Trajectory-Based Operations (TBO) - Joint Planning and ...
Trajectory-Based Operations (TBO) - Joint Planning and ...
Trajectory-Based Operations (TBO) - Joint Planning and ...
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<strong>Trajectory</strong>-<strong>Based</strong> <strong>Operations</strong> (<strong>TBO</strong>)<br />
Study Team Report<br />
<strong>TBO</strong> flows from experience gained in mid-term implementation of trajectory operations. <strong>TBO</strong> is the<br />
concept of an Air Traffic Management (ATM) system in which every aircraft that is operating in <strong>and</strong><br />
managed by the system is represented via a 4DT. A 4DT includes a series of points from departure to<br />
arrival representing the aircraft’s path in four dimensions: lateral (latitude <strong>and</strong> longitude), vertical<br />
(altitude), <strong>and</strong> time. Every managed aircraft known to the system has a 4DT either provided by the<br />
user or derived from a flight plan for the type of operation. Increasingly, the trajectories used are much<br />
more accurate than those in use today. High performing aircraft are flying the trajectory via Flight<br />
Management System (FMS), using more precise navigation capabilities. The nature of the aircraft’s<br />
adherence to the trajectory is based on the aircraft’s capabilities <strong>and</strong> the type of operation being<br />
conducted. In this way, operations are performance based, meaning that improved services are<br />
available to better-equipped aircraft.<br />
The 4DT is quite complex. Its creation must consider not only the individual aircraft performance, but<br />
also the interaction of the aircraft with other aircraft in the airspace. The 4DT extends its complexity to<br />
consider weather, security, user preferences, the airspace <strong>and</strong> airport configuration, flight procedures,<br />
<strong>and</strong> environmental performance. The 4DT itself can have performance tolerances that vary with the<br />
conditions <strong>and</strong> density of the traffic. For example, the time element of the 4DT can be seconds or<br />
minutes. Altitude can be either an assigned altitude or a block of altitude. Lateral precision, normally<br />
measured in RNP, can have values in miles in low-density airspace to fractions of a mile on approach.<br />
This is why the 4DT starts with pre-negotiation flight planning <strong>and</strong> is followed by negotiation with the<br />
ANSP. Once agreed to, the 4DT is executed as planned. This is not to mean that the operator/user can<br />
expect to have a clear path to top of descent at destination top of descent from takeoff. Updates by the<br />
aircraft, based on its performance, will require periodic update with more current information to<br />
support separation based on <strong>TBO</strong>. Changes can be expected from the ANSP based on changes in flow<br />
constraints. Execution of the 4DT is impacted by the addition or subtraction of downstream<br />
constraints, winds aloft, the need to protect airspace for other aircraft, <strong>and</strong> changes in use of airspace.<br />
To the extent possible, trajectories, from initial flight plans through any subsequent changes, are<br />
managed through negotiations among the users <strong>and</strong> the ANSP. Trajectories are used for flight<br />
planning, advisory services, airspace security, sequencing, spacing, separation, <strong>and</strong> congestion<br />
management. Any changes to the flight (aside from time-critical safety clearances) are communicated<br />
through or to the trajectory. To be effective, the trajectory must be maintained <strong>and</strong> updated at all times<br />
to reflect the latest flight plan, intent information, or clearance.<br />
During pre-flight, the users share trajectory intent information with the ANSP <strong>and</strong> have improved<br />
awareness of current <strong>and</strong> predicted availability of National Airspace System (NAS) resources,<br />
including expected constraint information. The ANSP aggregates the trajectory intent information<br />
across all user classes for improved planning. The resulting negotiated trajectory reflects user intent<br />
<strong>and</strong> provides a common basis for access to resources <strong>and</strong> knowledge of system constraints. While<br />
flights are airborne, the ANSP uses the trajectory to manage separation with support from problem<br />
detection/resolution automation. Throughout the day, the trajectories are aggregated by ANSP flow<br />
management automation to assess potential congestion problems, evaluate alternatives collaboratively,<br />
<strong>and</strong> then implement strategies with aircraft-specific clearances. After flight completion, trajectories<br />
are used for post analysis <strong>and</strong> monitoring of system performance by the ANSP <strong>and</strong> by the users. At the<br />
end of the mid-term for NextGen, initial applications such as paired approaches, pair-wise delegated<br />
separation, <strong>and</strong> Required Time of Arrival (RTA) clearances will be available.<br />
<strong>Joint</strong> <strong>Planning</strong> <strong>and</strong> Development Office<br />
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