The AIM-120 Advanced Medium Range Air-to- Air Missile (AMRAAM) was developed jointly by the US Air Force and Navy to succeed the AIM-7 Sparrow III. A 1980 Memorandum Of Understanding (MOU) between the United States, Great Britain, and (West) Germany agreed that the medium-range missile would also be produced in Europe. Non way signed the MOU in 1989 and France has observer sta­tus within the European group.

The General Motors -Hughes AIM-120A began full-scale development in December 1981. Flight tests began 1985 and series pro­duction of an initial purchase of 105 missiles began in October 1987. The AIM-120A is cur­rently in production at Hughes Aircraft, with Raytheon as a second source. Hughes and Raytheon delivered the first production AMRAAMs to the Air Force in January 1989. An improved AIM-120C, with aerodynamic and electronic refinements, is undergoing service trials in 1996.

The AIM-120A is 12 feet long, seven inches in diameter and weighs approximately 350 pounds. The front fins span 1.75 feet and the rear fins span 2.1 feet. A Hercules high-thrust solid rocket motor boosts the missile over 40 miles at speeds in excess of Mach 4.

Unlike the AIM-7, whose target must be continuously illuminated by the launch air­craft’s radar, the AIM-120 is fitted with an active radar seeker whose five-inch antenna is energized by a small Traveling-Wave-Tube (TWT) transmitter. To operate the missile most effectively, the launch aircraft needs a track-while-scan radar and the ability to assign targets to more than one missile simultaneously. The active monopulse seeker uses a pulse- Doppler programmable waveform to penetrate clutter and precipitation. Rapid automatic gain control and digital signal processing con­tribute to the seeker’s Electronic Counter Countermeasures (ECCM) capabilities.

After launch, the missile can operate autonomously, turning on its active seeker at a preset time or distance. Alternatively, it can receive mid-course guidance updates to refine its terminal homing track. When presented with more than one target AMRAAM will choose a particular target and ignore the oth­ers. The continuous-rod warhead of the AIM-7 has been replaced by a blast-fragmentation warhead with a ‘smart’ fuze.

The AIM-120A outperforms the AIM-7 in all flight regimes, despite being only two-thirds as heavy. Unlike the AIM-7, the AIM-120A is capa­ble of being rail-mounted, allowing it to replace AIM-9 Sidewinders.

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