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Technical Notes: Influence of Pitch‐Lag Coupling on Damping Requirements to Stabilize “Ground/Air Resonance”

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Pitch‐lag coupling is known to affect the damping required to stabilize “ground resonance” or hover “air resonance,” but published design information is lacking. Trends are examined here using a linear analysis. The influence of pitch‐lag coupling is shown to depend on fuselage and blade lag natural frequencies and hub height above the fuselage e.g. It can reduce the lag damping required in hover to stabilize one mode but can also destabilize another to the extent that more lag damping is required for stability with certain values of pitch‐lag coupling. Mare landing gear damping can be required for “ground resonance” stability if advantage is taken of reduced lag damping requirements for hover. Nonetheless, parametric variations show that, for certain configurations, pitch‐lag coupling can be used to reduce overall lag damping requirements.

Document Type: Research Article


Affiliations: Rotorcraft Technology Center, Rensselaer Polytechnic Institute, Troy, N.Y.

Publication date: October 1, 1992

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  • The Journal of the American Helicopter Society is the world's only scientific journal dedicated to vertical flight technology. It is a peer-reviewed technical journal published quarterly by AHS International and presents innovative papers covering the state-of-the-art in all disciplines of rotorcraft design, research and development. (Please note that AHS members receive significant discounts on articles and subscriptions.)

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