Enhancement of an Engineering Simulation Model to Improve the Correlation with Flight Test Data in Climb/Descent and Autorotation

Abstract

A high-fidelity engineering simulation model has been developed in FLIGHTLAB for a Sikorsky production helicopter to support future design modifications. The simulation model consists of major subsystems for main rotor, tail rotor, fuselage, empennage, landing gear, flight control system, and propulsion system. As the manufacturer, Sikorsky was able to provide a complete and validated set of model data and a large database of flight test records to ensure the model quality and fidelity. Although the model correlation with test data is satisfactory in most flight conditions including hover, low-speed flight, level flight, and vertical climb, some model-data discrepancies were seen in the forward climb/descent and autorotation test cases. An additional study was conducted at Sikorsky to investigate these discrepancies. Based on the study, a set of model enhancements were developed to improve the model correlation with test data in forward climb/descent and autorotation. These enhancements allow for adjustment of certain semi-empirical corrections to address model limitations at these challenging conditions such as fuselage characteristics and interference at high angles of attack and rotor inflow and interference at low collective settings and near 90-degree wake skew. These enhancements were carefully designed such that the effects were localized so that the model-data correlation was not adversely impacted in other flight conditions. The model-data correlation in forward climb/descent and autorotation were significantly improved by implementing these model enhancements with little to no impact on the other flight conditions resulting in a high-fidelity engineering simulation model validated in the entire flight envelope.