aircraft.
Redesigned late wing
As the Spitfire gained more power and was able to fly at greater speeds the risk of aileron reversal was increasing so the Supermarine design team set about redesigning the wings to counter this possibility. The original wing design had a theoretical aileron-reversal speed of 580 mph (930 km/h), which was somewhat lower than that of some contemporary fighters. The new wing of the Spitfire F Mk 21 and its successors was designed to help alleviate this problem; the wing's stiffness was increased by 47 percent and a new design of aileron using piano hinges and geared trim tabs meant the theoretical aileron-reversal speed was increased to 825 mph (1,328 km/h). This wing entered service on the Spitfire XXI. The standard armament was now four 20mm Hispano IIs or the shorter, lighter Hispano V cannons, each with 150 rounds per gun.