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The Folland Gnat is a British compact swept-wing subsonic fighter aircraft that was developed and produced by Folland Aircraft. Envisioned as an affordable light fighter in contrast to the rising cost and size of typical combat aircraft, it was procured as a trainer aircraft for the Royal Air Force (RAF) as well as by export customers, who used the Gnat in both combat and training capacities.
Designed by W. E. W. Petter, the Gnat has its origins in the preceding private venture Folland Midge. The issuing of Operational Requirement OR.303 by the British Air Ministry served to motivate the type's development; the Gnat was later submitted to meet this requirement. Its design allowed for its construction and maintenance tasks to be carried out without specialised tools, making it suitable for use in countries that had not yet become highly industrialised.Taylor 1969, p. 365.Willis 2008, p. 40. The Gnat has been viewed as a major motivating factor towards the issuing of the NATO NBMR-1 requirement, which sought to make available a common strike/attack light fighter with which to equip the air forces of the various NATO members.
Although never used as a fighter by the Royal Air Force (RAF), the Gnat T.1 jet trainer variant was adopted and operated for some time. In the United Kingdom, the Gnat became well known due to its prominent use as the display aircraft of the RAF's Red Arrows aerobatic team. The Gnat F.1 was exported to Finland, Yugoslavia and India. The Indian Air Force became the largest operator and eventually manufactured the aircraft licence-built. Impressed by its performance during combat, India proceeded to develop the improved HAL Ajeet, a modified variant of the Gnat. In British service, the Gnat was replaced by the Hawker Siddeley Hawk.
Petter examined the prospects for producing a more affordable but capable "light fighter", including a survey of available modern engines to power the type. Having identified suitable powerplant arrangements along with methods of making multiple key design aspects, such as the manufacturing of the fuselage and wings, more affordable, Folland promptly commenced work upon this lightweight fighter concept, financing the project using existing company funds. The light fighter project soon received the Fo-141 designation along with the name Gnat. Flight 20 August 1954, p. 228. 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. Flight 3 April 1953, p. 426.
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. The emergence of new lightweight turbojet engines, several of which were well advanced in their own development process, also enabled the envisioned light fighter concept to be realised. The Gnat was initially intended to be powered by a Bristol BE-22 Saturn turbojet engine, capable of generating 3,800 lbf (16.9 kN 1,724 kgp) of thrust. However, development of the Saturn was cancelled; in its place, the more capable but not immediately available Bristol Orpheus turbojet engine was adopted instead.
In order that the project would not be delayed before reaching the prototype stage, Petter's unarmed proof-of-concept demonstrator for the Gnat was instead powered by the less powerful Armstrong Siddeley Viper 101 turbojet engine, capable of generating 1,640 lbf (7.3 kN / 744 kgp) of thrust. While using a different powerplant from later-built prototypes and production aircraft, the demonstrator still used a nearly identical airframe along with similar onboard systems so that these could be proved in advance of the Gnat itself being built. This demonstrator was designated Folland Midge. On 11 August 1954, the Midge performed its maiden flight, piloted by Folland's chief test pilot Edward Tennant. Flight 20 August 1954, p. 229. 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.Frédriksen 2001, p. 133. 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.Willis 2008, p. 43. 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. On 18 July 1955, the Folland prototype, serial number G-39-2, first flew from RAF Boscombe Down, Wiltshire..
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). Although the Gnat's development is considered a factor which motivated the Mutual Weapons Development Team to issue the NATO NBMR-1 requirement for a low level strike/attack light fighter, the Gnat itself was not evaluated in the competition, which was won by the Fiat G.91. "Fighter Competition with a Worthwhile Prize". New Scientist, 2(46), 3 October 1957, p. 10. ISSN 0262-4079. 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. "Bright Future for Light Fighters." New Scientist, 4(80), 29 May 1958, p. 56. ISSN 0262-4079. The Hawker Hunter was selected as the eventual winner of the fly-off competition.
Folland proposed the two-seat Fo. 144 Gnat Trainer. The trainer model featured several changes, including the adoption of a new wing with additional fuel capacity, which in turn allowed for more internal space within the fuselage to be allocated for additional equipment. A more powerful variant of the Orpheus engine was also used, while the length of the forward fuselage area was increased, and the tail surfaces were enlarged. The inboard ailerons of the fighter variant were reconfigured to an arrangement of outboard ailerons and conventional flaps. On 7 January 1958, an initial contract for 14 pre-production Gnat trainers was issued.Willis 2008, p. 53.
On 31 August 1959, the prototype Gnat Trainer conducted its maiden flight from RAF Chilbolton, Hampshire.Burnet 1982, p. 62. 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.Burnet 1982, p. 63. The final Gnat T.1 for the RAF was delivered in May 1965.
In 1960, Maurice Brennan joined Folland as its chief engineer and director. Hawker Siddeley wanted to use his knowledge of variable-geometry wings in future designs.Wood 1975, p. 197. 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 hydraulics-driven positioned at the inner ends of the wings. The wings could be swept from 20 degrees to 70 degrees; at the 70-degree position, longitudinal control was maintained by wing tip-mounted , and at the 20-degree position by a retractable canard arrangement. Auto-stabilisation was also to be used. By providing Trim tab with the canard, a large tailplane was not needed, as would have been on designs without a canard configuration.Wood 1975, pp. 198–199.
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.Wood 1975, p. 199. 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.
The Gnat design used a conventional metal stressed-skin structure, with extensive flush-. To reduce workload and cost, intensive fabrication methods such as machining, forging, and casting were minimised. The airframe could be constructed using simple jigs without any specialised skills or tooling. The wing (for example) could be produced at a quarter of the cost, with less than one-fifth the labour, required for the wings of other contemporary fighter aircraft. Similarly, the layout and construction techniques used allow the airframe to be rapidly disassembled into its major subsections, without the use of cranes or ladders; the Gnat was vastly easier to service than most other aircraft.
Gnat F.1 proved initially problematic in the harsh Finnish conditions. Finland was the first operational user of Gnat F.1, and the plane still had many issues yet to be resolved. All Gnats were grounded for half a year on 26 August 1958 after the destruction of GN-102 due to a technical design error in its hydraulic system, and the aircraft soon became the subject of severe criticism. Three other aircraft were also destroyed in other accidents, with two pilots ejection seat and one being killed. Once the initial problems were ironed out, the plane proved to be extremely manoeuvrable and had good performance in the air, but also to be very maintenance intensive. The availability of spare parts was always an issue, and its maintenance a challenge to the conscript mechanics. The Gnats were removed from active service in 1972 when the Häme Wing moved to Rovaniemi, and when the new Saab 35 Drakens were brought into use.
Unlike the RAF, the IAF did not operate trainer variants of the Gnat. The Gnat had a tendency to pitch up sharply on raising the undercarriage; almost all new pilots would find it difficult to control the anticipated pitch up. Consequently, the Gnat was an extremely difficult aircraft to handle in the early stages of training, so IAF pilots generally qualified first on Hawker Hunter trainers, which gave them experience on powered controls. A pilot would then do a brief full throttle run on the runway in the Gnat, before flying solo. With sufficient experience, pilots would exploit the nimble mini-sized aircraft to its limits.
The Gnat proved to be a frustrating opponent for the larger and heavier Canadair Sabre operated by Pakistan.Bingham 2002.. "Canadair CL-13 Sabre." RCAF. Retrieved 4 November 2010. The Gnat's success during the 1965 and 1971 Indo-Pakistani Wars was dependent on tactics, pilot skill, and sortie context. Tactics utilised by IAF Gnat pilots included drawing Sabre pilots into vertical contests, where the Sabres were at a disadvantage. As the Gnat was lightweight and compact in shape, it was hard to see, especially at the low levels where most dogfights took place.
is credited by many independent and Indian sources as having shot down seven North American F-86 Sabres in the Indo-Pakistani War of 1965.Rakshak, Bharat. "Indian Air Force Combat Kills, Indo Pakistan War 1965." History. Retrieved 4 November 2010.Spick 2002, p. 161. One Gnat was captured by Pakistani forces, following a forced landing, during the initial phase of the 1965 war. IAF Squadron Leader Brij Pal Singh Sikand later reported that he had experienced a complete electrical failure on his Gnat, after separating from his formation to fight a lone Sabre; Sikand landed at an abandoned Pakistani airstrip at Pasrur. Two PAF Lockheed F-104 Starfighter pilots subsequently claimed a role in forcing down Sikand's Gnat. (2005). 9788173046414 ISBN 9788173046414.. (This Gnat has since been displayed at the Pakistan Air Force Museum, Karachi.) On 16 December 1965, after a ceasefire was agreed, a Pakistani Cessna O-1 was also shot down by a Gnat pilot.
Gnats were used again by India in the Indo-Pakistani War of 1971.Pike, John. "Squadron 22 'Swifts'." Global Security. Retrieved 4 November 2010. "Folland Gnat F1." RAF Museum. Retrieved: 4 November 2010. Apart from air defence operations, in the Bangladesh Liberation War, Gnats flew anti-shipping operations, ground attack, bomber/transport escort and close air support operations. During the Battle of Boyra the first over East Pakistan (Bangladesh) took place. IAF Gnats shot down two PAF Canadair Sabres and badly damaged one. Another dogfight involving a Gnat was over Srinagar airfield where a lone Indian pilot held out against six Sabres, shooting two in the process, before being shot down.Mirza. Wg Cdr Salim Baig, PAF. "Air Battles" Bharat Rakshak. December 1971. Retrieved 4 November 2010. "Official Citation of the PVC to NIrmal Jit Singh Sekhon." Bharat Rakshak. Retrieved 4 November 2010. "Param Vir Chakra." Bharat Rakshak. Retrieved 4 November 2010. Gnat pilot Nirmal Jit Singh Sekhon was posthumously honoured with the Param Vir Chakra (India's highest gallantry award), becoming the only member of the IAF to be given the award.
The Gnat was nicknamed "Sabre Slayer" within the IAF, since most of its combat kills during the two wars were against PAF Sabres – despite the Canadair Sabre Mk 6 being widely regarded as the best dogfighter of its era.Bingham 2002.. "Canadair CL-13 Sabre." RCAF. Retrieved 4 November 2010. Tactics called for Gnats taking on the Sabres in the vertical, where the Sabres were at a disadvantage. As the Gnat was lightweight and compact in shape, it was hard to see, especially at the low levels where most dogfights took place. While the IAF was impressed by the Gnat's performance in the two wars, the aircraft had many technical problems including hydraulics, a temperamental pair of Aden 30 mm cannons which often failed in-flight, significant "bent thrust" on take-off, leading to many aborted take-offs and an unreliable control system. To address these failings, the IAF issued a requirement for an improved "Gnat II" in 1972, at first specifying that the new version was to be optimised as an interceptor but then expanding the specification to include ground attack. Over 175 of an Hindustan Aeronautics Limited licence-built variant, the HAL Ajeet ( ajeet meaning "unconquerable"), were produced in Bangalore. The Ajeet, in effect, expanded the IAF's Gnat fleet, and the two types were reportedly phased out in tandem, with their final retirement occurring in 1991.
Several ex-IAF Folland Gnats have survived, in private hands. Some Gnats, including one that had participated in the 1971 war in East Pakistan, were presented to the Bangladesh Air Force. "Folland/HAL Gnat." Warbirds of India. Retrieved 31 January 2011.
Once pilots graduated from basic training on the BAC Jet Provost and gained their wings they were selected for one of three streams: fast jet, multi-engined, or helicopter. Those selected for fast jets were posted to RAF Valley for advanced training on the Gnat T.1, typically 70 hours of flying. Students would then move on to operational training using the Hawker Hunter, followed by a posting to an operational conversion unit for the type of aircraft to be flown.
Following the introduction of the Hawker Siddeley Hawk into the training role as a replacement the Gnats were withdrawn from service. The largest operator 4 FTS retired its last Gnat in November 1978. Most of the retired Gnats were delivered to No. 1 School of Technical Training at RAF Halton and other training establishments to be used as ground training airframes. When the RAF had no need for the Gnats as training airframes they were sold off. Many were bought by private operators and some are still flying today. The final RAF operator of the Gnat was the Red Arrows, which retained their aircraft through the 1979 display season. The team received its first Hawk in August 1979 and converted fully from the Gnat for the 1980 display season. Coventry Evening Telegraph Saturday 18 August 1979, page 14
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