Rotorcraft Simulation Modelling and Validation for Control Design and Load Prediction

This paper describes the development and validation of a high fidelity simulation model of the Bell-412 in the FLIGHTLAB environment for handling qualities and flight control investigations. The base-line rotor model features a rigid, articulated blade-element formulation with flap and lag degrees of freedom. The spring strengths and locations are chosen to match the first flap and lag frequency of the soft-in-plane, hingeless Bell-412 rotor hub. The other key features of the base–line model are the inclusion of lag damper dynamics and a finite state dynamic inflow model. The base-line model gives good agreement for onaxis responses compared with flight test data over the speed range 15-120kt. However, prediction of-off axis responses are less satisfactory. Several model enhancement options available in FLIGHTLAB were introduced to obtain an improved off-axis response. It is shown that the pitch/roll off-axis responses in transient manoeuvres can be improved significantly by including the wake geometry distortion effect in the Peters-He finite state dynamic inflow model.