The Supermarine Seafire was a naval version of the Supermarine Spitfire adapted for operation from aircraft carriers. The name Seafire was arrived at by abbreviating the longer name Sea Spitfire.
Origins of the Seafire
The Admiralty first showed an interest in the idea of a carrier-borne Spitfire in May 1938 when, during a meeting with Richard Fairey (of Fairey Aviation), Fairey proposed that his company could design and build such an aircraft. The idea met with a negative response and the matter was dropped. As a result, the Fleet Air Arm (FAA), at that point still part of the Royal Air Force, was forced into having to order Blackburn Rocs and Gloster Sea Gladiators, both of which proved to be woefully inadequate. Upon the outbreak of the Second World War, many of the aircraft operated by the FAA were considered to be obsolete in comparison to Germany's land-based fighters; thus the need for more capable aircraft was readily apparent. As the Hawker Hurricane had quickly proven to be adaptable to carrier-based operations, there was considerable interest in navalising the Spitfire as well.
The matter of a seaborne Spitfire was raised again in November 1939 when the Air Ministry allowed a Commander Ermen to fly a Spitfire I. After his first flight in R6718 Ermen learned that Joseph Smith, Chief Designer at Supermarine had been instructed to fit an "A-frame" arrestor hook on a Spitfire and that this had flown on 16 October; a drawing of this aircraft had been shown to the FAA on 27 October. After further discussions Supermarine submitted a drawing of a Spitfire with folding wings and an arrestor hook. In this case the wings were designed with a fold just outboard of the undercarriage bays; the outer wings would swivel and fold backwards, parallel with the fuselage. On 29 February 1940 the Admiralty asked the Air Ministry to sanction the production of 50 folding-wing Spitfires, with the first deliveries to start in July. For various reasons Winston Churchill, who was First Lord of the Admiralty cancelled the order, writing to Lord Beaverbrook: "I regard it as of very great importance that the production of Fulmars should be kept going".
At a time of need for land Spitfires, the diversion of resources to the construction of a naval variant would reduce Spitfire production. To partially cover the gap until the Fulmar's replacement (Specification N.5/40 – which would be the Fairey Firefly) was able to enter service, Grumman Wildcats were ordered from the US for the FAA. These would enter service towards the end of 1940 as the Martlet.
In late 1941 and early 1942, the Admiralty assessed the Spitfire for possible conversion. In late 1941, a total of 48 Spitfire Mk Vb were converted by Air Training Service Ltd. at Hamble to become "hooked Spitfires". This was the Seafire Mk Ib and would be the first of several Seafire variants to reach the Royal Navy's Fleet Air Arm. This version of the Seafire was mainly used to allow the Royal Navy to gain experience in operating the Spitfire on aircraft carriers. The main structural change was made to the lower rear fuselage which incorporated an A-frame style arrestor hook and strengthened lower longerons. It was soon discovered that the fuselage, especially around hatches, was too weak for carrier operations. In an attempt to alleviate this condition, reinforcing strips were riveted around hatch openings and along the main fuselage longerons. A further 118 Seafire Mk Ib's incorporating the fuselage reinforcements were modified from Spitfire Vbs by Cunliffe-Owen at Eastleigh and Air Training Service. These aircraft were equipped with NavalHF radio equipment and IFF equipment as well as a Type 72 homing beacon. In these and all subsequent Seafires the instruments were re-calibrated to read kn and nmi rather than mph and mi. The fixed armament was the same as that of the Spitfire Vb; two 20 mm (.79 in) Hispano Mk II cannon with 60 rpg fed from a "drum" magazine and four .303 in (7.7 mm) Browning machine guns with 350 rpg. Provision was also made to carry a 30 gal (136 l) "slipper" fuel tank under the fuselage. In June 1942, the first deliveries of the Seafire took place to 807 Squadron. Another front line unit, 801 Squadron operated this version on board HMS Furious from October 1942 through to September 1944.
The second semi-naval variant of the Seafire and the first to be built as such, was the Seafire F Mk IIc which was based on the Spitfire Vc. The Vc had several refinements over the Spitfire Vb. Apart from the modifications included in the main batch of Seafire Ibs this version incorporated catapult spools, and a single slinging lug on either side of the fuselage, just behind the engine bulkhead. Three subtypes were produced, the F Mk IIc and FR Mk IIc (fighter reconnaissance), powered by a Merlin 46, and the L Mk IIc powered by a low altitude Merlin 32 specifically manufactured for naval use. This version of the Merlin used a "cropped" supercharger impellor to provide greater power at low altitudes than the standard engines; delivering 1,585 hp (1,182 kW) at 2,750 ft (838 m). Both engine models drove a four bladed 10 ft 9 in (3.28 m) diameter Rotol propeller. Because this version used the "C" wing the Hispano cannon were fed from a 120-round belt magazine, otherwise the armament was the same as that of the Ib; the FR also carried twoF24 cameras. After trials of Rocket Assisted Take Off Gear (RATOG) apparatus (small solid-fuel rocket motors which could be attached to the fuselage or wings of aircraft to help shorten the take-off run) in February 1943, this equipment became a standard fitting available for all Seafires. However, many FAA pilots rarely used RATOG, in part as there was little need for it, and due to the risks posed by an instance of asymmetric ignition.
The IIc was the first of the Seafires to be deployed operationally in large numbers, with Supermarine building 262 and 110 being built by Westland,[nb 1] who also built 30 Seafire Mk III (Hybrid) (Mk IIIs without folding wings).[nb 2] Although developed for aircraft carrier use, this version still lacked the folding wings needed to allow them to be used on board some Royal Navy carriers, some of which had small aircraft elevators unable to accommodate the full wingspan of the Seafires.
The Seafire F Mk III was the first true carrier adaptation of the Spitfire design. It was developed from the Seafire Mk IIC, but incorporated manually folding wings allowing more of these aircraft to be spotted on deck or in the hangars below. Supermarine devised a system of two straight chordwise folds; a break was introduced immediately outboard of the wheel-wells from which the wing hinged upwards and slightly angled towards the fuselage. A second hinge at each wingtip join allowed the tips to fold down (when the wings were folded the wingtips were folded outwards). This version used the more powerful Merlin 55 (F Mk III and FR Mk III) or Merlin 55M (L Mk III), driving the same four-bladed propeller unit used by the IIC series; the Merlin 55M was another version of the Merlin for maximum performance at low altitude. Other modifications that were made on the Spitfire made their way to the Seafire as well including a slim Aero-Vee air filter and six-stack ejector type exhausts. The shorter barrelled, lightweight Hispano Mk V cannon were introduced during production as were overload fuel tank fittings in the wings This Mark was built in larger numbers than any other Seafire variant; of the 1,220 manufactured Westland built 870 and Cunliffe Owen 350. In 1947 12 Mk IIIs were stripped of their naval equipment by Supermarine and delivered to the Irish Air Corps.
After the Mk III series the next Seafire variant to appear was the Seafire F Mk XV, which was powered by a Griffon VI - single-stage supercharger, rated at 1,850 hp (1,379 kW) at 2,000 ft (610 ft) driving a 10 ft 5 in Rotol propeller. Designed in response to Specification N.4/43 this appeared to be a naval Spitfire F Mk XII; in reality the Mk XV was an amalgamation of a strengthened Seafire III airframe and wings with the wing fuel tanks, retractable tailwheel, larger elevators and broad-chord "pointed" rudder of the Spitfire VIII. The engine cowling was different to that of the Spitfire XII series, being secured with a larger number of fasteners and lacking the acorn shaped blister behind the spinner. The final 30 Mk XVs were built with the blown "teardrop" cockpit canopy and cut down rear fuselage introduced on the Spitfire Mk XVI. On the first 50 aircraft manufactured by Cunliffe-Owen a heavier, strengthened A-frame arrestor hook was fitted to cope with the greater weight. On subsequent Mk XVs a new form of "sting" type arrestor hook was used; this version was attached to the reinforced rudder post at the rear of the fuselage and was housed in a fairing below the base of the shortened rudder. A vee-shaped guard forward of the tailwheel prevented arrestor wires getting tangled up with the tailwheel.
390 Seafire XVs were built by Cunliffe-Owen and Westland from late 1944. Six prototypes had been built by Supermarine.
One problem which immediately surfaced was the poor deck behaviour of this mark, especially on take-off. At full power the slipstream of the propeller, which swung to the left (as opposed to the Merlin, which swung to the right), often forced the Seafire to swing to starboard, even with the rudder hard over on opposite lock. This sometimes led to a collision with the carrier's island. The undercarriage oleo legs were still the same of those of the much lighter Merlin engined Spitfires, meaning that the swing was often accompanied by a series of hops. As an interim measure it was recommended that pilots avoid using full power on take-off (+10 lb "boost" maximum was recommended). There were also problems involved with this swing being strongly accentuated in the event of an asymmetric firing of the RATOG equipment. In the event none of the "first generation" Griffon-engine Seafires were to use RATOG at sea unless they were ranged forward of the first crash barrier on deck.
Operational Seafire F.XVIIs of No. 1831 Squadron RNVR at RNAS Stretton
The Seafire F Mk XVII was a modified Mk XV; the most important change was the reinforced main undercarriage which used longer oleos and a lower rebound ratio. This went some way towards taming the deck behaviour of the Mk XV, reduced the propensity of the propeller tips "pecking" the deck during an arrested landing and the softer oleos stopped the aircraft from occasionally bouncing over the arrestor wires and into the crash barrier. Most production XVIIs had the cut down rear fuselage and teardrop canopy (the windscreen was modified to a rounded section, with narrow quarter windows, rather than the flat windscreen used on Spitfires) and an extra 33 gallon fuel tank fitted in the rear fuselage. The wings were reinforced, with a stronger mainspar necessitated by the new undercarriage, and they were able to carry heavier underwing loads than previous Seafire variants. 232 of this variant were built by Westland (212) and Cunliffe-Owen(20).
The Seafire F Mk 45 and FR Mk 45 was the next version of the Seafire to be built and the first to use a Griffon 60 series engine with a two-stage, two speed supercharger. The prototype TM379 had been modified from aSpitfire F Mk 21 prototype by Cunliffe-Owen and featured a "sting" arrestor hook. Because this version was considered to be an "interim" type the wing, which was unchanged from that of the Spitfire 21, was non-folding. The fuel capacity of this variant was 120 gal (545 l) distributed in two main forward fuselage tanks: the lower tank carried 48 gal (218 l) while the upper tank carried 36 gal (163 l), plus two fuel tanks built into the leading edges of the wings with capacities of 12.5 (57 l) and 5.5 gal (25 l) respectively. The Seafire F Mk 45 entered service with 778 Squadron in November 1946 and a few were modified to FR Mk 45s in March 1947 by being fitted with two F24 cameras in the rear fuselage. Fifty F Mk 45s were built by the Castle Bromwich factory.
The Seafire F Mk 46 and FR Mk 46 was a Spitfire F Mk 22 modified to naval standard and featured the cut down rear fuselage and "teardrop" canopy. Again the wing had not been modified to fold. The electrical equipment was changed from a 12 volt system to 24 volts. The fuel system was modified over that of the Seafire 45 to incorporate an extra 32 gal (145 l) fuel tank in the rear fuselage, while the wings were plumbed to allow for a 22.5 gal (102 l) combat tank to be carried underneath each wing. In addition a 50 gal (227 l) drop tank could be carried under the fuselage. In April 1947, a decision was made to replace the Griffon 61s or 64s driving a five bladedRotol propeller unit with Griffon 85s or 87s driving two three bladed Rotol contra-rotating propellers. All but the first few incorporated larger tail units from the Spiteful and Seafang. These two changes transformed the handling of the aircraft by eliminating the powerful swing to starboard of previous Griffon engined variants. 200 of the Mk 46s were ordered but only 24 were built, all by Supermarine.