Missile AAM-4

Technical research for a medium-range air-to-air missile began in 1985, with formal design work commencing in 1994. Live testing of the XAAM-4 prototype was conducted in 1996 using a modified F-4EJ Kai. The missile entered service in September 1999 as a replacement for the AIM-7 Sparrow. An updated version, the AAM-4B, entered production in 2010.

The AAM-4 is a beyond-visual-range missile utilizing a two-stage solid-fuel rocket motor. For guidance, it employs inertial, datalink, and semi-active radar homing during the mid-course phase, transitioning to active radar homing for terminal engagement. The control system uses fuzzy guidance logic to calculate flight paths based on 70 variables, which facilitates energy retention and electronic counter-countermeasures (ECCM) by cross-referencing datalink, inertial, and radar information. The seeker utilizes frequency modulation to reduce detection by radar warning receivers and employs a gallium arsenide semiconductor field-effect transistor (FET) for lock-on and anti-clutter performance.

The AAM-4B variant incorporates an Active Electronically Scanned Array (AESA) radar seeker utilizing gallium nitride (GaN) semiconductors. This seeker operates in the Ka band and is capable of Synthetic Aperture Radar (SAR) imaging. The missile is equipped with a directional blast-fragmentation warhead containing 600 steel segments capable of 7.7mm penetration. Detonation is triggered by either an impact fuse or a four-quadrant radar proximity fuse. The proximity fuse is frequency-modulated to resist electronic interference and has a four-to-six-second arming period. Engagement capabilities include aircraft, cruise missiles, and air-to-surface missiles, though interception of the latter two is restricted to front-aspect profiles.

The AAM-4 is operated by the Japan Air Self-Defense Force. It is deployed on F-15J aircraft, specifically post-J-MSIP models and those that have undergone Inspection and Repair as Necessary (IRAN). It is also integrated into the F-2 fighter following the installation of J/APG-2 radar systems. The missile is not compatible with the F-35 Lightning II due to the physical dimensions of its control fins and the requirement for a specific radio transceiver. Variants include the XRIM-4, a naval surface-launched version, and the AAM-4TDR, a test model featuring a throttleable ducted rocket with thrust vectoring. A joint program to integrate AAM-4 seeker technology with the Meteor airframe, designated JNAAM, was initiated but subsequently canceled.