Airborne four channel fiber coupled vector laser Doppler anemometer system

Area of Science:

• Aerospace Engineering
• Optical Measurement Techniques
• Fluid Dynamics

Background:

• Accurate measurement of flight parameters like true airspeed, angle of attack, and angle of sideslip is critical for aircraft operation and safety.
• Traditional methods can be limited, necessitating advanced techniques for precise, non-intrusive airflow measurement.
• Laser Doppler Anemometry (LDA) offers a promising optical approach for measuring wind vectors outside the aircraft boundary layer.

Purpose of the Study:

• To develop and experimentally validate an airborne vector Laser Doppler Anemometer (LDA) system for measuring airflow outside the boundary layer.
• To assess the system's capability in directly deriving primary flight data, including true airspeed, angle of attack, and angle of sideslip.
• To investigate the influence of interchangeable telescopes on LDA sensitivity and signal rate for optimized performance.

Main Methods:

• Development of an experimental airborne LDA system equipped with interchangeable telescopes.
• Integration of a Field Programmable Gate Array (FPGA) data acquisition system for real-time processing and off-line analysis.
• Conducting an airborne measurement campaign to collect flight data.

Main Results:

• The airborne LDA system successfully measured true airspeed with a residual error of 1% when compared to a five-hole flow sensor.
• The angle of sideslip was determined with a standard deviation of residual error of 0.6°.
• The angle of attack was measured with a standard deviation of residual error of 0.2°.

Conclusions:

• Airborne vector LDA is a viable and accurate optical technique for measuring airflow outside the aircraft boundary layer.
• The developed system can directly derive key flight parameters with high precision, comparable to established sensors.
• This technology holds significant potential for enhancing flight data acquisition and aviation safety.