Aircraft wake vortices for the first time measured by airborne Doppler Lidar

Smoke generator mounted to the wing of DLR aircraft ATTAS ­(source: DLR) . Trace of smoke as seen out of the floor window of the DLR aircraft Falcon flying above the ATTAS aircraft (source: DLR) . Wind lidar system installed inside the DLR aircraft Falcon (source: DLR)

­As part of the European project AWIATOR, the detection and characterisation of wake vortices behind an aircraft by a lidar system on-board a second aircraft has been proven as feasible. During the try-out tests, the wake vortices generated by the DLR test aircraft ATTAS flying at 2000 m altitude were measured downward pointing from the DLR research aircraft Falcon flying approximately 900 m above the vortices. For this purpose, the coherent lidar of the institute was equipped with a new scanning device and installed above the floor window of the Falcon. Since the ATTAS is a relatively small aircraft producing relatively weak vortices, a smoke generator was mounted on the left wing of the aircraft to increase the backscatter signal of the port vortex. Until now, it was only possible to measure wake vortices near the ground. The airborne method now allows the characterisation of wake vortices above the atmospheric boundary layer. Based on these promising results, the new measurement strategy shall be applied in the next phase of AWIATOR tests in January/February 2006.