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Aviation History
1925
1925 - 0126.PDF
MARCH 5, 1925 THE DE HAVILLAND "MOTH 60 H.P. "Cirrus" Engine FROM whichever point of view one regards it, the de Havilland" Moth " must be considered a very fine little aeroplane. It may be argued that it is not a light plane, in the sense ofthe term that has come to be commonly accepted, but it is a low-power aeroplane with a good performance, and it ishoped to be. although naturally this still has to be proved, one THE D.H. "MOTH " : View showing undercarriage and mounting of the "Cirrus " engine. In the next machine the exhaust pipe will be on the port side. of the most reliable little machines of modern times. Infact, the first aim of the designers of machine as well as engine has been this particular feature. The engine, theAircraft Disposal Company's " Cirrus," described and illus- trated in FLIGHT last week, is of fairly large capacity (4,500 c.c],and is capable of flying the machine quite strongly without being run at its maximum permissible " revs." This,naturally, means that there is a good power reserve to enable the machine to take off from a reasonably small field, so thatthe " Moth." as the new machine is called, will, both on this account and also because of the fairly high top speed whichenables headway to be made against a head wind, be well suited to cross-country flying or touring. In fact, the" Moth " is distinctly more than an " aerodrome machine " (i.e.. an aeroplane mainly used for short flights in the vicinityof an aerodrome), and should, provided the reliability proves as good as expected, be extremely useful for a variety ofpurposes. The designers naturally hope that it will be adopted for use by the light 'plane clubs, as it is particularlysuitable for school work and " joy-riding," but one"can foresee a number of other uses to which the '" Moth " can be putAs a fairly low-priced machine for the owner-pilot the type should have much to recommend it, especially as its construc-tion is of the simplest and most straightforward, while the " Cirrus " engine is so much of the motor-car type that anyonewith motor-car experience should easily be able to look after it. Moreover, the engine has been designed to give very longservice without overhaul, so that the maintenance should be well within the capabilities of the average motorist. Thenthere is the question of the employment of low-power aero- planes in the Dominions. Here, also, the " Moth " should beextremely useful, as its performance enables it to fight adverse weather conditions, while its landing speed is low enough to enable the machine to be put down in a small field. Altogether,therefore, if orders are forthcoming in sufficient numbers to allow of placing it on a production basis, one can foreseea very bright future for the de Havilland " Moth." There is still the question of the Air Ministry airworthiness certificate,but we understand that the second machine, now nearing completion, is being built under A.I.D.isupervision, and that,therefore, the type may confidently be expected to be " approved." On Mondaypf this week the De Havilland Aircraft Co., Ltd.,had invited a number of press representatives to visit the Stag Lane works in order to inspect the " Moth " and towatch it flying. The aerodrome was in a deplorable condition after the incessant rains, and the " Moth " sank in up to itsaxle in the mud, but for all that it got off with a relatively short run, and, once in the air. the climb was extremely goodA large number of passengers were carried, and incidentally the visitors were, probably quite unconsciously, paying atribute to the " Cirrus " engine by waiting their turn for a " flip," the thought never occurring to them that the enginemight refuse work We were among the passengers carried during the day, andperhaps a few impressions may be of interest. The machine got away very well, and once off, Mr. Hroad, the well-knownde Havilland test pilot, climbed her at 1,800 r.p.m. and an air speed of 50-55 m.p.h., at which speed she rapidly gainedheight. The dav was somewhat bumpy, but the " Moth appeared tn rise and fall on an even keel, and no tendencyto pitching was "bserved. In a series of steep curves it wa-- "bserved that the amount of ailen>n movement was verysmall, an indication that, although only the lower plane i> fitted with ailerons, lateral control is ample. In normalstraightforward flying the ailerons were used surprisingly little, the large dihedral evidently being sufficient to givegood stability, yet not so large as to make the machine " wallow." As there was no control stick fitted in the forwardcockpit we were not able to ascertain how much elevator control is required, but observation from the ground didnot reveal any large movement in ordinary manffiuvrcs. The rudder bar in the forward cockpit moved \ ery little indeed. THE D.H. " MOTH " : This photograph shows thearrangement of the cockpits. Note also the gravity petrol tank on the top centre-section. 126
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