Hostname: page-component-77c89778f8-cnmwb Total loading time: 0 Render date: 2024-07-20T18:24:26.808Z Has data issue: false hasContentIssue false
  • English
  • Français

The Derivation and Use of Aerodynamic Transfer Functions of Airframes

Published online by Cambridge University Press:  28 July 2016

F. R. J. Spearman
F. R. J. Spearman*
Affiliation:
Ministry of Supply
Get access Rights & Permissions [Opens in a new window]

Summary

The aerodynamic characteristics of airframes are expressed as aerodynamic transfer functions, giving the relationships between input and output for each of the three separate planes of motion, roll, pitch, and yaw. By assuming no cross-coupling between planes and linear aerodynamics, and by making certain other assumptions, which apply particularly to conventional airframes with fixed wings and rear controls, relatively simple approximate algebraic transfer functions giving the relationships between the control surface deflection (the input) and any airframe motion (the output), are obtained.

The open loop aerodynamic transfer functions thus obtained are used as part of the auto-pilot block diagram, in which the performance of other components, such as actuators, instruments and electrical networks, are also expressed in transfer function form. The aerodynamic transfer functions are useful in auto-pilot evolution and synthesis in that they aid selection of the airframe motions to be measured, modified, and fed back to close the auto-pilot loop.

For mathematical assessment of closed loop performance and stability, open loop transient and frequency responses are used, and curves of airframe responses are plotted in linear, logarithmic and polar form by standard methods from the aerodynamic transfer functions. Some methods of using these curves, which follow the general lines adopted in servo-mechanism and electronic amplifier design, are explained briefly.

Analogue computers are frequently used when the computations to be made are so complicated as to need the use of a computing machine. The aerodynamic transfer functions then form one block of the simulator set-up, and on larger computers the more exact form, including any non-linearities and cross-coupling effects, can be used.

Type
Research Article
Information
The Aeronautical Journal , Volume 59 , Issue 539 , November 1955 , pp. 743 - 761
Copyright
Copyright © Royal Aeronautical Society 1955

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Brown, G. S. and Campbell, D. P. (1948). Principles of Servomechanisms. Chapman & Hall Ltd., London, 1948.Google Scholar
James, H. M., Nichols, N. B. and Phillips, R. S. (1947). Theory of Servomechanisms. McGraw-Hill Book Co., New York, 1947.Google Scholar
West, J. C. (1953). Textbook of Servomechanisms. English Universities Press Ltd., 1953.Google Scholar
2. Wass, C. A. A. (1955). Introduction to Analogue Computing. Pergamon Press, London, 1955.Google Scholar
Diprose, K. V. (1955). Analogue Computing in Aeronautics. Journal of the Royal Aeronautical Society, Vol. 59, No. 535, p. 479, July 1955.CrossRefGoogle Scholar
Korn, G. A. and Korn, T. M. (1952). Electric Analog Computers. McGraw-Hill Book Co., New York, 1952.Google Scholar
3. Spearman, F. R. J., Gait, J. J., Hemingway, A. V. and Hynes, R. W. Tridac, A Large Analogue Computing Machine. Paper to be published by the Institution of Electrical Engineers.Google Scholar
4. Lamb, H. (1920). Higher Mechanics. Cambridge University Press, 1920.Google Scholar
5. Brown, G. S. and Campbell, D. P. (1948). Principles of Servomechanisms, Chapter 11.Google Scholar
Wass, C. A. A. and Hayman, E. G. An Approximate Method of Deriving the Transient Response of a Linear System from the Frequency Response. Unpublished Ministry of Supply Report.Google Scholar