Unsteady Aerodynamic Analysis under Wind Shear Effect by EKF Method on FDR Data

Severe wind shear may become a significant threat to airplanes especially during the landing or taking off periods. This paper describes an approach with using Extended Kalman Filter (EKF) to estimate wind field, flight path and velocity, and aerodynamic coefficients so that the effect of wind shear on airplane motion can be analyzed. Onboard flight data recorder (FDR) is a useful resource due to its multi-sensor data structure. A set of FDR data from a Boeing 737-800 flight landing on an international airport was analyzed for this study. The data consisted of Inertial Navigation System (INS) information, radio altitude, ground speed, drift angle, and air data. An additional Global Positioning System (GPS) survey to the ground trajectory was performed. The GPS survey result was used to verify the EKF estimation accuracy. The result shows that the wind speed started decreasing 30 seconds before the landing and sharply decreased during the flare period. In addition, the wind direction changed rapidly during the flare period. The unsteady aerodynamic behavior due to this severe wind shear effect is observed through the EKF method. The major impact of the wind shear is on side force coefficient which is sharply increased during the flare period. As a result, the airplane ran out of the runway after its landing but was able to taxi back.