Optimal profile descent with 4-D trajectory

Optimal Profile Descents or Continuous Descent Approaches enable aircraft to descend continuously from cruise altitude to the bottom of descent or an initial approach fix without level path segments. By using idle or near-idle thrust during descent, Optimal Profile Descents provide significant benefits for reducing fuel consumption and engine noise. However, to utilize Optimal Profile Descents without reducing the traffic throughput around an airport, a Required Time of Arrival is usually imposed at a metering waypoint to safely merge incoming traffic. The 4-dimensional trajectory of an Optimal Profile Descent that complies with a Required Time of Arrival is generally constructed in-flight by a Flight Management System, while taking into account up-to-date data for wind and temperature. In addition, path constraints, such as speed and altitude restrictions, are considered in the generation of the 4-dimensional trajectory. This paper presents a design, named as Optimal E∗, to construct the 4-dimensional flight trajectories for Optimal Profile Descents. Optimal E∗ uses a layered method to ensure its computational efficiency so that it can be hosted inside a Flight Management System as an embedded module. The Optimal E∗ design has been tested in a simulation environment and results show significant benefits to airliners or the Air Force in terms of reduced fuel cost and carbon emission. The simulation test results are also presented in this paper.