FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1963
1963 - 0195.PDF
fUC' T International, 7 February 1963 In lis article I propose to stick mainly to the Area Control problem, since it is here that I believe the Beacon concept to be technically most revolutionary. The recommendations on Ap proach Control are perhaps politically revolutionary in respect of separating jet, turboprop and piston-engined aircraft, but the ATC system itself remains essentially the same, though speeded up by a gradual extension of automatics. The Report visualizes an interim period of about five years for the ad hot improvement of the present air traffic control system; it then estimates that it should be practicable to introduce the "recom mended system," involving a fundamental revision of the airways and terminal area patterns. I give the authors full marks for courage here. It is no easy task to replan the airways lattice (in three dimen sions, not two as before) and they might have been forgiven if they had taken refuge with Mr Marples who, speaking of the road problem the other day, said: "People live in cities, they work in cities We cannot bulldoze whole cities and begin again. We have to reconcile the buildings and amenities which we cherish with the growth of the motor car as a personal conveyance." Translated into the context of aviation, such a policy would have frozen the existing air traffic complex and, in the most congested areas, either brought the whole flow to a slow grinding halt or one or two aircraft to a quick grinding halt. But luckily civil aviation does not have to consider bulldozing cities: in terms of real estate its highways are relatively free and flexible and, apart from military zoning, only a renegade group from the large body of "general aviation," buzzing about in the lower levels of the FIRs with inadequate communication or radio navigation equipment, prevents the airways from being re-orientated to any desired pattern. Of course, on a VOR-based system you would have to shift a few transmitters, but most of the change would be a matter of laying cables and installing more advanced equipment in existing buildings, a process hardly new to air traffic control. However, having agreed with the Report in the matter of funda mentally revising the airway patterns, I find myself disagreeing with the second major concept, namely, that:— "// is fundamental that the control system have continuously available on the ground position information on all aircraft in the system, either ground derived or automatically received from the aircraft or a combination of the two. The system should not depend on pilot reports and the position information should be independent of the pilot's navigational means. "It is proposed that radar and beacon data, as well as flight plans, be primary sources of information for the enroute traffic control system, instead of being supplementary as at present and as envisaged in the Data Processing Central (DPC) under development." Too Good to be True? Taking the en route case, all traffic (civil and military) flying above 14,500ft will be on "predetermined routes" under an Area Control system. The total air carrier and military movements in US air space in 1965 are predicted to be nearly 10m and it would therefore seem reasonable to suppose that about 7.5m of these will be in the upper levels (over 14,500ft) for a substantial proportion of the flight. This means 20,000 movements per day in the upper airspace. Now, as I understand this "predetermined route" business (I cannot find the definition in any ICAO Annex), you can go anywhere at any time provided that you get a clearance; however, for your con venience as much as that of Area Control, you normally select tracks, between Vortac stations—that is, if you are civil traffic; if you are military, you would do so provided that it was not too incon venient and, judging from UK experience, it would seem that this might cover 70 per cent of military operations. The Report visualizes that there will be some co-ordination of clearances at the flight-plan stage so that en route conflict is at least not built in at the start of a flight; however, bearing in mind the 30 per cent random military traffic (perhaps 3,000 movements per day) and the odd private flier up there on CVR,* the Report is realistic enough to anticipate that en route conflict has not altogether been ruled out; and so it says:— Controlled Visual Flight, a new concept not being discussed here. 18? "The presentation of extrapolated flight plan data on relevant aircraft together with the radar and beacon video would permit the controller to monitor and (by means of a light gun or joy stick) correct the flight plan whenever the aircraft had deviated from it by a significant amount. Additional conflict probing would be done by the computer on the basis of the updated and corrected plan. The computer would periodically review and extend the conflict probes on all flight plans . . ." "The radar display and radio communication with pilots should be the primary tools used by the controller of IFR and C VR enroute traffic. The radar display would show the video from radar or beacon, the extrapolated flight plan and, in alphanu meric symbols, the identification and altitude of aircraft. Most of the bookkeeping should be done by automatic digital computers which would have high speed alphanumeric displays to send messages to the controller and suitable keys through which to receive signals from the controller.'" Perhaps I am a long way behind the industry here, but the above reads a little too smoothly for me, at least if we are talking in terms of equipment available in five years (1966, if one takes the Report as 1961). Exactly what computer tie-up is behind this "conflict probing" ? Where are all the VHF frequencies coming from so that the controller can issue vectors on the more or less continuous basis required by this concept? And how, on the basis of freely selected "predetermined routes" which will traverse area boundaries at many points, will one radar controller be able to make a hand over (American, "hand-off") to the next? The Chicago Indiano- polis radar experiment scarcely goes far enough to demonstrate the problem of a boundary rather than a point hand-over. The Hardware Requirement Let us deal first with the hardware requirement implicit in any concept of ground-vectored navigation. On this the Beacon Report says:— "The US Air Force now has an extensive network of radars; co-operative programs for joint use with FAA of some of them are proceeding well, if slowly. The FAA has approximately 80 air route surveillance radars (ARSR's) commissioned or funded. . ." "Substantial effort will be required to net all of the required radars so their data can be displayed at appropriate centers. Microwave relays are available and in use by FAA, but many more will be required . . . In any case, the cost and complexity of this portion of the system does not appear to be controlling." I don't know how these things work, I don't know the depth of Uncle Sam's pocket, and perhaps the fuller Design for the National Airspace Utilisation System (just released,) will, when it reaches me, make the whole thing clear; but meantime—from expressions like "substantial effort," "many more will be required," "the cost and complexity does not appear to be controlling"—I have the feeling that the wool is being pulled over my eyes, so I find myself making little thumbnail calculations. Using the very naive but convenient picture I have of a US air space of 2m sq miles, one primary surveillance radar aerial serving a radius of 100 n.m., and taking into account one-third of the area as being wasted in overlap, giving about 20,000 sq n.m. coverage per aerial—I make about 100 systems needed to serve Area Control alone. Allowing for asymmetry, terrain, etc, I expect this is in fact well under the mark. Add This and That The above takes into account only primary radar, but Beacon visualizes secondary and height-finding radar as essential to its proposed air traffic control system. I understand that between these three radar sources it is necessary to provide considerable site spacing in order to prevent mutual interference; on the other hand, it is necessary to provide synchronization circuits so as to programme the pulses and aerial rotations; and it is also necessary to provide for control from the Centre in respect of variable gain, anti-clutter and rain-echo reduction. By the time that one has installed the three separately sited radars and their standbys, the above interconnections and controls by radio links and cable, subsidiary equipment in the way of side-lobe suppressors, garble sensors and single or double defruiters—one begins to suspect that
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
