GROUND VIBRATIONS TESTS FOR THE HIGH SPEED DOLPHIN HELICOPTER

This paper deals with the ground vibrations tests of the High Speed Dolphin helicopter and with their implications. On the one hand. It describes the two tested airframe configurations (aircraft with or without the main gear box and the engines), the test equipments (sensors and actuators), and the test methodology (modal analysis algorithms). The main tests results are then presented by showing some measured transfer functions, modal characteristics and non linearities concerning the 5. Hz - 45. Hz frequency band. On the other hand, the ground vibrations tests results are compared with the predictions derived from an airframe finite element model. The discrepancies especially observed around the rotor harmonics prove the necessity to update the finite element model. Last, the ground vibrations tests results are used to improve a dynamic behavior prediction model of the helicopter in flight by coupling them with a rotor dynamics and aerodynamics model. The correlations between flight tests results and predicted ones are very attractive.