Wind Measurement Using a Three-Beam Laser Air Motion Sensor on a High-Speed Research Aircraft

A three-beam version of the NCAR Laser Air Motion Sensor (LAMS) has recently been tested on the NSF/NCAR Gulfstream V research aircraft. This follows previous use of a single-beam system, which provided calibration of the measurement of the longitudinal wind component with estimated standard error of about 0.1 m/s. The new system features three beams emanating from a single housing mounted under the wing of the GV. The beams are focused about 15 m from the housing at angles 35 degrees from the longitudinal axis of the aircraft and at azimuthal angles about this axis of (0, -120, 120) degrees from the upward direction. The system also includes an inertial reference system that is mounted in the pod with the sensor windows so that wing or pod motions are measured.

Because the sensor is mounted under the wing, the measurements must be transformed to an Earth-based reference system, with corrections for the attitude changes of the aircraft. The required transformations will be documented, and the resulting measurements will be compared to those from the standard wind-sensing system on the aircraft. These comparisons will be used to determine new calibrations of the sideslip and angle-of-attack measurements on the aircraft and so to calibrate the conventional measurements. Constant-rate turns will be used to check the validity of the wind measurements from both systems.