AN/APQ-171

The AN/APQ-171 is a dual-channel, frequency-agile, forward-looking multimode airborne radar operating in the Ku band (IEEE designation) or J band (NATO designation). Developed for the General Dynamics F-111C/F Aardvark, it offers terrain-following, situation, terrain-avoidance, and ground map modes. As an improved version of the AN/APQ-128, its primary function is terrain-following, automatically controlling the aircraft at a preselected clearance height to enable low-altitude flight and reduce detection probability. The radar features small, flat array antennas with 148 slot radiators and an instrumented range of 12,000 feet (3.7 km), with a mean time between critical failures (MTBCF) of 50 hours. Its identical dual channels enhance reliability and mission success, allowing one channel to be set at a different elevation angle for early warning of terrain changes, thereby improving low-level flight safety.

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