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compelled to miss 30 percent of their missions due to
weather. With the new procedures, only about 11 percent of missions are missed due to weather.
The success of these operations can be attributed in large
part to the collaborative efforts between the helicopter
industry and the FAA. There are currently 289 special
use helicopter procedures, with more being added. There
are also 37 public use helicopter approaches. Of these,
18 are to runways and 19 are to heliports or points-inspace (PinS).
REDUCED VERTICAL SEPARATION MINIMUMS
The U.S. domestic reduced vertical separation minimums (DRVSM) program has reduced the vertical
separation from the traditional 2,000-foot minimum
to a 1,000-foot minimum above FL 290, which allows
aircraft to fly a more optimal profile, thereby saving
fuel while increasing airspace capacity. The FAA has
implemented DRVSM between FL 290 and FL 410
(inclusive) in the airspace of the contiguous 48 states,
Alaska, and in Gulf of Mexico airspace where the FAA
provides air traffic services. DRVSM is expected to
result in fuel savings for the airlines of as much as $5
billion by 2016. Full DRVSM adds six additional usable
altitudes above FL 290 to those available using the former
vertical separation minimums. DRVSM users experience
increased benefits nationwide, similar to those already
achieved in oceanic areas where RVSM is operational. In
domestic airspace, however, operational differences create unique challenges. Domestic U.S. airspace contains a
wider variety of aircraft types, higher-density traffic, and
an increased percentage of climbing and descending traffic. This, in conjunction with an intricate route structure
with numerous major crossing points, creates a more
demanding environment for the implementation of
DRVSM than that experienced in applying RVSM on
international oceanic routes. As more flights increase
demands on our finite domestic airspace, DRVSM helps
to reduce fuel burn and departure delays and increases
flight level availability, airspace capacity, and controller
flexibility.
FAA RADAR SYSTEMS
The FAA operates two basic radar systems; airport
surveillance radar (ASR) and air route surveillance
radar (ARSR). Both of these surveillance systems use
primary and secondary radar returns, as well as
sophisticated computers and software programs
designed to give the controller additional information,
such as aircraft speed and altitude.
AIRPORT SURVEILLANCE RADAR
The direction and coordination of IFR traffic within
specific terminal areas is delegated to airport surveillance radar (ASR) facilities. Approach and departure
control manage traffic at airports with ASR. This radar
system is designed to provide relatively short-range
coverage in the airport vicinity and to serve as an expeditious means of handling terminal area traffic. The
ASR also can be used as an instrument approach aid.
Terminal radar approach control facilities (TRACONs)
provide radar and nonradar services at major airports.
The primary responsibility of each TRACON is to
ensure safe separation of aircraft transitioning from
departure to cruise flight or from cruise to a landing
approach.
Most ASR facilities throughout the country use a form
of automated radar terminal system (ARTS). This system has several different configurations that depend on
the computer equipment and software programs used.
Usually the busiest terminals in the country have the
most sophisticated computers and programs. The type of
1-17
system installed is designated by a suffix of numbers
and letters. For example, an ARTS-IIIA installation can
detect, track, and predict primary, as well as secondary,
radar returns. [Figure 1-13]
On a controller’s radar screen, ARTS equipment automatically provides a continuous display of an aircraft’s
position, altitude, groundspeed, and other pertinent
information. This information is updated continuously
as the aircraft progresses through the terminal area. To
gain maximum benefit from the system, each aircraft in
the area must be equipped with a Mode C altitude encoding transponder, although this is not an operational
requirement. Direct altitude readouts eliminate the need
for time consuming verbal communication between controllers and pilots to verify altitude. This helps to
increase the number of aircraft that may be handled by
one controller at a given time.
The FAA has begun replacing the ARTS systems with
newer equipment in some areas. The new system is
called STARS, for Standard Terminal Automation
Replacement System. STARS is discussed in more
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Instrument Procedures Handbook (IPH)仪表程序手册上(25)
