The British Automatic Gun-Laying Turret (AGLT) was a radar-aimed FN50 turret fitted to some Lancaster 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 known under the codename Village Inn during development.
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 ND712 and the Lancaster Mark IIIs JB705 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 Fraser-Nash turret. It worked on a wavelength of 9.1 cm with a pulse repetition frequency of 660 per second. 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.
Initially, ranging information was provided only at the transmitter situated in the navigator's compartment and was read-off to the gunner over the intercom, the gunner using foot pedals to set the target range on the sight. In production equipment the process was made automatic, the range information being fed electronically directly into the gunsight, with the navigator's "running commentary" only being retained for the benefit of the rest of the crew. The gunner simply maneuvered his guns to place the "blip" in the center of the gunsight's reticle, and opened fire when the range was appropriate. Windage, bullet drop and other factors were already calculated by the gunsight.
Village Inn was eventually produced in three Marks:
AGLT Mark I - initial design.
AGLT Mark II - modified, improved, Mark I - soon discontinued.
AGLT Mark III - scanning aerial mounted remotely from turret. Scan independent of turret's movements.
A similar type of system was produced in the US by the Emerson Company, St Louis, when an Emerson Model III tail turret was equipped with the Emerson APG8 Blind Tracking Radar and fitted to the Canadian-built Lancaster KB805. The system was found to have no advantages over the British system and the project was subsequently dropped.