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 The continuous-rod warhead of the AIM-7 has been replaced by a blast-fragmentation warhead with a ‘smart’ fuze.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.