Aircraft Engineering THE MONTHLY ORGAN OF THE AERONAUTICAL ENGINEERING PROFESSION VOL XXVII No 314 APRIL 1955 turbine engines in relation to their thrust and the advances it makes possible should be used to ensure the safety and reliability of the WO lectures have been delivered recently which to some extent landing operation before going too far in gathering economic ad impinge on the same aspect of, more particularly, commercial vantages. Taviation, though from very different points of view. The two papers to which we refer are that on 'Structural Safety' delivered by PROFESSOR PUGSLEY before the Preston Branch of the Royal Aero A Philosophical Approach nautical Society and the Brancker Memorial Lecture on 'The Influ PROFESSOR PUGSLEY is concerned, as his title shows, more with the ence on Civil Aviation of Some Current Researches' by SIR ARNOLD aeroplane when on its way in the air. His paper is also, characteris HAL L to the Institute of Transport. tically, an exercise in philosophy and less concerned with detail— though he has, of course, much to say on fatigue. His theme is that there has now been much consideration of the statistical method of A Recurring Theme studying the structural safety problem—more especially in regard to It is not, we think, giving an undue bias to the general trend of fatigue—and that it is time that a more humanistic, or indeed ethical SIR ARNOLD'S lecture to say that the underlying theme was a plea for or moral, approach be made to the matter. Recent large-scale lower take-off and, especially, landing approach speeds. Right at the accidents, he says, have brought to mind an approach to the diffi outset he sets the stage by saying that it is towards greater reliability culty that, though economic in form, is human in basis. It is this. and safety in civil aviation, rather than very long term possibilities When a small aeroplane crashes and its one or two passengers are that attention should be directed. The accident due, for example, to killed it is regrettable, but the rest of the world treats it as motor troubles of navigation, to storm, to landing in bad weather, must be car accidents are commonly treated. Even if the accident is shown to totally mastered. It is usually the case, he goes on, that advances in be due to structural failure, unless there is a rapid succession of such performance of aircraft can be taken in several ways, for example, accidents, the public reaction is still small. When, however, a large in lifting great weights, in reducing operating costs, in lower approach civil aeroplane with some fifty passengers crashes the reaction is not and landing speeds. In his first figure he gives the direct operating only national but international. A second such accident brings such cost of a high subsonic class of aircraft designed for the non-stop pressure to bear that the whole fleet of aeroplanes may be grounded. London—New York flight as a function of the payload and the land The overall effect, though not deliberately economic, can be meas ing approach speed. In the very next paragraph he deals with the ured in economic terms, and we seem to have here the basis for a economic effects of size of wing and again returns to his theme by discussion of human risks as set by the public sense of human pointing out that if fuel were carried in the fuselage, or in nacelles values. attached to the wing, the smaller wing possible would, at high design payloads, result in a fast landing approach speed. An Invidious Choice It is impossible to go on quoting from the paper but it is not too much to say that in it almost every possible improvement in the per The two papers seem to us of great importance when read formance of an airliner is related to its effect on approach and land together. Reduced to essentials, the point at issue becomes the very ing speeds. simple one of whether we are to cater in our airliners of the future for We are labouring the point because it is the first time we remember maximum operational economic benefits—profitability—or the highest possible degree of safety. Both authors are agreed that we a speaker with the technical qualifications of SIR ARNOLD HALL cannot have both. A very nice question in ethics therefore arises. when dealing with the design aspect of aeroplanes laying so much The question is who is to have the responsibility of making the stress on this matter of landing speeds, to which he returns again and again. Halfway through the lecture he devotes a section to take-off choice. The designer's duty seems to be merely to produce the best and landing characteristics and shows how the improvement in possible aeroplane to fulfil the specification, in which the decision has presumably already been made. The operator, who presents the thrust to weight ratio of turbo-jet engines and the possibility of tap specification, is not in the best position to make the choice since he is ping some of the huge volumes of air going through them to increase necessarily influenced by the demand for profits, or at any rate the the efficiency of flaps may help in obtaining more control at lower landing speeds—apart from the newly developed deflexion of thrust avoidance of losses. The odium of arriving at a reasonable compro method. He, again, points the moral by emphasizing that if advantage mise between the nearest approach to absolute safety and the attain ment of highest possible economy in operation must then, as far as is to be taken of any reduction of flying speed obtained, conventional we can see, ultimately rest fairly and squarely on licensing author controls must be made more effective or be replaced, wholly or ities—or, in other words, Governments. The sooner this is realized, partially, by other means. and faced, the better. He further pleads that the benefits of the very light weight of
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Apr 1, 1955
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