Automatic Gun - Laying Turret The British Automatic Gun - Laying Turret ( AGLT ) was a radar - aimed FN121 turret fitted to some Lancaster and 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 . The system , known as TR3548 , 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 ( 3 GHz ) with a pulse repetition frequency of 660 hertz . The magnetron used was the CV . 186 of approx 35 kW . 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 centre 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 . The first squadron to use Village Inn operationally was No . 101 Squadron RAF , based at Ludford Magna , in the autumn of 1944 , followed soon afterwards by No . 49 in the attack on Darmstadt on September 11 / 12 , 156 and 635 Squadrons . Village Inn was eventually produced in four Marks : AGLT Mark I — initial design — Airborne Radio Installation ( ARI ) 5559 . AGLT Mark II — modified , improved , Mark I — soon discontinued — ARI 5561 . AGLT Mark III — scanning aerial mounted remotely from turret . Scan independent of turret ' s movements — ARI 5562 . AGLT Mark IV — ARI 5632 The system was also fitted to the Rose turret on at least one Avro Lincoln B . Mk II , although how many so - fitted is not known at present . Some Lincolns fitted with the Boulton Paul Type D tail turret also incorporated the equipment . 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 .