Site Name: RAF Sopley ('AVO') R3 GCI ROTOR Station
OS Grid Ref: SZ162978
RSG site visit 23rd May 2000
[Source: Nick Catford]
The Ground Control Intercept (GCI) was designed to fill this gap, providing inland coverage to Filter Rooms, Sector Operations Centres (SOC) and Gun Operations Rooms (GOR) in addition to the control of defence fighters combating enemy aircraft by day and night. Sopley was operational 24 hours a day, every day, with a three watch system of staffing.
The GCI system had an extremely convoluted and complex history. The programme was subject to rapid change, some projects being superceded whilst still in the workshop, whilst others were conducted in the field and then retrospectively fitted to other radars. For example, in the spring of 1941 an experimental modification to the height finding at Sopley resulted in the other five original sets being 'Sopleyfied'. Changes in enemy tactics also meant that the siting of GCI's was constantly being subjected to review and revision.
Layout of a mobile GCI operations room
The other type 8 radars were:
The 8e was a Mk IV GCI mobile with only a GCI capability, none of these 8e convoys were used in this manner. They were modified with conversion kits to provide facilities for GCI, COL (Chain Overseas Low) or CH (B) Chain Home, Beam) working and when converted became the AMES type 15 Mk 1 mobile GCI Convoy.
The mobiles were the first of three stages, the Intermediates were the second stage, pending the construction of the permanent, brick built, multifunctional 'Final' GCI with the much delayed Type 7 radar array built over an underground chamber containing the transmitter, and capable of conducting several interceptions simultaneously.
Operational trials started on the first Ground Control Interception radar station at Durrington (near Worthing) on 29th November 1940 and by 3rd December, 36 practice interceptions had been completed. With the success of Durrington, five more GCI stations were proposed with the first mobile installation established at Sopley in December 1940.
The mobile Type 8 radar was designed at the Telecommunications Research
Establishment at Worth Matravers in Dorset and built at the War Office/Ministry
of Supply Air
Defence Research and Development Establishment (ADRDE) in nearby
Christchurch. It was adapted from Army Gun Laying trackers and had two
manually rotated aerials rotated by airmen pedalling in the cabin mounted
on the aerial trailer behind the aerial array.
The aerial's alignment onto a target was originally a manual process
with airmen pedalling to operate a mechanical linkage to turn the aerial.
The fighter controllers used a bell code and mechanical indicators.
The aerial's sweep could also be reversed or concentrated in a defined
sector of the sky giving a more frequent update of the track information
than a 360 degree scan during the later stages of an intercept.
Photo: Mobile GCI at RAF Sopley on 5th January 1941
The transmitter aerial was fed by a transmitter in an adjacent lorry while the receiver aerial was fed into the operations trailer via a receiver vehicle where a range of displays indicated bearing, range and height and incorporated a Plan Position Indicator [PPI] display with the radar display equipment to drive the PPI's in the Control Van
The ops room had a crew of three, a height finder operator, a fighter controller and a plotter. From the beginning Sopley seems to have been equipped with Identification Friend or Foe (IFF).
By early 1941, Sopley had become the most effective GCI station with over one hundred successful night interceptions which were achieved by the fighter controllers at Sopley working in conjunction with Bristol Beaufighter night fighter squadrons who destroyed 27 enemy aircraft, more than twice the success rate of any other GCI.
This was an unusual arrangement, the normal course of events was for one or the other but not both.
The intermediate transportable installation at Sopley with a Type 8C radar with transmitter and reciver aerials above and below the gantry
Plan of a typical GCI intermediate operations hut
Click here to continue the history of RAF Sopley
[Source: Nick Catford]
Last updated 7th September 2006
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