The Effects of Control System Stiffness Models on the Dynamic Stall Behavior of a Helicopter

The control system stiffness of an UH-60A helicopter was measured. A description of the measurement and the results is provided. The measured control system stiffness values were used within a comprehensive analysis, CAMRAD II, to establish a baseline calculation of the rotor system during an extreme thrust condition causing dynamic stall on the rotor. The baseline CAMRAD II model is compared to measured blade shake test data and level flight, high thrust, flight test data also showing dynamic stall from the UH-60A Airloads Program to validate the baseline calculations. An evaluation of the sensitivity of the rotor system response to different control system stiffness models was made. The calculated results show that the rotor system response is significantly improved using an accurate control system model when dynamic stall is present.