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Aviation History
1950
1950 - 0062.PDF
42- FLIGHT, 12 January 1956 LONDON AIRPORT GROUND TRAFFIC . : . distributed along the building face and "island" stands between the inner and outer taxiways it was found that adequate provision could be made to accommodate all pos- sible aircraft in the Central Area. The stands for aircraft of 300ft span are being placed on one of the '' islands'' on the northern faces of the terminal. In the layout finally adopted, stands of 150ft turning-circle are provided on the inner and outer aprons on the S.W. and S.E. faces and on the inner apron of the N.E. face; stands of 175ft turning- circle on the inner apron of the N.W. face and on the outer apron of the N.E. face; island stands of 300ft turning-circle on the outer apron of the N.W. face. Xn this way 64 stands are provided. This number can be increased to 71 if the 300ft stands on the outer apron of the N.W. face are used by aircraft of up to 175ft turning-circle. A theoretical relationship between hourly aircraft movements and number of stands required is shown in Fig. 3. On a basis of assumed occupancy periods of various lengths it was found that, in practice, and allowing for delays in refilling the stands, 61 stands were required at one time or another throughout the hour. On the basis of a provision for 64 stands there were two 300ft and one 150ft stand vacant throughout the hour. The two 300ft stands could become five of 175ft if desired. The study showed that it would be practical to allocate aircraft to a particular face of the Central Area according to their type of service, since the size of aircraft used on any given type of service should be more or less uniform; it was considered impossible, however, to allocate stands more speci- fically than this. In one given case jt was assumed that: — 2 aircraft occupy stands for 60 inin. 26 aircraft occupy stands for 40 min. ••.--'; 85 aircraft occupy stands for 20 min. - ' 10 aircraft occupy stands for 35 min. 7 aircraft do not use tnt Central Area. While such handling times have not yet been generally achieved, says the report, it should be possible to reduce the times to those stated before the airport has to handle a high movement-rate. Interim Stage,—The interim stage in the development of the airport is considered to set problems similar to those which will occur in the two final stages of construction, and from information gained in the operations during this stage, the necessary modifications can be made in the final layouts in respect of routing, control of ground movement, use of vehicles, manoeuvring of aircraft and passenger handling. Routing plans were devised for the interim stage to give a one-way flow past the terminal buildings planned for the eastern faces, to keep taxying distances to a minimum, and to stimulate as far as possible the final routing plan. The rout- ing in south-westerly wind conditions .is show.n in Fig. 4. Certain modifications are necessary, however— for example, in the diagram reproduced on page 43 the take-off path will be rather long until the tunnel is complete under No. 1 runway, when a more direct route to take-off can be established. It was assumed that the number of stands available will be 15 of 150ft, this being the number of inner stands which could be accom- modated during this stage. Two further stands would be available later on the outer aprons of the N.E. and S.E. faces and the temporary surface-road access would be replaced by the tunnel. For the interim stage layout a movement study was carried out on the same lines as those previously mentioned. A movement rate of 30 aircraft per hour was assumed, divided into 18 landings and 12 take-offs. The aircraft were classified as long-haul, short-haul and transit, the number of aircraft involved being 8, 20 and 2 respectively and the assumed stand occupancy 40, 20 and 35 min respectively. It was found that the routing of a single-taxiway layout was satisfactory and gave a minimum of non-cumu- lative delays. Use of the northern terminal in conjunction with the interim terminal in the Central Area would be most unsatisfactory, as taxying distances would be excessive. The number of stands used was 15, which was thought adequate to cater for the movement-rate examined, provided that the stand-occupancy times postulated can be achieved. When dual runway operation commences, however, while handling facilities are still confined to the Eastern faces,' it will be necessary to have full use of the outer stands in order to accommodate all the aircraft movements. Ground Movement Control.—The high rate of aircraft- movement envisaged, particularly in conditions of poor visibility, together with the need for minimum delay on a complicated system of taxiways, points to the necessity for a positive and speedy (although flexible) system of traffic direc- tion, with some form of automatic position-reporting to the Controller, who in bad weather will not be able to see all of the movement-area. Existing systems of directing traffic by " leading-in vans," lamp signals or R/T. are not capable of expansion to cover the projected movement rate. A control system is therefore needed to meet the following requirements: — (a) To give a positive indication to aircraft of the route tobe followed between starting point and destination (unloading stand, runway or maintenance area). (b) To permit the selection of routes from any one point onthe airport to any other. (c) To permit the selection, in sequence, of crossing routes, theinformation being " stored" and released (in the order selected), as the previous traffic passes the intersections. (d) To provide automatic safety-locks within the system to prevent aircraft colliding. (e) To report back automatically to the Controller the progress along a selected path of aircraft or vehicle. (f) To report back automatically to the Controller anv dangerous situation arising from the misinterpretation of signals. (g) To report from one phase of Coritrol to another, e.g., Air Traffic Control to Ground Movement Control, the order in which aircraft would pass given points to enable them to be marshalled into the correct stands. Examination of the problem as elaborated above made it apparent that radar can, at best, only provide a broad super- vision of movement and that with anything approaching the hoped-for utilization of the airport, the associated R/T. channels would become overloaded. The solution appears to lie in ground detection of the aircraft position by electrical means and to approximate closely to a railvvay-block-signalling system. Within this field the following three sub-divisions can be made: Category I, requirements (a), (b), (c) and (d): Category II, requirements (e) and (f); Category III, require- • ment (g). Category I could be met by the installation of an almost normal railway signalling system, the usual signals being replaced by lights countersunk into the concrete surfaces. In view of the complexity of the routes to be selected and the need for speed, automatic selection of all intermediate "points" would be necessary on the setting-up of a route, so that appropriate switches at the start and finish of the path, when selected, would operate a whole route. This selec- tion would be coupled with the provisions of requirement. For requirement (c) a route-selection storage indicator would permit the selection in sequence of crossing routes. Category II, the indication of the position of aircraft, it was Fig. 3. Theoretical relations between hourly aircraft movements and the number of stands, passengers, vehicles and channels required are shown in the four graphs reproduced below. K5 155 « No. OF A/fc MOVEMENTS/HR4O MIN OCCUPANCY ASSUMED OCCUPANCY2O MIN OCCUPANCY 2OG&' " " 3OAb'' ' ' '*>OO'''' 'SOW No OF PASSENGERS. SO 900 . li 5 : 1 • « 12 i .INIUSE AT ONE TIME ACREOUIRED. HANDLING CHANNELS REQUIRED/FACE
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