Aerodynamic Analysis of a Jet Transport in Windshear Encounter During Landing

Stability and control characteristics of a nominally controllable jet transport airplane that ran off the runway after touchdown during windshear encounter are evaluated based on the data in the onboard flight data recorder (FDR). To determine these characteristics, the recorded wind profile is first improved, and then the unsteady aerodynamic models for the aircraft in dynamic ground effect are estimated. The recorded wind field is improved through the extended-Kalman-filter (EKF) technique to reconstruct the wind profile along the flight path from the data in the FDR. The windshear guideline is reviewed and compared with the airport weather data. To analyze the windshear effect in more detail, unsteady aerodynamic models for the aircraft are developed based on two artificial intelligent methods, the fuzzy-logic modeling and the feed-forward neural networks, applied to the processed FDR data. The stability and control characteristics are then estimated by using these aerodynamic models. The results indicate that a less favorable dynamic ground effect exists near touchdown in crosswind. In addition, the dynamic motion is shown to exhibit directional instability, unstable yaw damping, and loss of control effectiveness near the ground in a combined crab and sideslip landing in unsteady windshear conditions.