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Aviation History
1934
1934 - 1148.PDF
1150 FLIGHT. NOVEMBER I, 1934. A SECTION FOR OWNER-PILOTS AND CLUB MEHBERS TIE successful completion of a long flight in condi-tions such as those under which the MacRobertsonair race was flown depends primarily on the reli- ability of the power unit. The strain imposed on the engine is relatively greater in such circumstances than that to which the aircraft structure itself is put. Aeroplane designers to-day are able to produce aircraft knowing full well that they will function satisfactorily under gruelling conditions. Those responsible for the de- sign of the '' Comets '' have proved how exact is this science so far as the construction of machines of the fixed wing variety are concerned. The modern aeroplane will not fail its pilot in fundamental flying qualities, although components of recent introduc- tion, such as retractile undercarriages, of which designers have yet to gain ex- perience, may let him down. In an event of this kind, although the modern power unit is no whit less reli- able than the aircraft itself, the pilot needs to give very close attention to the capacity of the engine; many a race has been lost by lack of restraint in the handling of the power unit. An early advantage gained by running an engine all out may be dearly bought at a later stage. The successful participa- tor in a long distance race is he who knows just what his engine is capable of, and who does not ask too much. The present-day power unit, in careful and experienced hands, will give a high performance over lengthy periods, provided that it has been properly prepared. If one de- mands continuous and efficient running, then every care must be taken to see that all its component parts are in first-rate condition. A faulty magneto or an ill-adjusted carburetter may mean just the difference between success and failure. Preparing for a Long Flight WHILST this close attention to detail is particularlynecessary in preparing for a big race, it is no less de- sirable as a preliminary to a long flight undertaken in more leisurely conditions. The private owner who decides to use his aeroplane for a journey to one of the Dominions will not want to emulate the record breakers. He will do very well indeed if he keeps up a steady seven hours' flying day by day. This, with a rest of one day each week, would • enable him to reach, say, Melbourne in eighteen or nine- teen days Such a flight would involve, on the average light air- craft of modern design, about 120 hours' flying, and a pro- perly overhauled machine should be capable of completing such a journey, with minor adjustments en route, so long as the engine is run well within its capacity. Before starting out on my flight to Australia my machine had done about 100 hours since last going into the shops. I therefore decided that my "Gipsy III," an engine which has so faithfully served its pilot on many a record flight, should be given a straightforward top overhaul. Cylinder heads and pistons were removed and decarbon- ised. All rocker brackets were taken down, immersed in NOTES by LORD SEMPILL A.F.C., F.R.Ae.S. nitric acid, and scrutinised for cracks. Valve seats were recut to 30 deg., and valves reground. All inlet valves were found to be in good order, but three exhaust valves, being somewhat burned after 800 hours' running, were scrapped. It may be interesting to describe the effect of the use of upper cylinder lubricant which I have used recently. This overhaul gave an opportunity to judge its value, and there would appear to be no doubt that, used in the correct proportion to fuel, it has very beneficial results, some of which are indicated below. In examining the various parts of the . engine from this point of view, it was found that the upper portion of the cylin- der, which is just swept by the piston, was in a far better condition than is usu- ally the case. Instead of the cylinder at the end of the travel being rather dry and somewhat ingrained with carbon, it was free from carbon and well lubricated. In this case the pistons showed a some- what heavier carbon deposit than usual, but this might have been due to using on certain occasions an excessive quan- tity of the upper cylinder lubricant, and to the fact that, prior to coming into the shops, the machine had been used for a series of short journeys. The carbon thus formed was of a kind that would no doubt have been burnt off on a long run where the engine had time to get thoroughly warmed up. The neck of the valves, or that part above the guides, was also found to have more than the usual amount of carbon deposit, but with the engine running hot this would probably be burnt off in the same manner. In other respects the pistons were found to be in better condition than is normally expected. The upper land, or the part of the piston above the rings, instead of being, as usual, rather dry and ingrained with carbon, was well lubricated and showed no signs of ingrained carbon deposit on the work- ing surfaces. The valves and the valve guides, both exhaust and inlet, were in much better condition than normal, both indicating that they had been well lubricated. As a rule, valve stems and guides are dry, and signs of " picking up " are quite evident. It was obvious that the use of upper cylinder lubricant saved considerable expense on replace- ments which, in the ordinary way, is often a heavy item. Upper Cylinder Lubrication -•- THE full advantage of using this lubricant is, of course,only obtained on unworn engines in good condition. Used on new or overhauled engines, there is no doubt that it obviates a great deal of the wear which results in run- ning the engine from cold before the oil supply is warmed up and circulating properly. I have found also that the slow running of the motor was considerably improved. In practice I have the upper cylinder lubricant put into my starboard wing tank only. I warm up the engine from this tank, afterwards running on both, and, what I consider equally important, switch on to this tank again at the end of a flight, running the engine slowly for a minute or two before switching off. (Continued on p. 1151.)
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