WE VIBRATE - RE-PUSHING THE ENVELOPE (G550 HALO TGI FLIGHT TESTING)

Abstract

Abstract: DLR's High Altitude and Long Range Research Aircraft (HALO), a heavily modified Gulfstream G550 (GV-SP), is a high-performance platform. The baseline HALO modifications of the G550 enable DLR's and partnering scientists to equip the aircraft with various pieces of hardware for probing and analyzing the surrounding atmosphere 'in-situ'. A key role for in-situ measurements plays DLR's standard Trace Gas Inlet (TGI), a structure that enables probing the atmosphere outside the aircraft's boundary layer. Due to the new and previously untested design of the TGIs, the high number of installable TGIs and their design derivatives (~ 20 pieces over the whole fuselage) and the resulting number of combinations, DLR chose a careful build-up approach to first assess the two baseline TGI designs in flight at different fuselage positions, followed by a step-by-step testing of multiple combinations of TGI designs, design derivatives and fuselage positions, slowly increasing the complexity of the setup. The achieved main goal of the flight tests was certification of the inlets to supplemental type certificate (STC) status. The flight test program encountered vibration issues during the build-up procedure resulting in the need of close vibration monitoring and a partly redesign of the TGIs trailing edge. The extensive testing also resulted in the development of a simple vibration measuring technique and an efficiency increase of the flight test methods.