Aircraft time-2d longitudinal guidance based on spatial inversion of flight dynamics

With the growth of civil aviation traffic capacity, safety and environmental considerations urge today for the development of guidance systems with improved accuracy for spatial and temporal trajectory tracking. This should induce increased capacity by allowing safe operations at minimum separation standards. Also, at take-off and landing, trajectory dispersion should be reduced resulting in controlled noise impacts on airport surrounding communities. Current civil aviation guidance systems operate with real time corrective actions to maintain the aircraft trajectory as close as possible to the planned trajectory. In this paper, we consider the problems of designing new longitudinal guidance control laws for an autopilot so that accurate vertical tracking and overfly time are better insured. Instead of using time as the independent variable to describe the guidance dynamics of the aircraft, we adopt distance to land, which can be considered today to be available online with acceptable accuracy and availability. A new representation of aircraft longitudinal guidance dynamics is developed according to this spatial variable. Then a nonlinear inverse control law based-on this new proposed spatial representation of guidance dynamics is established to make the aircraft follow accurately a vertical profile and a desired airspeed. The desired airspeed is then regulated to make the aircraft overfly different waypoints according to a planned timetable. Then simulations experiments with different wind conditions are performed for a transportation aircraft performing a general descent approach for landing. These simulation results are compared with those obtained from a classical time-based guidance control law.