The Supermarine Seafire Mk.Ib was a version of the Spitfire Mk.V converted to serve as an interim naval fighter before the arrival of a purpose-built Seafire.
The Admiralty had failed in an attempt to procure a naval version of the Spitfire I in 1940, but by 1941 it was clear that the Fleet Air Arm needed a modern fighter, and the Air Ministry agreed to release a number of Spitfire Mk.Is and 48 Mk Vbs. Two Spitfire Vs (AD205 and AD371) were sent to Worthy Down, where by the end of 1941 they had been equipped with arrestor hooks and catapult spools. By the end of 1941 a third Spitfire, BL676, had been sent to RNAS Arbroath, where it was given an A-frame arrestor hook, and was used for deck trails. It was joined by AD371 in February 1942.
BL676's next move was from Arbroath to the Air Service Training Unit, where it was converted into the first fully modified Seafire. This involved fitting it with catapult spools, slinging points, a tropical filter and a 30 gallon auxiliary fuel tank and strengthening the fuselage at key points. It already had an arrestor hook. The aircraft emerged on 23 March 1942 with a new name, Seafire (the name was suggested by the wife of one of the design team, and replaced Sea Spitfire), and a new serial number, MB328.
The Air Service Training Unit was given a contract to convert 48 Spitfire Vbs to the Seafire Ib standard, although without catapult spools (it isn't entirely clear if this includes MB328).
Cunliffe-Owen at Southampton, a Supermarine subcontractor, were given a contract to produce 118 Seafire Ibs, complete with catapult spools, bringing production up to 166 aircraft.
The Seafire Ib had a limited front line career. The first aircraft entered service in June 1942, and No.801 Squadron was fully equipped with the type by the time in embarked on HMS Furious in October 1942. No.842 Squadron also received a number of Seafire Ibs before joining the Furious in the summer of 1943.
The Seafire Ib was also used in small numbers by No.1 and No.2 Naval Fighter Schools, the School of Naval Warfare, RNAS Lee-on-Solent, RNAS Stretton, and No.760 (Reserve) Squadron.
Supermarine Type 340
Engine: Single-speed single-stage supercharged Merlin 45 or 46
Power: 1,470hp or 1,415hp
Wing span: 36ft 10in
Length: 30ft 2.5in
Height: 11ft 5.5in
Empty Weight: 5,100lb
Loaded Weight: 6,700lb
Max Speed: 365mph at 16,000ft
Service Ceiling: 36,400ft
Range: 492 miles
Armament: Two Hispano 20mm cannon and four 0.303in Browning machine guns
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