Origins and context
The vertical program was shelved in 1966. If the officially-dictated formula was indeed attractive, it was hard to put into practice. The lift jets were costly and unable to deliver enough thrust. Also, this type of aircraft’s limited warhead capabilities and range, paired with its need for substantial ground logistics, hampered its versatility.
The Ministry of Armed Forces saw the deadlock and asked for an alternative solution. The Air Force staff requested studies on fixed as well as variable-sweep aircraft. First, it looked into a single-jet low-altitude intruder. One of this project’s main goals was to reduce the delta wings’ high approach speeds, using lift-augmented swept wings. Dassault’s project, the Mirage F2 project, never made it beyond the prototype stage. Simultaneously, in 1964, the Ministry of Armed Forces asked for a study on a variable-sweep aircraft for the Air Force and Naval Aviation. It placed an order for Dassault’s experimental prototype, a two-seater Mirage G powered by a single Pratt & Whitney TF 306 jet, in October 1965. In spite of its technical success, this aircraft never secured an order for serial production. Its American engine, once again, raised the issue of national independence in the defense field. Dassault is the only company to have developed vertical take-off and landing formulas in 10 years.
The Mirage G was an experimental aircraft with a single Pratt & Whitney/Snecma TF 306 turbofan. It took over from the fixed-wing prototype Mirage F2, to which it was similar in terms of size and technology (the fuselage and engine configuration were identical). The Air Force and Naval Aviation both expressed interest in it.
In February 1965, the Mirage III G, designed by Jean-Jacques Samin and Jean-Paul Emoré, was adopted by the Defense Ministry. Four months later, the dossier was submitted to the Defense authorities and a scale model of the Mirage III G was presented at the Paris Air Show.
One major problem remained to be solved: the wing movement mechanism.
By the fall of 1965, a lot of progress had been made. The wing pivot position had been determined at a point slightly flush of the fuselage. Several Dassault patents were placed on the discovery.
On October 18, 1965, while Anglo-French negotiations on the joint swing-wing project were going on, the Defense Ministry placed an order for a Mirage G experimental variable geometry aircraft. The first drawings were begun immediately, and manufacturing work on the prototype began in January 1966.
On the 13th and 14th of March, 1967, a delegation from BAC led by Mr. Greenwood, came to visit the prototype, then under construction at Saint-Cloud. On May 27, the airframe, for which the general assembly was now complete, was presented for the first time on static display at the Paris Air Show.
The aircraft made an initial short hop at Melun-Villaroche on October 18, then – after being dismantled – was taken to Istres, where it made two more on November 16 and 17.
On the 18th, it made its maiden flight, with a 20º wing setting, piloted by Jean Coureau. It landed at 120 knots. Only two years had gone by since the first pencil-mark on the drawing-board.
On November 24, during the aircraft’s 5th sortie, the wing setting was moved back to 55º and it reached Mach 1.15. The following day, during its 7th sortie, and with the wing at the maximum 70º, it reached Mach 1.5.
On November 30 (sortie nº 9) it took off with a full load (15,020 kg) in 450 m and reached Mach 1.6.
On December 8, only three weeks after the first flight, Jean Coureau reached Mach 2.1 with the maximum sweepback setting.
In 20 flights and less than two months, a flight envelope had been opened up extending to Mach 2.1 and 700 knots. The low-altitude performance was extraordinary: approach speed 125 knots, touch-down at 108, wings maneuverable at 3 g.
Despite the impressive results, the program was abandoned in 1968.
In France, although the Air Force general staff was satisfied with the tests on the single-engine Mirage G, they opted for an aircraft with twin Snecma Atar 9 K 50s for strike reconnaissance and remote electronic warfare missions (the RAGEL program).
On September 15, 1967, Jean-Claude Brabant’s team was assigned the task of defining the initial specifications for a twin-engine swing-wing aircraft. One year later, an order was placed for two experimental two-seaters with twin Atar 9 K 50 engines, christened Mirage G4.
On October 11, 1968, the Air Force’s Materials Program Bureau issued a set of technical specifications:
“The aircraft must be capable of carrying either a nuclear weapon, or a large quantity of conventional weapons. The main launching mode for the nuclear weapon is to be low-altitude launching, at high subsonic speeds to begin with, and later at low supersonic speeds. At a later date, we envisage equipping the aircraft with a nuclear air-to-ground missile.”
The Air Force accepted the top speed of Mach 2.2, imposed by the choice of the Atar 9 K 50, but asked that the structure be capable of Mach 2.5, in order that Snecma M 53s might be fitted at a later date.
Economic difficulties following on the social turmoil of May 1968, added to uncertainty over the order for production-standard G4s, obliged the director of the Service Technique de l’Aéronautique – after consulting with the Air Force general staff – to put the project on hold. It had been discovered that the cost of the program (an order for 60 aircraft had been envisaged) was beyond the means of the Air Force, which had, moreover, changed the mission priority in favor of an interceptor version.
The order for the two G4 prototypes had not been canceled, but there were developments in the program. For the production series, the Air Force general staff now wanted a twin-engine single-seater for interception missions, with a shorter range than the G4, since a smaller aircraft would be less expensive. These aircraft took the name G8, and were to be equipped with M 53 turbo-jets.
The two-seat Mirage G4 01 changed its name to G8 01. Its first flight, at Istres on May 8, 1971, was piloted by Jean-Marie Saget. On the 13th, during its 4th sortie, it reached Mach 2.03 with a 70º sweepback angle. It touched down at 118 knots, demonstrating the type of velocity differential that could be achieved with the swing-wing in conjunction with sophisticated high-lift devices, as compared with a delta wing.
The second prototype, G4 02, then under construction, was transformed into the single-seat Mirage G8 02 by taking out the rear seat. It was equipped with Snecma 9 K 50 turbo-jets and given a simplified weapons system – that of the F 1 supplemented by the navigation system of the Milan.
Mirage G8 02 made its maiden flight at Istres, on July 13, 1972, piloted by Jean-Marie Saget. For its first anniversary – and its 74th sortie – on July 13, 1973, it achieved the highest speed ever for an aircraft in Western Europe: Mach 2.34 at 42,000 ft. In 1995, that record still stands.