The AGM-122 Sidearm is a small Anti Radiation Missile, carried on the Army AH 64A/D Apache and Marine Corps AH-1W SuperCobra attack helicopters for self defense against anti aircraft gun and SAM radars. The AGM-122A SIDEARM weapon system consists of an air launched guided missile, which employs passive radar detection, proportional navigation guidance, and an active optical target detecting device. The missile utilizes the LAU-7 series launcher. The SIDEARM utilizes an AIM-9C SIDEWINDER guidance section modified to detect and track a radiating ground-based air defense system radar. The target detecting device is modified for air-to-surface use, employing forward hemisphere acquisition capability. SIDEARM shares a high degree of commonality with SIDEWINDER AIM-9L/M aft components. The AIM-9L/M warhead, safe and arm device, rocket motor, and wings are redesignated SIDEARM-unique at the time they are painted green. The LAU-7 SIDEWINDER launcher provides the electronic and mechanical interface between the missile and launch aircraft. The LAU-7 internal cooling capability (nitrogen bottle) is not used for SIDEARM application.
The AGM-122A is a rebuilt AIM-9C Sidewinder, a semi-active radar homing missile using a conically scanning semi-active seeker. Originally designed for the F-8 Crusader, it was unique among the Sidewinder variants, which are all otherwise infra-red guided. In the mid-1980s several hundred of these missiles were refurbished and redesignated as the AGM-122A Sidearm in response to a Marine Corpsrequirement for a lightweight Anti-Radiation Missile to arm Marine Corps AV-8s, A-4s and helicopters.
Modifications developed at the China Lake Naval Weapons Center and produced by Motorola included improved semi-active seeker electronics to provide coverage of the greater bandwidth required to home in on a range of air defense radars. The AIM-9C's original Mk.17 motor and WDU-17 warhead were retained, with the substitution of a DSU-15 active fuse. Control electronics were modified to command an immediate pop-up after low-level launch to provide a dive attack on the target radar.
Although the resulting capability was vulnerable to countermeasures and rather limited compared to more robust anti-radar missiles such as HARM , it does provide a useful self-defense capability against low-level anti-helicopter threats such as the ZSU-23 or SA-8.