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Aviation History
1948
1948 - 0653.PDF
and AIRCRAFT ENGINEER Editoriil Direct* G. G:OFFREY SMITH. M.8.E. tiitit - -CM. POULSEN Assistant Editor - MAURICE A. SMITH, D.F.C. (VV/NG CDfi., R.A.F.V.K.) Art Editor - - JOHN YOXALL FIRST AERONAUTICAL WEEKLY IN THE WORLD •• FOUNDED WO?.. Editorial, Advertising and Publishing Offices: Telegrams : Flightpres, Sediit, London. DORSET HOUSE, STAMFORD STREET, LONDON, S.E.I Telephone : Waterloo 33)3 (60 lines.) COVENTRY: 8-10, CORPORATION ST. Telegrams : Autocar, Coventry. Telephone : Coventry 5210. BIRMINGHAM, 2: KING EDWARD HOUSE, NEW STREET. Telegrams : Autopress, Birmingham. Telephone : Midland 7191 (7 lines). MANCHESTER, 3 : 260, DEANSGATE. Telegrams : Iliffe, Manchester. Telephone : Blackfriars 4412. GLASGOW, C.2: 26B, RENHELD ST. Telegrams : Iliffe, Glasgow. Tefephone: Central 4857 SUBSCRIPTION RATES : Home *nd Abroad : Year, £3 I 0. 6 months, C\ 10 6. No. 2055 Vol. Llll May 13th, 1948 Thursdays, One Shilling jhe Outlook Complexity Problems . ... nI F there are any who still do not believe that present- day aircraft and their systems are complicated, they can be quickly convinced by being shown under the floor, behind the instrument panel, in the accessory section, or into the inner-wing leading edge in an ' of today's modern transports." Few would dispute the truth of that statement, taker from one of the papers read before the National Aero- nautic and Air Transport Meeting of the American Society of" Automotive Engineers, held in New York la?r* rnontrr^, The author of the paper was Mr. L. R. Koepnick, tfijef engineer of Transcontinental and Western Air, Inc. la examining the causes of the complexity of modern air transports, Mr. Koemick comes to the conclusion that, although tompleMTy is bound to exist, several bodies are responsible for making it worse than it need be. As originators of the initial specifications, the air lines and other customers are to a great extent responsible. Manufacturers have not always installed the simplest and most direct systems to meet the requirements estab- lished by the specifications, and so they are also re- sponsible. Government regulations, in some instances, promote the complexity, and therefore the Government is also responsible. Mr. Koepnick added a fourth: the equipment manufacturer. Three interesting examples were given of how mech- anical complexity affects delay records in T.W.A. The simple DC-3, over a period of six months, averaged 122 flying hours per mechanical delay. The slightly more complicated four-engined Boeing 307 averaged 84 hours per mechanical delay, and the fairly complicated Con- stellation 60 hours. On a basis of number of miles "own per passenger per delay, the three corresponding figures were : DC-3, 20,700 ; Boeing 307, 17,200 ; Con- stellation, 16,800. Among the whole of T.W.A.'s fleet of no aircraft, 95 per cent of delays were caused by the systems and accessories and only 5 per cent by struc- tural items. The flight controls caused practically no mechanical delays, due chiefly to the fact that they are designed by the same structure-minded group as that which designs the actual structure, and so are given as much consideration as the basic structure. Mr. Koepnick makes the very true observation (true in this country no less than in the United States) that the systems other than flight controls still appear to be "orphans," and that the designers of these systems compete with each other to obtain space and passage through structural members for their systems. In many cases, he pointed out, it is found that systems which are incompatible have to pass through the same small opening in a structure member. .... and Their SolutionW HILE accepting the fact that a good deal of complexity is unavoidable in modern aircraft, due to the demand for so many systems to deal with the navigational needs and other services, Mr. Koepnick believes that much can be done to improve matters. He quotes, as an example of the sort of thing which the manufacturer can do for his part, the very extensive and complete mock-up built by Lockheeds for pre-flight testing of the hydraulic system. What, per- haps, caused so much trouble to be taken in this par- ticular case was that the flight controls were to be operated by the hydraulic system, and so Lockheeds planned the mock-up for checking what they termed the "what-ifs." What if a pipe line to a flap cylinder ruptures? That sort of question. The result of this extensive testing was that the Constellation system has caused far less trouble in service than was expected, and less than much simpler systems in other aircraft. Mr. Koepnick is not, however, content with taking trouble over the initial testing of complicated systems.
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