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Aviation History
1963
1963 - 2129.PDF
930 FLIGHT International, 5 December ]%j TALKING AIRLINE SAFETY Two Further Papers from the Flight Safety Symposium In "Flight International" for November 14 (page 791) and November 21 (page 831) we published six papers given at the symposium held recently in London by the Flight Safety Committee. On this and the following page are two further contributions. DEVELOPMENTS IN PILOT-AIDS By A. M. A. Majendie, MA, FRAeS* I HOPE I can be forgiven for starting on a somewhat personal note. On leaving the airline world in order to take an appointment in industry, 1 did so full of idealism to crusade for better devices to help the cause of safety. Disillusionment soon came. In describing the operational thinking behind a new piece of equipment to the vice-president of a foreign airline I went to some pains to describe the various types of failure that could occur, and the warning and protective arrangements included in the design to cover all eventuali ties. At the end of my account our potential customer turned to me and said that we clearly had little confidence in the reliability of our design, and said that he would prefer one in which the manufacturer could have greater confidence, and without the extra elaboration needed to cope with possible failures. Admittedly this was some years ago, but even today it is depressing for a supplier of equipment to find how often safety is not a saleable commodity. A really honest design attempting to cater for the statistically remote contingencies, so often the cause of accidents, can easily price itself out of the market in com petition with quite simple-minded designs which have never been subjected to a full operational/technical fault analysis. This leads me to another point. In assessing cockpit equipment in general, and instrumentation in particular, a great deal gets left to the purely subjective judgment of a few development or project pilots. All too often they attempt to decide on the suitability and safety of an indicator from its ease of use. Operational accuracy and genuine safety are by no means necessarily related to the ease with which a pilot can use a device, particularly in the first few hours of his acquaintanceship with it. There are some signs of a growing awareness of this particular problem, and I would put in a plea for an objective and analytic approach to become the rule rather than the exception. Advanced Flight Control Systems From these rather general thoughts I would now like to pass on to consider the possible effects on air safety of the introduction of the advanced flight control systems being fitted to the next generation of subsonic jet airliners. The first and obvious fact about these new systems is that they increase the range and scale of facilities available to the pilot. This presents the obvious danger of obscuring the wood by the trees, and possibly making it difficult to establish quite simple matters. The extended scope provided can only be justified if proper rationaliza tion and integration of all the functions are carried through in a logical and systematic manner. Inevitably, the different features of such systems then become much more closely interdependent, and both design and modifica tion have to be handled from the point of view of the overall systems concept. To this extent any attempt to incorporate appar ently minor changes in the system to suit the particular ideas of a certain operator are more likely to affect the overall safety standard than in the case of simpler and less integrated arrangements. The primary purpose of these advanced systems is to control the aircraft with great accuracy, in more critical conditions, and with greater safety. The emphasis being placed on automatic control to this end means inevitably that the pilot is going to be able to commit * Director, S. Smith <£ Sons (England) Ltd and managing director, Smiths A viation Division. himself into situations which will be difficult to handle by conven tional manual means. This can lead to two sources of danger. In the first place it is manifestly essential that the equipment shall be correctly handled and adequately serviceable. A fairly heavy preoccupation is inevitable within the confines of the cockpit area in carrying through the necessary drills, in making the required selections and in checking the appropriate indicators. Secondly, with high rates of descent through complex patterns, and approaches to land in marginal to zero-zero conditions, it is vital that the captain at least shall continue to maintain effective orientation in judging the progress of his craft in relation both to the ground and to his final intended point of touchdown. This latter function can conveniently be called his "out-look" in contrast to the "in-look" needed in relation to the complex of equipment under his control. A fine balance has then to be drawn between "in-look" and "out-look." In critical conditions preoccupation with either one at the expense of the other is bound to be dangerous. The question I would ask is this. Is it reasonable to expect a single individual to preserve this overall balance between "out-look" and "in-loolc"? As the use of automatics becomes more and more routine in the final critical phases of a flight, so will the impor tance of this question grow. . If technical problems arise within the cockpit, the crew can easily become so preoccupied with the situation as to lose proper con tinuity in following their progress in relation to the outside world. No foreseeable situation should be capable of occurring within the cockpit which prevents at least one of the pilots from preserving his "out-look." Great care is going to be needed in this respect in laying down crew duties, and apportioning action under emergency conditions. But loss of "out-look" can also occur in quite a different way. The dangers of using a human operator in the role of a passive monitor of an automatically controlled system are well known. Boredom and inattention can easily develop over the years, and both "out-look" and "in-look" can suffer accordingly. Intelligent participation is an essential ingredient if safety is to be dependent on human supervision. Once again very careful thought is needed in crew policy when we come to exploit the future potential of advanced systems. A final word in this connection on monitoring devices. Very few of their warnings are absolute and comprehensive, and in general the level of protection which they provide can only be assessed by a detailed analysis. It is not reasonable to expect a pilot to remember all the possible qualifications of every such device in the cockpit. As an act of policy flags and lights, etc, should only be referred to as failure warning indicators when they provide this service absolutely. If their function is more limited this should be indicated by their name or reference—as, for example, power-failure indicator, comparator indicator, gyro-spin indicator, and the like. New or Additional Aids I would now like to turn your thoughts away from these new and complicated systems to consider what contribution to flight safety can be offered by simpler, new or addi tional aids to the pilot within the fairly immediate future. It is logical to start with take-off. Most people who have studied the problem are unhappy about the lack of precise and adequate instrumentation to control the take-off manoeuvre. I do not want to enter the lists on behalf of any particular system, but only to leave with you the nagging knowledge that all is not well in this area. Some work is being done, but I doubt if it is being progressed anything like as vigorously as it should be. Allied to this is the general problem of undue dependence °n single instrument indications in critical phases of flight. The im plications of a.s.i. failure on take-off or final approach, altimeter malfunctioning during let-down, errors in Mach number indication at high speed, and so on, can all be cause for disquiet. Do we really analyse and face up to all the possibilities with which we are ljvmS day by day ? Automatic monitors of many of these critical functions could be provided if anyone wants them. Such devices might also
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