Trajectory-Based Operations (TBO) - Joint Planning and ...

Trajectory-Based Operations (TBO)
Study Team Report
typically been negotiated and agreed upon through collaborative air traffic management (CATM)
procedures.
For most airspace and operations, trajectories will include some flexibility (sometimes referred to as
“windows”) that allows the operator to optimize within limits without renegotiating the trajectory.
This might apply to an aircraft choosing a path in real time between thunderstorms. Conformance
monitoring on the ground considers the range of these windows, so minor maneuvering is authorized
within the context of the 4D contract.
In 2025, aircraft will vary widely in their ability to accurately adhere to a 4DT and in their ability to
exchange trajectory information with the ground. At the lower end of performance, some aircraft are
only capable of adhering to wide lateral trajectories and flexible timing requirements (windows), while
high-performing aircraft can transmit via data link detailed 4D trajectories that can be executed with
high accuracy. In general, NAS operations and ANSP decision-support automation must be designed
to deal with the entire spectrum of aircraft capabilities. However, significant operational efficiencies
can be gained by taking advantage of the additional information-sharing capabilities and performance
accuracies of high-performing aircraft.
The far-term JPDO Operational Improvements include a self-separation capability, which may be
restricted to airspace where only self-separating aircraft can operate 5 or may include mixed-equipage
environments where some aircraft are self-separating while others are ANSP-managed 6 . There are also
a number of pair-wise delegated separation operations in mid- and far-term NextGen, such as airborne
merging and spacing, parallel runway operations, and oceanic procedures. Self-separating aircraft
separate themselves using ADS-B as the primary means of airborne surveillance. ADS-B provides the
location and velocity vector, plus the near-term intent of other self-separating aircraft in the vicinity.
Research is required to determine how to safely and effectively utilize the capabilities of these
advanced aircraft in increasing efficiency and throughput of NextGen operations. When an aircraft has
been delegated some separation responsibility; there needs to be sufficient flexibility in the trajectory
that maneuvers for separation can be accomplished without trajectory negotiation. In this case, the
trajectory might be constrained only sufficiently to support traffic flow management and would be
virtually useless for separation management decisions. However, these self-separating aircraft are
themselves operating based on highly accurate trajectories, which are continuously maintained to be
conflict free using onboard strategic and tactical conflict detection and resolution functionality.
To ensure predictable operations, trajectory changes that result in the near-term generation of new
conflicts are not acceptable. To sustain situational awareness, the new trajectory path is broadcast via
ADS-B before the aircraft begins maneuvering. This is especially important outside of the range of any
ANSP surveillance. If this highly accurate trajectory were made available to the ground via data link,
then the ANSP decision-support automation could accurately predict the movement of both selfseparating
and delegated-separation aircraft. If future ANSP separation management decision-support
automation were designed to effectively use this more accurate information for conflict detection and
resolution functions, then more effective use of airspace capacity should result. Thus, an open research
question is whether there should, in fact, be two trajectories in effect for these aircraft: a negotiated
5
6
OI-0362 Self-Separation Airspace Operations
OI-0363 Delegated Separation – Complex Procedures
Joint Planning and Development Office
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