CONTROL OF AIRCRAFT UNDER SEVERE WIND SHEAR CONDITIONS (LANDING APPROACH, MICROBURST, DOPPLER RADAR)

Several airliner crashes in the past decade have been attributed to very strong low-altitude wind shear. Recently, meteorologists have identified "microbursts", in which aircraft encounter a mix of severe headwinds, downdrafts, and tailwinds over just a few miles during takeoff or landing.; This research uses feedforward techniques to control a Short Take-Off & Landing transport during landing approach, assuming knowledge of the wind states. At the same time, feedback is used to augment stability and handle modeling and estimation errors. Current and future wind states can be detected by ground-based Doppler radars that scan the glide slope, as demonstrated in the Joint Airport Weather Study project. Estimates of the current wind states can also be derived from onboard sensors.; Three different methods for designing time-invariant feedforward controller are discussed: asymptotic disturbance rejection, linear quadratic disturbance rejection, and differential game. Simulations show that the controllers maintain a satisfactory approach path and airspeed under most wind shear conditions, without causing too high an angle-of-attack or excessive throttle activity. However, controls are saturated at the most severe parts of the wind shear patterns.; A Wind Shear Penetration Index is proposed. It gives an indication of the ability of an aircraft to penetrate wind shear, and may establish a wind threshold above which the aircraft should not attempt landing or take-off.; A general software package for control design is presented in the Appendix.