Applicability of a Counterpropagating Laser Airspeed Sensor to Aircraft Flight Regimes

This paper presents the investigation of the applicability of a counterpropagating laser airspeed sensor system to measure airflow velocity in the subsonic-to-transonic aircraft flight regimes. The system uses the Doppler shift of an absorption line in the -band of molecular oxygen near 760 nm combined with an independent measurement of the static pressure and temperature to determine the true airspeed. The unique experimental arrangement using laser diodes allows the possibility for fully analog signal processing, while the size and weight of the system would be appropriate for most commercial aircraft or unmanned aerial vehicles flying today. Static pressure and velocity regimes were investigated in wind-tunnel tests from static pressures of 20 to 150 kPa (altitude equivalent 40,000 ft to subsea-level) and airspeeds of 5 to . It is concluded that counterpropagating laser airspeed sensor is a viable airspeed instrument for these aircraft flight regimes as well as a safety-enhancing possible alternative or supplement to pitot-based air data systems.