FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1950
1950 - 0412.PDF
276 FLIGHT. 2 March 1950 TEST-FLIGHT NAVIGATION..: speeds showed a high order of accuracy when compared with the known T.A.S. and Met. winds on the various sections. .In an area nearer to the transmitters, and flying a course across a close-packed lattice—say, along the South Coast—Decca should provide an extremely accurate means of checking ground-speed and consumption figures. Previous to the Dublin trip the equipment had already been used on pressurization tests up to a height of 20,000ft over cloud, and on one occasion it was used successfully for horning on a particular point of the coast after a descent through low cloud in gathering darkness. In many ways the very first test of the equipment pro- vided the most effective demonstration. Two multi-course circuits were flown above cloud on the automatic pilot. Each turning point proved to be correct after a descent for viaual check, and on one Boctor an accurate let-down was completed after two turning-point had been passed in blind conditions. Safety checks were, of course, made through- out against V^H.F. bearings, but no alterations to course were required other than those demanded by the Decca fixes, and the final landing showed the references to be correct to within a few hundred yards. This, in spite of the fact that several continuous spiral descents had been made in the course of the flight. At the present time, Saunders-Roe, Ltd., are making a trial installation of Decca equipment in a Sunderland with the object of establishing operating techniques for the use of Decca in the flight trials of the prototype Princess. The system has much to offer in this regard, so the hire charge of ^350 p.a. seems reasonably low. This would apply even if the system was used for navigational purposes alone, but if it can be turned to account in establishing such things as A.S.I, position-error (by virtue of ground-speed measure- ment) and, also, unstick distances, then its value as a flight- test instrument will be greatly enhanced. Whether or not the equipment can be used in these connections depends on the prior determination of signal lane position in reference to known topographical features. THE FUTURE of AIR-TRAFFIC CONTROL Symposium of Papers Read to Institute of Navigation. MANY of the aspects of the increasingly complexproblems with which civil aviation is today con-fronted"were enumerated in a symposium of papers read before a meeting of the Institute of Navigation at the Royal Geographical Society in London on February 17th. Digests appear below. THE CONTROLLER'S VIEWPOINT IN a paper entitled "The Controller's Viewpoint," Mr.M. A Young (an M.C.A. traffic-control officer) beganwith a brief history of the control organization in Britain from the days of its inception in 1920. He then showed how particularly in Britain—the war had interrupted develop- ment of a control system, and how, when it ended, civil avia- tion had restarted With ;i miscellaneous collection of ground services. In the hope of early I.C.A.O. agreement on aids und procedures only the most urgent problems were tackled. Procedures had to be based on the inaccurate M.F. aids which were carried by most aircraft and were therefore far from ideal. The old adage of making bricks without straw could never be more aptly applied than to post-war control plans in the U.K. which, he said, were based on pre-war outmoded organization, some pre-war outmoded navigation facilities, a hodge- podge of communications, pre-war outmoded civil airports plus discarded military airfields in locations unplanned for civil operations, non-existent procedures and outmoded legis- lation. These facts, together with a reluctance to forge ahead until international agreement (with the eventual I.C.A.O. activities) assured a measure of progressive uniformity with adjacent countries, had provided the possible build-up to date. In the United States, on the other hand, a system, used exclusively by English-speaking crews, was developed along logical and progressive lines using as its foundation a single equipment—M.F. four-course ranges. The speaker continued, '' The smoothness of operation of such a uniform system with compulsory airborne equipment is unquestionable. ~ That its oresent-day adequacy is not a matter for complacency, how- ever, is recognized by those responsible authorities on the other side of the Atlantic. Incidentally, that such an obsolescent, if not obsolete, system is now being implemented extremely slowly in this country is not a prospect of which one could be very enthusiastic." Mr. Young considered that the problem.which must now be faced was that of traffic control in relation to aircraft which must attain a high cruising altitude as soon as possible after take-off and maintain that altitude for as long as possible commensurate with a semi-powered descent to a virtual straight-in approach. The picture was further complicated by the fact that, in spite of an ever-increasing tendency towards higher maximum cruising speeds, the 100 m.p.h. type of aircraft seemed for ever with US. For the future, the speaker envisaged requirements as being firstly an accurate basic navigation aid providing complete area cover which would enable pilots to determine at any time their track, distance and time to run to any point in the area. Parallel tracks between terminals could "be flown and the present large horizonfcft"' separations reduced without loss of safety. Routes would consequently be more direct and econ- omical and there would be more flexibility in choice«f cruising altitude and rates of climb and descent. The second require- ment, he stated, was for an improved communication system. The pilot and controller should be in direct communication without intermediaries. To avoid overloading of channels all possible information should be passed by ground-to-ground links leaving air-to-ground channels for use only when the •flight deviated from plan. He also emphasized the need for a radar monitoring function and the presentation of an intel- ligible picture to the controller. It was his l»elief, he said, that traffic problems resolved long before the aircraft arrived at their destinations would have a direct advantageous effect on the safe maximum utilization of runways at terminals. NAVIGATIONAL ACCURACY . G. E. BELL, of the M.C.A. Operational Research section, gave a resume of many detailed observations obtained during the course of lengthy research, into the study of the rate of traffic-flow at large airports. A consideration of the essential characteristics of this flow showed, he said, that it is not generally possible to draw up reasonable schedules for all aircraft and therefore the arrival pattern must be largely random. Some delays are inevitable, their magnitude depend- ing on the arrival rate and the landing interval, but they could nevertheless be usefully reduced by speeding-up chosen aircraft by approximately 10 per cent for the last hour of flight, pro- vided that the revised E.T.A.s were accurately kept. Accuracy of E.T.A. alone, although not directly reducing the delays, would considerably alleviate congestion near airports. An extensive examination of the accuracy of navigation actually achieved by aircraft flying over South-East England (as observed with ground radar equipment) had shown that, in general, position-reporting accuracy in I.F.R. conditions was poor, the average error being of the order of six miles. It had been found that aircraft entering the Metropolitan Control Zone pass, on the average, about one mile from the entry beacon, but with E.T.A. errors of five minutes or more. About 15 per cent of aircraft near the beacons in I.F.R. were more than 500ft from their allotted height, the average error in straight and level flight being about 220ft. Overshoots of several hundred feet were noticed to be a common practice when aircraft were changing height. Near airports, accuracy was even less, particularly in turns, when the average loss of height was approximately 400ft. It appeared, said Dr. Bell, that the required standards of height-keeping in relation to r,oooft separations could be attained by current methods, since the majority of aircraft flew within acceptable limits, although the existence of a relatively small but important number observed well outside the accept- able limits, suggested a certain measure of careless flying. The present performance of the best 80 per cent was not good enough to permit altitude separations of 500ft, and it seemed that height-keeping with a standard deviation of some 2"'ft was about the limit possible with present practice. The limited evidence available suggested, said the speaker,
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
