Optimizing Aircraft Trajectories with Multiple Cruise Altitudes in the Presence of Winds

Abstract

This study develops a trajectory-optimization algorithm for approximately minimizing aircraft travel time and fuel burn by combining a method for computing minimum-time routes in winds on multiple horizontal planes and an aircraft fuel burn model for generating fuel-optimal vertical profiles. It is applied to assess the potential benefits of flying user-preferred routes for commercial cargo flights operating between Anchorage, Alaska and major airports in Asia and the contiguous United States. Flying wind-optimal trajectories with a fuel-optimal vertical profile reduces average fuel burn of international flights cruising at a single altitude by 1–3%. The potential fuel savings of performing en route step climbs are not significant for many shorter domestic cargo flights that have only one step climb. Wind-optimal trajectories reduce fuel burn and travel time relative to the flight-plan route by up to 3% for the domestic cargo flights. However, for transoceanic traffic, the fuel burn savings could be as much as 10%. The actual savings in operations will vary from the simulation results due to differences in the aircraft models and user-defined cost indices. In general, the savings are proportional to trip length, and depend on the en route wind conditions and aircraft types.