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Aeromechanical stability of helicopters with composite rotor blades in forward flightThe aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forward flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.
Document ID
19930051907
Document Type
Conference Paper
Authors
Smith, Edward C. (NASA Langley Research Center Hampton, VA, United States)
Chopra, Inderjit (Maryland Univ. College Park, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1992
Publication Information
Publication: In: AHS, Annual Forum, 48th, Washington, June 3-5, 1992, Proceedings. Vol. 1 (A93-35901 14-01)
Subject Category
AIRCRAFT DESIGN, TESTING AND PERFORMANCE
Funding Number(s)
CONTRACT_GRANT: NAG1-1253
CONTRACT_GRANT: DAAL03-88-C-0002
Distribution Limits
Public
Copyright
Other