Folland Gnat

Origins In October 1950, W. E. W. "Teddy" Petter, a British aircraft designer formerly of Westland Aircraft and English Electric, joined Folland Aircraft as its managing director and chief engineer. Almost immediately upon joining the firm, Petter conducted a study into the economics behind modern fighter manufacturing, and concluded that many combat aircraft entailed far too great a cost in terms of man-hours and material to be readily mass-produced during a major conflict. Development of the Gnat and the specifics of its design were heavily influenced by the issuing of Operational Requirement OR.303, which sought a capable lightweight fighter aircraft. Work to develop the Gnat went ahead, irrespective of any external orders or financing; there was no funding provided to support the type's early development from any British government department, such as the Ministry of Supply. Petter believed that a compact and simplified fighter would offer the advantages of low purchase and operational costs, and that the Gnat should be capable of being manufactured both cheaply and easily. Despite the low-powered engine, the compact jet was able to break Mach 1 while in a dive and proved to be very agile during its flying trials. On 26 September 1955, the Midge was destroyed in a crash, which had possibly been due to human error by a pilot from a potential overseas purchaser. The Midge, partly due to its nature as a private venture, had only a short lifespan, however had served as a proof-of-concept demonstrator for the subsequent aircraft. It had failed to interest the RAF as a combat aircraft at that time, but officers did issue encouragement of the development of a similar aircraft for training purposes. The larger Gnat, which was being developed in parallel with the Midge, was an improved version of the original fighter design; it was differentiated by larger air intakes to suit the Orpheus engine, a slightly larger wing, and provision for the installation of a 30 mm ADEN cannon in each intake lip. The first prototype Gnat was built as a private venture by Folland. Subsequently, six further aircraft were ordered by the British Ministry of Supply for evaluation purposes. Although the evaluation by the British brought no orders for the lightweight fighter, orders were placed by Finland and Yugoslavia. India placed a large order for the type, which included a licence for production by Hindustan Aeronautics Limited (HAL). However, the Gnat was evaluated in 1958 by the RAF as a replacement for the de Havilland Venom, as well as other light aircraft such as the BAC Jet Provost. The Hawker Hunter was selected as the eventual winner of the fly-off competition. Trainer Although RAF interest in the possibilities for using the Gnat as a fighter had waned, Folland identified a potential use for the type as a trainer aircraft. Accordingly, the aircraft was modified to conform with the requirements of Specification T.185D, which had called for an advanced two-seat trainer aircraft that could transition pilots between the current de Havilland Vampire T 11 and operational fighters, such as the supersonic English Electric Lightning. On 31 August 1959, the prototype Gnat Trainer conducted its maiden flight from Chilbolton airfield, Hampshire. The Ministry did not at first place a production order as they were concerned about the size and ability of the company to take on a large order. Following the take over of Folland by Hawker Siddeley Aviation (becoming the Hamble division), further orders for 30, 20 and 41 trainers were placed between February 1960 and March 1962, receiving the designation Gnat T Mk. 1. The final Gnat T.1 for the RAF was delivered in May 1965. Further development Folland sought to develop more capable versions of the Gnat; one of the more substantial of these proposals was tentatively designated as the Gnat Mk.5. This model was to be capable of supersonic speeds and was intended to be made available in both single-seat and twin-seat configurations, enabling its use in the trainer and interceptor role. The Gnat 5 was to be powered by either a pair of Rolls-Royce RB153R engines or two Viper 20 engines; in the interceptor role, it would be also equipped with a Ferranti AI.23 Airpass radar and armed with a pair of de Havilland Firestreak air-to-air missiles. Under his direction, a variable geometry wing was applied to the basic Gnat 5 design to produce two different configurations – one tailless and one with a conventional tail – for a multipurpose fighter/strike/trainer, designated the Fo.147. The design used a unique mechanism to sweep the wings; this mechanism used a combination of tracks positioned on the fuselage sides, the centerline, and on the underside of the wings, and was actuated by hydraulically-driven ball screws positioned at the inner ends of the wings. The Fo.147 was to have been capable of speeds in excess of Mach 2, with the speed limit set by the temperature of the structure as a result of kinetic heating. It had a maximum all-up weight of , comparing well with the Gnat 5's more restrictive maximum. According to aviation author Derek Wood, the Fo.147: "would have provided a first-class flying test-bed for variable geometry theories...even a VG conversion of the standard Gnat Mk 2 fighter would have been an invaluable research tool". However, neither the Fo.147 nor its successor, the Fo.148, would be developed to the prototype stage; the RAF showed little interest in the need for a variable-geometry trainer, although it intended to procure the General Dynamics F-111K strike aircraft. ==Design==