Folland Gnat

Folland Aircraft

Company type	Private company
Industry	Aerospace
Founded	1950
Founder	W. E. W. Petter
Headquarters	United Kingdom
Products	Folland Gnat fighter and trainer aircraft

The Folland Gnat is a compact British swept-wing subsonic fighter aircraft developed by Folland Aircraft to provide an economical light fighter option amid escalating costs of combat aircraft. It fulfilled roles as a trainer aircraft for the Royal Air Force (RAF) and was also exported for both combat and training purposes.

Conceived by W. E. W. Petter, the Gnat originated from the privately funded Folland Midge. Its development was driven by the British Air Ministry's Operational Requirement OR.303. The design emphasized ease of manufacture and maintenance without the need for specialised equipment, making it attractive to less industrialised nations. Additionally, the Gnat influenced NATO’s NBMR-1 specification aimed at standardizing a light fighter across allied air forces.

While the RAF did not deploy the Gnat as a frontline fighter, it adopted the Gnat T.1 variant as a trainer, gaining prominence through use by the RAF's Red Arrows aerobatic squadron. The Gnat F.1 saw export success in Finland, Yugoslavia, and India, with India becoming the largest operator and producing the aircraft under licence. Drawing on operational experience, India further developed an enhanced model known as the HAL Ajeet. Eventually, the RAF phased out the Gnat in favour of the Hawker Siddeley Hawk.

Origins

In October 1950, British aircraft designer W. E. W. Petter, previously associated with Westland Aircraft and English Electric, joined Folland Aircraft as managing director and chief engineer. He observed that many fighters in service at the time, including the RAF’s Hawker Hunter and Gloster Javelin, were expensive to produce in large quantities during wartime.

Petter began investigating ways to create a "light fighter" that would be both capable and affordable, focusing on selecting appropriate engines and cost-efficient manufacturing techniques. This initiative led Folland to privately finance development of the Fo-141 Gnat. Although aligned with Operational Requirement OR.303 for a lightweight fighter, initial government funding was not provided.

The goal was to design a compact and straightforward fighter with low acquisition and operating expenses. Advances in small turbojet engines made this feasible. Originally planned to use the Bristol BE-22 Saturn engine delivering 3,800 lbf thrust, its cancellation necessitated switching to the more powerful Bristol Orpheus engine.

To expedite progress, an unarmed demonstrator—the Fo-139 Midge—was constructed using a less powerful Armstrong Siddeley Viper 101 engine generating 1,640 lbf thrust. Despite reduced power, it achieved Mach 1 in a dive and showed notable agility during flight testing. The Midge was lost in a crash in September 1955, likely due to pilot error.

Although it had a brief operational life and was not adopted by the RAF as a fighter, the Midge paved the way for developing a similar trainer aircraft. The subsequent larger Gnat incorporated bigger air intakes to accommodate the Orpheus engine, expanded wingspan, and mounting points for two 30 mm ADEN cannons. The prototype first took flight on 18 July 1955 at RAF Boscombe Down.

Despite no orders from the RAF for its fighter version, Finland, Yugoslavia, and India procured units; India obtained licence production rights via Hindustan Aeronautics Limited (HAL). Although it influenced NATO’s NBMR-1 competition (eventually won by Fiat G.91), the Gnat itself was not submitted. The RAF evaluated it in 1958 as a potential replacement for de Havilland Venom and BAC Jet Provost but ultimately selected the Hawker Hunter instead.

Trainer

As RAF enthusiasm for the Gnat as a frontline fighter diminished, Folland adapted the aircraft for use as a trainer. The design was altered to comply with Specification T.185D, aimed at producing an advanced two-seat trainer to facilitate pilot progression from the de Havilland Vampire T 11 to high-performance fighters such as the English Electric Lightning.

The Fo.144 Gnat Trainer featured a twin-seat configuration with a newly designed wing that increased internal fuel storage, thereby freeing up space for additional equipment. It was equipped with an enhanced variant of the Orpheus engine, had a lengthened forward fuselage, larger tail surfaces, and updated control surfaces including outboard ailerons and traditional flaps. On 7 January 1958, a contract was awarded for 14 pre-production trainer units.

The prototype conducted its maiden flight on 31 August 1959 at RAF Chilbolton. Initial reservations from the Ministry regarding Folland’s production capacity caused delays in placing full production orders. Following Folland’s acquisition by Hawker Siddeley Aviation, which became the Hamble division, subsequent orders for 30, then 20, and finally 41 trainers were placed between 1960 and 1962. These aircraft were designated Gnat T Mk. 1. The last RAF Gnat T.1 was delivered in May 1965.

Further development

Folland continued to explore advanced versions of the Gnat, particularly the supersonic-capable Gnat Mk.5, designed in both single- and two-seat variants for training and interceptor functions. Powered by twin Rolls-Royce RB153R or Viper 20 engines, it was intended to incorporate Ferranti AI.23 Airpass radar and be armed with de Havilland Firestreak air-to-air missiles. The Mk.5 was projected to achieve speeds up to Mach 2 and climb to 50,000 feet within three minutes. Folland anticipated producing a prototype by late 1962 and achieving operational status within five years.

In 1960, Maurice Brennan joined as chief engineer to apply his expertise in variable-geometry wing designs from Hawker Siddeley. This expertise led to the Fo.147 concept featuring two variants (tailless and conventional tail) designed as a versatile fighter/strike/trainer aircraft with hydraulically adjustable wings sweeping between 20° and 70°. Pitch control at high sweep angles was managed via wingtip elevons, while retractable canards provided longitudinal stability at low sweep settings, reducing the need for large tailplanes.

The Fo.147 promised speeds exceeding Mach 2, constrained only by structural thermal limits, with a maximum takeoff weight surpassing that of the Gnat Mk.5. Aviation historian Derek Wood highlighted its potential as a pioneering platform for variable geometry technology testing. Despite these advancements, neither the Fo.147 nor its successor Fo.148 proceeded beyond design stages due to limited RAF interest, even though plans existed to procure the General Dynamics F-111K strike aircraft.

Design

The Folland Gnat was engineered as a lightweight fighter tailored for dual roles as both a trainer and combat aircraft capable of ground-attack and day-fighter missions. Its cockpit incorporated typical fighter features such as full pressurisation, environmental controls, and an ejection seat. According to Folland's assessments, the Gnat offered benefits over traditional fighters in terms of cost efficiency, maintenance hours, handling characteristics, serviceability, and ease of transport. Its tricycle landing gear configuration allowed it to operate effectively from rudimentary grass airfields owing to its light weight.

Constructed using conventional metal stressed-skin techniques with extensive flush riveting, the Gnat’s airframe was designed to minimize production costs and labor intensity by reducing reliance on machining, forging, and casting processes. The airframe could be assembled utilizing straightforward jigs without requiring specialized tooling or skills; for instance, its wing represented only one-quarter of the cost and demanded less than one-fifth of the labor compared to wings of contemporary fighter aircraft. Additionally, the design facilitated rapid disassembly into major components without cranes or ladders, enhancing maintainability beyond that of most comparable aircraft.

Finland

Beginning on 30 July 1958, the Finnish Air Force took delivery of 13 Gnats, which included 11 fighters and 2 photo-reconnaissance variants. Initial deployment highlighted several maintenance difficulties and technical faults. Although a 1957 licensing agreement authorized Valmet to manufacture Gnats in Tampere, no units were ultimately produced locally. On 31 July 1958, Finnish ace Major Lauri Pekuri became the first Finnish pilot to surpass the sound barrier while piloting a Gnat.

The Gnat F.1 encountered operational challenges in Finland’s demanding environment. As the inaugural operational user, Finland faced unresolved design flaws that led to a six-month grounding following a hydraulic failure that caused the loss of GN-102. The aircraft was subject to scrutiny after three additional losses; two pilots successfully ejected, while one fatal accident occurred. Once initial issues were resolved, the Gnat demonstrated excellent maneuverability and solid performance but demanded rigorous maintenance. The scarcity of spare parts posed ongoing difficulties, particularly for conscript mechanics. Ultimately, the Gnats were retired in 1972 when Häme Wing moved to Rovaniemi and Saab 35 Drakens replaced them.

India

In September 1956, India signed a contract for domestic production of both the aircraft and its Orpheus engine. The first batch of 13 Gnats for the Indian Air Force (IAF) was assembled at Hamble-le-Rice in the United Kingdom, followed by partial assembly and then complete manufacturing by Hindustan Aircraft. The initial IAF Gnat took flight in the UK on 11 January 1958 and was delivered to India later that month. The conversion of the first squadron occurred in March 1960. The first Gnat constructed entirely in India flew in May 1962, with deliveries continuing until January 1974.

Contrary to the RAF’s practice, the IAF did not operate dedicated trainer variants of the Gnat. Early handling proved difficult due to a pronounced pitch-up tendency during landing gear retraction; therefore, pilots initially trained on Hawker Hunter trainers before rapidly transitioning to solo flights in the Gnat. Skilled aviators fully exploited its agility.

The Gnat established itself as a formidable opponent against the larger Canadair Sabres operated by Pakistan. Its effectiveness during the Indo-Pakistani Wars of 1965 and 1971 stemmed from tactical use, pilot proficiency, and mission circumstances. IAF pilots engaged Sabres in vertical dogfights where the Gnat held an advantage. Its compact size rendered it difficult to detect at low altitudes. This combat success earned it the nickname "Sabre Slayer" despite drawbacks such as hydraulic system problems and unreliable cannon armament.

One pilot flying a Gnat is credited with downing seven Pakistani Sabres during the 1965 conflict. A captured Gnat is currently exhibited at the Pakistan Air Force Museum in Karachi. During the 1971 war, Gnats were extensively deployed across roles including air defense, anti-shipping strikes, ground attack, bomber escort, and close air support missions. Pilot Nirmal Jit Singh Sekhon was posthumously awarded India’s highest gallantry honor.

To overcome operational shortcomings, the IAF introduced an improved model known as "Gnat II" in 1972. More than 175 HAL-built HAL Ajeet fighters were manufactured in Bangalore; these expanded upon and eventually supplanted the original Gnat fleet until their joint retirement in 1991.

Several former IAF Gnats remain preserved in private collections; some were transferred as gifts to the Bangladesh Air Force following their involvement in the 1971 conflict.

United Kingdom

The initial batch of production Gnat T.1 aircraft for the Royal Air Force arrived in February 1962 at the Central Flying School based at RAF Little Rissington. The main user became the 4 Flying Training School stationed at RAF Valley, which took delivery of its first unit in November 1962. In 1964, 4 FTS established the Yellowjacks aerobatic squadron flying all-yellow Gnats; this team was rebranded in 1965 as the Red Arrows, who continued to operate the Gnat until 1979 as the RAF’s premier aerobatic display team. The final Gnat T.1 for the RAF was handed over to the Red Arrows on 14 May 1965.

Following initial instruction on the BAC Jet Provost, pilots destined for fast jets progressed to RAF Valley, where they completed roughly 70 hours on the Gnat T.1 before advancing to operational training on the Hawker Hunter and subsequent conversion units.

The arrival of the Hawker Siddeley Hawk trainer prompted the gradual retirement of Gnats; 4 FTS phased out its last Gnat in November 1978. Withdrawn aircraft were often reassigned to ground training facilities such as RAF Halton before being sold, with many entering private hands and some remaining flight-capable. The Red Arrows were the last RAF operators, performing with Gnats throughout their 1979 season before transitioning entirely to Hawks in 1980.

Yugoslavia

Yugoslavia tested two Gnat F.1 units, which were delivered by rail following their maiden flight on 7 June 1958. These aircraft were operated by the national flight test center, but no further procurement ensued. One crashed in October 1958, while the other is preserved in Serbia.

Variants

Fo.140 Gnat

Prototype lightweight fighter developed privately, with a single example constructed.

Fo.141 Gnat

Gnat F.1

Single-seat lightweight fighter exported to Finland, India, and Yugoslavia; fifty manufactured by Folland at Hamble and under license in India as the HAL Gnat.

Gnat FR.1

One Finnish example fitted with three Vinten cameras mounted in the nose; a second aircraft modified by the Ministry of Supply joined it, both delivered on 12 October 1960.

Fo.142 Gnat / Gnat F.2

Intended upgraded F.1 featuring a thinner wing and Bristol Orpheus engine with simplified reheat (BOr.12SR), aimed at Mach 1.5 speeds and improved climb performance; development halted due to lack of engine support.

Fo.143 Gnat / Gnat F.4

Proposed interceptor variant equipped with radar and guided weapon systems; never constructed.

Fo.144 Gnat Trainer / Gnat T.1

Two-seat advanced trainer version produced for the RAF; a total of 105 built by Hawker Siddeley.

Gnat F.5

Planned enhanced model featuring a larger wing and twin Rolls-Royce RB153 engines with reheat, designed with carrier operations in mind.

Fo.146

Two-seat variable-geometry wing design combining features from Mk5 and Trainer models, powered by twin RB153 engines with thrust-reversers; intended as an advanced trainer or fighter.

HAL Ajeet

Indian-developed derivative of the Gnat F.1.

HAL Ajeet Trainer

Tandem two-seat trainer based on HAL Ajeet for use by the Indian Air Force, distinct from the RAF’s Gnat T.1.

Operators

• Finnish Air Force
  • Häme Wing
    • HävLLv 11
    • HävLLv 21

• Indian Air Force
  • No.2 Squadron
  • No.9 Squadron
  • No.15 Squadron
  • No.18 Squadron
  • No.21 Squadron
  • No.22 Squadron
  • No.23 Squadron
  • No.24 Squadron

• Royal Aircraft Establishment operated a single former RAF Gnat T.1 from Bedford for experimental purposes.
• Royal Air Force
  • Central Flying School
    • Yellowjacks aerobatic team
  • 4 Flying Training School, RAF Valley
    • Red Arrows aerobatic team

Accidents and incidents

• 31 July 1956: The prototype G-39-2 was lost following tailplane flutter at Stockbridge; pilot Teddy Tennant successfully ejected, marking the inaugural deployment of the Folland/Saab ejection seat.
• 26 August 1958: Finnish Air Force GN-102 crashed near Tampere caused by a hydraulic system design flaw; the pilot ejected safely.
• 15 October 1958: Developmental F.1 XK767 suffered a fatal accident at Stapleford, likely due to control malfunction.
• 13 April 1966: RAF Gnat T.1 XP507 impacted the sea during its approach to RAF Valley.
• 23 August 1967: RAF Gnat T.1 XP512 experienced a tailplane system seizure and crashed on Rhosneigr beach; the instructor sustained serious injuries, but there were no civilian casualties.
• 26 March 1969: RAF Gnat T.1 XR573 of the Red Arrows crashed amid formation training.
• 20 January 1971: Two RAF Gnat T.1 aircraft, XR545 and XR986, collided and crashed during Red Arrows practice sessions at RAF Kemble.
• 3 September 1975: RAF Gnat T.1 XS103 collided with an Italian F-104 near Leck, Germany; both pilots landed safely, though the Gnat was written off.
• 28 October 1975: RAF Gnat T.1 XR571 was declared a write-off following a hard landing at RAF Valley.
• 30 April 1976: A mid-air collision between two RAF Gnat T.1s, XP536 and XR983, resulted in crashes over North Wales.
• 30 June 1976: RAF Gnat T.1 XM707 was abandoned near RAF Kemble after losing tailplane control.
• 8 October 1976: RAF Gnat T.1 'XR996' crashed during approach to RAF Shawbury, resulting in the loss of both crew members.
• 10 January 1991: N3XR crashed in Shreveport, Louisiana due to fuel starvation, causing two fatalities.
• 29 July 2013: Gnat T.1 XS105 (N18GT) was destroyed in a crash near Georgetown, South Carolina.
• 1 August 2015: At CarFest North festival in Cheshire, Gnat T.1 XP504 (marked XS111) crashed, killing pilot Kevin Whyman; no injuries occurred on the ground.

Surviving aircraft

A number of Gnats continue to exist today, with several maintained in flying condition primarily within the United States and United Kingdom, alongside others exhibited in museums and public collections.

Notable appearances in media

In the 1991 comedy film Hot Shots!, four privately owned Gnat T.1s along with an Ajeet portrayed fictional US Navy carrier-based "Oscar EW-5894 Phallus" tactical fighter bombers piloted by Navy aviators.

Bibliography

• Bridgman, Leonard. Jane's All the World's Aircraft 1958–59. London: Sampson Low, Marston & Company, Ltd., 1958.
• Burnet, Charles. "Folland's (G)Natty Fighters." AIR Enthusiast Twenty-four, April–July 1984. Bromley, Kent, UK: Pilot Press, 1984.
• Chopra, Pushpindar. "Fly with a Sting." Air International, Volume 7, No. 2, August 1974.
• "Folland Midge: The Viper Powered Precursor of the Gnat begins Flying Trials." Flight, 20 August 1954, Vol. 66, No. 2378. pp. 228–229.
• Frédriksen, John C. International Warbirds: An Illustrated Guide to World Military Aircraft, 1914–2000. Santa Barbara, CA: ABC-CLIO, 2001. .
• Ross, Andrew L. The Political Economy of Defense: Issues and Perspectives. Westport, CT: Greenwood Press, 1991. .
• Spick, Mike. Illustrated Directory of Fighters. Osceola, WI: Zenith Press, 2002. .
• Taylor, John W.R. "Folland Gnat." Combat Aircraft of the World from 1909 to the present. New York: GP Putnam's Sons, 1969. .
• "Thoughts on the Gnat." Flight, 3 April 1953. pp. 425–426.
• Willis, David. "The Folland Gnat (Database)." Aeroplane, September 2008.
• Wood, Derek. Project Cancelled. Macdonald and Jane's Publishers, 1975. .

External links

• "Insights into the Gnat"
• Folland Gnat Trainer – comprehensive analysis in Flight featuring a cutaway illustration
• De Havilland Aviation Ltd maintains Europe's sole airworthy former Red Arrows Gnat, XR537 (G-NATY).
• Thunder and Lightnings
• Cockpit restoration project of XM692
• The Wolfpack in operation