Fiat G.91

The Fiat G.91 was an Italian jet fighter aircraft. It was the winner of the NATO competition in 1953 as standard equipment for Allied air forces. It entered in operational service with the Italian Air Force in 1961, with the West German Luftwaffe, in 1962, and later with the Portuguese Air Force. It was in production for 19 years. 756 aircraft were completed, including the prototypes and pre-production models. The assembly lines were finally closed in 1977. The Fiat G.91 enjoyed a long service life that extended over 35 years. It was widely used by Portugal in the Portuguese Colonial War in Africa. A twin-engined variant was known as the Fiat/Aeritalia G.91Y.

Design and development
In December 1953, NATO Supreme Command issued specifications for a new light tactical support aircraft. European manufacturers were invited to submit their designs for this requested Light Weight Strike Fighter role. The G.91 was designed to this specification by the Italian engineer Giuseppe Gabrielli, hence the "G" designation. The competition was intended to produce an aircraft that was light, small, expendable, equipped with basic weapons and avionics and capable of operating with minimal ground support. These specifications were developed for two reasons: the first was the nuclear threat to large air bases, many cheaper aircraft could be better dispersed, and the other was to counter the trend towards larger and more expensive aircraft.

The technical requirements were:
 * 1,100 m (3,610 ft) takeoff distance over a 15 m (49 ft) obstacle
 * Capability to operate from grass strips and streets
 * Maximum speed of Mach 0.95
 * Range of 280 km (170 mi) with 10 minutes over the target
 * Armoured protection for the pilot and the fuel tanks
 * 4 × 12.7 mm (.5 in) or 2 × 20 mm or 30 mm guns
 * A maximum of 2,200 kg (4,850 lb) empty weight and 4,700 kg (10,360 lb) max weight

The challenge of providing an engine that matched the requirements of lightness and power, reliability and ease of maintenance was solved by using the Bristol Siddeley Orpheus turbojet.

The designs were required within two months of the competition. The special committee had to choose from eight projects. Besides the G.91, these included the Northrop N-156, Dassault Mystère XXVI (future Dassault Étendard IV), Sud-Est Baroudeur, Aerfer Sagittario II and the Breguet Taon Br.1001. These designs were assessed starting on 18 March 1953 by AGARD (Advisory Group for Aeronautical Research and Development) under the leadership of Von Karman.

Project selections took 18 months to complete. The first result was announced on 30 June 1955: the winning projects were, in order: the Breguet Br. 1001 Taon and the Fiat G.91. A third was added to these two aircraft: the Mystère XXVI, and three prototypes of this design were also ordered. The G.91 first flew on 9 August 1956 at the Caselle airfield, Turin, in the hands of Chief Test Pilot Riccardo Bignamini, with a seven-month lead over the Dassault prototype and almost a year ahead of the Breguet Taon.

The intensive series of tests that followed the maiden flight was not without its setbacks. The most serious problem was the elimination of aeroelastic vibrations which, on 20 February 1957, led to the destruction of the first G.91 prototype. The re-engineering work to cure the problem was very extensive and resulted in the second prototype being fitted with a larger tail, a 6 cm (2 in) higher canopy, a ventral fin and some other modifications. This aircraft flew in July 1957, but it was not sent to the final evaluation. The third and fourth G.91 prototypes were sent to France, for the competition.

The final selection of the competing designs was planned for late 1957. In September 1957, at the Centre d'Essais en Vol at Brétigny-sur-Orge, in France, the three rival aircraft types met for evaluation trials. During the trials the Italian aircraft performed impressively and, in January 1958, the Fiat G.91 was officially declared the winner.

Following a meeting of NATO Defence Ministers in April 1958 it was agreed that the G.91 would be the first NATO lightweight strike fighter, it would be followed in 1961 by the Breguet Taon. A production meeting was planned for May 1958 to discuss the production of the aircraft with financial support from the United States, the Americans would provide some of the finance for the French, German and Italian aircraft and pay for the Turkish aircraft. The defence ministers reached agreement to order 50 aircraft for each country.

Given the large economic and commercial interests at stake, there was a certain amount of controversy surrounding this decision. After the loss of the G.91 prototype, the French government preferred to pursue development of the locally-designed Étendard. The British government similarly ignored the competition to concentrate on Hawker Hunter production for the same role. The Italian government also ordered the G.91 for the Italian Air Force before the results of the competition were known. These pre-production machines would later go on to serve for many years with the Italian aerobatic team, the Frecce Tricolori as the G.91 PAN. The type was also considered by Austria, Norway, Switzerland, and even the United States Army, which briefly evaluated the type as a possible Forward Air Control aircraft before relinquishing all fixed-wing aircraft operations to the Air Force.

Production


Aeritalia built 174 G.91s for Italy, plus 144 R/3 variants for West Germany (including 50 that had been ordered and then cancelled by Greece and Turkey). The German order involved a production run of 294 G.91s built in Germany by Flugzeug-Union Süd (a consortium of former competitors Messerschmitt, Heinkel and Dornier). These were the first combat aircraft built in Germany since World War II. The first order was for 50 machines from Aeritalia, then Dornier and other German firms had an order for 232 machines, later increased to 294. The Luftwaffe (German Air Force) also bought 44 G-91T/3 two-seat trainers and another 22 were produced in Germany, ending production in 1972.

The Luftwaffe had intended to equip a further four wings with the G.91R/3 but initial operating experience with the type left the Luftwaffe disappointed with the aircraft's performance and further orders were cut. Some Luftwaffe G.91s were emblazoned with "pig" emblems as a comment on the aircraft's lacklustre performance.

Italian service


The first G.91s entered service with the Italian Air Force in August 1958, with 103mo Gruppo, 5a Aerobrigata, called "Caccia Tattici Leggeri (CTL)", based at Pratica di Mare Air Force Base, the same with Reparto Sperimentale di Volo. The next operational unit was 14mo Gruppo, Seconda Aerobrigata in 1961. This unit had its role shifted to tactical support, because its groups were 14mo, 103mo (dispatched from 5 A/B to this Aerobrigade) and 13mo (only in reserve). All of them were based at Treviso-Sant'Angelo.

The last G.91 was phased out and retired by Italy in 1995.

German service
Forty-five G.91 T/3 Fiat built two-seat trainer aircraft were ordered for the Luftwaffe, the first 35 being allocated to Waffenschule 50 (Weapon School 50) with the balance of the order divided between operational units. 22 aircraft were built by Dornier between 1971 and 1973, these aircraft were used to train Weapons Systems Officers for the F-4 Phantom. Five Fiat built G.91R/3 aircraft were delivered to Erprobungstelle 61 for trials with subsequent deliveries being allocated to Aufklarungsgeschwader 53 based at Erding, near Munich along with Waffenschule 50. The first Dornier-built example of this variant was flight tested on 20 July 1961. The G.91R/3 equipped four newly formed Leichten Kampfgeschwadern (light attack wings), often replacing former F-84 Thunderstreak units.

Fifty G.91 R/4 aircraft were taken up from a cancelled Greek/Turkish order but being unsuitable for operational use were used as training aircraft and were operated solely by Waffenschule 50. When the initial training programme was completed the R4 was retired in 1966, 40 surviving airframes were sold to Portugal. Other R/4 aircraft remained in Germany and were transferred to ground instructional use or displayed at recruitment presentations.

On 1 January 1970, the Luftwaffe fleet consisted of 310 G.91 R/3 and 40 G.91T aircraft, and by 1976 only 20 of the R/3s had been lost to accidents, a loss rate of 6%. The G.91 R/3 was to be replaced in the early 1980s by the Dassault/Dornier Alpha Jet which operated in the same role, with the last G.91s being retired in 1982.

Portuguese service
From 1961, Portugal became involved in fighting against nationalist movements in its African overseas territories, the series of conflicts becoming known as the Portuguese Colonial War. Portugal had deployed a detachment of F-86 Sabres to Portuguese Guinea in August 1961, prior to the outbreak of major fighting, but was forced to withdraw the jet fighters back to Europe owing to pressure from the United States and the United Nations, who imposed an arms embargo. This left a gap in air cover for Portugal's African colonies, both in the close air support role, and in the air defence role.

In 1965, as the scale of fighting increased, Portugal attempted to purchase 100 surplus Canadian built Sabre Mk 6s from West Germany, but instead, it was offered 40 G.91R/4s, which had originally been built for Greece and Turkey and which differed from the rest of the Luftwaffe G.91s sufficiently to create maintenance problems in exchange for allowing Germany to build and use an airbase at Beja in Portugal for training.

G.91s arrived in Portuguese Guinea in 1966, equipping Esquadra 121 Tigres based at Bissau, and being used for reconnaissance and close support with rockets, napalm and bombs against PAIGC rebels. When the PAIGC started to be supplied with Soviet-made Strela 2 (NATO designation SA-7 Grail) MANPADS in early 1973, these immediately became a threat to Portuguese air superiority. On 25 March 1973, and 28 March, two FAP G.91s were shot down by missiles within three days, with a further two lost to conventional ground fire later in the year. (By comparison, only two G.91s had been lost in Guinea from 1966 to 1973. ) A final G.91 was lost to a missile on 31 January 1974, while Strelas were also responsible for the loss of a T-6 Texan and two Do.27K-2s.



G.91s deployed to Mozambique at the end of 1968, equipping Esquadra 502 Jaguares ininitally at Beira, later moving to Nacala, with a second squadron Esquadra 702 Escorpiões (Scorpions) forming in September 1970 at Tete, flying against FRELIMO forces. Fremilo also received Strelas in 1973, although unlike elsewhere, the Portuguese in Mozambique did not lose any aircraft to missiles with Chinese support, even if it forced Portuguese pilots to change their tactics. The only G.91 destroyed in combat in Mozambique was the serial number 5429, flown by Lt. Emilio Lourenço: his plane was destroyed and Lourenço killed by a premature detonation of its bombs while flying a strike against rebel positions on 15 March 1973.

In 1973, with the United Nations weapons embargo against Portugal, the Air Force faced problems purchasing further numbers of close air support aircraft. An attempt was then made to acquire more Fiat G.91s from Germany by having Dornier disassembling the aircraft and then selling them as spare parts to Switzerland and Spain. These spare parts would be later sold to Portugal and assembled locally with different serial numbers. However, the deal did not follow through as the German government vetoed it.

In April 1974, the Portuguese government fell in the Carnation Revolution, with the new government seeking to grant its colonies independence. Portugal withdrew its G.91s from Guinea when it was granted independence in 1974, with its forces also leaving Mozambique. One of the G.91 squadrons was briefly deployed to Angola in late 1974, in order to try to prevent fighting between rival FNLA and UNITA forces, being finally withdrawn back to Portugal in January 1975.

In 1976, a second purchase of 14 G.91 R/3s and 7 G.91 T/3 trainers was made from Germany, which were followed by further aircraft when the G.91 was withdrawn from Luftwaffe service in from 1980 to 1982, giving a total of 70 R/3s and 26 T/3s, although not all of these entered service, with many being broken up for spare parts. Portugal finally phased out the last of its G.91s in 1993.

Variants


Trainer and reconnaissance variants were produced right from the start of G.91 production, but the basic design of the aircraft remained virtually unchanged throughout almost the entire production run of the aircraft. The one major difference is that the R series aircraft were single-seaters, while the T series aircraft had two seats. To accommodate the extra seat, the T series aircraft had a slightly longer fuselage.
 * G.91 – Prototypes and pre-production aircraft.
 * G.91R/1 – Light attack/reconnaissance aircraft, fitted with modified nose housing three cameras.
 * G.91R/1A – Revised instrumentation.
 * G.91R/1B – Strengthened airframe.
 * G.91R/3 – Single-seat ground-attack, reconnaissance version for the Luftwaffe. Powered by a Rolls-Royce Orpheus turbojet engine. Armed with two 30 mm DEFA cannons.
 * G.91R/4 – Similar to the G.91R/3, but armed with four 12.7 mm (0.5 in) Colt-Browning machine guns. Powered by a Rolls-Royce Orpheus turbojet engine.
 * G.91T/1 – Trainer version of G.91R/1 for Italian Air Force.
 * G.91T/3 – Trainer version for Luftwaffe.
 * G.91PAN  – Aerobatic display aircraft for Frecce Tricolori, converted from pre-production G.91s.

G.91Y
An additional 67 aircraft built by Aeritalia were significantly uprated from earlier versions. These single-seat aircraft, designated G.91Y and nicknamed "Yankee", replaced the original Bristol Siddeley Orpheus engine with two General Electric J85 units. The G.91Y first flew on 12 December 1966 and displayed an improvement in speed, range, payload, and manoeuvrability. The maximum speed was increased to 1,110 km/h (690 mph, 600 kn, Mach 0.91). The machine guns were replaced by a pair of DEFA 552 30 mm cannon with 125 rounds per gun. All the aircraft built served with the Italian Air Force.

Operators

 * German Air Force (Luftwaffe)
 * Aufklärungsgeschwader 53
 * Aufklärungsgeschwader 54
 * Erprobungstelle 61
 * Leichtes Kampfgeschwader 41
 * Leichtes Kampfgeschwader 42
 * Leichtes Kampfgeschwader 43
 * Leichtes Kampfgeschwader 44
 * Waffenschule 50
 * Hellenic Air Force Evaluation operator, four aircraft in service, but retired.
 * Italian Air Force
 * Frecce Tricolori
 * Portuguese Air Force (1966–1993)
 * United States Army – Evaluated two aircraft (1 G.91R/1, 1 G.91R/3) in 1961.
 * United States Air Force – Also an evaluation operator with two aircraft.
 * Portuguese Air Force (1966–1993)
 * United States Army – Evaluated two aircraft (1 G.91R/1, 1 G.91R/3) in 1961.
 * United States Air Force – Also an evaluation operator with two aircraft.
 * United States Army – Evaluated two aircraft (1 G.91R/1, 1 G.91R/3) in 1961.
 * United States Air Force – Also an evaluation operator with two aircraft.

Aircraft on display
There are numerous examples preserved in museums around the world.