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Aviation History
1949
1949 - 0508.PDF
326 FLIGHT MARCH 17TH, 1949 AIR SAFETY DEBATED Some Contrasting Opinions on the R.Ae.S. Quartet of Lectures MR. NORTH'S paper on The Theoretical Aspects ofAirworthiness and Safety was the first of the fourpresented at the lull-day Discussion on Air Satety held at the Royal Aeronautical Society, March 5th.* In thanking the lecturer for his contribution, the President of the Society. DR. H. ROXBEE Cox, confessed that he had found the paper difficult to read, but his difficulty was due to the un- familiarity of Mr. North's approach to a difficult problem. He felt, however, that by his exposition Mr. North had shown the advantage of the spoken over the written word. In a contributed comment, read by Dr. D. M. A. Leggett, on Mr. North's paper, PROFESSOR A. TUSTIN, of Birmingham University, suggested that its subject-matter could best be understood and appreciated as an analysis of the nature of human judgment. Professor Tustin thought that the schem- atization of the problem as a " game" on a chequer-board seemed to be very close to the kind of process we habitually used in " judgments," and averred that much was to be gained from schematic representation if not too much was sought. What chiefly emerged was a clear understanding of why the problem was baffling, not an answer to it. PROFESSOR A. A. HALL commented that Mr. North had used the language of statistics, of psychology and of physiology. He wondered if it was necessary to argue by analogy and in terms with which we were not entirely familiar, although he did not argue against cross-feeding between sciences. He was not certain that such matters could be discussed without risking the introduction of false analogies or unfamiliar false signs. The matter, he said, was one of statistics and they could be a very bad master. For example, if the chance of being killed were one in two, that did not mean that one could be half- killed twice. From being half-killed twice one could recover, but it was not possible to recover after being killed. [To this Mr. North later replied that he would regard the half killed as being defined by the fact that the amount of dis-benefit, if it were multiplied, would be equivalent to that of one man killed.] Prof. Hall said that things happened to aircraft long before , they came to be treated statistically and, in consequence, it was wise to deal with statistical facts with a certain degree of care. Discussing aircraft reliability, Professor Hall said it carried two terms, one being the mean life, whilst the other, which was more important, was the spread over the mean life. He felt that they should take a great deal more trouble than they did about engineering tolerances, and there was more in it than just tolerances in respect of good fits, as the factors demanding tolerances were those which caused variation in life. Commenting on Mr. North's theory of the "unique move" MR. J. R. WOMERSLEY said that having thought about what happened immediately before an accident, he did not consider that there was^always a unique move It could be appreciated in one/or two^ample. case^riut where a multiplicity of means of avoiding aVl agcideot were' presented, there might be an in- finity of choices at the last moment. -» •"• / Lessons from Accidents PROFESSOR' A. (Jf PUG%LEY Expressed regret that the author pi the paper did not enlarge on the empirical approach. Much of our *j/prk in tint country had followed this approach until about f:en years ago, using lessons drawn from one accident , after another to build up a common law upsn which were based "*" tfe^airwoJIfHhess requirements. The approach had continued to' a lesser degree during the last ten years. He considered .that f-hey should make long-term judgment by studying a series of accidents instead of attaching too much significance to individual accidents. He thought that one of the main ftinctions of an airworthiness authority was to investigate the cause and analyse experience. He also felt that although they had always endeavoured to disqualify the incompetent and dishonest a code of practice should be produced for the benefit of those who were less experienced in the manufacture of air- craft. He would prefer to see the airworthiness authority ensuring that aircraft were airworthy rather than that they were perfectly safe. MR. N. E. ROWE was not sure that he understood the state- ment, made in the paper, that it was quite unreasonable to relate any qualities of an aircraft directly to risk of accident, because it seemed that if an aircraft had particular qualities * Abstracts of the four papers appeared in>ast week's issue of Flight. of stability and control, or bad features in approach to land, the risk of accident in that aircraft might be very different from the risk in another. In replying to other critics of his approach, MR. NORTH said that the human factor was predominant, that it was the centre, and that he did not think many such problems could be " discussed except around the behaviour of the human being., * Finally, he regarded it as very doubtful whether or not flying had become any safer in his lifetime. It had become much more enterprising and the great technical developments in air- craft seemed to be used to enable us to do more, rather than used to raise the standard of safety. A. CDRE. VERNON BROWN, Chief Inspector ot Accidents, opened the discussion which followed Dr. Bergin's lecture on The Physiological Aspects of Air Safety. He considered it one of the most interesting lectures he had heard and referred to difficulties between the wars in stimulating among doctors an active interest in flying—their services, he considered, could be very valuable in accident investigation. The Air Commodore '"" thought that too little attention was paid to the effect of fear in the air, a subject which was not accepted for investigation in the Services. Fatigue, he said, was a cause for anxiety at all times. Another speaker suggested that pilots were more likely to succumb to fear under fatigue, and that their ability to over- come the condition could not be measured in normal circum- stances. Pilot Error j : MR. SCOTT HALL, of the Ministry of Supply, referred to accidents attributed to errors of judgment, which he thought pointed to the need for high intelligence among pilots, with par- ticular emphasis upon speed of reaction. DR. BARBOUR, of B.E.A., approved Dr. Bergin's appeal to designers but quoted losses in the first world war in which 90 per cent of the deaths v^ere due to pilot error. He advocated that the other physical abilities of human beings should be used to relieve those faculties which were overworked and which caused fatigue. He agreed that designers were very much concerned in the safety factor and emphasized that the aircraft should be made to fit the pilot and that pilots should not be required to accustom themselves to different designs. The pilot remained the most important link in flying, but it was significant that he was examined only every six months. MR. DICKSON defended the designer in his efforts to provide a standard cockpit layout and asked Dr. Bergin what, from the medical point of view, would be the best composition and type of lighting for helicopter operations, bearing in mind the procedure and technique adopted by the Helicopter Experi- mental Unit. DR. BERGIN later replied that single lights gave false impressions to pilots in the air. It was rather strange, he said, that an impression of movement always accompanied a single light; that condition could be abolished, however, f by the use of several lights in different planes, or by inter- rupting vision |hrough the installation of flashing lights which had trw same effect as the pilot blinking his eyes. In reply to the appeal (made in Captain James's Paper on Air Safety from the Pilot's Point of View) for adoption of a standard cockpit layout, MR. GEORGE EDWARDS, chief flesigner of Vickers Armstrongs, suggested that users should co-operate and decide on a standard layout, since designers were only too willing to conform. He also appreciated the necessity for sensitive reaction to controls. His personal experience of crash-proof tanks was one of considerable success and he knew of one positive case where lives had been saved through their installation. He thought, also, that every window should be an emergency exit and that passengers should face backwards. Mr. Edwards could see no necessity for using combustion heaters in aircraft. It was better, he said, to use the heat from other sources. With reference to structural failures, he thought that there was equal danger, when landing in adverse conditions, through instrument failure. He also thought that we should get back to lower stalling speeds and consequent low landing speeds. The greatest difficulty was economic in that the users wanted all the advantages and were not willing to forsake payload. Development of the turbine engine was a measure towards safety, he thought. MR. MARCUS LANGLEY raised an interesting point by asking., the Inspector of Accidents for a definition of pilot error since he thought it could be an engineer's " let out." He suggested B 24
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