Flight Test of Technology for Virtual Monitoring of Loads

Technology for real-time virtual monitoring of loads on rotor system dynamic components was validated in a series of flight tests conducted on U.S. Army RASCAL JUH-60A helicopter at Moffett Field, CA in 2010, 2011, and 2012. Real-time software produced estimates of load waveforms for eight key structural loads in the rotor system, including main rotor shaft bending, main rotor shaft torque, push-rod loads, servo loads, and stationary scissor loads. For virtual monitoring of loads using only measured aircraft states, the correlation between the instantaneous estimated and actual loads for dynamic components in the rotating frame was in the range 0.81-0.98, and the correlation between instantaneous estimated and actual loads for dynamic components in the fixed frame was in the range 0.36-0.78. For loads monitoring using the measured aircraft state and the flap motion of one rotor blade, the correlation between instantaneous estimated and actual loads for dynamic components in the rotating frame was in the range 0.92-0.99, and the correlation between instantaneous estimated and actual loads for dynamic components in the fixed frame was in the range 0.86-0.91. The availability of technology for accurate real-time virtual monitoring of loads may enable advances in structural usage monitoring, load-alleviating controls, and structural fault detection and isolation.