Dassault Mirage IV
The Dassault Mirage IV is a supersonic strategic bomber and deep-reconnaissance aircraft developed and produced by the French aircraft manufacturer Dassault Aviation.
Development of the Mirage IV began in the mid-1950s in response to a need for a supersonic carrier aircraft for France's independent nuclear deterrent. Dassault competed with other aircraft manufacturers, such as Sud Aviation and Nord Aviation, to have its proposal built, which was viewed as being both cheaper and simpler to develop in part due to it drawing upon the earlier Dassault Mirage III fighter. While originally intended as a dedicated bomber, a reconnaissance variant would also be developed. The first prototype, Mirage IV 01, performed its maiden flight on 17 June 1959; it set a new world record for speed over a 1000-kilometre closed circuit of 1,822 km/h on 19 September 1960. The first production-standard aircraft was completed during December 1963 and the Mirage IV entered service with the French Air Force in October 1964.
For many years, the type was a vital part of the nuclear triad of the Force de Frappe, France's nuclear deterrent striking force. While initially intended for a high-altitude mission profile, the fleet was modified during the 1960s to be flown at low altitude instead in response to increasingly capable anti-aircraft systems. This vulnerability also led to an increasing emphasis of other platforms for the nuclear deterrent platform, such as land-based missiles and submarine-launched ballistic missile. The fleet received various updates during its service life, including modifications to carry and launch the nuclear Air-Sol Moyenne Portée stand-off missile in place of gravity-dropped bombs. During 1996, the Mirage IV was retired from the nuclear strike role in favour of the newer Dassault Mirage 2000N, while the last examples of the type were withdrawn from operational service in 2005. There was investigations into potential export sales of the Mirage IV; during the 1960s, it was proposed that Dassault enter into a partnership with the British Aircraft Corporation to jointly produce a Mirage IV variant for the Royal Air Force and potentially for other export customers, but this project did not come to fruition. The Mirage IV was ultimately not adopted by any other operators.
Development
Origins
During the 1950s, France embarked on an extensive military program to produce nuclear weapons; however, it was acknowledged that existing French aircraft were unsuitable for the task of delivering the weapons. Thus, the development of a supersonic bomber designed to carry out the delivery mission started in 1956 as a part of the wider development of France's independent nuclear deterrent. In May 1956, the Guy Mollet government drew up a specification for an aerially-refuelable supersonic bomber capable of carrying a three tonne, 5.2-metre-long nuclear bomb 2,000 km. According to aviation authors Bill Gunston and Peter Gilchrist, the specification's inclusion of supersonic speed was "surprising" to many at the time.The final specifications, jointly defined by government authorities and Dassault staff, were approved on 20 March 1957. Sud Aviation and Nord Aviation both submitted competing proposals, both based on existing aircraft; Sud Aviation proposed the Super Vautour, a stretched Sud Aviation Vautour with thrust SNECMA Atar engines and a combat radius of at Mach 0.9. Dassault's proposal for what became the Mirage IV was chosen on the basis of lower cost and anticipated simpler development, being based upon a proposed early 1956 twin-engined night-fighter derived from the Dassault Mirage III fighter and the unbuilt Mirage II interceptor. In April 1957, Dassault were informed that they had won the design competition.
Dassault's resulting prototype, designated Mirage IV 01, visually resembled the Mirage IIIA, despite possessing double the wing surface, being powered by two engines instead of one, and having twice the unladen weight. The Mirage IV also carried three times more internal fuel than the Mirage III. The aircraft's aerodynamic features were very similar to the Mirage III's, but required an entirely new structure and layout. This prototype was long, had an wingspan, of wing area, and weighed approximately. It was considerably more advanced than the Mirage III, incorporating new features such as machined and chem-milled planks, tapered sheets, a small amount of titanium, and integral fuel tanks in many locations including the leading portion of the tailfin.
The 01 was an experimental prototype built to explore and solve the problems stemming from prolonged supersonic flight. At the time, no aircraft had been designed to cruise at over Mach 1.8 for long periods of time and there were sizable technological and operational uncertainties. Weapon-related issues were another issue. Building the 01 in Dassault's Saint-Cloud plant near Paris took 18 months. In late 1958, the aircraft was transferred to the Melun-Villaroche flight testing area for finishing touches and ground tests. On 17 June 1959, French General Roland Glavany, on a five-year leave from the French Air Force since 1954, took the 01 for its maiden flight.
On 19 September 1960, René Bigand increased the world record for speed on a 1000-kilometre closed circuit to 1,822 km/h around Paris and the Melun base. Flight 138, on 23 September, corroborated the initial performance and pushed the record on a 500 km closed circuit to an average of 1,972 km/h, flying between Mach 2.08 and Mach 2.14. The Mirage IV 01 prototype underwent minor modifications during testing in the autumn of 1959, most noticeably, the tail was enlarged.
Production
In order to increase range, studies were made of a significantly larger Mirage IVB design, powered by two Snecma license-built Pratt & Whitney J75 engines and having a wing area of 120 m² compared to 70 m² of the prototype IV, as well as a speed of Mach 2.4 and a gross weight of. The Mirage IVB proposal had been instigated as a response to interest by de Gaulle in ensuring that two-way strike missions could be flown. However, development of the aircraft was ultimately cancelled in July 1959 due to the greater cost involved, a decision having been taken to rely upon aerial refueling instead also being a factor.With the Mirage IVB considered to be too expensive, the medium-sized Mirage IVA, slightly larger than the first prototype, was chosen for three more prototypes to be produced. This aircraft had a wing area of and weighed about On 4 April 1960, a formal order for 50 production Mirage IVA aircraft was issued. The three prototype aircraft were built between 1961 and 1963, with first flights on 12 October 1961, 1 June 1962, and 23 January 1963. By 1962, the second prototype had conducted simulated nuclear bombing runs in the trials range at Colomb-Bechar in southern Algeria. The third prototype was equipped with the navigation/bombing systems and flight refuelling probe. The fourth prototype Mirage IVA-04 was essentially representative of the production aircraft that would follow.
For production, various portions of the aircraft were subcontracted to Sud Aviation and Breguet Aviation, which was still a separate company from Dassault until 1967; Dassault manufactured the front fuselage and flight-control system internally. Manufacture of both the prototypes and subsequent production aircraft was often hindered by an explicit requirement that there would be no reliance upon foreign suppliers to maintain France's nuclear capabilities; due to this, the Mirage IV initially lacked an inertial navigation system as French industry could not yet produce this device.
On 7 December 1963, the first production Mirage IVA performed its maiden flight. A series of 62 aircraft was built, and they entered service between 1964 and 1968. Although Dassault had designed the Mirage IV for the low-level flight role right from the start, the final batch of 12 aircraft ordered in November 1964 differed from the earlier aircraft in several areas, including the flight controls, avionics, and structural details, for the purpose of providing improved low-level performance. It had been planned for this batch to be powered by the newer Pratt & Whitney/SNECMA TF106 turbofan engine. The improvements featured upon the last 12 Mirage IVs were later retroactively applied to the whole fleet.
In December 1963 Dassault proposed a Mirage IV-106 variant powered by two Snecma TF106 engines, an enlarged 105,000 gross-weight fuselage, terrain-avoidance radar, and armed with a proposed French version of the American Douglas GAM-87 Skybolt air-launched ballistic missile. This version would have been very costly, and ultimately was not ordered.
Proposed export variants
During 1963, the Australian government sought a replacement for the Royal Australian Air Force fleet of English Electric Canberra bombers, largely in response to the Indonesian Air Force's purchase of missile-armed Tupolev Tu-16 bombers. Dassault proposed a version of the Mirage IVA with Rolls-Royce Avon engines. Australian Air Marshall Frederick Scherger seriously considered purchase of the IVA in 1961 because it was considered to be proven hardware already in service, before settling on the General Dynamics F-111C. The IVA was one of five aircraft types that were short listed for the role, but the F-111C was eventually selected.In April 1965, the British Government cancelled the TSR-2 reconnaissance-strike aircraft. However the operational requirement still existed, so in response, Hawker Siddeley offered the Buccaneer S.2, the Americans the General Dynamics F-111K, while, in July 1965, Dassault and British Aircraft Corporation jointly proposed a modified Mirage IV. The Dassault/BAC aircraft, known as the Mirage IV* or Mirage IVS would be re-engined with more powerful Rolls-Royce Spey turbofan engines with a total of, larger, and use avionics planned for the TSR-2, although BAC preferred the French Antilope radar. Although designed by Dassault, the production was to be carried out jointly between Dassault and its subcontractors and BAC. The final assembly location was not determined before this proposal was rejected. The Mirage IV* was to carry a bombload of up to.
The Mirage IV* was claimed to meet nearly every RAF requirement except for field length, and some claim it exceeded the F-111 slightly in speed and had at least equal range. The estimated cost was £2.321 million per airframe or £2.067 million, less than the price of the F-111K. However Air Ministry and RAF studies of the proposal identified further modifications to meet the RAF low-level performance requirements. These included airframe strengthening and revised cockpit glazing to improve visibility for both the pilot and crew member. There was also a significant shortfall in range, despite the lengthened fuselage. BAC claimed that the British government evaluation into the Mirage IV* was "relatively superficial". RAF pilots who test-flew the Mirage IV were "favourably impressed" with its low-altitude handling. However, some British government officials, including Parliament members Julian Risdale and Roy Jenkins, questioned the Mirage IV*'s capacity to operate from unprepared airstrips or to operate at low level, or claimed that the F-111 was a superior aircraft "in a class of its own". Air historian Bill Gunston notes that low-level Mirage IV missions had been planned since 1963 and Mirage IVs operated regularly at low level since 1965, and argues that the ability of a strategic bomber to operate from unprepared airstrips is historically unimportant.
Ultimately, as much for strategic political reasons as for technical ones, the F-111K was preferred and the Spey-engined Mirage abandoned.
BAC and Dassault had also hoped to sell the Mirage IV* to France and to export the Mirage IV* to various nations, such as India, possibly Israel, and others; the lack of a British sale put an end to such possibilities. Some aviation journalists claim that the rejection of the Mirage IV* may have dampened French interest in joint Anglo-French cooperation.