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The Dassault Mirage IV

v1.1.0 / 01 feb 04 / greg goebel / public domain

* In the mid-1950s, the French decided to develop a nuclear deterrent force, which led to a need for a strategic bomber. As a interim measure, they simply built a scaled-up version of the Mirage III fighter, known as the "Mirage IV", with the expectation that it would be soon replaced by a more capable aircraft. It is said that there is nothing so permanent as a temporary solution, and the Mirage IV was still flying in combat at the end of the century, if admittedly in small numbers and as a spy plane, not a bomber. This document provides a history and description of the Mirage IV.



* The decision to acquire a nuclear strike capability would lead the French to eventually develop land-based and submarine-based missiles, as well as a strategic bomber, with work on the aircraft begun by Dassault in 1957. The company envisioned a scaled-up version of the Mirage III fighter, originally focusing on a "Mirage IVC" with twin Pratt & Whitney J75 turbojets, but finally settled on a smaller design, the "Mirage IVA", which was powered by twin Atar turbojets as used on the single-engine Mirage III.

The prototype Mirage IVA first flew on 17 June 1959, and was fitted with twin Atar 09C engines. It exceeded Mach 2 on its 33rd flight, and on 15 September 1960 set a world's record for a 1,000 kilometer (621 mile) closed circuit flight, with an average speed of 1,820 KPH (1,130.9 MPH / 982.1 KT).

It was followed by three preproduction machines, the first flying on 12 October 1961, after the French had detonated their first nuclear weapon in February 1960, and was closer to production spec, with a shorter tailfin. The last of the preproduction machines performed its initial flight on 23 January 1963. It was essentially production specification, with Atar 09K engines providing 46.1 kN (4,700 kgp / 10,400 lbf) dry thrust and 65.7 kN (6,700 kgp / 14,800 lbf) afterburning thrust each.

The Mirage IVA formally entered service with the French Armee de l'Air (AdA) in 1964. A total of 62 production Mirage IVAs was built between December 1963 and November 1966, consisting of an initial batch of 50 machines, followed by a second batch of 12. That gave total production of the Mirage IV, including prototypes and evaluation machines, as 66. In 1966, there were nine squadrons on alert, with each squadron maintaining at least one aircraft bombed-up and ready to take off on a moment's notice.

* The Mirage IVA had a configuration very similar to that of the Mirage III, though the bomber was scaled up by 50% in linear dimensions compared to the fighter and weighed about twice as much, and had twin engines instead of one. The Mirage IVA was an all-metal aircraft made mostly of aircraft aluminum. Its engines featured moveable inlet half-cones ("souris / mice") to compensate for different airflow conditions, as well as spring-loaded pressure relief doors set well back from the inlet lip to provide additional airflow for takeoffs.

Other noticeable differences from the Mirage III were the tandem cockpit for pilot and navigator and a much more elaborate landing gear system. The two aircrew got in and out of the aircraft through individual rear-hinged canopies. The pilot had a poor rearward view, while the navigator only had a small window on each side of the cockpit, though he also had a periscope that extended through the floor to provide a downward view. Both sat on Martin Baker Mark BM.4 ejection seats, license built by Hispano, and the cockpit was climate conditioned. The main gear bogeys featured four tires in a two-by-two arrangement, with the main gear retracting from the wing in towards the fuselage. The steerable nose gear had two tires and was long to give the aircraft a nose-up attitude for takeoffs. It retracted towards the rear. All landing gear was hydraulically operated.

The Mirage IVA's low-mounted wing had the 60 degree sweep of the Mirage III, but featured a thinner chord of 3.8% at the root. This relatively thinner wing was permitted by the aircraft's greater size and was better suited for supersonic flight. There was a small sawcut about two-thirds of the way down the leading edge of each wing to prevent airflow separation over the wingtips. Each wing featured independently controllable side-by-side elevons in the rear and an airbrake on the top forward corner, with all these surfaces hydraulically operated. The wing contained integral fuel tanks as did the tailfin, and there was a large amount of tankage in the center fuselage as well, which precluded fitting a bombbay.

Since delta wings demand a lot of runway to for takeoff, a loaded Mirage IVA was fitted with rocket-assisted take-off (RATO) boosters, four attached at the rear of each wing. The RATO boosters were discarded after take-off. With RATO boosters and the heavy-duty landing gear, the Mirage IVA was in principle capable of operating from rough airstrips. Since deltas also tend to land "hot", a ribbon-style brake parachute was fitted in a fairing in the base of the tail.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                11.85 meters        38 feet 10.5 inches
   wing area               78.0 sq_meters      839.61 sq_feet
   length                  23.50 meters        77 feet 1.2 inches
   height                  5.65 meters         18 feet 6.4 inches

   empty weight            14,500 kilograms    32,000 pounds
   max loaded weight       31,600 kilograms    70,000 pounds

   maximum speed           2,335 KPH           1,450 MPH / 1,260 KT
   service ceiling         20,000 meters       65,600 feet
   range                   3,200 kilometers    2,000 MI / 1,740 NMI
   _____________________   _________________   _______________________

* Despite the fact that the Mirage IVA had no bombbay, was crammed full of fuel tanks, and was also generally fitted with twin 2,500 liter (660 US gallon) drop tanks, its range for its assigned mission of penetrating Soviet airspace was still marginal. The French expected to acquire a more formidable bomber later, but eventually gave up on developing a follow-on and settled for a fleet of 12 Boeing KC-135F tankers to give the Mirage IVA a chance to get back home after destroying its target. The bomber's long needle nose was actually a midair-refueling probe. There was a retractable spotlight under the nose to assist in midair refueling at night or in foul weather.

There was a circular radome on the belly of the aircraft, just behind the air intakes, which was initially for a Thomson-CSF DRAA 8A navigation radar. Other avionics included a Marconi Doppler navigation system; a Dassault flight computer; a SFENA autopilot system; a Thomson-CSF Type BF radar warning receiver (RWR); as well as IFF (identification friend or foe transponder) and VHF/UHF radio systems. An OMERA Robot strike camera was fitted under the nose. There were two stores pylons on each wing, with the inner "wet" pylon normally used for a drop tank and the outer one used for countermeasures gear. A Philips BOZ 100 chaff-flare pod was usually mounted on the right outer pylon, while a Thomson-CSF Barem automatic jammer pod was mounted on the left.

The weapon for which the Mirage IVA was designed, the 60 kilotonne AN-22 nuclear weapon, fit into a recess in the fuselage. A ferry tank could also be plugged into the recess. The AN-22 was modified after late 1967 to be parachute-retarded, when it was realized that the Mirage IVA could not expect to penetrate Soviet airspace at high altitude. If the drop tanks were not carried, the Mirage IVA could carry six 1,200 kilogram (2,645 pound) conventional bombs or four AS-37 Martel anti-radar missiles, though conventional strike was apparently never more than a secondary mission at best.



* After the British government cancelled the British Aircraft Corporation (BAC) TSR.2 low-level strike aircraft in 1965, a "Mirage IV*" was proposed as a replacement for the British Royal Air Force. The Mirage IV* would have been license-built by BAC and was to have featured the avionics suite developed for the TSR.2, as well as a fuselage extension of 61 centimeters (2 feet) and twin Rolls-Royce Spey 25R afterburning turbofans, providing 93.4 kN (9,525 kgp / 21,000 lbf) thrust each.

The British government didn't bite on the idea, preferring to acquire the American General Dynamics F-111K instead. That didn't work out either, with Britain cancelling orders for the F-111K after the program suffered considerable delays and cost escalation. The RAF finally received a modestly modified version of the Royal Navy's Blackburn Buccaneer carrier based strike aircraft, which turned out to be a fine solution, but that is another story discussed elsewhere.

* In the late 1970s, twelve Mirage IVAs were relegated to the strategic reconnaissance mission by replacing the AN-22 bomb with the CT-52 sensor pod, providing a capability along the lines of a "poor man's SR-71". The sensor pod was reconfigurable, a typical configuration being three low-altitude OMERA 35 film cameras, three high-altitude OMERA 36 film cameras, and a Wildt mapping film camera. A SAT Super Cyclone infrared linescan imager could be swapped out for one of the OMERA 36 high-altitude cameras. The reconnaissance variant was designated "Mirage IVR". It appears that changes to the airframe were restricted to wiring and controls for the CT-52 pod.

* In the 1980s, the Mirage IV obtained a new lease on life in the bomber role when a number were rebuilt to carry the ASMP ramjet-powered stand-off missile with a 300 kilotonne warhead, instead of the AN-22 free-fall bomb. These aircraft were originally given the designation of "Mirage IVN", where the "N" stood for "Nucleaire", but soon were redesignated "Mirage IVP", where "P" stood for "Penetration".

This was a substantial upgrade, including the addition of interface gear to allow the bomber to interact with the missile; fit of a new Thomson-CSF ARCANA pulse-Doppler radar with high-resolution ground-mapping capability, replacing the original DRAA 8A navigation radar; dual SAGEM Uliss inertial navigation units; a Thomson-CSF Serval RWR; and addition of a center pylon for carriage of the ASMP. The first of two Mirage IVP prototype conversions performed its first flight in 1982. The first of 18 production conversions was delivered to the AdA in 1985, with all conversions completed in a few years.

* By the end of the century, all Mirage IV bombers had been retired, with the Mirage 2000 replacing them as the carrier for the ASMP missile. However, five Mirage IVRs were still in service, and three of these made significant contributions to the NATO air campaign against Yugoslavia in the spring of 1999. These machines performed high altitude, high speed overflights of Yugoslavian territory, observing about 20 targets on a mission.

While the CT-52 pod's cameras were all "wet film" instruments, the film was quickly developed, annotated, digitized, and electronically distributed after return to base, providing NATO commanders with up-to-date imagery intelligence.



* Judging the success of the Mirage IV is difficult, particularly since it has seen little active combat service. The aircraft was clearly a compromise type with many limitations, but it did fulfill its assigned mission, and served for long after it was to have been phased out. One judgement is less ambiguous. The Mirage IV was a sleek and elegant machine and pictures of it taking off with its roaring RATO boosters imply that it was impressive to watch as it climbed off into the sky.

* Sources include:

Various recent operational details for the Mirage IV were obtained from my archive of WORLD AIR POWER JOURNAL magazines.

* Revision history:

   v1.0   / 01 apr 00 / gvg
   v1.0.1 / 01 may 02 / gvg / Minor cosmetic update.
   v1.1.0 / 01 feb 04 / gvg / General enhancement of detail
This document was originally part of a comprehensive history of all the Mirage delta aircraft. As I obtained new information, that document proved clumsy, and so I broke it down into documents on the Mirage III/5/50, the Mirage 2000, and the Mirage IV.


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