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Ground Resonance of the Helicopter

Published online by Cambridge University Press:  26 October 2023

R M Howarth  and
C H Jones
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Summary

Self excited vibrations of helicopters on the ground have been the cause of several accidents It is, therefore, essential that the means of ensuring freedom from such phenomena should receive serious attention

The theory of R P COLEMAN, is briefly reviewed and compared with results obtained from model rotor tests This comparison affords general confirmation of the theoretical results

The theory of a rotor on idealised supports is applied to a single rotor helicopter of known hub impedance Then experimental methods for determining this impedance are described

Finally, the influence of Ground Resonance on undercarriage design is reviewed The influence of shock absorber struts and tyres on the coupled rigid body modes of the helicopter is discussed and three undercarriage schemes representing alternative approaches to ground resonance elimination are examined It is found that, with respect to ground resonance, the most advantageous system for land based operations is one in which all the helicopter-undercarriage modes have very low frequencies

An Appendix indicates the application of the theory to a twin rotor helicopter of any configuration

Type
Ordinary Meeting, 4th December, 1953
Information
The Journal of the Helicopter Association of Great Britain , Volume 7 , Issue 4 , April 1954 , pp. 168 - 189
Copyright
Copyright © Royal Aeronautical Society 1954

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Footnotes

The authors wish to acknowledge their debt to the Aircraft Division of the M O S for having given permission to show the film and use the experimental data presented They also wish to thank their colleagues at The Bristol Aeroplane Company for much helpful guidance

References

1 Hosegood, C T D “Early test flights in the Bristol Type 173 Helicopter” Journal of the Helicopter Association of Great Britain, July, 1953 Vol 7 No 1Google Scholar
2 Coleman, R P “Theory of Self Excited Mechanical Oscillations of hinged rotor blades” NACA ARR 3G29Google Scholar
3 Jones, C H “Investigation of the vibration of a model rotor in the plane of the blades, etc” Bristol Aeroplane Company Report No C R 669, Issue 2Google Scholar
4 Deutsch, M L “Ground Vibration of Helicopters” Journal of the Aeronautical Sciences May, 1946 Vol 13 No 5CrossRefGoogle Scholar