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Aviation History
1956
1956 - 1487.PDF
19 October 1956 641 NAVIGATION IN AIR TRANSPORT - Captain Majendies Presidential Address before the Institute of Navigation IN the introduction to his presidential address to the Institute of Naviga-tion, due to _be given last Tuesday, October 16, Capt. A. M. A. Majendie* said, "My predecessors in this office have been men ofconsiderable scientific and administrative distinction, able to talk with authority in their respective fields of learning. I, however, come beforeyou mainly as a practitioner of air navigation, the first such to be your president, and concerned mainly with the practical business of 'how toget there' in an imperfect and only partly understood world rather than with the elegant demonstrations of a theoretical technology." Furtherquotations, emphasizing specific points from Capt. Majendie's compre- hensive review—which had as its theme "The Place of Navigation inModern Air Transport"—are given below. SPECULATING recently on the future growth of air trans-port, a writer took as his motto: "Behold the turtle—sheadvances only by sticking her neck out." This is true not only of turtles, but exemplifies the spirit which is needed to meetthe challenge of the future. * * * The task of navigation in air transport is so to direct the path ofan aircraft that it can execute with safety any flight planned to come within its technical performance capability,and without loss to its practical operating and economic potential. How well this task can beachieved in practice depends on the three main component parts, which together make up theframework within which it has to be accomplished. These are the aircraft itself, the natural environ-ment in which it must be operated, and the artifi- cially created restrictions imposed by air trafficcontrol. The supersonic transport aircraft is hardly yetover the horizon of the future, but it cannot be ignored in any pattern of forward thinking. Theconsiderations which govern the operation of the subsonic machine need considerable modificationif they are to be applied to it. All that need be said here is that the general pattern may not be toodissimilar, but that there may well be a greater effective range of operating speeds and heights.Against this slight easement in flexibility of operation must be set a burning thirst for fuel, which will prescriberigid limitations to the duration of flight; to this, probably, only nuclear power is capable of providing a solution. * * * Viewed from the cockpit the surrounding atmosphere can be inmotion either horizontally or vertically, or both; can be hot or cold; and can be clear or cloudy. In addition, it can supportparticles of water in a variety of different guises, ranging from mist to hailstones, and can exhibit a considerable variety of electricalphenomena. The theme of this ocean of air is one of dynamic inconstancy, an ever-changing pattern of mood and motion. Manyof these phenomena are real enough to the pilot or navigator, but do not appear in the formal calculations of the aircraft's perform-ance engineer, or of the air traffic control planner. Despite the great advances in meteorological forecasting made in the lasttwenty years, it is clear that die pre-flight forecast can be little more than a generalized statement of probability, until such timeas real prediction can be achieved by computer techniques. * * * We are faced, then, with the need to operate our transportaircraft, which are by any standard sensitive and precise machines, in the highly irregular medium of the atmosphere. In order toobtain the best results from any particular flight, it is necessary to preserve an individual freedom of action, so that the navigationof the particular aircraft can be sufficiently flexible to enable it to adapt its plan of flight to meet the conditions actually encoun-tered. The independence of the aircraft from any prepared path in the horizontal, and its limited freedom of operation in thevertical, ensure that a large part of the flexibility needed will, in fact, be available from the standpoint of performance. Whetherit is possible to use this flexibility depends on two factors: first, whether sufficient information can be made available to assessthe actual weather situation throughout a flight, in order to deter- mine the optimum course of action: and, secondly, whether it ispossible for individual aircraft to retain the necessary freedom of manoeuvre without risk of collision between each other. *Formerly flight captain of B.O.A.C.'s Comet fleet; now aviation research liaison officer, Smiths Aircraft Instruments Ltd. In broad terms it may be said that the general approach to theproblem of air traffic control consists entirely of the denial to the aircraft of its principal and unique quality of three-dimensionalflexibility of manoeuvre: the three-dimensional problem of safe separation between aircraft having been found too intractable foreasy solution, the problem is simplified by reduction to a series of two-dimensional ones. This is achieved by confining aircraftto a limited number of selected flight levels. Having thus removed a large part of the vertical flexibility, the problem is still generallyfound to be too difficult unless aircraft are further restricted to defined tracks within the individual flight levels. A notableexception to this arrangement is the growing use of radar sequencing in the congested terminal areas around some of thebigger airports. However, the major problem remains, the out- come being to reduce the performance capabilities of the aircraftto those of a particularly fast express train, and its peculiar ability to afford free passage upwards as well as forwards is for thisreason largely annulled. It must not be thought that there is any easy solution to theproblem, or that the suggestion is being made that alternative methods of providing safe separation between air-craft could have been made successfully in prac- tice, and within the restrictive limits of time, tech-nical feasibility, and finance. Nevertheless, the outcome is a sorry business, and bodes little goodfor the healthy future development of air transport. Perhaps die most serious aspect of the matter isthe mentality it has engendered in the minds of many people, making it difficult for them to thinkof flight except in terms of rail tracks in the sky. The lecturer. Against this background we can review die placeof navigation in modern air transport. This can best be done by considering four sub-divisions.These are, respectively, die long-term planning of aerial transport; the planning of a particular flight;the en-route conduct of that flight; and, finally, the peculiar problems of approach and landing.Long-term planning must take into account two essentially different types of basic data. First theremust be an adequate grasp of the appropriate sciences and of the environmental circumstances of the opera-tions. These together provide the absolute framework of any plan. Secondly, diere are the relative limits set by human designor incapacity. It is these latter that die planner must keep con- stantly under review, for, if he does not, they may come to beaccepted as absolutely as must be those of the first type. Further- more, it is essential that the possible interaction of diese relativelimits be carefully watched, if progress is not to be impeded. Odierwise strange things may happen. If, for example, we allowtoo restrictive an approach on the part of those responsible for air traffic control to dominate our operational philosophy, this mayeventually affect the basic design of new aircraft types, and hinder what could otherwise be the unfettered development of appliedaeronautical science. At all times we must keep as our basic yard- stick what we could achieve in die absence of arbitrary or empiricallimitations, and make use to the full of the available technology and skills. One of the peculiar merits of die Institute of Naviga-tion is diat it is ideally suited to assist in providing such a yardstick. The problems of planning a particular flight are very much moreclearly defined, and offer considerably less scope for the exercise of individual judgment, mainly on account of the broad back-ground of current experience generally available. For this reason it is not too unusual nowadays to find diat flight planning hasbecome a more or less fixed routine conducted from a well developed set of rules. This is right and proper, and we couldfeel litde confidence in air transport were it to be odierwise. The essence of the problem in most types of air transport operation isto achieve a repetitive task with a high degree of consistency. It is right to expect such consistency naturally from the aircraft itself,for it is essentially a precision instrument. It is futile, however, to expect any such characteristics from its operational environ-ment, and dierein lies die heart of the problem: how to achieve consistency and reliability with a highly precise instrumentoperating to close tolerances in a fickle, and, to some extent, unpredictable medium? The short answer is, of course, obvious;to provide the craft with a flexibility of application that can at all times match the vagaries of its environment. If this couldbe achieved flight planning would consist mainly in setting out the limiting conditions likely to be encountered, and within which
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