The trade-off between trajectory predictability and potential fuel savings for continuous descent operations

Continuous Descent Operation with a required time of arrival is an environmentally friendly procedure that reduces fuel consumption and emissions. But its idle-thrust demand during flight limits the predictability of trajectory in time dimension, which can be reflected in constrained feasible arrival time window. This paper focuses on finding out the tradeoff relationship between fuel savings and trajectory predictability, with a fixed top of descent. Two conditions under the same scenario are considered and compared in the study. Results show that a time window of 16 seconds could be obtained within a tiny deviation from the minimum fuel consumption and the reachable time window can be enlarged as fuel cost increases. There exists a typical point of extra fuel cost, above which the rate of feasible time window extension becomes rather small.