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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 />

overcast <strong>and</strong> gradually decreasing to 1,000 feet with chance of heavy snow showers,<br />

gusts to 40 knots <strong>and</strong> icing in clouds <strong>and</strong> snow showers.<br />

12.6 Arrival/Approach <strong>and</strong> L<strong>and</strong>ing Assumptions<br />

For parallel runway operations:<br />

• While there are no current plans at IAD, many hub airports (including IAD) may have new<br />

parallel runways, spaced as close as 750 feet from an existing runway, by 2025. In order to<br />

show how closely spaced parallel runway operations work in concert with airborne merging<br />

<strong>and</strong> spacing <strong>and</strong> time-based spacing, a new parallel runway has been created for the IAD arrival<br />

scenario that is 750 feet from an existing runway.<br />

• The DTW to IAD scenario is based on one of several proposed concepts for closely spaced<br />

parallel runway operations. The concept is designed to accommodate dependent pairing of<br />

aircraft with dissimilar final approach speeds. The conformance zone is defined only by wake<br />

avoidance. The aircraft with the faster Final Approach Speed (FAS) is initially positioned<br />

behind the aircraft with the slower final approach speed. After the coupling point when the<br />

aircraft slow to their respective final approach speeds, before the SAP, the trailing faster<br />

aircraft may safely overtake the slower lead aircraft <strong>and</strong> move some distance ahead before<br />

l<strong>and</strong>ing, still staying within the conformance zone. Future research will determine whether<br />

passing can be safely conducted at runways spaced laterally as close as 750 feet. If passing is<br />

not supported, then aircraft pairs must have much closer final approach speeds.<br />

• Similar to dynamic wake spacing, the size of the conformance zone varies dynamically with<br />

environmental conditions, especially crosswind speed <strong>and</strong> direction.<br />

• The parallel runway breakout maneuver is not a 4DT since it does not specify the aircraft’s<br />

position as a function of time, but rather relative to the point at which the breakout is initiated.<br />

When an aircraft conducts a breakout maneuver, it has an open trajectory until closed by the<br />

ANSP.<br />

• An aircraft is not allowed to overtake another aircraft in the same stream/STAR unless they are<br />

traveling at different altitudes.<br />

• Much of the information exchange between the flight deck <strong>and</strong> ANSP will be via data link. For<br />

example, rather than today’s Automatic Terminal Information Service (ATIS) messaging, the<br />

aircraft will receive a data link message with current weather <strong>and</strong> airport configuration<br />

information.<br />

• By 2025, STARs supporting OPDs will be created for all arrivals for high-density airports.<br />

These OPD STARs will have a defined 2D route, but will have waypoint altitude crossing<br />

restrictions defined as a range of altitudes, defining a vertical volume designed to accommodate<br />

a variety of aircraft with different weights <strong>and</strong> performance characteristics.<br />

• In high-density traffic, an arrival stream will contain a string of aircraft conducting airborne<br />

merging <strong>and</strong> spacing to a runway. A complicating factor in spacing is the need to accommodate<br />

stabilized approaches for aircraft with different final approach speeds (i.e., the aircraft must<br />

slow to its appropriate approach speed <strong>and</strong> be configured for l<strong>and</strong>ing before descending below<br />

1000 ft AGL). The spacing 4DTs must include a buffer to accommodate differences in<br />

approach speeds because a faster aircraft will be gaining on the aircraft ahead, while a slower<br />

aircraft will be falling behind the aircraft ahead during the last three nm of the approach.<br />

<strong>Joint</strong> <strong>Planning</strong> <strong>and</strong> Development Office<br />

35

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