Off-Axis Dynamics and Simulator Fidelity

The Vehicle Simulation group at the University of Toronto Institute for Aerospace Studies has a number of real-time helicopter models for piloted simulations, which are currently in the process of being updated and improved. These models were previously developed at UTIAS and represent the CH-124 Sea King, CH-149 Cormorant, and Bell 206 JetRanger. An ongoing concern with helicopter simulations is that they often have an incorrect off-axis response to cyclic control inputs when compared with the corresponding flight test data, as such this is an aspect targeted for improvement. Several theories have been put forth in the literature to explain this discrepancy, and the more commonly suggested contributing factors include the influence of dynamic wake distortion, rotor blade elasticity, and unsteady blade airfoil aerodynamics. These three possible solutions have been added to the UTIAS helicopter models to improve the off-axis response and evaluate their effectiveness. This paper examines the impact of these changes from a pilot-in-the-loop perspective, including an attempt to quantify the perceived changes using simulation fidelity ratings. Since this is a newly developed metric for evaluating simulators not previously applied to this facility, the simulator was first evaluated using the original baseline vehicle models. Through this process, experience could be gained in the usage of the fidelity rating scale, while also examining what effect changes to the off-axis dynamics in particular had on the overall simulator fidelity rating obtained.