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Aviation History
1948
1948 - 2159.PDF
DECEMBER I6TH, 1948 FLIGHT Development of a New Aircraft with a sufficient degree of accuracy to en-sure that it was representative of the air- craft as designed and would not differ fromsubsequent production machines. The manner in which the experimentaldepartment fitted into the main works or- ganization differed from firm to firm, anddepended on local conditions. Certain fun- damental requirements, however, were essen-tial to the success of the department. These were: —\. The ability to produce or control the manufacture of all the parts which goto make up the prototype. 2. Its own facilities for designing andmaking experimental jigs and fixtures. :-3f . 3- Adequate component and final assembly : space and a flight test hangar adjacent to an airfield suitable for experimentalriving. 4. Skilled personnel with the " experi-mental " outlook led by men possessed of great enthusiasm, unlimited patience,inexhaustible energy and an unflagging sense of humour. The intelligent assessment of the degreeof accuracy with which tooling needed to .be done was of great importance. Where.- mating parts could be assembled successfully • even if they were a few thousandths off the-theoretical dimension, it was a waste of (time and money to jig them to a thousandth. • TEST RIGS THE use of full-sized rigs in the shop,to test the functioning of as many of •: the aircraft services as-vossible, was rightlyv. becoming common practice. Much time in •-•.prototype flight testing could be saved by"Yintensive operation on these ground rigs. ;"Fuel, hydraulic and electrical systems should,: be tested as thoroughly as possible with all "the components in their right geometricalposition. Undercarriages should be mounted .and functioned thousands of times beforefinal installation in the aircraft. The closest possible liaison between the•••• drawing office and the experimental shop was necessary. In fact, the construction of-.; a prototype and its test flying were as much '; a part of the design as the original schem-ing and drawing. Setting up in the experimental shot) asection from the production planning office was a good thing. Members of this section. should advise on the nature of the tooling, particularly as to whether a tool was suit-- able for subsequent production. They should •.see that the production people kept a closewatch on all stages of the prototype con- struction. In view of the limited production likely to prevail during the present period, it wasincumbent on the design office to make its . aircraft capable x>f accurate reproduction ' with cheap and limited tooling. Complicateddesigns, only made producible by the large wartime quantities involved and the in-genuity of the tool designer, could no longer be tolerated. FLIGHT TESTING THE flight testing of a new type of air-craft could be divided into two maincategories. First, exploratory tests of power unit suitability, performance, handling ofcontrols and the functioning of heating, pres- surization and other systems.The second main category of flight tests were those required to obtain official clear-ance. The schedule of tests to coyer C. of A. requirements entails approximately 60 hours'flying This applied equally to military aircraft which had to satisfy A.P.970 require-ments. ' As the aircraft had been tested already in the most adverse conditions andany faults rectified, these tests should be straightforward and without snags. In the past, lack of suitable weather hadconsiderably lengthened the time taken to complete the flight test schedule. It wasnow the practice to have every prototype -aircraft fitted with full radio and " G aids, A a and a navigator/ wireless-operator was ineluded in the crew. Good testing conditions were often obtained above ten-tenths cloud,and it was only on comparatively few days that the weather was too bad for flying,provided that the necessary radio aids were available. This system also gave the manu-facturer experience of the behaviour o[ the aircraft in bad weather. Apart from the tests to prove that theaircraft met official requirements, various operational tests had to be made beforereleasing to the customer. These include checks on the behaviour oi engines andairframe in icing conditions, radio and radar efficiency and, if possible, performance andsuitability in tropical temperatures. The reliability of stability, handling andperformance tests depended upon accurate loading and C.G positions. It was mostdesirable that the aircraft should be able to be pushed on to scales in the hangarfloor in its loaded condition before each flight. All this flying time piled up the cost,and the author was convinced that much unnecessary duplication of testing by theconstructors and by Boscombe Down took place. Just as design approval was grantedto a firm in order to relieve the K.A.K. of the necessity of checking all the calcula-tions, so should1 a similar approval be ex- tended to a firm's flight organization. Once this approval was granted, the con-structor's flight test report would be, in the main, accepted. Boscombe Down could thenpick out for checking salient points such as -stalling characteristics, engine-cut case,and, no doubt, longitudinal stability in the condition in which their last aircraft gavetrouble. CONCLUSIONS JF the foregoing organization was usedefficiently, and some of the reforms out-lined in the early part of the paper were made, a new time scale might be possible.As an example, it was not considered un- reasonable that for a civil transport of40,000 lb all-up weight, the lapsed time from the placing of the order to the first proto-type flight could be two years. A further 18 months might be needed to complete thefirst production aircraft and 12 months more before a number of aircraft were operatingon the routes. This total of four and a half years, while reducing developmenttimes and costs to reasonable proportions, at the same time took a fair account of theperiod required for all necessary pre-service trials and the cure of the usual "teethingtroubles." If he had been critical of -some of theconditions obtaining in British aviation, said Mr. Edwards, it was in the hope thatby drawing attention.to certain shortcomings he might have made some contributiontowards their removal. He firmly believed that the British aircraft industry wanted,above all things, to build efficient aircraft; to see them used by the R.A.F. and thenational corporations; and to further its already considerable contributions towardsthe struggle to increase exports. Recent experience had led the author tobelieve that airframe costs of some /16 per pound of gross weight were possible. Air-craft of a revolutionary design embodying features previously untried would naturallytend to go higher. The breakdown of this figure was as follows: — i per Ibgross wt. Percentage 1. Design to C. of A.standard 4-3 26 2. Mock-ups, wind• tunnel models, etc. 1.4 8 3. Test pieces 1.8 114. Two prototypes 8.3 52 ,5. Flight testing to C.of A. Standard 0.5 3 No allowance could be made for engine de-velopment, as a successful engine would 735 generally He used in a numbei ol types, andits CUM accordingly shared by them. It had been said that our AmericanIrienils. when looking for a needle in a. haystack, proceed, with great determinationand colossal effort, to tear down the whole stack. We, with our more limited resources,spent a little more time walking round the haystack before bearing down upon it. Itmight be that we could only manage to grab a handful; but we frequently foundit to be the one containing the much-prized needle So long as we preserved this groatnational trait, the country need have no fear that the Uritish aircralt industry wouldfail it, cither in peace or in war. DISCUSSION IN spite ol a long discussion period whichlollowed Mr. Edwards' lecture, the chairman, Dr. Koxbce Cox, had to apply" the guillotine" while there were still several people wishing to speak. It is un-derstood that Mr. Edwards is now dealing with a very large number of written ques-tions. Mr. N. E. Rowe (B.E.A.) said there wasnothing like concentrating on a well-designed aircraft, and agreed that the best way tocut development costs was to get a machine right the first time. Although some of thebest civil aircraft had seen long service in an air lorce, their design had owed nothingto military aviation. Instances were the D.C.3, Empire flying boat and Constellation.It would be a good thing for civil operators to discuss military requirements in theearliest stages of the formulation of their requirements. It might be possible that weshould get better military types by modify- ing basic civil aircraft. Regarding the costof the general organization of the aircraft industry, throughout the world the industrywas maintained as a defence potential and, as such, money spent on developing newtypes should come from the public purse. The high cost of a new prototype should bepart of the support to the industry as a whole. The general aim was for aircraftto last ten years. If the right size of air- craft was not designed civil aviation wouldbe very much restricted because of airport difficulties. Mr. Rowe asked for Mr. Ed-wards' views on research into structural materials, finishes, etc. Mr. R, E. Bishop (de HaviUand) stressedthe necessity of serviceability. He sometimes wondered how the very large civil aircraftbeing built in this country and in America were going to be kept serviceable. Solutionsof maintenance problems were almost im- possible. Too much time was spent bysenior people writing requirements when the effort should be in the drawing office gettingthe aircraft safe by good detail design. Both military and civil aircraft must be made tolast longer. One should start with a really good design and adapt it to the varioustypes. The Mosquito was originally a light bomber, no mention being made of use asa fighter. The designers took the simple precaution of seeing that there was room forguns, and as a result it was easy to make it a fighter when the request came a fewmonths later. The present tendency to make one basic type of aircraft suitable for R.A.F.and Navy was right. Operationally the re- quirements of night and day fighters wereidentical in both Services, and Mr. Bishop did not think R.A.F. pilots would mindlanding a bit slower. "-i • It sTiould not be necessary to build a pro-totype other than as" a Research aircraft. Too many prototypes .had been built inrecent yea.rs vwl^ich, had not gone into pro-duction', r^auSfe-Sfcifey^ were not properly thought out.' The Empire flying boat camestraight off the drawing board, was built in quantity and was a great success. Mr. W. E.W.Petter. (English Electric)said that perhaps the principal job of a chief designer was to maintain full employ-ment of his organization. The question of time and cutting down costs depended onhaving a highly qualified staff to get the thing right the first time. He thought thechief designer ought to control the experi- mental shop, where speed was a problem.
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