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Aviation History
1944
1944 - 0498.PDF
2 56 FLIGHT MARCH OTH, 1944 NEW ROLLS-ROYCE GRIFFON during qualities so important a problem with an engine of high power and light weight. The new Griffon is a masterpiece of compact design; indeed, it is extremely difficult to determine immediately whether the latest Spitfire, has a Griffon or a Merlin engine, for the reason that it has been found possible, notwithstanding the increased cylinder dimensions and power, to apply the engine without structural altera tions to the airframe. One of the illustrations shows Indicator Discusses Topics of the Day that the design ot the supercharger and the system of carburation has been considerably amended and made still more compact. The engine, too, reveals that two-stage supercharging is not employed on this particular example, as there are no signs of an intercooler. In these days when high-powered units are so badly needed the advent of the Rolls-Royce Griffon marks a notable advance in aero engine design. G. S. Sorting Out the Snags Dealing with the Inevitable Unreliability of the Modern Aircraft : Science versus Ingenuity : When the Experts are Floored : Mechanical SnagAxunters A TO the average person's mind, an aircraft is like a car or a locomotive—just something that goes on and on until, perhaps, it requires an overhaul after a definite number of hours in the air. Up to a point, that is quite true of many of the individual items, but it is most certainly not true of the machine taken as a whole. Some better-known engines, for instance, can be left alone for very considerable periods, and a modern airframe—to use a Service word—may be left about in the open more or less/ indefinitely. Maintenance people must sometimes wish that an aircraft consisted only of an engine and an airfraffle. In fact, the present-day flying machine is, in detail/fust about the most unreliable thing that has ever been/made unless it is maintained with day-to-day precision. fltiw-ill nearly always fly, but its mere ability to fly doesn'^ cbout for very much nowadays, and operators, whether Seivica or civil, have had to set up a most complicated organisa tion of technical and semi-technical people in order to make sure that their aircraft not only fly but continue to do %p with the utmost reliability in all conditions. Very few\ individuals outside the flying world realise just how great a proportion of man-hours are required for every aircraft if it is to be kept in the air day after day. For the most part, the snags that have to be cleared up all the time are not vitally serious ones. It may be found, lor instance, that the starboard hydraulic pump has sheared during,the previous day's flying, or that certain haywire characteristics have been reported in the operation of the directional gyro. There is, admittedly, another hydraulic pump, and a perfect gyro may not be vitally necessary for flying on the day in question, but a line must be drawn somewhere, and it would be quite hopeless if items of even much less importance were allowed to remain unserviceable. 90 per Cent. Maintenance So the operator must have a servicing organisation which is absolutely water-tight and must carry a stock of spares, both of complete aircraft and bits, which will remove entirely the possibility that a service will fail to run, or a job fail to be carried out. Maintenance has really become more than ninety per cent, of the business of flying. For every single person there may be in the aircraft itself, there are hundreds on the ground. When and if the airline system of the world becomes as far-reaching and complete as the optimists would have us believe it will, the air field and aircraft servicing organisation will be the most immense and expensive thing that has ever been known in the history of the world's technical development. Air craft bits are necessarily expensive and the sort of tech nical personnel who know how to dj^.1 with these bits need to be both well-trained and well-pjIFd; or they should be. What is. wanted most of all nowadays is a series of short cuts to operating efficiency. Ijptead of letting a bunch of experts scratch their heads fc#hours and have everything in the world pulled to piejps at great expense when a mysterious snag has develq^d, we should have a series of test rigs which wilK oncejand for all, discover the cause of the tro«tl*j^nd\^o sjpe an immense amount of time and trVublPV^^i Hgs*re now available for dealing with certain\yd\|irfual )MSW, but they are usually of the labora tory stanHijrd and arjrmtended to be used on the suspected item tf/^NLthis has been removed from the machine. We vHwch cajf be hauled up to the aircraft while it is %C/he tarmac and while the crew are still discussing the ^lilrijent and its pjlmts of diagnosis. Using Test Rigs Hydraulics, electrics and instruments we. shall always have with us, and most of the minor ailments in aircraft \fome uncjer these headings. Test pilots have evolved, by expvrierrce, various means of boiling down the basic sources of troubles from these causes, but we are dealing with the ordinary rim of pilots and crews whose stories may be just a little vague and-^vho have not developed the habit of going into the problem while they are still in the air. And, in any case, some troubles cannot be diagnosed with imme diate accuracy by even the most experienced test pilots or snag-hunters. One can cite dozens of examples, starting with the simplest of all—the suspect air-speed indicator. The instru ment can be taken out and calibrated, the pressure head can be taken off and checked, the lines can be blown through—but no one is quite certain, unless a definite error has been found in the instrument itself, whether the trouble has been cured until a test flight has been made. The ordinary pilot might notice that the gyro horizon is a bit slow in building itself up and is not too accurate in the air; he would snag the instrument, .^i^pilot who has made a study of such things might also notice at the same time that the directional gyro "topples" a little too easily and that the rate of turn shown on the turn indicator is rather less than usual. For him the cause-of the horizon's peculiarity would immediately be rediagnosed 1 as a partial failure in the vacuum system as a whole, while the less interested pilot would concentrate his disfavour on the one instrument which appeared to be giving most trouble. The indicated maximum controlled revolutions of the V
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