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Aviation History
1934
1934 - 1359.PDF
DECEMBER 20, 1934. FLIGHT. 1363 equip every aerodrome and field with the right type of transmitter, details of which have not yet been worked out. "It is," he said to me privately after the "Pip- kin" had been grounded, "positively pitiful that two great and intelligent Governments, yours and ours, should be so blind to the possibilities of the Stunk Automatic Wireless Pilot Finder." However, to return to the actual test. During the take- off there are very distinct signs of directional instability with a strong tendency to swing to starboard. After several attempts and some conversation with Mr. Piphurst I eventually discovered that the best method was to face down wind before opening up. This swinging character- istic is doubtless explained by the fact that, owing to difficulties with the engine manufacturers, the port and starboard units are of slightly different powers. That on the port side is a 720 h.p. Junkers " Jumo 5," and that on the starboard side is a 65 h.p. Pobjoy "Cascade." Once safely in the air, I thought of Mr. Piphurst's shouted claim that with larger rudder area and re-rigged wings it would be possible to take off across wind down long, narrow fields—a point which, he claims, is of particular value to the private owner. Actual flying, with the "Jumo 5" throttled, is ex- tremely easy, though the split ailerons appear to give hardly enough control, and show, at the same time, a marked drag at all speeds. The climb from ground level to 1,000 ft. was stop-watched at 9 min. 15.32 sec. Turns to the right are easily carried out, but to the left are im- possible ; Mr. Piphurst is approaching the Parliamentary Air Sub-Committee with the idea of standardising the direction of all landing and other circuits. Spins to the right are perfectly normal up to fourteen turns—the proximity of the ground interfered with further experiment—but those to the left are too slow to be of any value in providing a method of steep descent. It was with considerable interest that I moved the flap control after bringing the gliding speed down to 102 m.p.h. Immediately the left could be felt to be leaving as the flow was broken, yet the ingrowing tips allowed the machine to retain its lateral stability as well as some small measure of aileron drag for turning purposes (the flow over the rudder and elevators, of course, had been stemmed). Mr. Piphurst has fitted a pitot tube in a vertical position, and a second A.S.I, on the dashboard gives the sinking rate. This should be checked as soon as possible. However, I intended that the smart undercarriage should be given a thorough test with the rest of this interesting machine, and deliberately allowed this vertical velocity to exceed the recommended 93 m.p.h. After supervising the shovelling-up of the machine into a hand-cart, Mr. Piphurst told me that he proposes to start work on a second "Pipkin" just as soon as he receives the support of his shareholders at the next meet- ing of the Piphurst Airplane Retrogression Corp., Inc. H. A. T. AN ACOUSTIC ALTIMETER Interesting French Echo-sounding DeviceT HE principle of echo sounding is, of course, not new, and attempts have previously been made to adapt the system, which has proved successful for shipping, to the rather more difficult problems of air navigation. Hitherto these efforts have not met with out- standing success, but an in- strument designed by French inventors appears to bring the problem one step nearer solution. At any rate, the new instrument has, after exhaustive tests, been approved by the French Air Ministry. The Dubois-Laboureur aerial sounding device depends, like other echo-timing instruments, upon the principle of emitting a sound and timing the interval between the emis- sion of the sound and the reception of the echo at the point of emission. In this particular instrument the source of the sound emitted is a special siren driven by a small electric motor. The note emitted has a musical frequency of 1,600 cycles, and is of very short duration (thirteeen- thousandths of a second). The receiver consists of an electromagnetic microphone very slightly out of phase with the sound signals, and of a sensitive amplifier so designed The principle of echo sounding as to exclude the engine and other noises but to amplify the sound of the echo. Timing is done by a chrono- scope which measures with a. precision of six ten- thousandths of a second the time elapsed between the emission of the sound signal and the reception of the echo. On the instrument board is mounted a special altimeter having two scales, one indica- ting heights from 5 to 40 metres (16 to 130ft.), and the other for greater altitudes, from 30 to 250 metres (100 to 820ft.). The emitter and receiver, each of which is provided with a horn, are mounted in the fuselage of the aircraft, near the tail The small diagram shows the basic principle oE the system. There is little doubt that the Dubois-Laboureur echo sounder works satisfactorily over reasonably flat country, but it would appear doubtful whether reliable readings can be obtained in mountainous country where the slopes are steep. The manufacturers, Constructions Electio- Mechaniques d'Asniers, of 236, Avenue d'Argenteuil, Asniers (Seine), France, are ready to give demonstrations. A Northern Passage THE Air Ministry's advice (Notice to Airmen No. 114, 1934)to aircraft flying between Scotland and Northern Irelandwithout radio equipment recalls that the Automobile Associa- tion pioneered this route in 1930 for aircraft visiting the UlsterT.T. Race at Belfast , . Describing at that time the special signalling service whichthe A A. organised, Flight stated that aircraft should make a low circuit over the Coastguard Station at Portpatrick inScotland and another circuit over the Coastguard Station at Black Head (Co. Antrim). Portpatrick would then notifyAldergrove R.A.F. Aerodrome (tor Belfast) by wireless of an aeroplane's departure, while the Coastguard at Black Headwould telephone to Aldergrove news of its safe crossing. This arrangement involved the provision by the Air Ministryof a special radio installation at Aldergrove, but the experimental signalling service worked most satisfactorily,thanks to close co-operation between the Air Ministry, G.P.O., Board of Trade and the Automobile Association. The only difference between this and the present schemelies in the use of Orloo. Head Coastguard Station on the Co. Down coast, while there is now direct telephonic communi-cation between the two Coastguard stations.
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