Dynamics of the McDonnell Douglas Large Scale Dynamic Rig and Dynamic Calibration of the Rotor Balance

https://doi.org/10.21949/14034721994PDFTech ReportWind tunnelsRotorsMechanical propertiesAerodynamicsPerformanceLSDRLarge Scale Dynamic RigMDART rotorMcDonnell Douglas Advanced Rotor TechnologyShake testNguyen, KhanhLau, BentonAmes Research CenterNTL-AVIATION-Aviation Safety/AirworthinessUS Transportation CollectionA shake test was performed on the Large Scale Dynamic Rig in the 40- by 80-Foot Wind Tunnel in support of the McDonnell Douglas Advanced Rotor Technology (MDART) Test Program. The shake test identifies the hub modes and the dynamic calibration matrix of the rotor balance. For hub mode identification, three configurations were tested: wind tunnel scale unlocked with dampers engaged and disengaged, and wind tunnel scale locked. Test data were analyzed with a multi-degree-of-freedom time domain algorithm to identify the modal properties of the hub modes. The damping of the low frequency hub modes (ground resonance modes) increases significantly with the wind tunnel dampers engaged. For dynamic calibration of the rotor balance, the shake test was performed only with the wind tunnel dampers engaged. The dynamic calibration matrix, computed from theshake test data using a least squares error method, is used to correct the five-per-rev vibratory balance readings. The corrections are large for the side force, moderate for the axial force and inplane hub moments, and small for the normal force.84