Monica, Boozer, Fishpond (a rear warniing radar attachment for H2S) and AGLT were all designed at the request of
Bomber Command specifically to defend its own aircraft while over enemy territory. They were not intended, at least to begin with, for more general use. And BC never reached a point with any of these sets whereby its entire fleet was fitted with them.
Monica - the story began in late 1940 but it was mid-1942 before any trials could begin. General introduction to Bomber Command aircraft was delayed by worries that it would quickly be jammed and thereby made obsolete. Then it was decided that it couldn't be introduced piecemeal, it had to be introduced in quantity across the BC fleet starting with the Halifax squadrons. Both retrofitting to existing in-service aircraft as well as production line fitting of the necessary wiring began in Spring 1943 with the first operational use in June 1943.
Monica Mk.I only gave an audible warning to the crew of an aircraft when the radar detected. The range was initially set at 1,000 yards which was rapidly found to be too great for aircraft operating in a bomber stream. There was no directional indication nor any IFF facility. Its use also interfered with some other systems like Oboe. And it couldn't be used below 3,000ft due to ground returns (so any use in Coastal Command would have been severely limited). So it generated a lot of false alarms. In July 1943 sets were modified to allow selection of ranges of 1,000, 800, 600 & 400 yards as automatic settings to be selected at the choice of the squadron commanders.
By late 1943 it had been decided to give Monica a visual display. 650 ASV.II sets were taken from Coastal Command to produce Monica IIIA sets in early 1944. That was followed by a productionised Monica IIIB. But at that stage not all the BC aircraft intended to get Monica had received a set.
As 1944 went on the loss rates amonst Monica equippped aircraft gradually increased. In July a Ju 88G-6 landed at Woodbridge by mistake and delivered to the RAF an entire suite of the lastest Luftwaffe radars and homing devices. That included a FuG 227 Flensburg set designed to home on the Monica radar emissions. The result was that BC, with the exception of 100 Group, stopped using Monica in Sept 1944.
Boozer entered service at the end of 1942 initially as a passive system to detect Luftwaffe ground control and gun laying radars. It was enough to help a BC aircraft to avoid areas of flak & searchlights in particular. On receipt of a signal it lit a red light in the aircraft. In developed double channel form it could differentiate GCI from GL radars, indicated by different intensities of red light, and in triple channel form it could also detect early Luftwaffe AI radars, lighting a yellow light in the aircraft. It was late 1943 before the latter set was available. The lights were in both the pilot's cockpit and the wireless operator's station. By Aug 1943 about 400 BC aircraft had received any form of Boozer set.
CC made some limited use of Boozer in 1943/44 tuned to U-boat radar frequencies but BC had priority for the equipment.
Boozer was removed from all BC aircraft except Mosquitoes in Sept 1944 because it was no longer effective against the S.N.2 radar then being fitted to Luftwaffe night fighters (another gift from the Woodbridge Ju 88) and it was no longer effective against GCI/GL radars.
A full description of the development of these systems can be found in the RAF Signals Narrative Vol III starting at page 357 for anyone who wants more detail.
Thematic Studies Airborne Forces Airborne Forces 32.3 MB Arnhem: The Air Reconnaissance Story - Third Edition 2024 14 MB - Airfield Air Defence Since 1933 8.4 MB - Air Sea Rescue 22
www.raf.mod.uk
RAF Signal Narrative vol VI from p 163 covers CC use of radar detection systems including the limited use of Bagful, Boozer & Greenbottle.
But once U-boats began to use schnorkels from mid-1944 and spent the great majority of their time underwater, the need for radar detectors by CC more or less disappeared.
