French Swingers; The Dassault Mirage G

April 6, 2023

The following is a story of pride, ambition, intrigue and murder. Well, OK, not literal murder, unless you count killing off competition. It also interweaves a bit, so bear with me.

In the early 1960s French aircraft builder Dassault were flying high – and I don’t just mean their products. The company had had a number of their military designs do extremely well in international sales, best typified by the success they were enjoying in marketing their latest fighter, the Mirage III.


But Dassault were not about to let their achievements go to their heads, and they were actively looking to develop the next generation of combat aircraft. A number of designs were investigated, including a version of the Mirage III capable of vertical take-off and landing, but soon Dassault and the French Air Force’s attention fixed onto one of these proposed aircraft in particular; the Mirage F2.

In 1963 the French Air Force drew up requirements for a low-level supersonic intruder to replace their aging attack aircraft, and in response Dassault created the F2. This featured a two-man crew and sought to rectify some of the issues identified from the Mirage III.

Firstly, that aircraft’s distinctive tailless delta design required the aircraft to use long runways and this was something the French Air Force wanted to not be constrained by, wanting a “rough field” capability for its new attack aircraft. So, the Mirage F2 moved the wing to a high position and added a more conventional tail.


French jet engines were also somewhat lagging behind technically compared to many other countries designs, tending to be heavy and fuel inefficient for their output. So, the new aircraft was to have an American engine, a version of the Pratt & Whitney TF30. This was a cutting edge turbofan design that was intended to be used in the United States new TFX design that was shaping up on drawing boards and would ultimately lead to the F-111.

In fact, we can broadly consider the Mirage F2 to be roughly equivalent to an intermediate between the USAF’s F-105 Thunderchief then in service and the later F-111.

But the F2 was not to enjoy the success of these other designs, because though prototypes were built and flew successfully for the first time in June 1966, by that point things were changing. In May France had pulled out of the NATO command structure and had effectively expelled NATO units from the country.

The French Air Force now really, really wanted an interceptor, and they requested that the F2 be converted into a single seat fighter for the job, designated the Mirage F3. But in fact, even this was soon dropped because another Dassault project seemed to be bearing interesting fruit that offered potentially better possibilities.

In 1964, as work on the Mirage F2 had been ongoing, the French Air Force asked Dassault to look into the prospects of a variable geometry design – colloquially a “swing-wing”. In this the wings pivot back and forward to change the lift and drag characteristics. For landing and take-off, the wings extend to provide maximum lift, while for high speed they retract to fold in tight next to the fuselage, minimising friction and drag.

The 1960s were indeed the prime time for the variable-wing concept, and a number of aircraft were designed and built in this decade that used them, including afore-mentioned F-111, the Soviet Mig-23 and, after delays that play a part in this story, the Panavia Tornado.

Because in 1965 both the French and British governments had started a joint project to create a multi-role, variable geometry aircraft that both nations would use. For Britain, the new aircraft, designated as the AFVG, would replace both the cancelled TSR-2 strike aircraft and potentially the Lightning as the RAF’s interceptor. As a result they were extremely keen to get cracking.

But though the French government of the time liked the idea, the French Air Force and, especially, Dassault, didn’t.

The initial interest for the French government was in using the AFVG as a carrier fighter. As a result the French Air Force was concerned that somewhere down the line they were going to get saddled with a design that wasn’t designed for them. Considering what happened to the American TFX program, that was probably correct.

But for Dassault the issue was that, quite frankly, they were not going to be running the show, the Brits were. To be fair, Dassault had seen enough of the post-war British aerospace industry to know that it had…issues (see my article on the Fairey Delta for more on that).

Whatever his reasons though, old man Dassault was not going to put up with the perfidious Anglaise messing up his business and so he and his company set about basically sabotaging the AFVG program. But to do that they had to have an alternative.

And that was the Mirage G.


Following on from the initial design studies and then the interest in a variable geometry aircraft that sparked the AFVG, Dassault basically went all out to get a swing-wing design into the air as soon as they could. They did that by basically taking the Mirage F2 design that they were working on and integrating variable geometry wings into it.

Construction of the Mirage G began in January 1966 and the prototype was ready for its first flight by November 1967. Who says competition doesn’t get things done!?


Despite the remarkably quick turnaround, the Mirage G seemed very good, as was demonstrated with an accelerated test program. In less than the two months the -G flew twenty times and demonstrated a top speed of Mach 2.1.

This success meant the aircraft achieved its goal…of getting France out of the AFVG program and securing Dassault’s independence in future projects. In June 1967 France withdrew from AFVG, throwing British defence plans into further disarray and ultimately playing a part in the British announcement that they were going to pull out their military commitments from Asia by 1971, the so-called “withdrawal from East of Suez”.

As a further aside it also left the British looking for new partners for a future aircraft to meet their now pressing needs, and that led to the creation of the Panavia group and the building of the Tornado.

So, the Mirage G left an interesting legacy for an aircraft that, even before it flew, was never going to see service. Because despite seeming like a very good potential aircraft, there a was a major problem with the Mirage G…its engine.

As said, in 1966 France broke from NATO and fell out with the United States because of it. And the Mirage G still used the American TF30 engine. This appears to have been a fine powerplant for the aircraft, producing 22,800lbf in afterburner.

But with the split between France and the United States, the French recognised that future cooperation was not going to happen, so if they wanted to one day to field the swing-wing Mirage they needed to fit French engines. And at the time, they just weren’t up to it…or at least individually.

So, in September 1967, even before the Mirage G first flew, the Dassault design team began work on a new variant that would use twin Atar 9K-50 turbojets, which were also used on the Dassault Mirage IV nuclear bomber and produced 15,800lbf each.

The new aircraft was designated as the Mirage G4, and two prototypes were ordered. The extra engine would obviously increase the weight of the Mirage G4, but the extra power was hoped to compensate. Indeed, projections were that the aircraft would be fully capable of Mach 2.2, and the Air Force specified that the airframe should be capable of Mach 2.5 as it was hoped to fit the new SNECMA M53 engines that were in development to future models of the Mirage G4.

This would still be a two-seater, and the French Air Force initially thought that it would make an excellent strike aircraft with both conventional and nuclear weapons, and they envisaged ordering as many as sixty of the type. But again, things changed rapidly (seems to be a theme here) and just a few months later in May 1968 it was decided that another version was instead required; the Mirage G8.

This would be a fighter/interceptor that would be smaller than the intended G4, hopefully making it cheaper, and the original prototypes would be built to this standard – one a single-seater, the other with two.


With the pressure off Dassault was able to take a more steady approach to building the two aircraft, while at the same time continuing to conduct flight testing of their swing-wing design with the original Mirage G. This was unfortunately lost in a crash in January 1971, but by this point the first G8, -01, the twin-seater, was well advanced and actually started its test program in May of that year.


This, like its forebear, showed good performance, surpassing Mach 2 on its fourth flight.

The G8 01 was joined the following year by the -02, the single-seat variant that had been expected to be the primary type.


This was even fitted with a basic weapon capability and the navigation equipment from the Dassault Milan fighter. Despite the fitting of equipment that made it notionally an operational aircraft, the Mirage G8 02 was not impacted in its performance, proving a real hot rod and in July 1973 it achieved a top speed of Mach 2.34.


However, despite the remarkable performance, the Mirage G8 was also caught up in that great killer of military programs – expense. Though the French Air Force might love to get their hands on the twin-engine, swing-wing Mirage’s, they simply couldn’t afford them at that point. And in fact, Dassault had already anticipated that possibility way back before the Mirage G was on the drawing board.

Remember the Mirage F2 and F3? Well, though those had been created to French Air Force requirements, Dassault had thought it prudent to start a simple, cheaper fighter program as a company venture for a backup in case of problems.

The Mirage F1.

And this, a cheaper, single-seat-and engine multirole aircraft, turned out to be exactly what the French Air Force ended up adopting. Plus, to further prove that Dassault knew their market, the F1 would also prove to be another major export success.

So, the Mirage G’s were cancelled, and that was the end of an extremely promising aircraft. It wasn’t all wasted, however.

The efforts Dassault put into the program were able to be applied to later designs such as the next generation Mirage 2000 and -4000, while the two remaining Mirage G8 prototypes are on display in museums in France.



The Dassault Mirage IV; Elegantly Lethal

Dassault Milan – the Moustachioed Gaul

French Eagle – the Dassault Mirage 4000

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