Knowledge-based trajectory control for engine-out aircraft

Aircraft total failure of engines or engine-out, is a dramatic situation which may end by a crash unless a flyable descent trajectory towards a safe landing place is adopted. Although it is now a rare event, there are many different reasons for engine-out. Since with engine-out any wrong decision taken by the pilot may lead to catastrophic consequences, it appears useful to develop an automatic emergency guidance mode for this situation. This new functionality could be integrated in a Flight Guidance System which should be able to select a proper landing site while proposing tactical decisions to fly a feasible trajectory towards this site. In this study, a proposal for the design of such guidance system is developed. First, considering space-indexed glide dynamics for a transportation aircraft, reverse dynamic programming is used to generate, starting from safe landing conditions, a full safe glide domain up to cruise conditions and composed of quasi steady trajectories. Then a neural network structure is designed to produce for any glide situation within the safe glide domain, a reference pitch angle proposed to the pilot in manual mode. Total energy is then considered to distinguish between over range, on range and out of range glide situations and provide directives for the use of airbrakes when necessary. Finally, a tentative integration of the produced information within the primary flight display is proposed. Numerical simulations are performed using data from a wide body transportation aircraft.