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Aviation History
1954
1954 - 0091.PDF
47 Two hypothetical Mach 2 aircraft used by Mr. Keith-Lucas to emphasize the difficulty of finding sufficient internal stowage volume for the large quantity of fuel and equipment required. The wings contribute little to this volume, particularly in the right-hand design, in which the thickness/ chord ratio would be about 4 or 5 per cent. DISCUSSING PRODUCTION . . . that integral construction was not confined to a particular size of aircraft, but was largely dictated by the intensity of end- loading per foot of stressed chord. Fatigue in integral struc tures might be more predictable than was at present the case, since the elimination of joints made the piece more nearly resenjible a test specimen. M$. F. E. JARLETT (student, College of Aeronautics) suggested that^at Mach 2, the only possible structural material was likely to be an alloy steel; materials such as D.T.D. 166, 138 or 389 wetii likely to give a wing from 10 to 40 per cent lighter than coUla be obtained with other alloys—and possibly with more interior space. Mr. Keith-Lucas replied that the use of steel might confer only a surprisingly small increase in permissible speed. MR. R. E. MILLS (Bristols) referred to the need for detailed standardization, and also commented on the lack of "production designers"—a new type of person. The lecturer said that standardization was essentially the enemy of progress, but it had to be considered. He wished that every craftsman in an office could serve a proper apprenticeship in the shops; too often the apprentice went quickly into the drawing office. MR. L. W. ROSENTHAL (Saunders-Roe) mentioned the difficulties of drawing modern structures and the fact that assembly of equipment was likely to be more difficult where the structure could not be broken down into constituent parts. He also brought up the problem of costing with regard to available man-hours, to which the lecturer replied that it was difficult to get at the truth, as his company had found when comparing production of the Canberra and Sturgeon; although the former aircraft required far more machining, the man-hours expended were much fewer, owing to the bigger production and better tech niques. The secret was the rapid turnover in the machine shop. A. CDRE. G. S. ROBERTS (M.o.S.) favoured the placing of prototype orders followed by a small production batch defined by a stiff specification with a note to the effect that concessions would be allowed on early aircraft, provided that the last machine of the batch would be a representative production job. MR. H. H. WILSON (Armstrong-Whitworth) said that Mg-Zr alloys were gradually being introduced, but were handicapped by their need for new plant and processes, such as hot-forming. MR. A. VINES (Faireys) jolted the conference with some forthright words regarding capital investment on new equipment and processes in this country and the United States. THE CHAIRMAN at this session, Mr. G. R. Edwards (managing director, aircraft division, Vickers-Armstrongs) commented that the British industry was "doing quite a lot" about which more would be heard in the fullness of time. PRODUCTION PROBLEMS ARISING FROM THE TREND OF DESIGN By G. H. Dowty, F.R.Ae.S., F.I.A.S., M.I.Mech.E., chairman and managing director, Dowty Group I WING to the indisposition of the author, this paper—which dealt with its subject from the equipment manufacturer's viewpoint—was read at short notice by Sir Roy Fedden, of the College of Aeronautics board of governors. It divided airborne equipment into two main categories: items tailor-made for a particular aircraft, and standardized components. In the first category the paper dealt at length with undercarriage design, and several illustrations showed the effect of modern trends on the subjects of weight control and dimensional accuracy. Modern production legs were machined throughout to main tain accurate weight-control, while higher tensile materials, such as 100-ton steels, were being used successfully. Six illustrations depicted respectively: a prototype undercarriage (forged light alloy billet 608 lb, finished leg 74 lb); the production counterpart of this undercarriage (die-forging 75 lb, finished leg 61 lb); a prototype leg for a well-known fighter (steel billet 538 lb, finished os job 78 lb); a smaller fitting (die-forging 74 lb, finished 27 lb); the main cast member for the bogie undercarriage of a well- known bomber (Mg-Zr casting 489 lb, finished 439 lb); and finally the corresponding member for the nose undercarriage of the same aircraft (306 lb as cast, 281 lb finished). The inference regarding the amount of machining required by forgings as opposed to castings was obvious, although the finished job might be heavier when cast, owing to poorer material characteristics. The paper then turned to various aspects of the quantity pro duction of close-tolerance equipment. Typical of the problems was the fact that, on a current fighter undercarriage, the angle between the retraction shaft and the axle was held to a tolerance of plus or minus five minutes of arc, this tolerance being affected by four separate details. Weight reduction was another factor to be considered, and light-alloy parts were now being substituted for steel, frequently by giving them a coating of a very hard anodic film, which had better wear-resistance than hard chrome plating. A similar process was now being carried out on magnesium. The production of standard equipment, such as fuel pumps, burners, and hydraulic pumps, was then described, and particular reference was made to the methods by which tolerances of the order of 0.0002in were obtained. The Discussion which followed dealt with Mr. Dowty's paper and also with that presented by Mr. S. P. Woodley, which we summarized last week. There appeared to be no specific questions directly aimed at Mr. Dowty's paper, although Sir Roy Fedden replied, on his behalf, to general questions as indicated in our last issue. USER PROBLEMS AFFECTING THE INDUSTRY By Air Marshal Sir R. Owen Jones, K.B.E., C.B., A.F.C., Controller of Engineering and Equipment, Air Ministry A FTER drawing a lurid picture of the exasperating behaviour **• of the Royal Air Force as a customer, Air Marshal Sir R. Owen Jones described the manner in which servicing was carried out in the R.A.F., in which on-the-spot rectification was effected wherever possible, second-line servicing took place on the station, and third- and fourth-line servicing required facilities and test gear available only at Maintenance Command bases or the manufacturer's works. Turning to the subject of modifications, the lecturer said that the situation had changed considerably in recent years, and we were now faced with the production of extremely complex air craft "off the drawing board." Although the lecturer felt this to be a fine concept, and did not advocate a return to the old procedure of building an aircraft and improving it before buying it in quantity, ordering off the drawing board inevitably threw an enormous load on to the Services in respect of modifications. As well as the Boscombe Down trials, the R.A.F. now con ducted intensive flying trials on the first deliveries of a new type, in the course of which eight aircraft put in a thousand hours' flying in the shortest possible time. This had been most valu able, although the work was handicapped if early deliveries were not fully complete aircraft. An example was a single- seater, now coming into service, which could require as much as 800 man-hours of B.2 modification outstanding on each machine at delivery, with the certainty of a like amount to come in the future. Incorporating modifications on this scale was an immense burden and was detrimental to the nation from every point of view. The air marshal then indulged in some plain speaking on the subject of spares—"literally our life-blood"—which had haunted him ever since he became responsible for them. The mainten ance spares should come along with the first aircraft, and should then match the subsequent production. In no aircraft instance had these spares been "100 per cent on the nail." Nothing was more discouraging to the Service than to have fine new aircraft
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