Analysis of windshear from airline flight data

Advanced analysis methods, applied to airline digital flight records and air traffic control radar tracking data, are providing new insight into atmospheric disturbances that cause serious operating problems for aircraft. Reviewed in this paper are performance-based methods for determining unmeasured flow angles and the possible influence of rain on lift and drag, and a state estimation procedure for determining winds along the flight path. The methods are applied to data records from the Delta Airlines flight 191 windshear accident at the Dallas-Ft. Worth Airport, Aug. 2, 1985, involving an L-1011 airliner on final approach. The results indicate that the aircraft encountered a strong downflow that exceeded 40ft/s along with a headwind-to-tailwind change that exceeded 100 ft/s. The outflow near the ground was accompanied by large, rapid changes in vertical wind, consistent with the presence of imbedded vortices. Although rain was present in the "downburst," the analysis showed no evidence of rain causing a loss in aircraft performance.