Identification of CH-53G Bare Airframe Dynamics in Forward Flight

Abstract

A six degree of freedom stability and control derivative model of a CH-53G helicopter was identified from flight test data to support flight control design activities using a frequency domain identification method. The model, representing the rigid body dynamics, is applicable in the frequency range of 0.2 to 10 rad/sec. Flight test data consisting of frequency sweeps and multistep inputs were collected in a dedicated test campaign. Data consistency was checked and unmeasured states were reconstructed. Frequency responses for the helicopter rigid body dynamics were calculated. A linear state-space model is fit to the frequency responses. Parameters are iteratively eliminated from the model structure based on robust metrics of parameter insensitivity and correlation. The final minimally parameterized model is driven with the recorded multistep control inputs and the predicted time histories are compared with the corresponding flight data.