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occurs, dropped to 10 per year.
SYSTEM CAPACITY
On the user side, there are more than 740,000 active
pilots operating over 319,000 commercial, regional,
general aviation, and military aircraft. This results in
more than 49,500 flights per day. Figure 1-6 depicts over
5,000 aircraft operating at the same time in the U.S.
shown on this Air Traffic Control System Command
Center (ATCSCC) screen.
TAKEOFFS AND LANDINGS
According to the FAA Administrator’s Fact Book for
March 2005, there were 46,873,000 operations at airports with FAA control towers, an average of more than
128,000 aircraft operations per day. These figures do not
include the tens of millions of operations at airports that
do not have a control tower. User demands on the NAS
are quickly exceeding the ability of current resources to
fulfill them. Delays in the NAS for 2004 were slightly
higher than in 2000, with a total of 455,786 delays of at
least 15 minutes in 2004, compared to 450,289 in 2000.
These illustrations of the increasing demands on the
NAS indicate that current FAA modernization efforts
are well justified. Nothing short of the integrated, systematic, cooperative, and comprehensive approach
spelled out by the OEP can bring the NAS to the safety
and efficiency standards that the flying public demands.
AIR TRAFFIC CONTROL
SYSTEM COMMAND CENTER
The task of managing the flow of air traffic within the
NAS is assigned to the Air Traffic Control System
1-7
Command Center (ATCSCC). Headquartered in
Herndon, Virginia, the ATCSCC has been operational
since 1994 and is located in one of the largest and
most sophisticated facilities of its kind. The ATCSCC
regulates air traffic at a national level when weather,
equipment, runway closures, or other conditions place
stress on the NAS. In these instances, traffic management specialists at the ATCSCC take action to modify
traffic demands in order to remain within system capacity.
They accomplish this in cooperation with:
• Airline personnel.
• Traffic management specialists at affected facilities.
• Air traffic controllers at affected facilities.
Efforts of the ATCSCC help minimize delays and congestion and maximize the overall use of the NAS,
thereby ensuring safe and efficient air travel within the
U.S. For example, if severe weather, military operations,
runway closures, special events, or other factors affect
air traffic for a particular region or airport, the ATCSCC
mobilizes its resources and various agency personnel to
analyze, coordinate, and reroute (if necessary) traffic to
foster maximum efficiency and utilization of the NAS.
The ATCSCC directs the operation of the traffic management (TM) system to provide a safe, orderly, and
expeditious flow of traffic while minimizing delays.
TM is apportioned into traffic management units
(TMUs), which monitor and balance traffic flows
within their areas of responsibility in accordance
with TM directives. TMUs help to ensure system
efficiency and effectiveness without compromising
safety, by providing the ATCSCC with advance
notice of planned outages and runway closures that
will impact the air traffic system, such as NAVAID
and radar shutdowns, runway closures, equipment
and computer malfunctions, and procedural changes.
[Figure 1-7 on page 1-8]
HOW THE SYSTEM COMPONENTS
WORK TOGETHER
The NAS comprises the common network of U.S. airspace, air navigation facilities, equipment, services,
airports and landing areas, aeronautical charts, information and services, rules and regulations, procedures,
technical information, manpower, and material.
Included are system components shared jointly with
the military. The underlying demand for air commerce
is people’s desire to travel for business and pleasure
and to ship cargo by air. This demand grows with the
economy independent of the capacity or performance
of the NAS. As the economy grows, more and more
people want to fly, whether the system can handle it or
Figure 1-6. Approximately 5,000 Aircraft in ATC System at One Time.
1-8
not. Realized demand refers to flight plans filed by the
airlines and other airspace users to access the system.
It is moderated by the airline’s understanding of the
number of flights that can be accommodated without
encountering unacceptable delay, and is limited by
the capacity for the system.
USERS
Despite a drop in air traffic after the September 11 terrorist attacks, air travel returned to 2000 levels within
three years and exceeded them in 2004. Industry forecasts predict growth in airline passenger traffic of
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Instrument Procedures Handbook (IPH)仪表程序手册上(17)
