Dassault Mirage IV - Design

Design

The Mirage IV shares design features and a visual resemblence to the Mirage III fighter, featuring a tailless delta wing and a single square-topped vertical fin. However, the wing is significantly thinner to allow better high-speed performance and has a thickness/chord ratio of only 3.8% at the root and 3.2% at the tip; this wing was the thinnest built in Europe at that time and one the thinnest in the world. While being significantly smaller than an expensive medium bomber proposal for the role, the Mirage IV was roughly three times the weight of the preceeding Mirage III.

The Mirage IV has two SNECMA Atar turbojets in the rear fuselage, with air intakes on both sides of the fuselage that had intake half-cone shock diffusers, known as souris ("mice"), which were moved forward as speed increased to reduce inlet turbulence. It can reach high supersonic speeds: the aircraft is redlined at Mach 2.2 at altitude because of airframe temperature restrictions, although it is capable of higher speeds. The aircraft has 14,000 liters (3,700 gal (US)) of internal fuel, and its engines are quite thirsty, especially in afterburner. While the first Mirage IV prototype was fitted with double-eyelid engine nozzles, a more complicated variable geometry nozzel was adopted for production aircraft.

The two-man crew, pilot and navigator, were seated in tandem cockpits, each housed under separate clamshell canopies. A bombing/navigation radar is housed within a radome in the fuselage under the intakes, aft of the cockpit; much of the Mirage IV's onboard avionics systems, such as communications, naviational instrumentation, and bombing equipment, were produced by Thomson-CSF. A refueling boom is built into the nose; aerial refuelling was necessary in most Mirage IV operations as the aircraft only had the fuel capacity, even with external drop tanks, to reach the Soviet Union's borders, thus refuelling was required to allow for a 'round trip'. In the event of nuclear war between the major powers, it was thought that there would be little point in having the fuel to return as the host air bases would have been destroyed; instead, surviving Mirage IVs would have diverted to land at bases in nearby neutral countries following the deployment of their nuclear ordinance.

The Mirage IV has two pylons under each wing, with the inboard pylons being normally used for large drop tanks of 2,500 liter (660 gal (US)) capacity. The outer pylons carry ECM and chaff/flare dispenser pods to supplement the internal jamming and countermeasures systems. On current aircraft, these are typically a Barax NG jammer pod under the port wing and a Boz expendables dispenser under the starboard wing. No cannon armament was fitted. The early Mirage IVA had a fuselage recess under the engines for a single AN-11 or AN-22 nuclear weapon of 60 kt yield. The Mirage IV can carry 12 solid-fuel rockets diagonally down below the wing flaps, for rocket-assisted take off (RATO).

From 1972 onward, 12 aircraft were also equipped to carry the CT52 reconnaissance pod in the bomb recess. The CT52 is available in either BA (Basse Altitude, low-level) or HA (Haute Altitude, high-altitude) versions with three or four long-range cameras; a third configuration is an infrared line scanner. None of the CT52 has any digital systems, relying on older 'wet' film cameras. During the 1980s, a total of 18 Mirage IVs were retrofitted with a centerline pylon and associated equipment to carry and launch the nuclear ASMP stand-off missile. The Mirage IVA could theoretically carry up to six large conventional bombs at the cost of drop tanks and ECM pods, such armament was rarely fitted in practice.