 NASA AFRC; closed-form equations (based on beam theory); static deflection  Richards, L. and Ko, W. , "Process for using surface strain measurements to obtain operational loads for complex structures," US Patent #7715994, May 11, 2010  NASA AFRC; "sectional" bending moment, torsional moment, and shear force along the "beam".

No abstract

Risk reduction is the objective of the X-57 Maxwell aeroelasticity team. The X-57, NASA's experimental electric propulsion aircraft, has a long thin wing with primary propulsion systems located at the wing tips and high lift motors distributed along the span. Many of the classical aeroelastic concerns associated with such a configuration were addressed through early design decisions. The as-designed intermediate flight vehicle configurations show flutter mechanisms associated with flexible models of control surface systems -the stabilator, flaps and ailerons. Improvements to the analytical models, based on ground test data and project decisions about flight operations, show improved prospects of the vehicle being aeroelastically stable throughout the flight envelope. On-going ground testing and further analyses will lend credibility to the flutter predictions and vehicle safety.

As part of the National Aeronautics and Space Administration New Aviation Horizons initiative to demonstrate and validate future high-impact concepts and technologies, the X-57 Maxwell airplane -the first all-electric X-plane -was conceived to advance research in the area of electric propulsion to show the feasibility of minimizing fuel use, reducing emissions, and lowering noise during flight. Through several configuration modifications to the X-57 airplane, validation of electrical-powered flight with increasing efficiency between each modification when compared to the baseline original airplane is anticipated. In the case of the X-57 Modification II airplane, a ground vibration test was needed to identify the airplane structural modes and use them to update and validate the finite element model. To determine the airworthiness of the airplane, the updated finite element model will be utilized to investigate both classical and whirl flutters. The X-57 Modification II ground vibration test was performed by the National Aeronautics and Space Administration Armstrong Flight Research Center Flight Loads Laboratory. This paper will highlight the testing performed to acquire the modal data as well as the results.