Dassault Mirage IIIV

In August 1961, NATO released an updated revision of its VTOL strike fighter requirement, NATO Basic Military Requirement 3 (NBMR-3).[1] Specifications called for a supersonic V/STOL strike fighter with a combat radius of 460 kilometres (250 nmi). Cruise speed was to be Mach 0.92, with a dash speed of Mach 1.5.[2] The aircraft, with a 910-kilogram (2,000 lb) payload, had to be able to clear a 15-metre (50 ft) obstacle following a 150-metre (500 ft) takeoff roll.[3][4] Victory in this competition was viewed being of a high importance at the time as it was seem as being potentially "the first real NATO combat aircraft".[2]

During the 1950s and 1960, both French aircraft manufacturer Dassault Aviation and British aerospace company Hawker Siddeley Aviation (HSA) were deeply interested in vertical takeoff/landing (VTOL)-capable combat aircraft. HSA had already been keen to develop a new generation of combat aircraft that would be capable of supersonic speeds.[5] HSA's chief aircraft designer Sir Sydney Camm decided that the company should investigate the prospects of developing and manufacturing a viable combat-capable vertical take-off and landing (VTOL) fighter aircraft.[6] Along with the subsonic Hawker P.1121 fighter (which would become the Hawker Siddeley Harrier later on, a supersonic design, designated as the P.1150 was produced; however, the release of NBMR-3, and subsequent revisions to it, led to the P.1150 proposal being considered to be undersized and thus unsatisfactory, which led to a desire for a redesign.[2][N 1] The new, larger aircraft design soon emerged, which was initially designated as P.1150/3 prior to being redesignated as the P.1154.[4]

In January 1962, HSA submitted the P.1154 design to NATO via the Ministry of Aviation.[2] NBMR.3 attracted a total of eleven contenders, including Dassault's Mirage IIIV proposal, which would become viewed as the principal competitor to the P.1154. Substantial support for the Mirage IIIV came from Britain, work on the programme having involved the British Aircraft Corporation (BAC), while the Dassault-led design also held the favour of several members of the British Air Staff.[7][2] While the P.1154 was judged to be technically superior, the Mirage IIIV had acquired a greater level of political palatability due to the co-operative development and production aspects proposed for the programme, under which work was to be distributed across a number of member nations. Protracting political maneuvering by firms and national governments alike was deployed in attempts to secure their respective project's selection.[8]

In May 1962, the P.1154 emerged as the winner in the competition for the NBMR.3 over the Mirage IIIV.[7] While the Mirage IIIV had not been selected to meet NBMR-3, however this did not lead to orders for the rival P.1154 being placed.[8] The French government subsequently withdrew from participation once the Dassault design had not emerged victorious.[7][9] According to aviation author Jeffort, the Mirage IIIV had been rejected mainly because of its excessive complexity, using nine engines compared to the P.1154's single-engine approach.[10] However, NATO lacked any central budget, instead relying on individual member nations to actually procure military equipment, while the NBMR-3 selection went unheeded by all of the NATO member nations. Thus, in 1965, the whole NATO project was unceremoniously terminated.[8]

Since the Rolls-Royce RB162 lift engines which had been specified for the Mirage IIIV were not expected to be available before 1963, Dassault decided to modify the first Mirage III prototype into an interim VTOL testbed; in this configuration, it became the Balzac V. This was fitted with eight Rolls-Royce RB.108 lift engines along with a single unreheated Bristol Orpheus BOr 3 as the main engine.[11] According to aerospace publication Flight International, a key goal for the Balzac prototype was to prove the autopilot system, which was identical to the unit which was proposed use with the Mirage IIIV, as well as the lift and transition system.[12] The Balzac began tethered hovering on 12 October 1962 and achieved the first free hover only six days later. The first accelerating transition from vertical take-off to horizontal flight took place on its 17th sortie on 18 March 1963. The aircraft had two fatal accidents, one in January 1964 and one in September 1965. After the last accident the aircraft was not repaired.[13]

Dassault Mirage IIIV

In the meantime, the Balzac had led to the actual Mirage IIIV, which was roughly twice the size of the earlier aircraft. A pair of Mirage IIIV prototypes were constructed, the first of which conducted its first hovering trial on 12 February 1965.[14][15] It was powered by a single Pratt & Whitney JTF10 turbofan engine, designated as the TF104. The TF104 engine was originally evaluated on a specially-constructed aerial testbed aircraft, the Mirage IIIT, which shared many similarities to basic design of the Mirage IIIC design, with the exception of modifications in order to accommodate the selected engine.[16] The TF104 engine was quickly replaced by an upgraded TF106 engine, with thrust of 74.5 kN (16,750 lb_f), before the first prototype made its initial transition to forward flight in March 1966.[17] The prototype subsequently attained Mach 1.32 during test flights.

In June 1966, the second prototype, which featured a TF306 turbofan engine for forward thrust of 82.4 kN (18,500 lb_f), conducted its first flight. During September of that year, it attained Mach 2.04 in level flight, but was lost in an accident on 28 November 1966.[14] The Mirage IIIV was never able to take off vertically and successfully attain supersonic flight during the same flight.

The loss of the second prototype had effectively killed the program, and in fact killed any prospect of an operational Mach 2 vertical take-off fighter for decades. The competing Hawker P.1154 had been cancelled in 1965 by the government just as the prototypes were under construction; however, its subsonic cousin, the Hawker-Siddeley Kestrel VTOL attack aircraft was flying in tri-partite trials with the UK, US and West Germany. The French preferred the Mirage IIIV, and the international cooperation that would have been necessary to move the P.1154 into reality would never materialise.

Some of the P.1154 work contributed to the final operational vertical take-off fighter based on the Kestrel, the highly successful Harrier. The Mirage IIIV was never a realistic combat aircraft; the eight lift engines would likely have been a maintenance nightmare, and certainly their weight imposed a severe range and payload penalty on the aircraft.

• Buttler, Tony (2015). X-Planes of Europe. II: Military Prototype Aircraft from the Golden Age 1946–1974. Manchester, UK: Hikoki Publications. ISBN 978-1-90210-948-0.
• Breffort, Dominique and Andre Jouineau. "The Mirage III, 5, 50 and derivatives from 1955 to 2000." Planes and Pilots 6. Paris: Histoire et Collections, 2004. ISBN 2-913903-92-4.
• Carbonel, Jean-Christophe (2016). French Secret Projects. 1: Post War Fighters. Manchester, UK: Crecy Publishing. ISBN 978-1-91080-900-6.
• Jackson, Paul. Modern Combat Aircraft 23 - Mirage. London: Guild Publishing, 1985. ISBN 0-7110-1512-0.
• Jefford, C.G, ed. (2006). The RAF Harrier Story (PDF). London: Royal Air Force Historical Society. ISBN 0-9530345-2-6. Archived from the original (PDF) on 2011-01-05.
• Jenkins, Dennis R (1998). Boeing/BAe Harrier. Warbird Tech. 21. North Branch, Minnesota: Specialty Press. ISBN 1-58007-014-0.
• "Mirage IIIV." Flight International, 20 May 1965. pp. 774–775.
• Pérez, San Emeterio Carlos. Mirage: Espejismo de la técnica y de la política. Madrid: Armas 30. Editorial San Martin, 1978. ISBN 84-7140-158-4.