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Aviation History
1928
1928 - 0684.PDF
FLIGHT JULY 26, 1928 [" FLIGHT " Skttdus VARIOUS WAYS OF USING RUBBER SHOCK ABSORBERS : 1, on the little Klemm-Daimler. 2, the com- pression rubbers on the Albatros " ASS." 3, the enclosed rubbers in the undercarriage leg of the Bernard single-seater fighter. 4, one-half of the Fiat biplane chassis. BRITISH AERO INSTRUMENTS AT THEPARIS SHOW AMONGST aircraft accessories none are so important as theinstruments employed in navigating or controlling the aircraft, although we believe there are many who do not entirelyappreciate how absolutely essential they are, especially as regards navigating instruments. For ourselves, we areafraid we have not devoted as much space in FLIGHT todescriptions and the use of aero instruments as we have wished to do, but in the near future we hope to have a greatdeal more to say on this subject—which is really quite an interesting one. At the Paris Show, British instruments—which undoubtedlylead the world—were well represented on the Kirby-Smith stand. Here, in addition to the almost universally used" K.L.G." sparking plugs—another important aircraft accessory "—could be seen a dashboard on which weremounted a number of S. Smith and Sons (M.A.) aero instru- ments, while a full range of navigating, etc., instruments bythe well-known firm of Henry Hughes and Son, Ltd., were also exhibited. " Smith's " altimeters, air and engine speed indicators, andother instruments should be familiar to readers of FLIGHTfrom our descriptions of these that have appeared from time to time, but hitherto we have not had the opportunity ofdescribing any of the many interesting instruments produced by He ry Hughes and Son—for whom, incidentally. S. Smithand Sons are the selling agents. In the following notes, therefore, we propose to deal, briefly, with the instrumentsproduced by Henry Hughes and Son. First, let us refer to that instrument essential to everyaircraft—the compass, of which we find a variety of models to suit different requirements. They are of the aperiodic,or " dead-beat " type, evolved by the late Comm. Campbell, R.N., and Dr. F. S. Bennett, F.R.S.—a type that has super-seded all others for use on aircraft. The original " Husun " Aperiodic compass, with certainmodifications, is the 6/18 Mk. II and Mk. Ill, in which the " card " or magnetic element consists of eight filament wiresradiating from a centre carrying the iridium point, with six small magnets fixed underneath. Four of the filaments are lettered N.E.S.W., but only the N-S are directional, the others being for damping purposes only. It is provided with a grid ring, divided every 2°. Illumination is carried out by a small electric lamp on the side of the instrument. A further improvement on the 6/18 type is the P.2, which was used by Sir Alan Cobham on his big flights to the East, Africa, and Australia. It has an improved " card " and has been made more efficient by having the damping increased, the N-S filaments emphasised, and by the provision of four larger magnets instead of six smaller ones. A similar and smaller model to this, for light 'planes, is the Mk. IH A, which was used by Bert Hinkler on his Australian flight, while another, compact, model of the same type is the P.4, which has, amongst other improvements, the inside of the bowl painted black against which the N-S shows up white ; it is also fitted with a luminous " card " for night flying. Two other important models are the O.2, or Observer's instrument, and the O.3, which is supplied to the Air Ministry (see Fig. 1 in our illustration). The O.2 is fitted with an azimuth ring carrying reflector, shades and prism, and its " card " is a special adaptation of the filament aperiodic type carrying a 2-in. mica card marked with the cardinal points, divided every 2°. The O.3 is an improved model, with luminous reading for night flying. It also has auxiliary filaments which read on a centesimal scale mounted inside the bowl. This model is much more useful as a directional instrument, and can be read either direct on the centesimal scale or through the prism. Next we have the type 253 A.C., a pilot's or navigating compass, designed on the centesimal principle as in the O.3. This model is perhaps the simplest of all compasses to read. A second pattern of this model (see Fig. 4) is fitted with a domed or convex verge glass, which not only magnifies the " card " and scale, but brings up both so that the compass may be read when mounted level with the pilot's eye. The 253' D.B.—as used by Amundsen on his Polar Flight—is similar to the latter model, but having an additional thin mica ring card divided every degree, for direct reading on a lubber point. 628
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