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Aviation History
1971
1971 - 0327.PDF
302 AIR TRANSPORT. . . fUGHT International. 4 March 1971 West Drayton on view HUGH FIELD VISITS THE HOME OF MEDIATOR COINCIDENT WITH A VISIT by the Minister of State, Department of Trade and Industry, Mr Michael Noble, the London Air Traffic Control Centre at West Drayton was opened to the Press on February 25. Despite the volume of criticism that has surrounded the introduction of Mediator Stage One, the NATCS are justly proud of the facilities which were commissioned on Feb ruary 1. It was freely admitted by all concerned that one major computer sub-system had fallen far behind the time scale which had been planned but the decision had been taken to introduce the available new hardware, regardless of any possible shortcomings, rather than con tinue to operate in the previous accommodation any longer than necessary. Ignoring for the moment the vexed question of the shortfall in equipment, the integration of facilities at West Drayton is in itself a considerable achievement. Up until January 31 control of air traffic over southern England was effected by a procedural and a radar system running in parallel, the respective controllers being physically separated by a distance of three miles. Procedural hand ling of flight plans and clearances took place within the new LATCC building but the radar controllers remained in hutted accommodation on the north side of Heathrow. This technique was acceptable while it was possible to rely fundamentally on procedural control with radar as the safety back-up but, of late, the priorities have been becoming reversed with an ever-increasing load falling upon the radar controller. The control suites introduced in the new operations room at West Drayton acknowledge that radar is the crux of the system; the controller has available the procedural information but his basic tool is his radar presentation and much development work has gone into devising a clean and clear picture. Mediator is based on the total use of secondary radar incorporating Mode C altitude readout, but this does not imply that primary radar will be abandoned quickly. The 22in picture at the heart of the control suite shows superimposed primary and secondary information and the selection of data presentation pro vided for the controller allows the greatest flexibility in choosing his source. The displays are designed for daylight viewing and the pictures are generated by a television scan technique using 1,000 vertical scan lines. Brightness can be con trolled at the console regardless of the strength or clarity of the raw radar input. Secondary radar information is transmitted in digital form from the radar head and is projected for the con troller as a small cross marking the position of the air craft with identification code and flight level figures along side. 4,096 SSR codes are now in use and the first two digits have been allotted so as to categorise types of traffic. Thus all London outbound flights to levels below 250 are given codes starting with 66; should a controller not need to be concerned with overflying flights, which would have codes starting with a different pair of figures, he can select the block of codes with which he is con cerned and delete the remainder. Airways suites are arranged to cater for two adjacent sectors; the two controllers are side by side in front of their respective displays with their assistants out at the wings of the suite. The central area is hooded so as to avoid reflections on the main displays and the vertical information displays, and the wings of the suite, which provide the racks for the flight progress strips, have their own bright lighting. Overall command of a suite is vested in a crew chief who is positioned between the two controllers so as to be able to overlook both displays. He can monitor the B/T interchange on either sector but all transmissions stem from the individual sector controller. Seven complete airways suites have been installed in the operations room, one at the moment being spare, and in addition there are two suites which are tailored to the needs of the terminal control area. The use of these suites has introduced an extra stage in the control of inbound and outbound aircraft (hence the additional frequencies that became effective on February 1) and it is at this stage that the flow of inbound aircraft is marshalled so as to hand over the Heathrow approach controller a steady stream of aircraft, regardless of their direction of origin. Flight strips are at present being produced by a Fer- ranti Hermes computer which is a modified form of the original Minicap which has operated at West Drayton for three years. The original core store of 8,000 words has been replaced by a 32,000-word store allowing the com puter to be re-programmed with the whole airways struc ture and enabling allowance to be made for such variables as the runways in use at Heathrow. The Flight Plan Pro cessing System prints flight progress strips but it is in Immediately below is the system control cell at West Drayton with serviceability shown on the tote board. At the bottom of the page, the communications control centre with triplicated VHF forward links in the racking. On the facing page, the Controlled Air Space operations room is seen with details of two of the sector control suites above, showing the 22inch horizontal displays
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