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Aviation History
1950
1950 - 0320.PDF
212 FLIGHT, 16 February 1950 PRODUCING A PROTOTYPE An Examination and Evaluation of the Art : Mr. C. T. Wilkins's R.Ae.S. Lecture ON Thursday last, February 9th, a Paper, entitled TheProducing of a Prototype Aircraft, was presented beforethe Royal Aeronautical Society by Mr. C. T. Wilkins, A.F.R.Ae.S., assistant chief designer to the de Havilland Air-craft Co., Ltd. Mr. Wilkins started by saying that, broadly speaking, therewere two kinds of prototypes: (1) the research aircraft with which to obtain specific data for a future production aircaft,and (ii) the first of a production order. If the project was in the first category, then it was right to build one or twoaircraft only; but if it was in the second, production aircraft should be built as near concurrently with the prototype as waspossible- An aircraft for production should represent a large enoughadvance in design to reach a potential market and, by develop- ment, to hold that market for many years. It should, however,not be so radical in conception as to make it unwise to proceed with quantity production without test-flying a prototype. The lecturer thought that too many aircraft were built firstas one or two prototypes, taking possibly two years or more to build, followed by, perhaps, one year of test-flying and modi-fication before production really got going. A further period of two years might elapse before the first production aircraftwas delivered to the operator, who might spend a further year in proving flights before the aircraft reached operational ser-vice—making, say, six years from the time when the prototype was started. This was far too long. During such a period, new develop-ments in operational requirements, power plants, and so on, might take place which, if incorporated in the design, wouldcause still further delays; if they were not incorporated the aircraft would be obsolescent before it reached operational ser-vice. It was far better to face modification on the production line than to wait for prototype development, so that a batchof operational aircraft could be delivered to the operator at the earliest possible moment from which experience in actual opera-tion could be obtained. In the meantime, the type could pro- gress, incorporating any development and, also, any pointswhich might arise from the operation of the delivered aircraft. Time was the all-important factor in the producing of aprototype. There was nothing worse than a project which drifted on and on, repeatedly being altered until everyone washeartily sick of the whole thing, for it meant that enthusiasm flagged, the costs rose and the whole project suffered. Soonafter the start of the design, a reasonable target-date should be set for the first flight. Value of Time - . - . . A meeting should be held periodically to keep a check onthe progress of the job, to let people know what was going on in a general way, and to let people bring up any points, suchas information required from the information department or stress office. Meetings and conferences generally, whetherinternal or external, should, nevertheless, be as infrequent, short and small as possible, for they could be shocking time-wasters. The maximum possible amount of overtime should be•worked, bearing in mind that, though overtime was costly in salaries, money was always saved by getting a job out quickly—owing, among other factors, to the reduced time for which overheads were being paid. Too-long hours should not beworked, and regular breaks in overtime should be provided, otherwise people would get stale and no benefit from overtimewould result. In order to keep down the number of men on the job, thedrawings should be of the minimum standard required to build the prototype. To save time, as much information aspossible should be put on one drawing. If, suggested Mr. Wilkins, the experimental department could build the aircraftfrom these drawings, so could the production department, pro- vided that every item was dimensioned correctly and had apart number. When production really got going, these draw- ings would need to be broken down and made into properproduction drawings in collaboration with the production department, and this would be the job of the productiondrawing office. The modern aircraft had become so complicated that, if thepresent trend persisted, there was a danger that the aircraft would no longer be a practical flying machine but wouldbecome a box of tricks which spent most of its life on the ground being made serviceable. Simplicity was the keynote to reliability, ease of maintenance, lightness and cheapness.Mr. Wilkins suggested that periodically the designer should stand back and ask himself: "Is everything incorporated inthis design absolutely necessary? Are there any relics from a scheme which has since been altered? Is something still beingdone in a certain way because it suited a previous scheme? " No new equipment should be accepted at its face value, butshould be studied in detail and discussed with the manufac- turers with a view to improving simplicity and lightness. Thefact that the equipment had been used on some other type, although valuable in that experience had thus been gainedwith it, did not necessarily mean that it was suitable for the current type. Without in any way detracting from the excellence of thework done by the S.B.A.C. Standards Panel, the lecturer believed that standard items should be confined to the smallerparts and that no attempt should be made to standardize things like controls, seats, and cockpit layout generally, asitems of this kind were an integral part of the aircraft and should be designed as such. It was so difficult in the design ofa successful modern aircraft to strike the exact balance of conflicting requirements, that any built-in compromises suchas large standard items could not be afforded if the best possible design was to result. Professional Status . ., '- -: J~ :.r. • In that section of his paper under the heading "DrawingOffice," Mr. Wilkins made a plea that the whole occupation of aircraft design should be more on the basis of a professionsuch as, for example, that of an architect, rather than being considered as something between a trade and a profession. Agood designer must first of all have enthusiasm for his job, a good technical knowledge, and an interest in aircraft generally.He must have sound basic mathematical and mechanical train- ing followed by, or concurrently with, practical experience inthe shops. There was, however, no need for him to be an artist. Many youngsters were put into drawing offices becausethey could draw ; these were usually the people who remained draughtsmen all their lives Dealing with the work of the stress office, the lecturer statedthat, in these days, when a modem aircraft structure presented probably the most difficult and refined structural problem ofany branch of engineering in the world, so complex had the problems become that theory went only a certain way toachieve the optimum structure, and recourse had to be made to full-scale testing. It was important that this testing be doneon the spot so that both designers and stressmen could watch the test in progress and reap the benefits of visual observationinstead of merely reading a report. Before the prototype had flown, a general programme offlight-testing should be prepared in conjunction with the chief designer and the aerodynamics department. It was importantto obtain as early as possible an overall picture of the capa- bilities of the aircraft rather than to spend hours of test-flyingin obtaining academic data which, useful as they might be, could be obtained at a later date. The important thing duringthe early test-flying was to keep the aircraft in the air. The aim should be, assuming no major snags and with goodorganization, to average about one hour's flying per day for the first TOO hours of test-flving. Any important snags foundshould be reported immediately, and, if a good night shift was provided, these snags could be dealt with overnight.The importance of the technical buying department in get- ting a prototype out quickly could not be over-emphasized.On its efficient working depended the avoidance of long delays in obtaining materials and proprietary equipment. Deliverydates of six months or more were often quoted for special materials. This could not be tolerated, and it was surprisingwhat could be done to improve on these dates by bringing pressure to bear on the suppliers and refusing to take "no"for an answer. To build a mock-up of the complete aircraft with wings andtail was, the lecturer thought, a waste of time and money. The location of the mock-up was important: ideally, it should bepositioned facing large doors or windows so that a distant view might be obtained from the cockpit. It was most misleadingwhen trying to assess the view to look at a blank wall. Every- thing in the cockpit should obviously be shown, even to thesmallest items and, wherever possible, the actual equipment should be used. Paper dials representing instruments wereuseless.
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