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Aviation History
1914
1914 - 0083.PDF
JANUARY 24, 1914 controls will work (i.e., that the critical angle has not been exceeded). It must be remembered that as the speed is greater than that registered by the velometer, so the centrifugal force is greater, and the total force on the wings is correspondingly increased. A lift accelerometer would be the best indicator to give warning of the over loading of the wings which accompanies too sharp a turn. This instrument has only up to now been used in an aeroplane for research, and has not so far been used as a permanent fitting, and in default of this the velometer and angle of bank must be watched. With regard to Mr. Booth's reference to gusts, it is a matter of experience that most gusts are so local that the greater part of the acceleration is over before any correcting can be done. In turbulent air it is usually sufficient to see that the mean reading of the velometer is above the safe minimum. I fear that Mr. Booth's "second test" will be found a failure. No flyer could fail to notice the fierce fluctuations which are produced in an undamped velo meter in a gusty wind. Mr. Booth would of course be right if every gust attacked every part of the aeroplane with equal intensity at the same instant and exactly in the direction of its travel. The turbulent motion of the wind is, however, very different from this. Gusts in every direction attack sometimes one part of the aero plane, sometimes another. At one moment a local head gust affecting only the pressure tube and the part of the wing near it will send the liquid up in the gauge and merely lift one wing a little. At the next, perhaps, an up gust will envelop the whole aeroplane, raising it with a sudden jerk, and leaving the liquid to fall far down in the tube owing to the temporary increase of apparent gravity. The fluctuations of an undamped instrument are, in fact, so great that considerable damping is usually necessary for ease of reading. When the aeroplane enters an extensive and strong up current, it may be necessary to use the elevator to » ® Mr. Frank McCIean's Progress along the Nile. ON the 16th inst. Mr. McClean arrived on his Short water- plane at Luxor, and later went on to Assuan, while two days later he made some nights to the delight of the great crowd which had gathered to see the machine. On Monday he started to continue his flight south to Khartoum, but after flying about 130 miles had to return to Assuan, owing to trouble with the motor. He has had very bad luck with his motor, and had to spend several days at Assiut on account of a broken ball race which distributed itself in the crank- case. IftlOHTl keep a safe reading, but the effects of most up gusts are so temporary that even if they cause the critical angle to be reached, no harm is done, so far as experience extends, i.e. with winds in which the maximum readings have reached 55 m.p.h., at the R.A.F. Observatory, at Pyestock. In the editorial remarks on Mr. Booth's article, it is to be observed that an ordinary U tube is referred to. Acceleration or tilting of this in its own plane will of course introduce a grave zero error. This difficulty has been overcome by Mr. F. Short's velometer, now used as a standard in the Army (and made by Messrs. Elliott Bros., Central Buildings, Westminster, and Messrs. Casella and Co., of 11, Rochester Row, Victoria Street. The method adopted is to split one limb of the U into two, putting half of it on each side of the other limb, thus: w. The two outer limbs are connected together at the top and both connected to the Pitot tube. Before leaving the subject, I should like to point out one more consideration which may have escaped the notice of scientists less experienced than Mr. Booth. In the matter of high flying it is necessary to go faster as the air gets thinner. This is allowed for on all air speed indicators as well as in the velometer, by the fact that the density of the air is one of the factors deter mining the reading. It will therefore be safe if pilots keep the instrumental reading above the known minimum safe reading. They will be travelling faster than when near the ground, but the angle of incidence will be the same. In conclusion, the above considerations will, it is hoped, show that there is no occasion for that vague dis trust of the velometer which Mr. Booth attributes to pilots. As long as the instrument and its connections are kept free from leaks and obstructions, so long may it be relied upon. And it is found that a short experience of its use convinces pilots of its value. E. T. BUSK, A.F.Ae.S. ® © Bonnier at Alexandria. ON his Nieuport monoplane, and accompanied by his pas senger, Bonnier, on the 14th inst., new from Cairo to Alexandria in 2 hours 20 mins. Marc Pourpe in Egypt. WITH the intention of making a sight-seeing tour through Egypt, Pourpe left Khartoum on his Morane-Saulnier monoplane on Monday. He arrived at Atbara 4 hrs. 10 mins. later and stayed there for the day. The next day he went on to Abu I lamed, a trip of 2 hrs. 20 mins. MR. FRANK McCLEAN IN EGYPT.—Banking on a sharp "taxi-turn" on the Nile on his 160 b.p. Gnome»engined Short waterplane. 83
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