RAH-66 Comanche Linear Aeroservoelastic Stability Analysis: Model Improvements and Flight Test Correlation

The RAH-66 Comanche linear aeroservoelastic (ASE) model provides concurrent handling qualities and closed-loop, high-frequency stability analyses. Using analytical models, flight and ground test data, and numerical model predictions, this paper describes new insights into problems of general relevance to the design and analysis of high-bandwidth rotorcraft which have come about as a result of the ASE model development effort. Empirical adjustments of the pitch-lag coupling of the bearingless main rotor to improve correlation with test data are presented. A new analysis of the unsteady thrust response of a ducted rotor in an arbitrary flight condition is developed and correlated to the Comanche’s FANTAIL™ behavior using a variety of test data. Improvements to the prediction of the fuselage elastic response based on flight data are discussed and the impact on predicted system stability margins is presented. Analytical insights into the threedimensional nature of a coupled elastic drivesystem model are discussed.