Introduction

SLEWC: Standby Local Early Warning System for UK MOD

 

Input from John Brown

BACKGROUND TO THE LEAD-UP TO SLEWC

With the English Electric Lightning F1 supersonic interceptor starting to be introduced from mid-1960 onwards, there was a view within Fighter Command that controllers might now need computer-aided facilities to carry out their work effectively; however, there was nothing available from the Royal Radar Establishment (RRE) at that time. In early 1962, John Burrow, Manager of the recently formed Aircraft Direction Division of Elliott Brothers (London) Ltd at Borehamwood, visited RAF Bentley Priory (Fighter Command’s HQ) seeking new business, and indicated that his engineers had foreseen this need and devised a scheme, using the Elliott 803 commercial computer, to control markers on a radar display, which could be used for tracking and providing interception data. The system was being called ‘FIREBRIGADE’.

 

At this point, I will digress for a moment: John Burrow had been the Marconi Radar Division lead salesman for ‘FUR HAT; however, having been successful in winning that contract, he soon after left the Company and went to Decca Radar, and later moved on to Elliott’s, where he was joined by Eric Kirk and Iorwerth Evans, both of whom he had valued highly at Decca’s.

 

A formal proposal was submitted to Fighter Command in April 1962, for one FIREBRIGADE system to be fully integrated with a Console 64 Phase 1a system. It would enable hostile and friendly aircraft to be tracked, and also provide control data for up to 12 simultaneous interceptions; the RAF could thereby evaluate the usefulness of computer-assistance in an operational setting. It was offered at an attractive fixed price, and a guaranteed delivery date; a contract was signed two months later.

 

FIREBRIGADE was installed at RAF Patrington and was extensively evaluated; it provided the fighter controllers with invaluable experience in the actual use of computer-assisted information, and paved the way for the later SLEWC installations at Boulmer and Neatishead, both of which used the more advanced Elliott 920c computer. FIREBRIGADE remained in operational use until April 1974, when Patrington closed as a result of Defence cuts.

 

By the late 1960s, NATO had re-assessed its defence philosophy, and changed its stance from the ‘Trip-Wire’ to one of ‘Flexible-Response’. The vulnerability of the centralised L1 building was acknowledged in this new scenario; furthermore, by the beginning of 1970, it was self-evident that the RAF West Drayton LINESMAN system would not be able to fulfil its full operational role. Thus the RAF decided to provide interception control and tracking facilities at Boulmer and Neatishead by the installation of SLEWC (Standby Local Early Warning and Control). The two other Master Radar Stations at Buchan and Patrington would carry on as previously. The two SLEWC installations, using the Elliott 920c computer (incorporating the experience acquired from FIREBRIGADE) became operational around 1972.

 

Input from Tom Vellacott
I was posted to Neatishead in 70 and then in 71 went on courses at Borehamwood for the data handling system and Chelmsford for the displays etc. RAF shifts started working in SLEWC at Neatishead from 71 onwards, although there was still a Marconi presence until late 73. There was also a SLEWC at Boulmer and the only difference, as far as I can remember, was that Neatishead had a simulator used to train the ops people.

 

Input from Steve Bousfield

The input from Tom Vellacott is correct. The SLEWC system at Neatishead did indeed have an integrated simulator, though a standalone but connected one was later added at Boulmer.

 

The SLEWC  data handling systems were designed to be transportable, though they never were, and used very expensive ATR style packing rather than conventional 19in racks. The 920C computer was itself a militarised unit in an ATR case.

 

The simulator that was added at Boulmer was a more ‘commercial’ beast. It used the commercial version of the 920C computer, the 905, and its simulation hardware was packed in 19in racks

 

Maybe there should also be some mention of the GL161 systems which preceded SLEWC and which were fully transportable, including the radar. They were Elliott / Plessey systems but did an essentially similar job as SLEWC.  They used the Sperry TPS34  V-beam tactical radar. The RAF ordered 6 of these systems and the electronics were, as far as I can make out, of an earlier generation to SLEWC. The early systems used 920A or 920B computers ( I don’t know which).  Singapore certainly inherited one of these systems but as to where and when they were deployed, I don’t know. Perhaps someone can shed some light.

Input from Ian Dormer

(who worked at the SLEWC Support Unit at RAF Wattisham in the early 70s.)
The RAF had the Tinsmith and SLEWC Support Unit (TSSU) at RAF Wattisham. Tinsmith was the 1ACC mobile unit with TPS-34 radar, GL161 and Elliott 920B computers, TSSU and 1ACC being on the old Anglia Radar site adjacent to the airfield.
As an RAF Sergeant I was sent on the first 920C computer course held at Wattisham in 1972 and on completion, course members became the 3rd line support team. Setting up the SLEWC Support Unit, we initially had a lot of support from GEC/Marconi people with fault diagnosis information and how to correctly use wire-wrap tools (the 920C having potted modules, wire wrapped to a back plane), a technique new to us. A pcb repair course was arranged which we attended at New Street, Chelmsford. The systems used the 900 series DTL and 9000 series TTL integrated circuits that I believe were manufactured by Marconi, possibly at Great Baddow, but don’t have further information. Memory was ferrite core in 8k blocks and input/output on punched paper tape.
As the system was technically air transportable for global use, some sub-units required temperature-cycled testing. As there was no facility at Wattisham, repaired units were taken to Borehamwood for this to be carried out.
The unit supported :
    Wattisham, in house machine, for trialling engineering developments and for the use of the software development team.
    Neatishead, one machine to run simulations and one live system.
    Boulmer.
I left the RAF in 1975 so my information ceases then. I do however volunteer at the Air Defence Radar Museum at Neatishead and note that the old computer room is now the ‘History Room’. Unfortunately no 920C computer parts are present but there are GL161 displays