Input from Ian Gillis
The Scottish Air Traffic Control Centre which was completed in the late 70s demonstrated the use of the Marconi Locus 16 multiprocessor in a distributed data processing configuration to provide the very high system reliability demanded of an ATC area control system. The system gave reliable service for many years until replaced in the mid-2000s by a system based on that employed at the New En-Route Centre (NERC) at Swanwick.
(The following is an extract from Harry Cole's unpublished draft of "A History of the Marconi Radar Company" 1997).
In the '70s, the legacy of a great deal of experience in the use of microelectronics bore a new fruit — the idea of using intercommunicating printed circuit boards by means of a 'highway' system. The architecture led to a very compact and flexible system of providing all sorts of facilities.
The engineering form, entitled 'Locus', used boards of a standard size with all contacts at one end which plugged into a multi-tracked 'mother' board at right angles to them. Thus, a standard 19-inch frame unit with its mother board could take all manner of different processors, all communicating through the highways on the mother board. This architecture endured for very many years and by 1990 had over 150 different types of processor that could be put together in a wide variety of roles.
In 1974 the UK CAA placed a contract with the Company for the provision of a new ATC Centre at Prestwick for the purpose of controlling the air traffic in the whole of the Scottish region of the UK. Its task was to take the data from radar outstations in the region and allow operators to select them for display and control. Tracking routines within the system made it possible to display targets in symbolic form, with leader lines emanating from the target. These lines had a length proportional to the target's speed and their bearing representing the target heading. The outstations had both primary and secondary radar sensors, so the Control displays had the most complete data on air traffic and it was possible to extract position, heading, speed, height and identity. In all there were over 30 PPI displays, each fed by Locus-engineered processors.
(This is an extract from the Marconi Radar Systems publication "Radar Systems International" 1978)
Marconi Radar Systems Limited has installed a massive system for the new Scottish Air Traffic Control Centre at Prestwick. It incorporates the world's most advanced ATC radar data processing system, based on the Locus 16 data processor, which can monitor all aircraft in 2 million cubic miles of airspace above Scotland, Northern England and the North Sea.
One of the first systems in the world to use synthetic 'clutter-free' radar information exclusively, it provides an automated radar data presentation which makes the control of aircraft in the Scottish terminal areas simple and extremely efficient. The controlled air space includes those areas around the rapidly expanding airports at Glasgow and Edinburgh, also the upper, middle and lower airspace in the Scottish Flight Information Region.
The Prestwick air traffic control centre will be linked via standard telephone cables to radar sites located in Scotland, Northern Ireland and Northern England. At the sites, most of which have Marconi primary radar, both the primary and secondary radar will be processed by plot extractor units to provide aircraft position, height and identity on all detected aircraft tracks, in the form of digital messages. These will then be fed to Prestwick, where four Locus 16's process the incoming radar messages and route the information through a narrow band data highway to twenty-nine Locus 16 display suites.
A typical display position
Each display suite holds its own operational and diagnostic programs and drives a 16in display. At Prestwick, the displays will have 28 levels of brilliance to suit the ambient light conditions of the control room, and a high enough 'refresh' rate' to eliminate flicker. By means of a radar head selection switch panel a controller will have access to radar information relevant to the sector he is controlling.
Reliability
Earlier ATC systems have been built around large centralized computing complexes in which a hardware failure may cause a complete system failure. By contrast, the system at Prestwick is based on the concept of ‘Distributed Data Processing'. All Locus 16 processors operate quite independently of each other, and failure in one will not affect the others. Additionally, any of the two types of processor can do the work of any of the others of its type, thus affording a high degree of overall reliability.
CMM
In 1973, the CAA, in a pilot scheme, adopted the Marconi CMM (Computerized Modular Monitoring) to control remotely the on-route radar at Raith Hill from its old control centre at Gails.
Radar Systems have supplied a simple control and monitoring system (based on the Marconi CMM .system) for the new Scottish Traffic Control Centre at a cost of about £180,000. The computer-based control monitoring system gathers system status information from the CAA equipment at Prestwick and from en-route radar stations at Stornoway and Lowther. The same network remotely controls CAA equipment at the out-stations.
Marconi CMM is a versatile control and monitoring system which can be built up from a range of hardware and software packages that meet the control, management maintenance requirements of almost any electronic or electro-mechanical equipment.
The system at Prestwick represents a great step forward in the supervision of radar in the exercise of traffic control, and contributes to the safety of air travel.
Comment by Ian - In 2006 the ATCOs were posting "Can we have the locus 16 back please????" - (http://www.pprune.org/archive/index.php/t-241253.htm)
Extract from Echo October 1980
I think this extension was just more display positions rather than functionality of either part.
SCATCC to be extended
The Company is to extend the Scottish Air Traffic Control Centre for the Civil Aviation Authority with more data processors and displays. The new ATC Centre at Prestwick became operational early this year. Since opening the Centre - which monitors aircraft in Northern England, the Atlantic Approaches and the North Sea, including Scotland - has operated a very advanced radar data processing and display system, supplied by Marconi Radar. The now well-established and versatile Locus 16 distributed processing technique has proved itself eminently suitable for air traffic control and many other complex civil and military data .handling systems.
Input from Derek Knight
The Prestwick centre was later re-designated ScOATCC for Scottish and Oceanic Air Traffic Control Centres. A CAA publication CAA Doc 259 dated 1982 provided good info. I cannot see a copy on their web site but maybe they could provide a copy and might also have one on the triple-myriad system at LATCC. Could be worth asking, they can only say no. Our bit was the domestic part only so ScATCC still applied but the Prestwick site was home to both centres (ScATCC and OATCC - memory on its mnemonic)
In late 80's from memory the track capacity within the Display Processors (one Locus bin supporting an operator driving a single S3017-10 display - there were 40-60 of these) and Radar Processor (another Locus bin that added call-sign info to plot data and did simple track smoothing - there were 5 plus another hot-spare of these) were all upgraded to increase the track capacity from circa 100 to 200. The upgrade increased the storage and added a second CPU board set into each Locus. That meant the original 2-card ALP1 (see Locus words in history) was replaced by two single card ALP6s where each of the later equated to an ALP1.
In 90s, another upgrade changed the comms network between the RPs to allow the spare to be used operationally. I cannot recall if we added another RP cabinet as the spare or not. That change also added a Motorola 68020 ALP (ALP8 I think) which had onboard storage and floating point to provide 'Short Term Conflict Alert' based on CAA-provided algorithms. The extra work for the software caused us problems with their tight time constraints and the very biased traffic flows - they were largely NW-SE or SE-NW with a huge drop on either side. So the track sorting as they passed across the system center point ate up time and the extra plots and messages on the network on that diagonal axis caused bottlenecks I recall.
They did seek a further upgrade but that was never taken as it made more sense to replicate the NERC system from down south; it was going to happen anyway