Benefit and Trade-Off Analysis of Continuous Descent Approach in Normal Traffic Conditions

Abstract

The continuous descent approach (CDA) has long been known as a fuel-efficient procedure because it eliminates level flights at low altitudes. However, many studies that examine fuel savings fail to consider the increased separation uncertainties that accompany CDA and that may cause extra fuel consumption for safe spacing. This study evaluates the fuel benefits of CDA at Hartsfield–Jackson Atlanta International Airport in Georgia and takes into account the delays that result from conflict resolutions. Fuel burn is estimated by using a corrected thrust-specific fuel consumption model that is designed specially for descent. The conflict-free CDAs are determined in such a way that total arrival delays are minimized in each look-ahead time window. Resultant delays are converted to speed advisory or air-holding commands executed in cruise phase to account for the impact of increased separations in CDAs. The fuel consumption of CDA is compared with that of real step-down trajectories extracted from radar track data. Results show that executing CDA to avoid conflicts does not guarantee fuel savings for individual arriving flights, but overall fuel consumption at the airport is reduced. The estimated fuel savings is less than that observed in the terminal airspace only because deconfliction entails extra fuel consumption for delay absorption beyond the immediate terminal airspace.