Strategies for Choosing Descent Flight-Path Angles for Small Jets

Abstract

A standard descent procedure with a fixed flight-path angle is proposed to improve trajectory predictability for arriving small jets in the transition airspace into congested terminal area. Three candidate strategies for selecting fuel-efficient and flyable descent flight-path angles are proposed. The three strategies vary in operational complexity and fuel-burn merits. To mitigate variation of wind among flights, the two simpler strategies are adapted to airport, directions of arrival, and time. Three major U.S. airports with different degrees of wind variation and disparate arrival traffic flows are analyzed. Results show that, when compared to the simple airport–static adaptation, the finest adaptation of the simpler strategies recover up to 50–75% of the extra fuel burn relative to the minimum-fuel strategy. Wind variation, descent altitude restrictions, arrival directions, and fleet composition all affect the fuel efficiency of the simple strategies. Tradeoffs between fuel burn and planned speed-brake usage in the choice of the flight-path angle are discussed. Fuel efficiency of simple strategies for the entire national airspace in the United States is estimated. Considerations and implications for air navigation service providers are discussed.