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Aviation History
1935
1935 - 0934.PDF
SUPPLEMENT TO FLIGHT 4486 U THE AIRCRAFT ENGINEER APRIL 25, 1935 Fig. 3. The aileron unit, showing operating valves and explanation of the reference letters appears in of the relay valve, as has already been described. This relative movement operates the main aileron valve and so causes the application of aileron angle by the movement of the servo-motor piston. As the servo-motor applies aileron angle, however, it simultaneously brings about a small rotary movement of the follow-up frame about the longitudinal axis of the outer gimbal ring in such a direc tion as to result in the reclosing of the relay valve, and when the relay valve is closed no further movement of the servo-motor piston, and hence no further application of aileron angle, can occur. It will thus be seen that the application of aileron angle is limited to an amount deter mined by the relative displacement of the aircraft with respect to the outer gimbal ring of the gyroscope. That is to say, the application of aileron angle is proportional to the actual angular displacement of the aircraft from the laterally level attitude. It will be appreciated that different aircraft require varying degrees of aileron movement for the correction of any given disturbance, and in order that the optimum adjustment may easily be obtained, provision is made for the adjustment of the relative lengths of the levers K. Adjustment of the lengths of these levers alters the effective gearing ratio connecting the movement of the servo-motor piston with the movement of the follow-up frame, and hence alters the degree of aileron angle which is applied for any given disturbance of the aircraft. As the aircraft re sponds to the control of the ailerons and returns to the level attitude so the aileron angle is progressively reduced, and, in actual fact, the aircraft returns to the level position by a highly damped or almost aperiodic oscillation. The only part of the control which has not been described is the centraliser unit, which serves to locate the gyroscope during the period when the control is not in use, or while the gyro scope is being run up to speed. This unit, however, is identical with that fitted to the rudder and elevator control, and will not, therefore, be described again. It remains to remark that the entire operation of the aileron mechanism is under the control of the pilot by means of the same '' main control cock'' which serves the rudder and elevator unit. The two units together form a three-axes automatic pilot capable of controlling any air craft, from the smallest to the largest, with the highest pre cision. The directional control will maintain the machine on a predetermined course within 3 deg. to 5 deg. per hour, and the pitch and roll attitudes are accurately stabilised within \ deg. Throughout the devel opment of the automatic pilot the foremost aim has been the production of a control of the highest possible precision/ Ex- An perience in the Royal Air Force over a period of five years has shown that reliability goes hand in hand with simplicity of de sign and operation, and it may be confidently expected that within a comparatively short period no commercial or freight-carrying aircraft will remain unequipped with automatic control. aileron servo-motor the text. A ** Symposium on Welding" Considerable aeronautical interest promises to attach to the so-called " Symposium on the Welding of Iron and Steel," to be held under the auspices of the Iron and Steel Institute in the Lecture Theatre of the Institution of Civil Engineers on May 2 and 3. The societies co-operat ing include the Royal Aeronautical Society, and papers have been promised by the Fokker Company of Holland; by Mr. R. F. Taylor, of A. V. Roe and Co., Ltd.; by Mr. J. B. Johnson, M.E., of the War Department Air Corps, Dayton, Ohio, U.S.A. ; and by Mr. H. Sutton, of the Royal Aircraft Establishment, Farnborough. The Dutch aircraft firm, N. V. Nederlandsche Vlieg- tuigenfabriek (Fokker) have longer experience of welding than any other aircraft constructor in the world. While A. V. Roe and Co. began welded construction by building certain Fokker types under licence, this firm has since developed methods of its own, differing from the original Fokker methods. America took up welding fairly early, and has applied it to high-grade steels.
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