Trajectory Synthesis for Air Traffic Automation

R. Slattery and Y. Zhao


Abstract

Trajectory synthesis algorithms that are key to the center-terminal radar
approach control automation system (CTAS) developed at NASA Ames Research
Center for air traffic control are discussed.  CTAS generates computer
advisories based on synthesized trajectories that help controllers to produce a
safe, efficient, and expeditious flow of traffic over the extended terminal
area.  Trajectories are synthesized from initial aircraft positions to a
metering fix or runway, depending on airspace.  The horizontal path is
constructed first from specified waypoints using straight lines and
constant-radius turns.  The vertical trajectory is divided into a series of
flight segments.  Three types of flight profiles are defined by connecting
selected segments in a predetermined order: fast, nominal, and slow.  Each
profile can produce a certain range of arrival times.  A second-order
Runge-Kutta scheme is used for integrating a set of simplified point-mass
equations to generate vertical trajectories.  Then, an iterative scheme is
employed to determine the speed that meets a specified arrival time.  Several
special case trajectories are also explained.  Two flight scenarios are used to
illustrate the use of trajectory synthesis algorithms.