326 AIRCRAFT ENGINEERIN G November, 1944 B y J . G. Willis , A.F.R.Ae.S., A.F.LAe.S.* N betting out to design an aeroplane for the However, taking a pound off the tare weight commercial or civil market most designers to put on the pay-load becomes a myth if the In this article the Author forcibly puts have primarily thought of their aeroplane pound is taken off the wrong place. The thing forward a view which we believe to be as a machine whose first and last function was tha t matters is a high percentage of flying time fundamentally true—that in civil avia t o fly at the highest cruising speed for the least tion the customer is less interested in the over a given period in relation to pay-load car efficiency and performance of the vehicle power; its structural form usually fitting in ried, which can only be assured by the closest than in his own comfort and safety. liaison between operator and manufacturer in with personal whims on wing-body combination, If air transport is to be sold to eliminating troublesome points. undercarriage type, tail location, type of spars the public, aeroplanes must be made and formers and so on. Some international agreement is also needed not only to be but to look safe and Having thus expressed his aerodynamic and on radio and its ground equipment to keep the comfortable structural viewpoint to his satisfaction, with a weight of this item down. Similarly, the larger hope tha t his judgment will prove to be the last aeroplane can be considerably simplified and word in aeroplanes, the various passenger, crew reduced in weight, as regards equipment and experience, and the requirements of the passen and baggage compartments are next fitted in to operation of the multifarious auxiliaries, by ger an d operating conditions, with due regard to suit, bu t rarely t o suit the customer. adopting the A.C. generator system with proper weight distribution. A possible fourth A new aeroplane is thu s often born as another constant speed drives; but here again standar layout of fifteen feet diameter to cover a double engineering achievement rather than a com dization is essential to reduce the burden of deck arrangement could be added to this range. mercial proposition. Consequently, the present maintenance and spares on operators. Comfortable and pleasant travelling a t reason mode of designing an aeroplane is, more often Along with the weather, power plants are the able cost should all be firmly impressed on the tha n not, to design something and then find greatest source of worry to all concerned, but passenger's mind as soon as he sees and enters somewhere for the people to sit—which does strict adherence to simplicity and fundamental his means of transport; the fact that it is an not seem right. principles of design, together with intensive aeroplane he is travelling in should not be forced Now, one has only to examine a large number flying on the installation, is the only way to upon him with the customary noise, poor ar of aircraft, from feeder line to quite large types, establish their reliability and reduce this item rangement of accommodation, awkward atti to realize the common formulae of design lay of maintenance in service. tud e of the aeroplane and flimsy furnishings, out. Yet one sees sufficient variation in minor etc. The lay-out of such models as those men The average passenger immediately assumes points of lay-out (such as wing plan form, tioned above should be based on these points. an artificial fatalistic attitude towards life when body length, tail arrangement and fuselage B y this means the aeroplane designer would he enters an aeroplane and feels tha t he is about shape) to justify the impression of how flexible also be able to have, wha t has always been lack to defeat Nature and some of her natural laws, the modern design really is. Each and all of ing in the past, an accurate weight analysis of th e obvious one of which is that he cannot these variations are claimed, in no uncertain th e cabin lay-out and furnishings. actually see what will keep him up in the air, manner, to give th e best all-round results; which I t should then be a relatively simple matte r to However, he instinctively knows that the en only goes to show what an ideal medium the air fit this ideal body arrangement into the aero gines are of first importance and his fatalism really is, in more ways tha n one. plane as a whole, at the aeroplane manufac assumes real proportions with the noise, clash However, this sort of analysis cuts both ways turer's works, and thus avoid most of the argu and bang and vibration which goes on during because it shows the air-line operator how he ments between the parties concerned regarding the take-off and climb. can make use of these apparently allowable the lay-out. The mighty roar which thrills schoolboys is variations in design in calling for changes in the not so acceptable to the average passenger and lay-out offered to him to suit his own particular Maintenance and Servicing it would be better if the "works", meaning requirements; and he usually makes use of these Points of maintenance and serviceability also airscrews and such things, were neither visible facts. require more emphasis than in the past. It nor audible to him. The elimination of this The inference of the foregoing is that it is a should be possible for all servicing and minor noise and vibration should begin at its source, relatively simple matter to design and build a points of maintenance to be carried out un bu t the aeroplane builder must contribute his modern aeroplane which will fly quite well; but obtrusively away from the cabin—if necessary, share as long as he continues to press for more the detail design, to make the aeroplane light up to a few minutes before the aeroplane takes and more boost. and cheap to produce with requisite strength off. Circular bodies of the sizes mentioned, if and serviceability, on the inevitably small scale I t might also be a good thing if power load standardized, open up immediate prospects for production of civil requirements, is far from ings and take-off runs were fixed for given gross the settling of common structural items such as weights by international agreement for fixed simple. windows, escape hatches, astrodomes, doors and periods, to allow essential refinements to catch With the exception of the small feeder-line similar fittings; which would allow component up with the more drastic methods of pushing up typ e of aeroplane, and some private types, the manufacturers to tool up these parts and offer a aeroplane performance. It is difficult to recon body can be take n as of circular form and three well-finished article at reasonable cost, to the cile the present trend of take-off and landing sizes—of diameters nine, ten or eleven feet, benefit of the industry as a whole. conditions with the art of flying. with a substantial parallel section—cover all The designer can design the lightest possible normal requirements. I t should thus be possible aeroplane to carry the maximum pay-load, Most of these requirements can be met by for the air-line operator to build representative regardless of cost but needing a great deal of determined and original planning with the right body mock-ups and fit them out according to maintenance and hence few flying hours over a interchange of ideas between designer and given period; or he can design a heavier more operator—and the understanding that the one *The Author is an Assistant Designer with Messrs. A. V. robust version, maybe costing less and needing is not competent to design a commercially Roe & Co., but his views should not necessarily be taken as those less maintenance. successful aeroplane without the other. of his Company.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Nov 1, 1944