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Aviation History
1912
1912 - 0424.PDF
AERONAUTICAL SOCIETY OF GREAT BRITAIN. OFFICIAL NOTICES AS SUPPLIED BY THE SECRETARY. Muting **** Thursday at the Royal United Service Institution, Whitehall, 8.30 p.m. Lecturer, /. H. Brannvell. Chairman, F. Grant (Jin'tTie, C.B., LL.D. (Director oj the Science Museum). Special General Meeting.—A special general meeting of the Society will be held on May 16th, at 8 p.m., at the Royal United Service Institution, Whitehall, for the purpose of amending Rule 27 in respect to Associate Members, in such form as shall make the subscription to that grade one guinea per annum and the entrance fee nil. Programme of Meetings.—To be held at the Royal United Service Institution. .May j6th, Thursday, S.30 p.m. Chairman, F. Grant Ogilvie, C.B., LL.D. F. H. Bramwell on "National Physical Laboratory Research." June 12th, Wednesday, 8.30 p.m. G. Holt Thomas on Hydro aeroplanes." _ „, _ . , Programme for Session 1912-13.—The meetings of 1912-13 Session will be held on second and fourth Wednesdays at the Royal United Service Institution, at 8.30 p.m., beginning October 9th. Additional to the papers already announced are : Lieut. R. Gregory on "Aerial Navigation"; E. H. Harper on "The Theory of Aeroplane Stability." Election of Members.—The following have been elected mem- ben of the Society :—G. P. Ottino and Lieut. C. Randall, R.N. T. O'B. HUBBARD, Secretary. ® 9 METEOROLOGY IN his lecture at the Aeronautical Society on Monday, April 29th, Capt. Ley said that the results of his observations on pilot balloons at Blackpool and Scllack last year showed that, even knowing the surface velocity of the wind and the gradient velocity of the wind, it was difficult to calculate the velocity at any given height without reference to topography owing to the impossibility of saying at what height the gradient-velocity would begin or the steep surface- gradient end. It was equally difficult without actual preliminary observation to say whether the wind would rotate in a clockwise or counter clock wise direction with increase in altitude. Both factors de|>end largely upon the topography of the locality, and so, also, it appears, does the oscillation of the horizontal velocity of the wind. On the open Blackpool coast it was 'safe to say that nearly the full gradient velocity would probably occur at a height of under 300 ft., whereas at Sellack in Herefordshire it would not probably occur in the lowest 2,500 ft. As regards the vertical motion of a wind, Capt. Ley applied the accepted theories of convergence of stream lines and collision of currents to the effect of the actual obstacles presented by the hills. It was seen that the Snowdon and Scafell hill areas were roughly 3,000 ft. in altitude and formed the extreme and controlling points of a large horseshoe-shaped range covered roughly by a 2,000 ft. contour. Thus in moving across this area we should expect a wind to show changes of horizontal velocity at these heights. Moreover, apart from temperature effects, the effect of obstructions would be both longitudinal and some lateral compression due to deflection, with rtomaqmnt vertical motion. The effect was well illustrated by balloons sent up in steady N.E. winds which had blown over the 2,000 ft. range and were moving towards the Snowdon area. These showed violent oscillations of horizontal velocity at about 2,000 and 3,000 ft. altitude, and strong ascending components of velocity with cloud just above 3,000 ft. Balloons from a westerly direction showed changes at 2,000 ft., with frequent vertical motion commencing or culminating at this altitude. Summing the results of 1910 and 1911, at Blackpool, it certainly appeared that the levels 1,500-2,000 ft., 3,300-3,500 ft. and 4,800- 5,200 ft., were critical levels in the N.W. of England, at which sudden changes in the three directions in space might be expected. Then, as regards the Wye Valley area, just north of Ross, 800- 1,000 ft., 2,000-2,500 ft., 3,300-3,500 ft., and 4,500-5,000 ft. appeared from balloons as critical levels. The lower level was seen 9 ® FOR PILOTS. to be roughly that of the ring of low hills, a few miles to the west, the 2,500 ft. level, that Jof the Black Mountains, and Breconshire range further still to W., the 3,500 ft. level, that of Snowdon range. Nothing appeared, however, to correspond with the 5,000 ft. level. The effect of frontal obstruction and squeezing into a narrower channel of the surface wind was clearly shown in balloons moving towards the eastern watershed by the throwing up of the wind on a line along the E. bank of the Wye on the ascending slopes and some 2 or 3 miles before the watershed was reached. This line represented at once the meeting of the downward and upward grazing lines of a westerly wind, the locality of compression due to deflection caused by the projections of the How Caple and Ross hills, and the place where the heated air of the valley is piled up. The result on a hot day, with strong wind, such as July 18th or 21st, 1911, was a startling upthrow of air, preceded by violent horizontal gusts and reaching, apparently, up to 3,500 ft. elevation. These hot days with fairly strong winds must be regarded as dangerous. Some of the lighter winds moving towards steep slopes were deflected almost at right angles and such deflection was pre ceded by vertical rise. An analysis of balloons at Limerick, in Ireland and Giossop, in Derbyshire, showed similar results; and it appeared that the 3,000 and 5,000 ft, were rough critical levels over the whole of the W. of England and Ireland, lower levels occuring according to the height of hill ranges in the vicinity of any given locality. The changes at such levels were principally evidenced by sudden change of vertical motion and oscillation of horizontal wind velocity. Ascending motions were reliably measured, as large as 350 ft. per minute, and the descending motions were not infrequently of 200 ft. per minute, though the larger ones did not appear to be more than 200 or 300 ft. thick. The frequency of cloud at 3,000 and 5,000 feet was remarkable. At Blackpool, if low cloud appeared it was fairly safe to estimate its height at one or other of these figures. As it was sometimes easy to measure the velocity of the shadow of a cloud, a careful study of a low cloud would be most valuable to an aviator. He would be able to judge of the height of a critical level and of the velocity of the current just above it. Of course, as in all other meteorological generalities there were many apparent exceptions, and very many cases in which changes at any altitude were too slight to be observable, nevertheless the tendencies certainly were permanent for any given wind direction in any given locality considered apart from general meteorological conditions. ® ® ® ® THE GOUGH-TURNER CLINOMETER. IN the accompanying illustration is seen a device—known as a clinometer—for indicating the inclination to the horizontal of an aeroplane or airship. It is manufactured by H. G. Turner, of Eldim G rove, Manchester, and consists of a curved glass tube containing a non-freezing liquid and an indicator ball. The position of the latter indicates on a graduated scale the exact angle the machine may make at any time. The principal feature of this device lies in the fact that it indicates angles correctly when subjected to vibration. It has licen tested on aeroplanes by Messrs. C. Grahame-White and Co., Ltd., and on airships by E. T. Willows and on H.M. airship "Gamma." It can also be adapted for use on motor cars and suhm.irines, and we understand that a modification of the clinometer is being made, called the banklinometer, for determining the correct angle d banking when making a turn on an aeroplane. The " Gough-Turner Clinometer "—a device for indicating the inclination made by an aeroplane or airship. 424
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