Automatic Gun-Laying Turret

The Automatic Gun-Laying Turret (AGLT) was a British radar-aimed FN121 turret fitted to some Avro Lancaster and Handley Page Halifax bombers in 1944. The AGLT system was devised to allow a target to be tracked and fired-on in total darkness, the target's range being accurately computed as well as allowing for lead and bullet drop. The system was referred to by the codename Village Inn during development, and given the number TR3548.

The system was devised by a team led by Dr Philip Dee and designed under the aegis of chief designer Dr Alan Hodgkin, after receiving a request from the Air Ministry for such a system in early 1943. Village Inn was evaluated and tested by the Telecommunications Research Establishment (TRE) at RAF Defford using the Lancaster Mark I serial number ND712 Lancaster Mark III JB705 and Mk II LL736 and LL737 and subsequently put into production.

The system consisted of a transmitter/receiver unit mounted in the navigator's compartment, operating through a conical scanning parabolic aerial attached to the standard Frazer-Nash turret. It worked on a wavelength of 9.1 cm (3 GHz) with a pulse repetition frequency of 660 hertz. The magnetron used was the CV.186 of approx 35kW. The electronics sent a signal back to the turret, where it was displayed on a cathode ray tube (CRT) display screen positioned adjacent to the gun sight, the image of which was projected on to the Mark IIC gyro gunsight via a semi-transparent mirror.

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