Rotary‐Wing Static Stability

Abstract The static stability of a rotary‐wing aircraft is established by observing its immediate response following a disturbance from a trimmed flight condition. For a helicopter, this can include rearwards, sideways, forwards, and hovering trimmed flight at constant altitude or in a climb or descent. The disturbance response of the main rotor dominates the helicopter response. Modeling this response is crucial in the development of stability and control derivative data to predict static and maneuver stabilities, the latter term describing a form of static stability where response to variations in angle of attack is assessed. Notwithstanding the complexities of the rotor system modeling, the flight‐testing techniques for static and maneuver stabilities from the pilot's perspective of the cockpit inceptor positions and applied forces are straightforward. The results from these flight tests for static stability contribute significantly to the overall assessment of an aircraft's stability, control, and response characteristics. However, the final assessment must include results from other dynamic stability and control response evaluations and from assigned handling quality ratings (HQRs) awarded by test pilots on completion of carefully planned handling tasks.