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Aviation History
1957
1957 - 0272.PDF
274 FLIGHT, 1 March 1957 THE AIR TRAFFIC CONTROL PROBLEM . . . including the U.K., is covered by two area-coverage naviga-tional aids of very great accuracy. These are Gee and Decca. The former, although meeting the accuracy requirement, hasfailed to find favour with most operators due to the presentation and need for "operation" each time a position is required. Thisinvolves referring an indicated reading to a special chart, and although the resulting fix is accurate to within a matter of yardsthe system has not been approved for reduction of existing standards of separation, due no doubt to the non-self-evident,non-continuous, cathode-ray-tube type of presentation. Decca, on the other hand, when equipped with Flight Logpresentation, almost completely meets the A.T.C. requirement for relaxing present separation standards. It is by now well knownthat the official U.K. view is that the basis of the A.T.C. pro- cedures in this country shall be Decca, and that reduced separa-tion standards shall be available to Decca-equipped aircraft. Notam 545 of July 31, 1956, established these new principles,the carriage of the Flight Log type of continuous pictorial-track- ing presentation being a condition. These separations are basedon the fact that Decca-equipped aircraft may fly prescribed tracks with very great accuracy, and at the same time be able instantlyto read off a position report as required. Thus a requirement for lateral separation is satisfied, the Decca aircraft being able tofly airways keeping well to the right of the centre line at all times. Even Decca aircraft flying the same airway on oppositeheadings can rely on an approximate separation of 10 n.m. as they pass each other. In the case of the London Control Areaspecial Decca entry points have been designated. Known as Decca points J, A, B, G and R these are located at the Southernand Eastern boundaries of the London FIR and Airways Red One, Amber One, Amber Two, Green One and Red One respec-tively. Aircraft with Decca report to A.T.C. when over these points, or give their E.T.A. at these points. Using Decca, aircraftflying the same and opposite headings are permitted to climb and descend through each other's altitude on parallel tracks, effectivelateral separation being achieved through the use of this aid. Considerable distortion is sometimes seen as a characteristic ofthe Flight Log chart, depending upon the Decca radiation pattern upon which it is drawn. But orthomorphism is not a require-ment, for the chart is not intended to be used for map-reading, but to provide a continuous display of position and to facilitateaccurate track-keeping. Just as the Mercator plotting chart is distorted in order to provide a simple rectilinear graticule basedon a sphere so the Flight Log chart is distorted to provide a rectilinear graticule from a hyperbolic pattern. In each case theorthomorphism suffers; the characteristic of a Flight Log chart is that a hyperbola takes the form of a straight line, while the scalevaries over the surface of the chart. But by superimposing tracks and geographical locations, together with radio facilities and con-trolled airspaces, and the like, this inherent distortion is of little account, provided that due allowance is made for the pattern uponwhich the chart has been constructed. The track from, say, Ferryfield to London Airport could not be conventionally drawnin by means of a ruler; but assuming this particular track was required it could easily be superimposed by first of all drawingit in on an ordinary Decca conical plotting chart. A number of Decca lattice co-ordinates would then be taken at intervals alongthe track and these plotted on the Flight Log chart from the Decca graticule included thereon. By linking these plots therequired track may be drawn in. . - . -.. A.T.C. in operation—controller in the tower at Renfrew, Glasgow, which also forms the subject of the heading illustration on page 277. It may be seen that the real problem facing A.T.C. is to permitthe natural growth of air traffic while at the same time retaining acceptable standards of safety. The U.K. has shown that a suitablemeans exists by which this object can be achieved. But its effect can only be really felt when all aircraft flying under A.T.C. rulescan make use of the same facilities. At present Decca represents the existing answer to the problem of airspace utilization; thebold step now would be for the authorities to make its use mandatory. Plans and Possibilities. From the foregoing a general ideawill have been obtained of the air traffic control structure in the U.K., the way in which it works, and the problems facing it.In conclusion, let us examine some of the alleged weaknesses of the system, and discuss briefly some means by which these weak-nesses may be removed, or at least minimized. In the considered opinion of the writer a possible weakness ofthe United Kingdom A.T.C. system may lie in the fact that it is a public service. The answer, it is submitted, might be to dis-establish the A.T.C. organization from the Ministry of Transport and Civil Aviation and to place it on a similar footing to itsmarine counterpart, Trinity House. After all, civil air transport is often referred to as the merchant service of the air. Again, although we have discussed the Decca system, and haveshown how it permits the reduction of separation standards, the need is still apparent for some additional aid that will guard againstpossible collision in mid-air. Various devices are under develop- ment, but few of these provide sufficient information. In the view of the writer the ideal might be for the pilot to beprovided with a pictorial representation of the traffic situation within a radius of some 30 n.m. of his actual position. Thiscould be achieved fairly simply by a combination of secondary ground radar and television. If every aircraft were compelledto carry a small transponder, weighing but a few pounds, and all controlled airspaces were covered by ground surveillancesecondary radar every aircraft flying within the range of the radar stations would be easily detected and identified by virtueof the coded replies from the airborne transponders, each air- craft emitting its own particular code reply. Assuming, now,that the ground radar screens were televised and continuously broadcast on separate radio channels a small, light televisionreceiver on board aircraft requiring the use of the aid would be able to provide the pilot with a picture of the airspace aroundhim, showing him not only his aircraft but any other aircraft within range as well. There is also a school of thought, especially strong in theUnited States, that believes that the answers to most of the problems facing A.T.C. may be solved by the use of electroniccomputers. Certainly the position is becoming too hectic for the human mind to deal with, especially with the imminence ofturbojet operations. The introduction of short and medium haul jet airliners in any quantity is going to call for a completerevision of control procedures, involving high altitude holding, and accelerated climbs and descents. It may well be that someform of completely automatic A.T.C. system, feeding direct to the autopilot by means of a radio link and couplers, could providethe answer. Finally, just to confirm the views expressed at Southend, letus listen to the views on this subject expressed in the House of Lords on November 28 of last year. Lord Ogmore, a formerMinister of Civil Aviation had, in the course of a debate, urged on the Government the need for improved international air safetymeasures. He stated that air traffic and the risk of collisions were increasing daily* and supported this by figures. Althoughthere had been only two accidents from this cause during the last eight years in the U.K. there had been 324 near missesin the past two years. This last fact alone perhaps serves to bring the seriousness of the matter home more effectively thanthe views of the A.T.C.O.s at Southend. FALOUSTE ENDURANCE TEST THE 134th Turbomeca Palouste IV gas generator was recentlysubjected to a repeat type-test and endurance test under French Air Ministry observation, from which it is reported to haveemerged "successfully." The original type-test had been completed with the 75th engine.Engine No. 134 was run under type-test conditions for just over 167 hours by the makers, stripped and found satisfactory. It wasthen put through two consecutive periods of 165 hr 37 min and 172 hr 33 min in the Ministry's test cells without stripping.Including some 8 hr 50 min of running before these tests were made, the engine is stated to have completed a total of 514 hr42 min without trouble. —•_.!!._' — 1? ~ '"v
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