Descent profile options for continuous descent arrival procedures within 3d path concept

Continuous descent approach/arrival (CDA) procedures with idle thrust descent have demonstrated significant reduction in community noise, fuel burn, emissions and flight time when compared with conventional step-down procedures. However, to date such CDA procedures have only been implemented in low traffic conditions. This is partly due to the fact that air traffic control (ATC) lacks the required ground automation to provide separation assurance services during CDA operations. Additionally, the deployment of CDA procedures in medium to high traffic conditions is hindered by the lack of capability on the ground to reliably predict the trajectory as executed by the airplane when descending under idle thrust. Insufficient or inaccurate knowledge on the ground regarding aircraft type, weight, aircraft specific operations and wind profiles in the flight management system (FMS), etc. can lead to large deviations between the ground computed profile and the actual profile flown. Partially powered, low thrust CDA along a geometric vertical path provides a possible alternative to idle descents. Geometric paths explicitly specify the vertical profile that the aircraft will fly and hence provide increased predictability on the ground and significantly improved common situational awareness in the air and on the ground. These benefits come at the expense of increased noise, fuel burn, emissions, and flight time for individual flight in comparison to idle thrust descents. With proper design, however, it can be shown that the increases can be quite reasonable. The higher predictability will make this descent concept feasible in high traffic conditions. The overall benefits in noise, fuel burn, and flight time for the entire arrival stream can still be much higher than the level achievable with current step-down procedures. When combined with the 3D path arrival management (3D PAM) concept using lateral path options, the resultant operational concept provides a highly predictable 3D descent trajectory and, with supporting ground automation, enables the implementation of CDA procedures in high traffic conditions. In this paper, we will report relevant design considerations for geometric path CDAs and trade-offs between this low thrust descent scheme and idle thrust descents. The implementation of this descent scheme within the 3D PAM concept will also be discussed.