Evaluation of Flight Loads Determined with MEMS Pressure Measurements

Kurzfassung

For the certification of new aircraft types, the determination of aerodynamic loads acting on the aircraft structure is a crucial task during every flight test program. An elaborate installation of strain gauges is normally used for measuring structural strain during extensive flight test maneuvers. In order to calculate the local forces and moments from these strain measurement careful calibration of the strain gauges is required. This is usually performed on ground by imposing known loads on the structure and recording the measured strains. An alternative method for load determination is to measure the prevailing pressure distribution on the structural surface. Then the aerodynamic loads acting on the aircraft components can be calculated by integrating the measured pressure distributions along the surface. When compared to the strain gauge method, the effort for calibration is significantly less, because the pressure sensors can be calibrated without being installed inside the aircraft structure. The measurement of pressure distributions is usually performed with pressure transducers and holes in the surfaces connected by tubing. This method requires a smooth fairing of the area instrumented with pressure taps and installation space for the tubing and the pressure transducers. Sensors based on MEMS technology offer many advantageous properties for this task because of their small size and direct measurement of absolute pressures without any tubing. Because of their potential benefits for flight testing the MEMS pressure sensors were part of a research project which focused on the evaluation of MEMS pressure sensors for the determination of flight loads. For this investigation the DLR research soaring plane Discus-2c was used.