Model incidence measurement using the SAAB Eloptopos system

For measuring the angle of attack of models in the NLR transonic wind tunnel, a SAAB Eloptopos system was acquired. The system consists of two infrared light-emitting diodes mounted for and aft in the fuselage of the model, two linear array charge coupled-device-cameras, and special processors. The cameras are mounted on the sidewall of the wind tunnel and have a viewing angle of 60° in the vertical direction. Thanks to an individual calibration and a special optimizing algorithm the camera resolution is enhanced to 0.001°. At a viewing distance of 1 m the resulting resolution in angle of attack of the model is typically 0.0026°. The system is individually calibrated for each model under wind-off conditions, using an extremely accurate gravity sensing inclinometer as a reference. This procedure ensures the required accuracy of 0.01° in angle of attack under wind-on conditions