Site Records

Site Name: RAF Sandwich ('YTM') R3 GCI ROTOR Radar Station

Final GCI
Ash Road, Sandwich, Kent
OS Grid Ref: TR320586
Rotor GCI
Marshborough Road, Ash, Kent
OS Grid Ref: TR303574


[Source: Nick Catford]

Following the outbreak of WW2 and the evaluation of the Chain Home (CH) and Chain Home Low (CHL) radars under operational conditions, a requirement were identified for control radar to aid the fighter interception of enemy aircraft.

The coastal CH and CHL radars all looked out from the UK, leaving a void inland, this void  relied on the Observer Corps (later Royal Observer Corps) for overland reporting, which was not effective in bad weather or at night.

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. The GCI station enabled fighter aircraft under their control to intercept hostile aircraft. after detection by the network of reporting Chain Home reporting radars.

The first GCI's were mobile, at the insistence of the Air Ministry who required maximum flexibility from the equipment and were the first phase of a three part programme, i.e.: Mobile, Intermediate (mobile or transportable) and then Final.

A typical Intermediate Transportable radar installation
In April 1942 the construction of a new GCI radar station started at Sandwich on the south side of Ash Road to the west of the town, with an Intermediate Transportable GCI installation completed by August of that year using an AMES Type8b radar. Due to serious enemy jamming the GCI function wasn't transferred from Willesborough to Sandwich immediately. Sandwich was not a self accounting station at this time, operating as a lodger unit did under
the administrative control of RAF Manston.

During WW1 Stonar Camp was built by the army on the south of Ramsgate Road to serve the Richborough Military Port. By the time RAF Sandwich was established this camp was vacant and it may have been used for accommodation. Other station personnel were billeted at houses in Sandwich and at the technical site which is an unusual practice. The Stonar Girls School moved out of the adjacent Stoner House in 1939 and the house was used for officers' accommodation.

Intermediate GCI’s 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.

Photo:The Happidrome at Sandwich, note the Type 14 radar plinth to the left of the two huts.

By 1943 the station had evolved into a GCI 'final' with a brick operations blocks, known as a 'Happidrome' (named after a BBC comedy radio programme featuring a farcical music hall where nothing seemed to go as planned and nobody quite knew what was happening - much like a GCI!!). The new Sandwich GCI site on the north side of Ash Road became operational on 15 June 1943. Its task was control any interceptions within the south east corner of Kent.

In December 1943, the installation of AMES Type 21 tactical control radar was started. This was the first installation of its kind and comprised an AMES Type 13 height finding radar together with AMES Type 14 search radar, both uniquely at this time mounted on plinths. The Type 21 was sited at selected vulnerable south east GCI stations to combat projected jamming of the 1.5 metre Type 7. Both the Type 13’s and Type 14’s were centimetric and operating on a different frequency. Development of the first AMES Type 13 began in September 1942 as a mobile height-measuring equipment but it was not produced in quantity. An improved Mark II version known as the Centimetre Height or CMH set was put into production in March 1943. A cheese aerial. By rocking the beam up and down, great accuracy and discrimination in height finding was possible. The need for similar performance in reading plan position led to the development of the Type 14, in which a cheese aerial was also employed. The

Type 13 Radar at RAF Sandwich
Type 14 rotating aerial rotated in the horizontal position. The Type 14 section of the Type 21 installation at Sandwich was ready for service by 18th January 1944 and the Type 13 Mk. II was ready shortly afterwards

Photo:Type 14 Radar at RAF Sandwich

The second installation was placed at Wartling and by June 1944 most of the important fixed GCI stations were equipped with Type 21 sets. It was found that the proportion of attempted interceptions resulting in enemy aircraft destroyed, or probably destroyed; during Window activity was significantly higher when the Type 21 equipment was brought into use. RAF Sandwich remained operational after the war and a Chain Home map dated March 1945 shows Sandwich as being equipped with Type 7 and Type 21 Mk II radars. In November 1946 Sandwich given the status of an independent RAF station. (Window was a jamming technique consisting of half wavelength strips of aluminium which were dropped in bundles from aircraft; it was shiny on one side and black on the other. When bundles were dropped every strip reacted as an aircraft to German radar).

Photo:RAF Sandwich Final GCI site. The happidrome can be seen bottom centre
with the Type 7 radar top left.

On the formation of 60 Group (the organisation to control all radar matters) the country was divided into Group Wing Areas.  By 1944 this had been adjusted to four areas with 70 Group in Scotland and the Islands, 73 Group in the Midlands, 75 Group in the Home Counties and South East England and 78 Group in the West Country. These areas were responsible for the technical support and administration (not to be confused with domestic administration which was the responsibility of he radar stations parent station). Operational command was still vested in Fighter Command thorough Group HQ’s and Sector Operations Centres. In November 1946, 75 Wing became Southern Signals Area.

In May 1947 there was a marked increase in night operations with three Bullseye exercises. On 9th May there was a free-for-all in which a GCI controlled Mosquito was used to carry out interceptions on all unidentified aircraft, an exercise that proved to be particularly interesting with all the Mosquito squadrons from RAF West Malling participating in these exercise. In addition to the night exercises there were two weeks of Metropolitan Flight Control.

In June 1945 a fire seriously damaged the Happidrome ops room, resulting in the deployment of mobile type 13 and 14 to maintain radar cover. The existing Type 7 services were transferred  to two rooms in the rest area as a temporary ops room at the opposite end of the Happidrome and were adapted and equipped  as control and reporting rooms. The control room had one

The Type 7 transmitter/receiver was located in an underground well
control position with the DR board, three DU5 radar consoles and a small plotting table. The reporting room has 3 DU5 radar consoles, two for PPI positions and one as a Type 7 radar height finder. The work of reforming the station’s radar facilities within the airmen’s restroom was completed by the end of May 1947 with the changeover to a static site  taking place in July. After the fire the Sergeants Mess, RAF Police & cooks moved to the technical site where the Orderly Room was extended and an additional hut was built. In February 1947 some personnel were billeted at Creighton House, The Barn and River House, all in Strand Street but after a few months they had all moved to Stonar House. In August 1947 Sandwich was operational as a static site with a forward VHF relay installed for Trimley Heath at the GCI VHF site at Ash.

Photo:The reporting room in a typical Happidrome

In July 1948 the Type 7, Type 14 and mobile Type 11 search radars were reported as being operational.

Click here to continue the history of RAF Sandwich

[Source: Nick Catford]

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