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Aviation History
1950
1950 - 0413.PDF
2 March 1950 that the present position finding was by no means good enoughfor control purposes, as apart from a surprisingly large number of aircraft which were really "lost," too many were observedmany miles away from their stated positions until very near the reporting beacons (which were in congested areas). Thissituation would be eased, he thought, when the Airways Plan was introduced, because such a system would facilitate goodtrack-keeping and provide more reference points. The question of good time-keeping had been shown to beoi paramount importance in connection with the smooth opera- tion of airports. With landings taking place at five-minuteintervals, as is the case at Northolt at present, E.T.A.s are required with an accuracy better than two minutes, while anyimprovement in the landing interval (and one of three minutes ought soon to be possible) would bring in stiffer requirements.With aircraft travelling along airways equipped with M.F. beacons at intervals of fifty miles or so, he considered that itshould be possible to maintain E.T.A.s to within two minutes with reasonable cape, but the high accuracies necessary forreally smooth operation around airports were outside the capa- city of the normal M.F, facilities, and demanded navigationaids of high precision. For the future, Dr. Bell considered that a highly accurateaid of the Zero Reader type, which would give a suitable pre- sentation to the pilot, was required. He emphasized, however,that whatever aids were developed, they should be suitable as regards both weight and cost for installation in even thesmallest types of aircraft, as in extensive air operations the margin of safety was governed by the standards of the poorestrather than the best air-crews. "VOICE OF INEXPERIENCE" AN entertainingly outspoken paper by A.V-M. D. C. T.Bennett entitled "The Voice of Inexperience" was read for him in his absence by S/L. D. Bower. London Control (said the speaker) is an example of theover-organization which has evolved since the end of the war —partly under the influence of expectations oi high trafficdensities, but more directly, I suspect, from a natural desire towards "Empire-building." When one notes the existenceof Area Control, Approach Control and finally (handling one aircraft at a time!) Airfield Control, all falling over one an-other with the best intentions in the world, then one cannot avoid such an unkind phrase as " Empire-building." Further,in practically all aircraft there are at least two reasonably intelligent human beings, and they have some idea of whatthey are doing; if we rely on these people even half as much as we do the controllers in " the tower," then surely we couldsimplify procedure considerably. Moreover, if we were to allow those same controllers to use their discretion a littleinstead of being bound by rigid rules, then 1 feel confident that traffic would soon flow normally again. I believe that the practical flying-control officers, particu-larly in Great Britain, deserve the greatest sympathy and support. As I see it, they are severely restricted by thiswicked god called "Standardization." Under the excuse of standard international procedures, flying-control officers areseriously impaired in carrying out a perfectly normal duty of assisting aircraft by reason of the fact that information is notreadily available to them. British flying-control officers suffer from poor and insufficient communications. Let us remember, basically, that in daylight and in goodvisibility no mandatory flying control whatever is necessary, or desirable in any way, and let us also remember that thisstatement applies equally to the "600 m.p.h. aircraft" be- cause, after all, even a Comet at low level has a very lowair-speed. The problem, therefore, resolves itself into two parts: (a) to give information in order to expedite landingsami take-offs in good conditions; and (b) to give information and instructions when blind or at night. The guiding prin-ciple should be to allow maximum freedom of command for the captain of the aircraft in all things in which he can bestdecide, but to give complete freedom to the control officer to give instructions where captains cannot decide. One of the excuses for our deficiencies in flying control sincethe end of the war has been lack of standardization of inter- national aids. That we should fail at Montreal to "sell"(»ee was deplorable but might have been a blessing had we immediately expanded and developed the use of Rebecca andits appropriate ground beacons. That we should to this day be contemplating the extended use of M.F. beacons and M.F.ranges is, in my view, a catastrophe. They are not only unsatisfactory in that they give no assistance to accurate tim-ing hut merely to directional aid—they also piove thoroughly unreliable in heavy static and thus fail in their object inthe very conditions when they are most requited. The use oi Rebecca on the Berlin Air Lift was a clear case in its favour.There, in spite of violent changes of wind and of slow report- ing thereof, spacing and timing remained good through-out. The one outstanding feature of flying control on this operation was in the early stages when there were no seniorofficers and no organization. During this happy period the control officers at Gatow worked with the mutual confidenceof the pilots concerned, even allowing two aircraft to sort themselves out when they were better able to do so than wasthe flying control officer concerned. The result was a higher landing rate, a far greater degree of safety and, incidentally,a far happier atmosphere than ever was subsequently achieved on the Airlift or, for that matter, in any other flying controlsystem I have known. It seems that, if really large numbers of aircraft are to behandled, we must as far as possible ensure the self-sufficiency of each, both with regard to (a) navigation aids and (b) land-ing aids, and then we must give each individual aircraft maxi- mum freedom with the minimum necessity ioi communica-tions with the ground within a traffic pattern vhich is more or less automatic. Such a pattern must obviously dependupon the circumstances, and London Area is, 111 my view, the most difficult in the world. It soems, however, that the four-quadrant system, whereby approaches into the zone are made from any one of four equally spaced points on its perimeterand exits are made through any one of four other points spaced approximate! 7 half-way between the entry points is a systemworthy of attention. By all means let us spiead in heigh; and in distance, but lateral displacement is also justifiablewhen one comes to the really high density which we must hope for, in spite of ourselves, in the London area. Then let us simplify communications by having one '' areaapproach" channel and one "airfield" channel for each air- port. To have Area Control, Approach Control and AirfieldControl is thoroughly dangerous and unnecessarily expensive. When, moreover, Airfield Control is on a frequency which isso congested that it is impossible to get a word in edgeways then the whole thing becomes dangerous—for, after all, it isonly "in the circuit" that collision risk goes up. Finally, whilst on the subject of communication, let us give guidanceto our foreign friends by exemplary procedures, while still permitting those who can speak English to r!o so naturallyand briefly. To sum up, therefore, I would say that oui requirementsare: (a) Freedom of command for the captain where applic- able, and (b) freedom of the air traffic officer to instruct wherenecessary (c) adequate telephonic communications, single-stage only for isolated airfields; two-stage for airfields in a highdensity area; (d) navigation aids in the following order of preference: (i) D.M.E. (Rebecca), (ii) Hyperbolic Fixing sys-tems (Gee, Decca, etc.), (iii) V.F.H'. multi-track ranges, (iv) V.H.F. D/F., (v) M.F. beacons adequate in number and inpower, (vi) radio ranges, (vii) ground D.F. stations—to this list must be added superimposed primary ground-radar forsurveillance where justified in high-density areas, (e) adequat" landing aids in the following order of preference: (i) B.A.B.S.,(ii) G.C.A., (iii) I.L.S., (iv) S.B.A. We must, of course, remember that landing aids, even witlithe assistance of flying control, are valueless in this climate •unless we have the one safety worthy of the name—i.e., Fido,which is, incidentally, not only a great safety device but also a great saving device. TERMINAL NAVIGATION IN a paper dealing with Terminal Navigation, Mr. D. Barnett(R.A.F. Transport Command) considered that the solu-tion to the traffic-control problem was to be found in the development of tracking and control systems of such high precision that the aircraft would never be permitted to get ofl track or off schedule for the last 20 minutes of its flight—a principle of control which he termed " preventive navigation." The speaker reviewed such varied systems at present in use as the A.D.F. system at La Guardia (claimed to have a handling capacity of 15-20'aircraft per hour in I.F.R. condition), the Transport Command controlled-landing system (employing medium-range navigation aids to define a circular traffic pattern in which the space/time characteristics are calculated by means of simple computers) and the direct-entry system used in Operation Plainfare. Mr. Barnett gave details of much of the practical work" which had been carried out to determine the possible accuracy of timing control along a track and enumerated factors which required further study, among them being the effect of slip- streams on the final approach, allowance for overshoots, and variations in aircraft and wind speeds. He considered that tht* ultimate solution to the rapid-landing problem was likely to be through the development of a means of measuring precisely each aircraft's position, coupled with computational mechanism by which each aircraft could follow ,1 known track and main- tain a known time-schedule.
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