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Aviation History
1948
1948 - 2156.PDF
734 FLIGHT DECEMBER I6TH, 1948 DEVELOPMENT OF A NEW AIRCRAFT PERSONNEL THE provision of such equipment in noway eliminated the need for carefuldissemination of the data obtained. The equipment was largely wasted unlessoperated by thoroughly able engineers whose training had been largely aero-dynamic. It was a fact that in America the considerable general engineering knowledgerequired to control high-powered and large wind tunnels had tended to give rise to ageneration of engineers with a general know- ledge of aerodynamics, rather than aero-dynamicists with a knowledge of general engineering. This must be avoided if atall possible. In this connection, the uni- versities could play a big part in givingaeronautical students a sufficient knowledge of general engineering to allow them to playtheir full part in this undoubtedly coming era of large wind tunnel equipment.No amount of lavish equipment, however, could dispense with the basic need for de-tailed investigation andJ analysis of the aerodynamic characteristics of the aircraft.The author's experience had convinced him that a good team of, say, a dozen aero-dynamicists, exclusive of wind tunnel staff, working on performance, stability and con-trol, would pay for itself many times over. He believed that a much more determinedand extended effort must be made to work out the controls, for example, before theprototype flies. Recent experience had con- vinced him that this could be done. The relationshipof the modern aero- dynamics office tothe remaining tech- nical staff, illus-trated graphically, was worth examin-ing. Taking the 100 PER CENT/ TECH. ^UBS. 4V AERODYNAMICS 4J WEIGHTS oFFioe+ G'B Distribution of design Rritish aircraft industry^ more bodies to writ~ aircraft than to analyse formance. total figures andreducing them to percentages, the result was anaverage for any firm. The low figure of 4.5 per cent for aero-dynamics, including as it did the wind tunnel staff, was a strikingfeature. Mr. Edwards considered that this low proportion mightwell be at the root of so much aerodynamic trouble and an aerodynamicsstrength of the order of 9 per cent of the total would be more balanced. MODIFICATION DIFFICULTIES T TNFORTUNATELY, in order to saveK,> time and cost, prototypes were made with little adjustment to the control sur-faces, flaps, tail setting and tail position. As a consequence, changes that were con-sidered advisable after early flights were often found to be impracticable because ofthe quick follow-up of the production air- craft. It was suggested that a sound half-way course could be carried out which should delay the prototype by no more thana few weeks and production not at all, if the saving in flight development time was takeninto account. This consisted of frankly treat- ing those parts which were known to givetrouble, on the type of aircraft under con- sideration, as fully experimental parts andmaking no attempt to productionize them until they had proved themselves. MOCK-UPS /CONCERNING mock-ups, Mr. Edwards\s said, on the one hand, the civil airline operator expects something approaching aprototype aircraft with complete furnishings picked out in four colours. On the other,the commercial manager's runs to a few packing cases, a ball of string and a boxof drawing pins. It was essential that all mock-up workshould come under the control of the project office, since this section had the greatestoverall conception of the aircraft. The prime purpose of the mock-up, toprovide information, should not toe over- looked. Finally, a mock-up should neverbe allowed to become so elaborate that it dissipated energies better employed in pro-ducing the actual prototype. STRESS OFFICE HPHE stress office could function in a-L variety of ways. In its most effective form it could be a healthy partner andcritic of the drawing office. In its lowest form it became merely a rubber stamp ofstrength approval on all drawings produced by the design office. This was usuallybrought about by lack of staff or insuffi- ciently experienced personnel.A major problem in the technical office to-day was to retain such men within theindustry. The solution would vary with each firm, but the aircraft industry mustoffer them prospects comparable with those which existed outside. AIRWORTHINESS ' I ""HERE was a definite need for one orJ- two men to become experts on air- worthiness requirements. They must checkall new regulations—a job requiring long experience and infinite patience—and seethat all applicable requirements were met. This work was done at one time by theR.T.O., but in the larger firms, where the administrative duties associated with thisoffice had greatly increased, it generally fell upon the constructor. The same applied,in some measure, to the case of the A.R.B. Surveyor. It was apparent that the need for closerairworthiness control had been appreciated, as shown by the appointment of airworthi-ness engineers in certain firms. MECHANICAL TESTING nPHE ability to handle all major tests-L within the firm was frequently absent because of lack of equipment. The policyalready outlined under wind tunnels must be adopted here also. The Governmentmust encourage the industry to supply its own major test gear in order to make itself-supporting for ad hoc tests and leave the national establishments free forresearch. WEIGHT CONTROL IT was fair to say that in most firms theweight office was a junior departmentand that the ideal form of weight control had to be solved. The numerical strengthof the department should be between one- half and one-third that of the stress office.It should be closely allied to the stress office, for preference under the same control.Like all junioTs, this department needed more care and attention from managementsthan the older and more experienced section of the technical office. It was believedthat such attention would be well repaid, and that a substantial contribution couldbe made by a well-trained weight control staff. Continuation of the Paper Read by Mr. G. R. Edwards Before the R.Ae.S. From Page 701, "Flight" Dec. 9th. DRAWING OFFICE WHEN all the basic problems had beenthoroughly examined in the project office, the new design passed into the draw-ing office and the next stage began. Initially, a new aircraft's life in the drawingoffice was an extension of the project stage. An early investigation into the feasibilityof the project design was essential. This must be done by senior draughtsmen andgroup leaders only. The office must be organized into groups sufficiently small forthe group leaders themselves to be designers and not administrators. In general, a maxi-mum of 15 in a group had been found to > work well. .'!Probably the most difficult decisions at this stage were those which concern scrap-ping a lot of drawing work when a better solution was apparent.Design for production must be instilled into every member of the staff. Mainten-ance problems, standards of finish and cock- pit arrangement, must all be part of everydraughtsman's education, and the present divorcement of draughtsmen from contactwith the actual aircraft was a bad thing. They must be enabled to see the problemsinvolved and, as far as possible, fly in the aircraft themselves. The senior aerodynamicand design staff, in the author's view, would do well to become pilots themselves. Itmade for a better understanding of the test pilot's problems and enabled them to gainhis confidence. Good services and working conditions wereessential to an efficient drawing office. Elimination of irritating delays by meansof a well-organized drawing stores and print room was well worth while. A well-runtechnical publications section ensured that the aircraft would be given a chance to workafter it had been built. So often in the past had the maintenance manuals arrivedin service long after the aircraft they de- scribed. A mould loft was an essential part of amodern design office. Profiles and lines should all be mathematically determinable.The practice of " fairing in " the lines by eye was an evil one. EXPERIMENTAL DEPT. THE role of an experimental departmentwas to provide information and pro- vide it quickly, said Mr. Edwards. That in-formation was required to enable satisfactory ^ production machines to be built.' It mightbe supplied by an aircraft which was the,, real prototype of a production version, or""lTby one which was more in the nature of a research aircraft, but would in the coarseof its flight testing supply much-needed data to enable the designers better to tackle thefinal job. There were four ways in which the ex-perimental department could provide the in- formation which was required by both de-sign and production sections. These were:—• 1. Confirmation of design office estimates,particularly on handling and perform- ance. z. Assessment " in the flesh " of the main-tenance features of the aircraft, to- gether with physical checks on its oper-ational efficiency. 3. Examination of production problemssuch as ease of assembly, riveting acces- sibility and best methods of jiggingwhile the prototype was still under con- struction. 4. Intimation to the drawing office of the '"inevitable drawing errors so that the production parts would be made offcorrected drawings. The prime factor in building a first pro-totype was speed. This must be reconciled ; c 32
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