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Perturbation solutions for the influence of forward flight on helicopter rotor flapping stabilityThe stability of the flapping motion of a helicopter rotor blade in forward flight is investigated, using a perturbation technique which gives analytic expressions for the eigenvalues, including the influence of the periodic aerodynamic forces in forward flight. The perturbation solutions are based on small advance ratio (the ratio of the helicopter forward speed to the rotor tip speed). The rotor configurations considered are a single, independent blade; a teetering rotor; a gimballed rotor with three, four, and five or more blades; and a rotor with N independent blades. The constant coefficient approximation with the equations and degrees of freedom in the nonrotating frame represents the flap dynamic reasonably well for the lower frequency modes, although it cannot, of course, be completely correct. The transfer function of the rotor flap response to sinusoidal pitch input is examined, as an alternative to the eigenvalues as a representation of the dynamic characteristics of the flap motion.
Document ID
19740023388
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Johnson, W. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 3, 2013
Publication Date
August 1, 1974
Subject Category
Aircraft
Report/Patent Number
NASA-TM-X-62361
Accession Number
74N31501
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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