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Flutter of an Aircraft Controlled by an Automatic Navigation System

Published online by Cambridge University Press:  04 July 2016

P. C. Parks*
Affiliation:
Formerly Bristol Aircraft Ltd., now University of Southampton

Extract

Automatic navigation systems for aircraft often use gyroscopes to measure the changes in the direction of motion of the aircraft they are controlling. These measurements are fed back to the mechanisms moving the control surfaces of the aircraft.

Such a system is usually designed, in the first instance, assuming the aircraft structure to be rigid and such that the system is then stable.

Now suppose the aircraft structure, considered elastic, is disturbed in flight by, say, a gust. Normal modes of vibration of the structure will be excited, the resulting oscillations will be detected by the gyroscope and fed as error signals to the control surface actuators. If the actuators are capable of following these error signals, the control surfaces will also oscillate, exciting the structure further and so completing the cycle. This cycle may be unstable.

Type
Technical Note
Copyright
Copyright © Royal Aeronautical Society 1961

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References

1.See for example Ramsay, A. S. (1947). Dynamics Part II. Cambridge University Press, pp. 206-8, 1947.Google Scholar
2.See for example Porter, A. (1954). An Introduction to Servo-mechanisms. Methuen & Co. Ltd., 1954.Google Scholar
3. For examples on the use of the operator D see Piaggio, H. T. H. (1948). Differential Equations. Bell & Sons, 1948.Google Scholar
4.Porter, A.Op. cit. pp. 48-49.Google Scholar
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7. For discussions of conventional flutter see for example SCANLAN, R. H. and Rosenbaum, R. (1951). Aircraft Vibration and Flutter. Macmillan, New York, 1951, Chapter 8; or Duncan, W. J. (1944). The Fundamentals of Flutter. R.A.E. Report Aero 1920, 1944.Google Scholar
8.Duncan, F. G. (1956). Resonance Test Response. Bristol Aircraft Ltd. Mathematical Services Report 42, Dec. 1956.Google Scholar
9.Lyons, D. J. (1961). Ballistic Research Rockets with particular reference to Black Knight. Journal of the Royal Aeronautical Society, p. 177, March 1961.Google Scholar