Identification and verification of frequency-domain models for XV-15 tilt-rotor aircraft dynamics

Abstract : Frequency-domain methods are used to extract the open-loop dynamics of the XV-15 tilt-rotor aircraft from flight test data for the cruise condition (V = 170 knots). The frequency responses are numerically fitted with transfer function forms to identify forms to identify equivalent model characteristics. The associated handling quality parameters meet or exceed Level II, Category A, requirements for fixed-wing military aircraft. Step response matching is used to verify the time-domain fidelity of the transfer-function models for the cruise and hover flight conditions. The transient responses of te model and aircraft are in close agreement in all cases, except for the normal acceleration response to elevator deflection in cruise. This discrepancy is probably due to the unmodeled rotor rpm dynamics identification and analysis is clearly demonstrated. Keywords: Tilt-Rotor aircraft; Parameter identification; Flight testing; Frequency-domain methods; Transfer function identification.