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

Trajectory-Based Operations (TBO)
Study Team Report
boundaries, and security functions can be built into the software that alert to specific flight profiles
during arrivals.
Consistent with integrated arrival/departure airspace management (OI-0307), there will be a number of
pre-defined configurations for arrival/departure airspace—including arrival/departure routes, airspace
boundaries, etc.—that are tailored to typical flow patterns and weather events. Certain routes can be bidirectional
and used for either arrival or departure, depending on the traffic situation and the location
of severe weather and visibility/ceiling conditions (OI-0303 and OI-0389).
In future high-density airspace, the arrival sub-segment will begin at an arrival meter fix before TOD
and end at an initial approach fix/merge point. Throughout the arrival and approach sub-segments,
aircraft will perform OPDs with either ground-based CTA, time-based spacing, or airborne merging
and spacing decision support tools managing spacing with CTA and/or relative spacing and time. A
follower’s time is relative, while a leader’s time is absolute. The selection of optimal TOD point is an
important aspect of performing an OPD. By 2025, a high-density metroplex airspace will have perhaps
as many as 20 or 30 different arrival meter fixes fanning out from initial points in the STARs. These
arrival meter fixes will be much further out than the 50 nm typical of today’s TRACON. In less dense
terminal airspace, published arrival meter fixes won’t be required.
The increased number of operations anticipated by 2025 will place a severe strain on the NAS,
especially in major metropolitan terminal airspace 10 . Traffic flowing in and out of the congested
terminal area will make more effective use of the airspace by extending terminal separation standards
(i.e., three nm instead of five nm lateral separation) and other terminal procedures (i.e., diverging
courses) to airspace farther away from today’s TRACON boundary. ANSP decision support tools will
help ensure efficient and smooth traffic flow into and out of high-density expanded terminal airspace.
Planning horizons are lengthened, allowing optimal runway sequencing. Arrivals are still far from
destination airports, and departure slots can be more easily reserved in arrival flows when necessary.
This is the great enabler that TBO brings. By projecting forward in time and space, each aircraft’s
performance can be combined to set the sequence and landing times for capable aircraft. Aircraft
unable to perform TBO would either be restricted from the high-density airspace, or be handled on a
time- and slot-available basis.
New procedures and airborne equipage will allow the use of very closely-spaced parallel runways
(VCSPR) in Instrument Meteorological Condition (IMC), with the same throughput as in Visual
Meteorological Condition (VMC). Arrival management ANSP decision support tools will assign
pairings of aircraft for landing prior to entry into the expanded terminal airspace. An aircraft can
typically be paired with another aircraft arriving from any of the other streams/STARS, and two
consecutive aircraft from the same STAR may be paired. The coupling point occurs on the final
approach approximately 12 nm from the runway threshold, and the two aircraft must maintain relative
longitudinal positioning within a “conformance zone” from this point through landing. Separation
10
The recession and continuing slow recovery have resulted in reduced airline capacity and decline in
operations. Whether or not 2025 represents a targeted year when demand exceeds capacity is in
question. However, the lead times for TBO development are such that the current economic impacts on
aviation should not be used as a predictor for targeting NextGen.
Joint Planning and Development Office
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