Description of the radar set, tactical-technical characteristics
Figure 1: Radar bay of F-111D with the dual channel AN/APQ-171 in the lower nose part
|pulse repetition time (PRT):
|pulse repetition frequency (PRF):
|12,000 ft (≙ 3.7 km)
|hits per scan:
AN/APQ-171 is operating in the Ku-band dual-channel, frequency agile, forward-looking multimode radar developed for the General Dynamics F-111C/F Aardvark. The radar provides terrain-following, situation, terrain-avoidance, and ground map modes of operation. It is an improved version of the AN/APQ-128.
The antennas are small, flat array antennas consisting of parallel-fed waveguides with a total of 148 individual slot radiators.
The radar's primary function is to operate as terrain-following radar to provide proper commands to control the aircraft automatically at a preselected set clearance height above the terrain. This measure allows the pilot to fly a low-altitude flight path following the earth's contours, thereby reducing the probability of detection. Each channel of the terrain-following radar is identical, providing system flexibility and improving overall system reliability and mission success. One of the channels can be set at a different elevation angle, allowing an early warning of abrupt changes in the height of obstacles in the terrain. This significantly improves safety during low-level flight.