S-97 RAIDER® GenHel Model Development and Correlation with Flight Test Data

Flight dynamics models for engineering simulation are vital to rotorcraft design and testing. This paper focuses on a multi-year effort to develop and improve the S-97 RAIDER® flight dynamics model in State-Space GenHel and to correlate the model with flight test data. State-Space GenHel (SSGH) is an upgraded version of legacy GenHel with a series of new/enhanced modeling capabilities. The S-97 model has been used to support conceptual, preliminary, and detailed air vehicle design, control laws (CLAWS) design and tuning, handling qualities evaluation, flight loads development, system integration lab (SIL) testing, flight testing, and test pilot training. During the ongoing flight test program, the SSGH model has been continuously updated to improve correlation with the test data. The correlation spans a wide range of flight conditions including hover, low speed flight, level flight, chirp tests at different speeds, and various maneuvers. A series of reduced-order models and corrections were implemented in SSGH to capture the complicated physics missed in the baseline model. High-fidelity analytical tools and component test data were used to derive the parameters for these reduced-order models and corrections, with which the model-data correlation has been significantly improved. The paper also discusses the challenges in tip clearance prediction and in modeling the rotor on propeller interference. This study shows that an engineering model, continuously improved using appropriate methods, can capture the flight dynamics characteristics of a high-speed compound helicopter with sufficient accuracy for supporting CLAWS design and flight test.