Development
The AAM-4 (developmental designation XAAM-4) medium-range air-to-air missile, is Japan's first attempt at developing such a sophisticated air combat weapon - one which features an active radar seeker. Japan's air-to-air missile programmes are highly classified, and few details have been released about the AAM-4 programme. The AAM-4 (service designation Type 99) is designed for use against aircraft and cruise missiles. It is claimed to offer a multiple launch engagement capability and to be highly resistant to ECCM techniques.It is known that work on the programme began as far back as 1985. Mitsubishi was reportedly awarded a USD15 million contract in 1993 for research studies into a replacement for the AIM-7 Sparrow missile. One option that was considered was the replacement of the semi-active radar homing seekers in Japan's inventory AIM-7s, by a new active radar seeker to deliver an enhanced, but low cost, BVR capability that could be rapidly fielded. Another option for the Japan Air Self Defense Force (JASDF) was the licensed production of the AIM-120 AMRAAM. Instead, Japan chose both to acquire the AMRAAM and proceed with its own active radar AAM development programme.The AAM-4 (XAAM-4) programme was managed by the Technical Research and Development Institute (TRDI), an agency of the Japan Defense Agency (JDA). Work on the missile has probably been conducted at the TRDI's Sapporo test centre (aerodynamic and propulsion test), Tsuchiura test centre (rocket motor testing) and the Nijima test centre (ground-launched testing). XAAM-4 development started in 1994 and 50 prototype missiles were contracted
