Anti-Circling Unit

Anti Circling
Unit
560150
Serial No ???
G.E.C. 1967

When a submarine launches a Torpedo the sensors in the weapon will seek the target and the weapon may seek over a wide area before locking on. It is important that the sensors do not home in on the launch vehicle so the anti-circling unit was developed to prevent this. An anti-¬circling device acts independently of the main heading reference, to detect 180° turns immediately after launch. Such devices were mechanical, relying on the inertial aspects of a gyroscope to detect the turn. FARL were asked by Gyro Division to investigate alternative means of implementing an anti-circling device. The most promising solution appears to be a monitor system to incorporate the integrity of the main strapdown attitude sensing unit (ASU). The monitor consists of a fourth rate gyro mounted skewed to the three orthogonal rate gyros of the ASU such that the output of the gyros can be compared; and a microprocessor to perform the inverse of the strapdown transformation.
The Mk 24 Tigerfish torpedo was a heavyweight acoustic homing torpedo used by the Royal Navy (RN) for several years and it is likely that this unit was developed for that programme. Marconi Avionics also developed the Attitude/Heading Reference System for both the UK Sting Ray and Spearfish heavyweight Torpedoes.
This item is also marked: "LCON 0347"