DUAV 4

The DUAV 4 was an active/passive helicopter dipping sonar. The DUAV 4 was designed to be used on light, ship-based, anti-submarine helicopters, the French navy's Lynx and with the helicopters of export customers.

This description refers to the sonar when in active service: Once the transducer is dipped below the surface -- typically 460 feet (140 meters) -- a fixed-frequency active mode at 20 MHz determines the target submarine's bearing, range and radial speed using Doppler....