Flight Test Evaluation of a Helicopter Airborne Lidar

The Japan Aerospace Exploration Agency (JAXA) has conducted ground and flight test evaluations of a prototype 1.5μm all-fiber pulsed coherent Doppler lidar produced by Mitsubishi Electric Corporation which aims to measure three-axis components of airspeed and detect atmospheric turbulence ahead of a helicopter. In the ground test, the lidar has proved its capability to detect atmospheric turbulence with a scale of several tens of meters by accurately measuring helicopter rotor downwash. For the flight test, the lidar was installed in JAXA’s MuPAL-e research helicopter and several flights were carried out to evaluate the accuracy of real-time airspeed calculation using lidar outputs and the format of a real-time pilot display. The lidar successfully measured three-axis airspeed components accurately even in low-airspeed flight regimes including hovering, backwards and sideways flight where the conventional Pitot-static system does not work and its capability as a helicopter airspeed sensor was proven. Some technical challenges were found for atmospheric turbulence detection such as increasing the detection range and improving the data analysis and presentation. These results will be utilized to establish the specifications of practical airborne lidars.