(USSR)

Notes: The “Trout Cheek” sonar is a conformal array carried in the submarine’s upper bow, which comes in several variants:

The basic passive-only array is carried in “Whiskey” class units. Active operations on these subs are crude, a separate omnidirectional pinger sends out a burst of sound and the operator has to try to localize the return echo.

On the “Romeo”, “Foxtrot” (pictured), “India”, “Golf”, “Bravo“, “Echo”, and “Juliett” classes, an active function is added by mounting the searchlight-style transducer of the Herkules MG-15 “Wolf Paw” (carried on small surface ships and the “Kynda” cruiser) immediately behind the conformal passive array. The transducer can be trained and fires single pings which concentrates the acoustic energy. This combination is often referred to as Herkules-Feniks. Performance is roughly comparable to the American AN/BQS-4 system. Range was about 3NM-5NM depending on conditions.

On some classes (such as the “Foxtrot”) there are additional hydrophones on the weather deck immediately above the array. These are unrelated acoustic intercept and UW comms sonars.

This is a slightly modified version used on some early nuclear submarines such as the “November” and “Hotel” classes. It was generally similar in function and range to “Trout Cheek”.