Coherent Laser Radar and the Problem of Aircraft Wake Vortices

Aircraft wake vortices have been studied with a 10·6 μm coherent c.w. lidar. Good agreement is found between the form of experimentally observed Doppler spectra and theoretical calculations and modelling. Detailed measurements of spectra have yielded core radii, tangent velocities and vortex velocity profiles which are in reasonable accord with theoretical formulations. During a two week trial over 130 aircraft passages were recorded with the lidar equipment. Even in low signal to noise conditions vortex spectra were recorded on most occasions at a level above expectation. The characteristic cusp-like features of such spectral records are illustrated with a novel colour display.