4-D Aircraft Flight Path Management in Real Time

Onboard guidance and control systems are used to monitor and control flight performance and to maintain up-to-date estimates of such critical variables as time-of-arrival and fuel reserves. Currently, arrival time and specification of the route are generated prior to takeoff by an offboard flight planning system. However, aircraft approaching high density terminal areas often waste fuel, particularly while awaiting approach clearance. This reduces the value of sophisticated preflight planning. Moreover, precise control of time-of-arrival (4-D control) will play a significant role in the future ATC system. This paper focuses on the 4-D flight path management problem in the vertical plane.