Method and apparatus for determining the airspeed of rotary wing aircraft

摘要

A method and apparatus for determining the airspeed of a rotary wing aircraft having a sustaining rotor (23) with a plurality of radially extending rotor blades (23A-23D) for rotation about a substantially vertical axis (24) comprises the steps of measuring an airflow sideslip angle ( beta ) established during rotation of each rotor blade (23A-23D) by the vector of a radial flow component (29) due to the relative wind vector and the rotational velocity (30) perpendicular to a blade feathering axis, producing a signal representative of the sideslip angle ( beta ), comparing the signal in processing means containing information on a known relationship between the sideslip angle ( beta ) and airspeed (VT) providing an output signal representative of the airspeed and wind direction to a display means (39) which may display both the airspeed and wind direction (43).