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Aviation History
1959
1959 - 0267.PDF
122 Left, the Plymouth/Strumble area of the lower U.K. airways, showing the airspace required for two parallel tracks with Decca and, shaded, the additional airspace required for the 16-mile-wide Vortac tracks. These were formulated last year at the fourth EUMED RAN conference. The black dots indicate Vortac stations. (Right) The same area, showing airspace requirements for upper airways with Decca parallel tracks and Vortac (shaded) using the same chain or beacons. The Vortac airways are 53 n.m. wide. This chart, too, was formulated by EUMED BRITAIN'S NAVAID PROPOSAL ... that the radio navigation system should provide for this possibility.The I.C.A.O. Jet Operations Requirements Panel recognized this when they recommended "the adoption of an accurate andreliable short-range navigational aid based on the area-coverage system and designed to provide pictorial presentation to the pilotin the cockpit." The U.K., continues the Ministry, is in agreement with thisstatement and is more than ever convinced that the growth of air traffic in general and the operation of turboprop and turbojetaircraft in particular will accentuate the need for a navigation aid which will: — (a) reduce lateral as well as longitudinal separation minima; (b) enable greater use to be made of lateral separation in order toprovide the greatest possible freedom in trie Vertical plane; (c) be capable of serving any air -route configuration without the costly, lengthy and difficult process of redeployment of ground facilities;(d) give the required quality of short-distance navigation?, service over sea areas;(e) permit flexibility in the siting of holding patterns anJ economy in their size;(f) enable pilots to make smooth and accurate approaches to both instrument and non-instrument runways;(g) provide accurate navigational information to helicopters as well as to high-flying turbojet aircraft;(h) provide the pilot with a continuous and accurate presentation of his position in a manner which will enable him to follow thedesired track during all stages of the flight; (i) be capable of integration with long-distance navigation aids so asto accommodate additional equipment progressively as the requirements develop;(j) be easy to site and maintain; -y . . - - (k) require no regular air calibration checks; and(1) provide a high coverage/cost ratio. For this reason, the U.K. will ask I.C.A.O. to adopt the DeccaNavigator as a supplementary standard to be used in those areas where VOR cannot by itself meet the requirements of trafficcontrol. In addition, it will be suggested that the Dectra system should eventually be adopted as the standard long-distance aidin those areas where it is required to provide the more accurate ground-reference guidance needed to meet A.T.C. requirements. Extensive trials of these two systems have shown that they havethe flexibility and accuracy necessary to meet the most exacting A.T.C. requirements and that they are capable of further develop-ment to provide such refinements as automatic flight control and automatic air-to-ground position reporting. The form ofpictorial presentation common to these systems, the Flight Log, is also compatible with Doppler and can be used to displaynavigational information from all or any of these sources. The M.T.C.A.'s statement concludes: "The policy advocatedby the U.K. will protect existing VOR and Doppler investments, make full use of the extensive Decca/Dectra coverage alreadyavailable and lead, eventually, to a fully integrated world-wide system." The table at right graphically illustrates the difference in cost, particularly recurrent cost, between Decca and Vortac. To allow twin- track working under certain conditions, Vortac beacons might have to be doubled, but Decca chains would not The same area once again, with airways 7.82 n.m. wide delineated by Vortac alone. This is a lower airways structure and "Victor" airways giving alternative tracks are provided where possible, but not in this particular area. Twin tracks ore formed by Vortac dog-legs COST OF VORTAC 39 Vortac 4 TVOR* Tota a. £37.000 fa. £8.500 VORTAC AND DECCA FOP. SINGLE- TRACK U.K. Capital£1,443,000 £34,000 £1.477.000 AIRWAYS DECCA Costs 4 Mk 10 chains M £225.000 Annual Recurrent Costs Maintenance and calibration of:—39 Vortac 4TVORAmortization 10 years:— 39 Vortac 4TVORInterest on capital i.a Tota <a £4,500 la £2,800 £175,500 £11.200 of equipment over fa £3,000 (a £600 5 per cent •Terminal VOR. £117,000£2,400 £73.850 £379,950 Total maintenance costs:—4 Mk 10 chains (a £17,000 per chain Amortization of equipment 10 years:— 4 Mk 10 chains® £20,000per chain Interest on capital "i 5 per cent £900,000 £900,000 £68,000 over £80,000 £45,000 £193,000
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