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Aviation History
1962
1962 - 0284.PDF
286 FLIGHT International, 22 February 1962 FLIGHT SYSTEMS on the whole, Beacon found that the en route capacity of the air ways is not yet exceeded. In the terminal area things are much more difficult, involving this time constant changes of aircraft height as well as the mixture of airline traffic with light aircraft. Certain short-term improvements were recommended. 1FR and VFR traffic should be separated in terminal areas—traffic advisory service, similar to special VFR, has already been instituted in the New York and Washington areas. Better radar presentations, simple electro-mechanical aids for radar hand-off, certain airport aids, and the increased use of computers with suitable input and output devices could all be introduced without delay. Work already done en improving aircraft conspicuity should be finalized and imple mented. The pre-war visual light beacon system for guiding light aircraft should be reintroduced in terminal areas. Use of radar for high-altitude jet advisory service should be expanded. To solve the initial separation problem of mixed traffic, Beacon suggests a more elaborate division of airspace, with the inclusion of speed limits and a new flight status called Controlled Visual Rules. The intriguing point about CVR, at least to British private pilots, is that it means the provision of ATC separation service on airways to pilots of private-licence standard who are navigating by sight of the ground. Below a given height, all aircraft would re forced to observe a speed limit in order to facilitate "see and be seen" collision avoidance. All flying above 14,500ft would be controlled, except that a higher "floor" of 24,000ft would be applied in the mountainous areas. On certain high-density routes, universal positive control would be extended downwards to, say, 8,000ft and the speed limit of about 200kt i.a.s. would apply from 8,000ft down to 3.000ft. Below 3,000ft all traffic would be VFR and the speed limit would apply to all aircraft. In low-density areas both 1FR and VFR traffic could continue to use the space between 14,500ft and 3,000ft without speed limit. The 8,000ft "floor" might be dropped even lower where traffic warranted it. When helicopter IFR flying becomes general, Beacon foresees special helicopter routes between 600ft and 1,500ft, mainly in terminal areas. Because of the short duration of such flights and the consequently serious effect of traffic delays, these routes would have to be reserved and through-clearances would have to be issued to cover complete journeys. En Route Control A statement of principle introduces the new en route control system, which Beacon outlines in some detail. It says first that position information on all aircraft in the system must be continuously available and, secondly, that this information must be derived on the ground or automatically received from the aircraft, or both. Position reports from the pilot based on the navigation information available to him should not be used. This strikes a welcome blow at the reporting-point procedure and closely resembles the conclusions arrived at in Britain. Radar and beacon data, as well as flight plans, must form a primary source of information for the ATC system—not a secondary source as at present envisaged in the Data Processing Central. Controllers must have actual radar video before them to ensure accuracy and continuity and to provide weather information. Synthetic displays with computer-generated tracks are not satis factory, because of loss of accuracy and lag when following turns. FAA has 80 air route surveillance radars (ARSRs) in service or "funded," and these will give full coverage of the continental USA at above 5,000ft, with the exception of one or two unimportant gaps. Performance of the ARSRs is good enough to track small twin-engined aircraft and they have shown 97 per cent reliability. Considerable work will be needed to provide the appropriate micro wave links and other facilities to pipe the radar information into the centres. Programmes to make joint use of USAF defence radars and of some of the links are going well, if slowly. AH aircraft of more than 12,5001b gross weight will in due course be obliged to carry transponders providing identity, signal enhancement and height telemetering from a sealed aneroid alti meter. Height information would be passed straight to the computer 'GH Ai.TITUt INTERMEDIN ALTITUDE LOW ALTITUDE ,000' 25 mi Beacon's suggested method of separating light aircraft, propeller-driven airliners and big jets at large airports, referred to on page 287. Each group would have its own holding points. The jets would have the straight-in approach path and converted to altitude a.m.s.l. Most aircraft above 14,500ft would have transponders, the few not so equipped being handled by radar video and flight plan altitude. Displays could be quite simply selected in height bands. Below 14,500ft the larger pro portion of beaconless aircraft would require more radar video. The radar display and radio communication with pilots would be the primary tools used by the controller of IFR and CVR en route traffic, the display would show the radar video or beacon responses, the extrapolated flight plan and, in alphanumeric symbols, the identification and altitude of aircraft. Most of the book-keeping would 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. In order to avoid overlap and confusion of data on closely spaced aircraft, the controller should be able to choose the relative position of alphanumeric data with respect to the beacon return or flight plan line, to eliminate the data or to select signals by altitude bands. The flight plan would be one of the most important elements in en route control and clearances would be arranged so that a com plete flight could be carried out with the minimum of alterations. Automatic computer conflict probe could be initiated whenever a new request was filed and conflicts would be notified on a con troller display. The presentation of extrapola'ed flight-plan data on relevant aircraft, together with use of the radar and beacon video, would permit the controller to monitor and (by means of a light gun or joystick) correct the flight plan whenever the aircraft had deviated from it by a significant amount. In order to be able to perform the air defence mission of a combined surveillance operation the computer would have to be aHe to track a number of friendly and hostile aircraft. For air traffic control this capability could be used to track those controlled aircraft that had no beacons. Although there are some operational advantages in combining data from more than one radar the techni cal disadvantages make such working inadvisable. There remains a hand-off problem, when a controller using one radar hands-off an aircraft to a controller using a different radar. In this process the centre computers which continuously exchange data can provide important assistance. With continuously displayed position information and provisions for radar and computer aided hand-off, together with the customary flight plan, only infrequent communication with the pilot should be required. This will greatly reduce the congestion of the radio fre quency spectrum and the cockpit load as well as enable a single controller to handle more aircraft. The computers would, of course, handle the communication of flight plans and tracks among themselves without bothering the controllers. Flight plans would also come directly to the computers from simple digital data entry devices located at various departure points for aircraft. Connection could be made by simply dialing the telephone number of the computer. The latter would do the usual checking, show weather effects and make conflict probes. The computer would keep each controller supplied with a printed set of current flight data. The report notes, in one of its few allusions to this system, that the Data Processing Central (DPC) en-route consoles under development do this, "but in a
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