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tactical altitude assignment program consists of published routes from hubs to airports 200 to 400 NM away.
Based on results of evaluation, it is not expected to be
implemented nationally, although it may remain available in local areas.
6-6
Beyond using existing facilities and procedures more
effectively, capacity can often be increased by making
relatively minor changes in air traffic procedures. For
example, in some instances, departure and arrival patterns have remained unchanged from when there was
very little air traffic, and congestion results when today’s
traffic tries to use them. Likewise, arrival and departure
procedures may overlap, either because they were based
on lower volumes and staffing or because they are based
on ground-based navigation. The interdependence of
arrival and departure routes tends to limit throughput in
both directions.
Separating departures from incoming traffic can simplify
the work of controllers, reduce vectoring, and make more
efficient use of terminal airspace. In the four corner post
configuration, four NAVAIDs form the four corners of
the TRACON area, roughly 60 NM from the primary airport. All arrivals to the area fly over one of these “corner
posts” (also called arrival meters or feeder fixes). The
outbound departure streams are spaced between the
arrival streams. [Figure 6-6]
As more and more aircraft are equipped for RNAV,
new arrival and departure routes are being created that
do not depend on very high frequency omni-directional range (VOR) airways or ground-based
NAVAIDs. Shifting traffic to new RNAV routes eases
congestion on existing airways. There are already several new RNAV routes in use and many more are being
developed.
SEPARATION STANDARDS
Current regulations permit a 3 NM separation within 40
NM of a single radar sensor. The FAA is looking at
ways to increase the use of the 3 NM separation standard to improve efficiency and maximize the volume
of traffic that can be safely moved into busy terminal
areas. The methods involve increasing the size of terminal areas to include more en route airspace,
redesigning airspace to encompass multiple airports
within a single ATC facility, and consolidating certain
TRACON facilities. This will involve major changes
on the ground for ATC facilities, and changes in
charts and procedures for pilots.
Figure 6-6. Four Corner Post Configuration.
6-7
As gaps are filled in arrival and departure streams and the
3 NM separation standard is applied more extensively,
traffic advisories from the traffic alert and collision avoidance system (TCAS) are bound to increase. While newer
software enhances functionality, provides more timely
resolution advisories, and eliminates many nuisance
alerts, data link technology based on GPS position information may offer even better results.
MAINTAINING RUNWAY USE
IN REDUCED VISIBILITY
Although traffic in congested airspace typically operates
under instrument flight rules (IFR), adverse weather and
actual instrument meteorological conditions (IMC) can
drastically reduce system capacity. Many parallel runways cannot be used simultaneously in IMC because of
the time delay and limited accuracy of terminal area
radar, and the runways are spaced closer than the minimum allowable distance for wake vortex separation.
LAAS AND WAAS IMPLEMENTATION
The wide area augmentation system (WAAS) became
available at most locations in 2003. Additional ground
reference stations are expected to become operational
in Canada, Mexico, and Alaska by 2008, providing
more complete WAAS coverage for the continental
United States. The local area augmentation system
(LAAS) provides even greater accuracy and may be
certified for use in precision approaches at some locations beginning in 2007.
Another benefit of LAAS and WAAS is that better
position information can be sent to controllers and
other aircraft. Automatic dependant surveillancebroadcast (ADS-B) uses GPS to provide much more
accurate location information than radar and
transponder systems. This position information is
broadcast to other ADS-equipped aircraft (as well as
ground facilities), providing pilots and controllers
with a more accurate real-time picture of traffic.
For full safety and effectiveness, every aircraft under
the control of ATC will need ADS-B. Until that occurs,
controllers must deal with a mix of ADS-B and
transponder-equipped aircraft. Equipment is already
available that can fuse the information from both
sources and show it on the same display. Traffic information service-broadcast (TIS-B) does just that.
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Instrument Procedures Handbook (IPH)仪表程序手册上(147)
