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Aviation History
1913
1913 - 0947.PDF
Flight, September 6, 1913. First Aero Weekly in the World. Founder and Editor: STANLEY SPOONER. A Journal devoted to the Interests, Practice, and Progress of Aerial Locomotion and Transport. OFFICIAL ORGAN OF THE ROYAL AERO CLUB OF THE UNITED KINGDOM. No. 245. (No. 36, Vol. V.)] SEPTEMBER 6, 1913. ("Registered at the G.P.O."| TWeekly, Price 3d. L as a Newspaper. J L Post Pree, 84d. Flicfet. Editorial Office: 44, ST. MARTIN'S LANE, LONDON, W.C. Telegrams: Truditur, Westrand, London. Telephone: Gerrard 1828. Annual Subscription Rates, Post Free. United Kingdom 15s. od. Abroad CONTENTS. 20s. od. Editorial Comment: Propeller Vibration in Flight The Corkscrew Twist... Model "C. H." Wright Hydro-Biplane (with scale drawing-) Royal Aero Club Notices Flying at Hendon Round Britain Waterplane Race Armchair Reflections. By The Dreamer From the British Flying Grounds British Notes of the Week Foreign Aviation News Deauville Waterplane Meeting The Theory of the Dunne Aeroplane Models. Edited by V. E. Johnson, M.A Correspondence l'AGE • 973 • 97+ • 979 yoj 98s 987 9-9 991 992 994 995 997 Propeller Vibration in Flight. ©RIAL COMMEHT. We draw our readers' special attention to a letter from Mr. J. W. Cloud, who is the Chief Engineer in England to the Westing- house Brake Co. Mr. Cloud has long been one of those who regards the gyroscopic couple of the rotating propeller and rotating engine as a serious factor in the control of aeroplanes. He bases his belief on the assumption that the slight angular disturbances to which the longitudinal axis of the aero plane is likely to be subjected on a gusty day, are far more rapid than those corresponding to quick turns in the air for which times have been taken and on which the gyroscopic couple has hitherto been calculated. It will be remembered that this matter of the gyroscopic couple has frequently been raised in these columns by various readers. It was raised also before the Depart mental Committee appointed to investigate the accidents to the Army monoplanes. In the report of that Com mittee will be found a reference to the matter in which it is shown that, on the basis of a quick turn in the air, the effect of the gyroscopic couple, regarded as an increase in load on the tail, is not of a magnitude greater than, or even as great as, would be likely to be caused by the direct action of a gust. Moreover, being definite in direction and amount, and coming at an appointed time, the pilot is in a far better position to counteract its effect. For a 100 h.p. Gnome engine and propeller the gyroscopic couple is in the order of 330 lb. ft. The value is approximately the same whether the conditions be those of a quick turn or the beginning of a quick dive. This value seems to be a very considerable quantity, but if its disturbing influence on the control were anything like as great as its numerical significance would suggest at first sight, it is surely remarkable that the matter has not been brought to a head by pilots themselves. Further than that, it would be extraordinary that pilots could do what they now accomplish were they not readily able to counteract this influence, for it is not a chance force that comes sometimes and is absent on others ; it is definite, and it is sure. When regarded as an increase of load on the tail to be counteracted by the rudder or the elevator, as the case may be, its numerical importance is seen to diminish appreciably. Thus for an organ of control, situated 10 feet from the centre of gravity of the machine, we have a force of 33 lbs., and if the control organ has 10 sq. ft. of effective area, the loading required to counteract this force is less than 35 lbs. per sq. ft. Both from the practical and the mathematical aspects of this particular problem, it would seem that there is no reason to take alarm at the forces in question, although there is undoubtedly every reason for the pilot to appreciate their existence, to understand their nature and amount, and to practise in the art of their control. If they were absent or neutralised it would be so much the better, of course, just as it would be desirable to eliminate the possibility of skidding from the driving of a motor car. Two propellers rotating in opposite directions is the proper solution, but the constructional convenience of a single propeller on certain types of aeroplane, and the undeniable service that has been accomplished by the rotary Gnome constitute, to say the least of it, a justifica tion for allowing the existence of the force in question, while the practical accomplishments of pilots afford a further justification for having permitted it to remain up to the present time. The absence of numerical data renders it impossible to theorise quantitatively on the possible influence of the gyroscopic couple caused by sudden, although slight, disturbances of the axis of the machine in nominally straight flight. It is, of course, a fact that the couple
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