Enabling real-time flight data processing in low aerosol environments

Aircraft typically use mechanical ports and probes protruding from the fuselage to acquire flight data such as true airspeed and angle of attack. Probe-less optical air data systems using laser Doppler anemometry offer an attractive alternative, but the technique faces challenges in real-world flight scenarios due to its reliance on scattering events and the difficulty to obtain these parameters in low-aerosol environments. Oliver Kliebisch and Peter Mahnke demonstrated a data processing scheme that enables real-time flight quantity measurements in these types of circumstances.

Rather than relying on the conventional time-domain trigger, the method uses the spectral signature of a signal. By applying Fourier transform to measurements taken from three independent angles, the technique reconstructs the original time signals for scattering events and recovers the relevant flight quantities.

The authors optimized this algorithm for single-particle scattering to estimate the Doppler shift of the signal, allowing for real-time data processing with low energy consumption. More sophisticated reconstruction mechanisms using this technique can be implemented.

“Current state-of-the-art air data sensors for airspeed rely on mechanical ports and fuselage-protruding probes,” said Kliebisch. “Our optical approach allows the direct, probe-less measurement of the total relative wind vector, and the only effective calibration necessary is the orientation of the sensor with respect to the fuselage, compared to conventional sensors, which have to be calibrated for a multitude of possible flight configurations.”

Kliebisch and Mahnke are currently working on integrating this approach onto research aircraft.

“The challenge is to build a laser-optical system which meets the requirements regarding robustness to harsh environments, cruise altitude conditions and aircraft certification standards,” Kliebisch said.

Source: “Real-time laser Doppler anemometry for optical air data applications in low aerosol environments,” by O. Kliebisch and P. Mahnke, Review of Scientific Instruments (2020). The article can be accessed at https://doi.org/10.1063/5.0014389 .