Time-Controlled Descent Guidance in Uncertain Winds

A procedure has been developed for constructing a statistical model of the altitude-dependent mean wind profile from the climatological data at particular locations. The model is constructed by fitting a Markov process, with altitude as the stage variable, to historical wind statistics. The wind model, together with the aircraft dynamics and the error characteristics of the navigation system, are incorporated in the design of a state estimator, which gives the minimum variance estimate of the aircraft state and the wind vector. The state and wind estimates are used as inputs to a linear feedback law for guiding the aircraft along the nominal trajectory. An example design of a time-constrained (4D RNAV) descent guidance system is presented, showing tracking accuracy, control activity, and probability of arrival time with and without the wind estimator.