De Havilland Sea Vixen - Development

Development

The aircraft was designated the DH.110 by de Havilland; a twin-engined all-weather fighter, development of which started in 1946 following discussions with the Admiralty of its requirements for jet all-weather fighters. De Havilland's design shared the twin-boom layout of the de Havilland Vampire, had an all-metal structure and featured swept wings. It was to be powered by two Rolls-Royce Avon engines, each capable of 7,500 lbf (33 kN) of thrust, which would allow the aircraft to be supersonic in a shallow dive. The DH 110 was the first British two seat combat aircraft to achieve supersonic speed. Armament was to be four 30 mm ADEN cannons. In January 1947, specifications N.40/46 and F.44/46 were issued by the British Air Ministry for similar night-fighters to equip the Fleet Air Arm (FAA) and Royal Air Force (RAF), with nine prototypes being ordered for the RAF (together with four of the competing Gloster Javelin) and four prototypes for the Fleet Air Arm. In 1949, however, the Royal Navy decided to buy the de Havilland Sea Venom, which as a development of an existing type was cheaper and available quickly to meet its immediate needs for a jet-powered night fighter to replace its piston-engined de Havilland Sea Hornets, while the RAF cut its order back to two prototypes. Despite this, de Havilland continued with the project.

The prototype took to the skies on 26 September 1951 piloted by John Cunningham; the aircraft's performance exceeded expectations, and by the following year it was regularly flying faster than the speed of sound. However, tragedy struck while the aircraft was being demonstrated at the Farnborough Airshow on 6 September 1952. Following a demonstration of its ability to break the sound barrier, the aircraft disintegrated, killing 31 people, including the crew of two: test pilot and record breaker John Derry and Tony Richards. The failure was traced to faulty design of the end sections of the main spar, which resulted in the outer ends of the wings shearing off during a high-rate turn. The subsequent shift in the DH.110's centre of lift caused the aircraft to lurch violently, creating forces of over 12 g, resulting in the cockpit and tail sections breaking away and the engines being torn from the airframe. One of the engines hit an area crowded with spectators at the end of the runway, causing the majority of casualties. Other spectators were injured by debris from the cockpit landing close to the main spectator enclosures alongside the runway. This incident led to a major restructuring of the safety regulations for air shows in the UK and since this crash no member of the public has died as a result of an airshow accident in the UK.

Owing to this incident, modifications were made to the second prototype, including the fitting of an all-moving tailplane, the modified aircraft not flying again until July 1954. By this time, the RAF had abandoned its interest in the DH.110, choosing instead the Gloster Javelin but the Fleet Air Arm decided to adopt the DH.110 to replace its interim Sea Venoms. In 1955, a semi-navalised variant was produced as a prototype, including changes of the leading edge profile and strengthening of the wings, making its first flight that same year. The following year, the aircraft made its first arrested deck landing on the fleet aircraft carrier HMS Ark Royal. The first true Sea Vixen, the Sea Vixen FAW.20 (fighter all-weather, later redesignated FAW.1), first flew on 20 March 1957; and on 2 July 1959, the first Sea Vixen equipped squadron formed.