Site Records

Site Name: RAF Boulmer ('EZS') GCI R3 ROTOR Radar Station & Control and Reporting Centre in the UK Air Surveillance and Control System

B1339 Lesbury
OS Grid Ref: NU240125

Sub Brit site visit 14th March 2005

[Source: Nick Catford]


By 1950, the threat of the Atomic bomb had caused a serious rethink in the organisation of air defence and a plan, codenamed ROTOR, was instituted to replace many of the existing stations with new protected underground operations rooms. Boulmer was specifically built on a new site as part of the Rotor programme but it did replace an existing WW2 Final GCI (happidrome) station at Northstead which had been fitted with a Type 7 search radar.

A site chosen for the new Ground Control Intercept (GCI) station was close to an existing airfield (RAF Boulmer) which had been returned to agriculture at the end of WW2.

The station was to have a two level underground operations room designated as an R3. The R3 was never intended to survive a direct hit from a nuclear weapon but was designed to withstand a near miss from Russian pattern bombing with 2,200lb armour-piercing high explosive bombs (BRAB) dropped from 35,000 feet.

The target date for completion of the station was 21st August 1953 and although not complete, the station opened on time with limited capabilities using an American AN/FPS3 long-range search radar and an AN/TPS10 height finder. The station was known as 500 Signals Unit under the control of RAF Acklington and part of 13 Group.

Cutaway drawing of an R3 underground GCI technical building
Drawn by Jason Blackiston

The R3 was complete and the site fully operational in September 1954. RAF Northstead closed and the personnel moved to the new domestic site at Boulmer. This was divided into two sites accommodating 'officers & NCOs' and 'other ranks'. The accommodation was Seco hutting with a married quarters estate.

The Type 7 radar at Boulmer was remotely sited a mile to the east of the technical site on the old airfield (now Field House Farm) with a ten core coaxial cable linking it to the R3.

The transmitter, receiver and motor for turning the aerial array were located underground in a bunker designated as an R7 and known as a 'well'. Because of the distance from the main site, this radar required its own IFF and an Mk 10 IFF was mounted on a Type 14 plinth, turntable and cabin. This arrangement of IFF and plinth was designated Type 79.

Remote Type 7
- Click here to see the site of RAF Boulmer's Remote Type 7 in 2004
This was located a short distance to the east of the R7 bunker with a small brick built electricity sub station alongside.

Remote VHF transmitter and receiver blocks were also sited at High Buston and a standby set house (generator) for the technical site was located at the 'other ranks' domestic site. Mobile reserve sites were also selected and prepared. Two CEW reserve sites at Embleton Moor and Christion Bank and an unknown GCI reserve site.
As built the following radars were fitted:

1 Remote Type 7 Mk III above an R7 well with a T79 IFF.
4 Type 13 MK VII mounted on 9' high concrete plinths.
2 Type 13 Mk VI mounted on 12' high concrete plinths.
1 Type 14 Mk VIII.
1 Type 14 Mk IX.
1 Type 54 Mk 3 mounted on a 200' tower for Centimetric early warning (CEW).
1 Type 79 Mk 1.

The underground operations room was ready for occupation in 1954 with the station coming fully on line as RAF Boulmer.
Due to supply and development problems with the introduction of a 'home-grown' long-range Centimetric Search Radar (Type 80) the station continued to use the American AN/FPS3 long range search radar and an AN/TPS10 height finder but in January 1956 a Decca Type 80 Mk. III search radar was finally installed and undergoing acceptance trials. The Type 80 was developed in the early 1950s from an experimental design based on the Type 14 Mk VI under the project code name Green Garlic; it replaced the earlier Type 7

Almost overnight, this radar made earlier air defence radars (dating from WW2) mostly redundant. The Type 80 improved the range of the station considerably with a range of up to 320 miles compared to the 90 mile range of the Type 7; this instantly made some of the earlier equipment obsolete. Following the installations of the Type 80 the two Type 14 radars were dismantled and removed. The Type 7 was kept in reserve in case of breakdown or maintenance of the Type 80.

Inside the R3, dramatic changes were also taking place. The large two storey operations room was superseded by a much smaller control room constructed on the top floor at the opposite end of the building. This included a 'well' in the floor for a photographic display unit (PDU) which allowed radar pictures to be projected up into a plotting table above. This apparatus, located in the room below was a Kelvin Hughes Photographic Projector; this comprised equipment that could record the radar image on 35 mm film, develop, fix and
dry the image and then project it up on to the plotting table in the control room on the floor above. The displayed image was only one minute behind real time. The PPI image from a high intensity cathode ray tube was projected on to the film through a focusing lens. Each revolution of the radar antenna took 15 seconds and it took this time to expose the film to a full revolution. At the end of the sweep, the frame would be moved on to be developed, whilst the next frame was exposed.

When the frame moved on at the end of the next sweep the image was fixed, it then moved on again to be dried.

Finally, the frame moved on once more where it was projected, via a mirror, to the underside of the frosted glass plotting table on the floor above. Meanwhile the next frame to be exposed had been following on through the process, so at the end of the next revolution this frame was projected, 15 seconds after its predecessor. As frame after frame was displayed on the map the plotters in the pit could place markers on the map to indicate friendly or hostile aircraft.

By December 1956, the main role of the station was a reporting role for Northern Sector and a standby reporting role for Eastern and Caledonian Sectors and for Killard Point in Northern Ireland.

Photo:The modified ROTOR guardhouse is the entrance to the R3 bunker. Click here to see a picture of the guardhouse before it was modified
Photo by Nick Catford

The station took part in Exercise FORMULATE in 1956. This involved 21 Meteors making a simulated attack from Germany on Northern Sector. The Type 80 performed well, although it was adversely affected by cloud cover, but the limited range of the Type 7 proved to be a handicap. RAF Seaton Snook also took part in the exercise using Type 7 and Type 13 radars and during the exercise 432 Light Anti Aircraft regiment defended the base.

Click here for more information and photographs of RAF Boulmer

[Source: Nick Catford]

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