Abstract
The 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.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 57-73 |
| Number of pages | 17 |
| Journal | Annual Forum Proceedings - American Helicopter Society |
| Volume | 1 |
| State | Published - Dec 1 1992 |
| Event | 48th Annual Forum Proceedings of the American Helicopter Society. Part 2 (of 2) - Washington, DC, USA Duration: Jun 3 1992 → Jun 5 1992 |
All Science Journal Classification (ASJC) codes
- Transportation
- Aerospace Engineering