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Today¡¯s National Airspace System (NAS) consists of a
complex collection of facilities, systems, equipment,
procedures, and airports operated by thousands of people to provide a safe and efficient flying environment.
The NAS includes:
• More than 690 air traffic control (ATC) facilities
with associated systems and equipment to provide
radar and communication service.
• Volumes of procedural and safety information necessary for users to operate in the system and for
Federal Aviation Administration (FAA) employees
to effectively provide essential services.
• More than 19,800 airports capable of accommodating an array of aircraft operations, many of
which support instrument flight rules (IFR) departures and arrivals.
• Approximately 11,120 air navigation facilities.
• Approximately 45,800 FAA employees who provide air traffic control, flight service, security,
field maintenance, certification, systems acquisitions, and a variety of other services.
• Approximately 13,000 instrument flight procedures as of September 2005, including 1,159
instrument landing system (ILS), 121 ILS
Category (CAT) II, 87 ILS CAT III, 7 ILS with
precision runway monitoring (PRM), 3 microwave
landing system (MLS), 1,261 nondirectional beacon (NDB), 2,638 VHF omnidirectional range
(VOR), and 3,530 area navigation (RNAV), 30
localizer type directional aid (LDA), 1,337 localizer (LOC), 17 simplified directional facility
(SDF), 607 standard instrument departure (SID),
and 356 standard terminal arrival (STAR).
• Approximately 48,200,000 instrument operations
logged by FAA towers annually, of which 30 percent are air carrier, 27 percent air taxi, 37 percent
general aviation, and 6 percent military.
America¡¯s aviation industry is projecting continued
increases in business, recreation, and personal travel.
The FAA expects airlines in the United States (U.S.) to
carry about 45 percent more passengers by the year 2015
than they do today. [Figure 1-1]
Figure 1-1. IFR Operations in the NAS.
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BRIEF HISTORY OF THE
NATIONAL AIRSPACE SYSTEM
About two decades after the introduction of powered
flight, aviation industry leaders believed that the airplane
would not reach its full commercial potential without federal action to improve and maintain safety standards. In
response to their concerns, the U.S. Congress passed the
Air Commerce Act of May 20, 1926, marking the onset of
the government¡¯s hand in regulating civil aviation. The
act charged the Secretary of Commerce with fostering air
commerce, issuing and enforcing air traffic rules, licensing pilots, certifying aircraft, establishing airways, and
operating and maintaining aids to air navigation. As commercial flying increased, the Bureau of Air Commerce¡ª
a division of the Department of Commerce¡ªencouraged
a group of airlines to establish the first three centers for
providing ATC along the airways. In 1936, the bureau
took over the centers and began to expand the ATC system. [Figure 1-2] The pioneer air traffic controllers used
maps, blackboards, and mental calculations to ensure
the safe separation of aircraft traveling along designated
routes between cities.
On the eve of America¡¯s entry into World War II, the
Civil Aeronautics Administration (CAA)¡ªcharged
with the responsibility for ATC, airman and aircraft
certification, safety enforcement, and airway development¡ªexpanded its role to cover takeoff and landing
operations at airports. Later, the addition of radar
helped controllers to keep abreast of the postwar boom
in commercial air transportation.
Following World War II, air travel increased, but with
the industry's growth came new problems. In 1956 a
midair collision over the Grand Canyon killed 128 people. The skies were getting too crowded for the existing
systems of aircraft separation, and with the introduction
of jet airliners in 1958 Congress responded by passing
the Federal Aviation Act of 1958, which transferred
CAA functions to the FAA (then the Federal Aviation
Agency). The act entrusted safety rulemaking to the
FAA, which also held the sole responsibility for developing and maintaining a common civil-military system
of air navigation and air traffic control. In 1967, the new
Department of Transportation (DOT) combined major
federal transportation responsibilities, including the
FAA (now the Federal Aviation Administration) and a
new National Transportation Safety Board (NTSB).
By the mid-1970s, the FAA had achieved a semi-automated ATC system based on
a marriage of radar and
computer technology. By
automating certain routine
tasks, the system allowed
controllers to concentrate
more efficiently on the task
of providing aircraft separation. Data appearing directly
on the controllers¡¯ scopes
provided the identity, altitude, and groundspeed of
aircraft carrying radar
beacons. Despite its effectiveness, this system required
continuous enhancement to
keep pace with the increased
air traffic of the late 1970s,
due in part to the competitive
environment created by airline deregulation.
To meet the challenge of
traffic growth, the FAA
unveiled the NAS Plan in
January 1982. The new plan
called for more advanced
systems for en route and terminal ATC, modernized
flight service stations, and
improvements in ground-to-air surveillance and communication. Continued ATC modernization under the
NAS Plan included such steps as the implementation of
Host Computer Systems (completed in 1988) that were
able to accommodate new programs needed for the
future. [Figure 1-3]
1935
1946
1970-2000
Figure 1-2. ATC System Expansion.
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In February 1991, the FAA replaced the NAS Plan with
the more comprehensive Capital Investment Plan (CIP),
which outlined a program for further enhancement of the
ATC system, including higher levels of automation as
well as new radar, communications, and weather forecasting systems. One of the CIP¡¯s programs currently
underway is the installation and upgrading of airport
surface radars to reduce runway incursions and prevent
accidents on airport runways and taxiways. The FAA is
also placing a high priority on speeding the application of
the GPS satellite technology to civil aeronautics. Another
notable ongoing program is encouraging progress toward
the implementation of Free Flight, a concept aimed at
increasing the efficiency of high-altitude operations.
NATIONAL AIRSPACE SYSTEM PLANS
FAA planners¡¯ efforts to devise a broad strategy to
address capacity issues resulted in the Operational
Evolution Plan (OEP)¡ªthe FAA¡¯s commitment to meet
the air transportation needs of the U.S. for the next ten
years.
To wage a coordinated strategy, OEP executives met with
representatives from the entire aviation community¡ª
including airlines, airports, aircraft manufacturers, service
providers, pilots, controllers, and passengers. They agreed
on four core problem areas:
• Arrival and departure rates.
• En route congestion.
• Airport weather conditions.
• En route severe weather.
The goal of the OEP is to expand
capacity, decrease delays, and
improve efficiency while maintaining safety and security. With
reliance on the strategic support of
the aviation community, the OEP is
limited in scope, and only contains
programs to be accomplished over a
ten-year period. Programs may move
faster, but the OEP sets the minimum
schedule. Considered a living document that matures over time, the OEP
is continually updated as decisions
are made, risks are identified and
mitigated, or new solutions to operational problems are discovered
through research.
An important contributor to FAA plans
is the Performance-Based Operations
Aviation Rulemaking Committee
(PARC). The objectives and scope of
PARC are to provide a forum for the
U.S. aviation community to discuss
and resolve issues, provide direction
for U.S. flight operations criteria, and produce U.S. consensus positions for global harmonization.
The general goal of the committee is to develop a
means to implement improvements in operations that
address safety, capacity, and efficiency objectives,
as tasked, that are consistent with international implementation. This committee provides a forum for the
FAA, other government entities, and affected
members of the aviation community to discuss issues
and to develop resolutions and processes to facilitate
the evolution of safe and efficient operations.
Current efforts associated with NAS modernization
come with the realization that all phases must be integrated. The evolution to an updated NAS must be well
orchestrated and balanced with the resources available.
Current plans for NAS modernization focus on three key
categories:
• Upgrading the infrastructure.
• Providing new safety features.
• Introducing new efficiency-oriented capabilities
into the existing system.
It is crucial that our NAS equipment is protected, as
lost radar, navigation signals, or communications
Figure 1-3. National Airspace
System Plan.
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capabilities can slow the flow of aircraft to a busy city,
which in turn, could cause delays throughout the entire
region, and possibly, the whole country.
The second category for modernization activities
focuses on upgrades concerning safety. Although we
cannot control the weather, it has a big impact on the
NAS. Fog in San Francisco, snow in Denver, thunderstorms in Kansas, wind in Chicago; all of these reduce
the safety and capacity of the NAS. Nevertheless, great
strides are being made in our ability to predict the
weather. Controllers are receiving better information
about winds and storms, and pilots are receiving better
information both before they take off and in flight¡ªall of
which makes flying safer. [Figure 1-4]
Another cornerstone of the FAA¡¯s future is improved navigational information available in the cockpit. The Wide
Area Augmentation System (WAAS) initially became
operational for aviation use on July 10, 2003. It improves
conventional GPS signal accuracy by an order of magnitude, from about 20 meters to 2 meters or less.
Moreover, the local area augmentation system
(LAAS) is being developed to provide even better
accuracy than GPS with WAAS. LAAS will provide
localized service for final approaches in poor weather
conditions at major airports. This additional navigational accuracy will be available in the cockpit and
will be used for other system enhancements. More
information about WAAS and LAAS is contained in
Chapters 5 and 6.
The Automatic Dependent Surveillance (ADS) system, currently being developed by the FAA and several
airlines, enables the aircraft to automatically transmit
its location to various receivers. This broadcast mode,
commonly referred to as ADS-B, is a signal that can
be received by other properly equipped aircraft and
ground based transceivers, which in turn feed the
automation system accurate aircraft position information. This more accurate information will be used to
improve the efficiency of the system¡ªthe third category of modernization goals.
Other key efficiency improvements are found in the
deployment of new tools designed to assist the controller. For example, most commercial aircraft
already have equipment to send their GPS positions
automatically to receiver stations over the ocean. This
key enhancement is necessary for all aircraft operating in oceanic airspace and allows more efficient use
of airspace. Another move is toward improving text
and graphical message exchange, which is the ultimate goal of the Controller Pilot Data Link
Communications (CPDLC) Program.
In the en route domain, the Display System
Replacement (DSR), along with the Host/Oceanic
Computer System Replacement (HOCSR) and
Eunomia projects, are the platforms and infrastructure for the future. These provide new displays to the
controllers, upgrade the computers to accept future
tools, and provide modern surveillance and flight
data processing capabilities. For CPDLC to work
effectively, it must be integrated with the en route
controller¡¯s workstation.
RNAV PLANS
Designing routes and airspace to reduce conflicts
between arrival and departure flows can be as simple as
adding extra routes or as comprehensive as a full redesign
in which multiple airports are jointly optimized. New
strategies are in place for taking advantage of existing
structures to departing aircraft through congested transition airspace. In other cases, RNAV procedures are used
to develop new routes that reduce flow complexity by
permitting aircraft to fly optimum routes with minimal
controller intervention. These new routes spread the flow
across the terminal and transition airspace so aircraft can
be separated with optimal lateral distances and altitudes in
and around the terminal area. In some cases, the addition
Figure 1-4. Modernization Activities Provide Improved Weather Information.
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of new routes alone is not sufficient, and redesign of existing routes and flows are required. Benefits are multiplied
when airspace surrounding more than one airport (e.g., in
a metropolitan area) can be jointly optimized.
SYSTEM SAFETY
Although hoping to decrease delays, improve system
capacity, and modernize facilities, the ultimate goal of the
NAS Plan is to improve system safety. If statistics are any
indication, the beneficial effect of the implementation of
the plan may already be underway as aviation safety
seems to have increased in recent years. The FAA has
made particular emphasis to not only reduce the number
of accidents in general, but also to make strides in curtailing controlled flight into terrain (CFIT) and runway
incursions as well as continue approach and landing
accident reduction (ALAR).
The term CFIT defines an accident in which a fully
qualified and certificated crew flies a properly working
airplane into the ground, water, or obstacles with no
apparent awareness by the pilots. A runway incursion is
defined as any occurrence at an airport involving an aircraft, vehicle, person, or object on the ground that creates
a collision hazard or results in a loss of separation with an
aircraft taking off, attempting to take off, landing, or
attempting to land. The term ALAR applies to an accident
that occurs during a visual approach, during an instrument
approach after passing the initial approach fix (IAF), or
during the landing maneuver. This term also applies to
accidents occurring when circling or when beginning a
missed approach procedure.
ACCIDENT RATES
The NTSB released airline accident statistics for 2004
that showed a decline from the previous year. Twentynine accidents on large U.S. air carriers were recorded in
2004, which is a decrease from the 54 accidents in 2003.
Accident rates for both general aviation airplanes and helicopters also decreased in 2004. General aviation airplane
accidents dropped from 1,742 to 1,595, while helicopter
accidents declined from 213 to 176. The number of accidents for commuter air services went up somewhat, from
2 accidents in 2003 to 5 in 2004. Air taxi operations went
from 76 accidents in 2003 to 68 accidents in 2004. These
numbers do not tell the whole story. Because the number
of flights and flight hours increased in 2004, accident
rates per 100,000 departures or per 100,000 flight hours
will likely be even lower.
Among the top priorities for accident prevention are
CFIT and ALAR. Pilots can decrease exposure to a
CFIT accident by identifying risk factors and remedies
prior to flight. [Figure 1-5] Additional actions on the
CFIT reduction front include equipping aircraft with
state-of-the art terrain awareness and warning systems
(TAWS), sometimes referred to as enhanced ground
proximity warning systems (EGPWS). This measure
alone is expected to reduce CFIT accidents by at least 90
Destination Risk Factors
Runway Lighting
Type of Operation
Airport Location
ATC Capabilities and Limitations
Controller/Pilot Common Language
Weather/Daylight Conditions
Approach Specifications
Departure Procedures
Crew Configuration
Specific Procedures Written and Implemented
Hazard Awareness Training for Crew
Aircraft Equipment
Risk Reduction Factors
Corporate/Company Management Awareness
Figure 1-5. CFIT Reduction.
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percent. With very few exceptions, all U.S. turbine powered airplanes with more than six passenger seats were
required to be equipped with TAWS by March 29, 2005.
Added training for aircrews and controllers is part of the
campaign to safeguard against CFIT, as well as making
greater use of approaches with vertical guidance that use
a constant angle descent path to the runway. This measure offers nearly a 70 percent potential reduction.
Another CFIT action plan involves a check of groundbased radars to ensure that the minimum safe altitude
warning (MSAW) feature functions correctly.
Like CFIT, the ALAR campaign features a menu of
actions, three of which involve crew training, altitude
awareness policies checklists, and smart alerting technology. These three alone offer a potential 20 to 25
percent reduction in approach and landing accidents.
Officials representing Safer Skies¡ªa ten-year collaborative effort between the FAA and the airline
industry¡ªbelieve that the combination of CFIT and
ALAR interventions will offer more than a 45 percent reduction in accidents.
RUNWAY INCURSION STATISTICS
While it is difficult to eliminate runway incursions,
technology offers the means for both controllers and
flight crews to create situational awareness of runway
incursions in sufficient time to prevent accidents.
Consequently, the FAA is taking actions that will
identify and implement technology solutions, in conjunction with training and procedural evaluation and
changes, to reduce runway accidents. Recently established programs that address runway incursions center
on identifying the potential severity of an incursion and
reducing the likelihood of incursions through training,
technology, communications, procedures, airport
signs/marking/lighting, data analysis, and developing
local solutions. The FAA¡¯s initiatives include:
• Promoting aviation community participation in
runway safety activities and solutions.
• Appointing nine regional Runway Safety Program
Managers.
• Providing training, education, and awareness for
pilots, controllers, and vehicle operators.
• Publishing an advisory circular for airport surface
operations.
• Increasing the visibility of runway hold line markings.
• Reviewing pilot-controller phraseology.
• Providing foreign air carrier pilot training, education, and awareness.
• Requiring all pilot checks, certifications, and flight
reviews to incorporate performance evaluations of
ground operations and test for knowledge.
• Increasing runway incursion action team site visits.
• Deploying high-technology operational systems
such as the Airport Surface Detection Equipment3 (ASDE-3) and Airport Surface Detection
Equipment-X (ASDE-X).
• Evaluating cockpit display avionics to provide
direct warning capability to flight crew(s) of both
large and small aircraft operators.
Statistics compiled for 2004 show that there were 310
runway incursions, down from 332 in 2003. The number
of Category A and Category B runway incursions, in
which there is significant potential for collision,
declined steadily from 2000 through 2003. There were
less than half as many such events in 2003 as in 2000.
The number of Category A incursions, in which separation decreases and participants take extreme action to
narrowly avoid a collision, or in which a collision
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
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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.
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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
around 4.3 percent per year. Commercial aviation is
expected to exceed one billion passengers by 2015. The
system is nearing the point of saturation, with limited
ability to grow unless major changes are brought about.
Adding to the growth challenge, users of the NAS cover a
wide spectrum in pilot skill and experience, aircraft types,
and air traffic service demands, creating a challenge to the
NAS to provide a variety of services that accommodate all
types of traffic. NAS users range from professional airline,
commuter, and corporate pilots to single-engine piston
pilots, as well as owner-operators of personal jets to military
jet fighter trainees.
AIRLINES
Though commercial air carrier aircraft traditionally
make up less than 5 percent of the civil aviation fleet,
they account for about 30 percent of the instrument
operations flown in civil aviation. Commercial air carriers are the most homogenous category of airspace users,
although there are some differences between U.S. trunk
carriers (major airlines)
and regional airlines
(commuters) in terms
of demand for ATC
services. Generally,
U.S. carriers operate
large, high performance airplanes that
cruise at altitudes
above 18,000 feet.
Conducted exclusively
under IFR, airline
flights follow established schedules and
operate in and out of
larger and betterequipped airports. In
terminal areas, however, they share airspace
and facilities with all
types of traffic and must
compete for airport
access with other users.
Airline pilots are highly
proficient and thoroughly familiar with the rules and procedures under which they must operate.
Some airlines are looking toward the use of larger
aircraft, with the potential to reduce airway and terminal congestion by transporting more people in
fewer aircraft. This is especially valuable at major
hub airports, where the number of operations
exceeds capacity at certain times of day. On the
other hand, the proliferation of larger aircraft also
requires changes to terminals (e.g., double-decker
jetways and better passenger throughput), rethinking
of rescue and fire-fighting strategies, taxiway fillet
changes, and perhaps stronger runways and
taxiways.
Commuter airlines also follow established schedules
and are flown by professional pilots. Commuters
characteristically operate smaller and lower performance aircraft in airspace that must often be shared by
general aviation (GA) aircraft, including visual flight
rules (VFR) traffic. As commuter operations have
grown in volume, they have created extra demands on
the airport and ATC systems. At one end, they use hub
airports along with other commercial carriers, which
contributes to growing congestion at major air traffic
hubs. IFR-equipped and operating under IFR like
other air carriers, commuter aircraft cannot be used to
full advantage unless the airport at the other end of
the flight, typically a small community airport, also is
capable of IFR operation. Thus, the growth of commuter air service has created pressure for additional
SEA
PDX
SFO
SJC
LAX
SAN
LAS
SLC
PHX
DEN
DFW
IAH
MCI
STL
MEM
BNA
IND
ATL
TPA
MCO
FLL
MIA
CLT
RDU
CVG
IAD
DCA
BWI
CLE
DTW
PIT
TEB
EWR
PHL
LGA
JFK
BOS
ORD
MDW
MSP
Figure 1-7. A real-time Airport Status page displayed on the ATCSCC Web site
(www.fly.faa.gov/flyfaa/usmap.jsp) provides general airport condition status. Though not flight
specific, it portrays current general airport trouble spots. Green indicates less than five-minute
delays. Yellow means departures and arrivals are experiencing delays of 16 to 45 minutes. Traffic
destined to orange locations is being delayed at the departure point. Red airports are experiencing taxi or airborne holding delays greater than 45 minutes. Blue indicates closed airports.
1-9
instrument approach procedures and control facilities
at smaller airports. A growing trend among the major
airlines is the proliferation of regional jets (RJs). RJs
are replacing turboprop aircraft and they are welcomed by some observers as saviors of high-quality
jet aircraft service to small communities. RJs are
likely to be a regular feature of the airline industry for
a long time because passengers and airlines overwhelmingly prefer RJs to turboprop service. From the
passengers¡¯ perspective, they are far more comfortable; and from the airlines¡¯ point of view, they are
more profitable. Thus, within a few years, most
regional air traffic in the continental U.S. will be by
jet, with turboprops filling a smaller role.
FAA and industry studies have investigated the underlying operational and economic environments of RJs on the
ATC system. They have revealed two distinct trends: (1)
growing airspace and airport congestion is exacerbated by
the rapid growth of RJ traffic, and (2) potential airport
infrastructure limitations may constrain airline business.
The FAA, the Center for Advanced Aviation System
Development (CAASD), major airlines, and others are
working to find mitigating strategies to address airline
congestion. With nearly 2,000 RJs already in use¡ªand
double that expected over the next few years¡ªthe success of these efforts is critical if growth in the regional
airline industry is to be sustained. [Figure 1-8]
CORPORATE AND FRACTIONAL OWNERSHIPS
Though technically considered under the GA umbrella,
the increasing use of sophisticated, IFR-equipped aircraft
by businesses and corporations has created a niche of its
own. By using larger high performance airplanes and
equipping them with the latest avionics, the business
portion of the GA fleet has created demands for ATC
services that more closely resemble commercial operators than the predominately VFR general aviation fleet.
GENERAL AVIATION
The tendency of GA aircraft owners to upgrade the performance and avionics of their aircraft increases the
demand for IFR services and for terminal airspace at airports. In response, the FAA has increased the extent of
controlled airspace and improved ATC facilities at major
airports. The safety of mixing IFR and VFR traffic is a
major concern, but the imposition of measures to separate and control both types of traffic creates more restrictions on airspace use and raises the level of aircraft
equipage and pilot qualification necessary for access.
MILITARY
From an operational point of view, military flight activities comprise a subsystem that must be fully integrated
within NAS. However, military aviation has unique
requirements that often are different from civil aviation
users. The military¡¯s need for designated training areas
and low-level routes located near their bases sometimes
conflicts with civilian users who need to detour around
these areas. In coordinating the development of ATC
systems and services for the armed forces, the FAA is
challenged to achieve a maximum degree of compatibility between civil and military aviation objectives.
ATC FACILITIES
FAA figures show that the NAS includes more than
18,300 airports, 21 ARTCCs, 197 TRACON facilities,
over 460 air traffic control towers (ATCTs), 58 flight
service stations and automated flight service stations
(FSSs/AFSSs), and approximately 4,500 air navigation
facilities. Several thousand pieces of maintainable
equipment including radar, communications switches,
ground-based navigation aids, computer displays, and
radios are used in NAS operations, and NAS components represent billions of dollars in investments by the
government. Additionally, the aviation industry has
invested significantly in ground facilities and avionics
systems designed to use the NAS. Approximately
47,000 FAA employees provide air traffic control, flight
service, security, field maintenance, certification, system acquisition, and other essential services.
Differing levels of ATC facilities vary in their structure and purpose. Traffic management at the national
level is led by the Command Center, which essentially ¡°owns¡± all airspace. Regional Centers, in turn,
sign Letters of Agreement (LOAs) with various
approach control facilities, delegating those facilities
chunks of airspace in which that approach control
facility has jurisdiction. The approach control facilities, in turn, sign LOAs with various towers that are
within that airspace, further delegating airspace and
Figure 1-8. Increasing use of regional jets is expected to have
a significant impact on traffic.
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responsibility. This ambiguity has created difficulties
in communication between the local facilities and the
Command Center. However, a decentralized structure
enables local flexibility and a tailoring of services to
meet the needs of users at the local level. Improved
communications between the Command Center and
local facilities could support enhanced safety and
efficiency while maintaining both centralized and
decentralized aspects to the ATC system.
AIR ROUTE TRAFFIC CONTROL CENTER
A Center¡¯s primary function is to control and separate
air traffic within a designated airspace, which may cover
more than 100,000 square miles, may span several
states, and extends from the base of the underlying controlled airspace up to Flight Level (FL) 600. There are
21 Centers located throughout the U.S., each of which is
divided into sectors. Controllers assigned to these sectors, which range from 50 to over 200 miles wide, guide
aircraft toward their intended destination by way of vectors and/or airway assignment, routing aircraft around
weather and other traffic. Centers employ 300 to 700
controllers, with more than 150 on duty during peak
hours at the busier facilities. A typical flight by a commercial airliner is handled mostly by the Centers.
TERMINAL RADAR APPROACH CONTROL
Terminal Radar Approach Control (TRACON) controllers work in dimly lit radar rooms located within
the control tower complex or in a separate building
located on or near the airport it serves. [Figure 1-9]
Using radarscopes, these controllers typically work
an area of airspace with a 50-mile radius and up to an
altitude of 17,000 feet. This airspace is configured to
provide service to a primary airport, but may include
other airports that are within 50 miles of the radar
service area. Aircraft within this area are provided
vectors to airports, around terrain, and weather, as
well as separation from other aircraft. Controllers in
TRACONs determine the arrival sequence for the control tower¡¯s designated airspace.
CONTROL TOWER
Controllers in this type of facility manage aircraft operations on the ground and within specified airspace
around an airport. The number of controllers in the
tower varies with the size of the airport. Small general
aviation airports typically have three or four controllers, while larger international airports can have up
to fifteen controllers talking to aircraft, processing
flight plans, and coordinating air traffic flow. Tower
controllers manage the ground movement of aircraft
around the airport and ensure appropriate spacing
between aircraft taking off and landing. In addition, it
is the responsibility of the control tower to determine
the landing sequence between aircraft under its control. Tower controllers issue a variety of instructions to
pilots, from how to enter a pattern for landing to how
to depart the airport for their destination.
FLIGHT SERVICE STATIONS
Flight Service Stations (FSSs) and Automated Flight
Service Stations (AFSSs) are air traffic facilities which
provide pilot briefings, en route communications and
VFR search and rescue services, assist lost aircraft and
aircraft in emergency situations, relay ATC clearances,
originate Notices to Airmen, broadcast aviation weather
and NAS information, receive and process IFR flight
plans, and monitor navigational aids (NAVAIDs). In addition, at selected locations, FSSs/AFSSs provide En route
Flight Advisory Service (Flight Watch), take weather
observations, issue airport advisories, and advise Customs
and Immigration of transborder flights.
Pilot Briefers at flight service stations render preflight,
in-flight, and emergency assistance to all pilots on
request. They give information about actual weather
conditions and forecasts for airports and flight paths,
relay air traffic control instructions between controllers
and pilots, assist pilots in emergency situations, and
initiate searches for missing or overdue aircraft.
FSSs/AFSSs provide information to all airspace users,
including the military. In October 2005, operation of
all FSSs/AFSSs, except those in Alaska, was turned
over to the Lockheed Martin Corporation. In the
months after the transition, 38 existing AFSSs are
slated to close, leaving 17 ¡°Legacy¡± stations and 3
¡°Hub¡± stations. Services to pilots are expected to be
equal to or better than prior to the change, and the
contract is expected to save the government about
$2.2 billion over ten years.
FLIGHT PLANS
Prior to flying in controlled airspace under IFR conditions or in Class A airspace, pilots are required to file a
flight plan. IFR (as well as VFR) flight plans provide
air traffic center computers with accurate and precise
routes required for flight data processing (FDP1 ). The
computer knows every route (published and unpub-
1
FDP maintains a model of the route and other details for each aircraft.
Figure 1-9. Terminal Radar Approach Control.
1-11
lished) and NAVAID, most intersections, and all airports, and can only process a flight plan if the proposed
routes and fixes connect properly. Center computers
also recognize preferred routes and know that forecast
or real-time weather may change arrival routes.
Centers and TRACONs now have a computer graphic
that can show every aircraft on a flight plan in the U.S.
as to its flight plan information and present position.
Despite their sophistication, center computers do not
overlap in coverage or information with other Centers,
so that flight requests not honored in one must be
repeated in the next.
RELEASE TIME
ATC uses an IFR release time2 in conjunction with
traffic management procedures to separate departing
aircraft from other traffic. For example, when controlling departures from an airport without a tower, the
controller limits the departure release to one aircraft at
any given time. Once that aircraft is airborne and radar
identified, then the following aircraft may be released
for departure, provided they meet the approved radar
separation (3 miles laterally or 1,000 feet vertically)
when the second aircraft comes airborne. Controllers
must take aircraft performances into account when
releasing successive departures, so that a B-747 HEAVY
aircraft is not released immediately after a departing
Cessna 172. Besides releasing fast aircraft before slow
ones, another technique commonly used for successive
departures is to have the first aircraft turn 30 to 40
degrees from runway heading after departure, and then
have the second aircraft depart on a SID or runway heading. Use of these techniques is common practice when
maximizing airport traffic capacity.
EXPECT DEPARTURE CLEARANCE TIME
Another tool that the FAA is implementing to increase
efficiency is the reduction of the standard expect departure clearance time3 (EDCT) requirement. The FAA has
drafted changes to augment and modify procedures contained in Ground Delay Programs (GDPs). Airlines may
now update their departure times by arranging their
flights¡¯ priorities to meet the controlled time of arrival.
In order to evaluate the effectiveness of the new software and the airline-supplied data, the actual departure
time parameter in relation to the EDCT has been
reduced. This change impacts all flights (commercial
and GA) operating to the nation¡¯s busiest airports.
Instead of the previous 25-minute EDCT window (5
minutes prior and 20 minutes after the EDCT), the new
requirement for GDP implementation is a 10-minute
window, and aircraft are required to depart within 5 minutes before or after their assigned EDCT. Using reduced
EDCT and other measures included in GDPs, ATC aims
at reducing the number of arrival slots issued to accommodate degraded arrival capacity at an airport affected
by weather. The creation of departure or ground delays
is less costly and safer than airborne holding delays in
the airspace at the arrival airport.
MANAGING SAFETY AND CAPACITY
SYSTEM DESIGN
The CAASD is aiding in the evolution towards free flight
with its work in developing new procedures necessary
for changing traffic patterns and aircraft with enhanced
capabilities, and also in identifying traffic flow constraints that can be eliminated. This work supports the
FAA¡¯s Operational Evolution Plan in the near-term.
Rapid changes in technology in the area of navigation
performance, including the change from ground-based
area navigation systems, provide the foundation for aviation¡¯s global evolution. This progress will be marked by
combining all elements of communication, navigation,
and surveillance (CNS) with air traffic management
(ATM) into tomorrow¡¯s CNS/ATM based systems. The
future CNS/ATM operating environment will be based
on navigation defined by geographic waypoints
expressed in latitude and longitude since instrument
procedures and flight routes will not require aircraft to
overfly ground-based navigation aids defining specific
points.
APPLICATION OF AREA NAVIGATION
RNAV airways provide more direct routings than the
current VOR-based airway system, giving pilots easier
access through terminal areas, while avoiding the circuitous routings now common in many busy Class B
areas. RNAV airways are a critical component to the
transition from ground-based navigation systems to GPS
navigation. RNAV routes help maintain the aircraft flow
through busy terminals by segregating arrival or departure traffic away from possibly interfering traffic flows.
Further, RNAV provides the potential for increasing airspace capacity both en route and in the terminal area in
several important ways.
Strategic use of RNAV airways nationwide is reducing
the cost of flying and providing aircraft owners more
benefits from their IFR-certified GPS receivers. Several
scenarios have been identified where RNAV routes provide a substantial benefit to users.
• Controllers are assigning routes that do not require
overflying ground-based NAVAIDs such as VORs.
• The lateral separation between aircraft tracks is
being reduced.
• RNAV routes lower altitude minimums on existing
Victor airways where ground-based NAVAID performance (minimum reception altitude) required
higher minimums.
2
A release time is a departure restriction issued to a pilot by ATC, specifying the earliest and latest time an aircraft may depart.
3
The runway release time assigned to an aircraft in a controlled departure time program and shown on the flight progress strip as an EDCT.
1-12
• RNAV routes may allow continued use of existing
airways where the ground-based NAVAID has
been decommissioned or where the signal is no
longer suitable for en route navigation.
• The route structure can be modified quickly and
easily to meet the changing requirements of the
user community.
• Shorter, simpler routes can be designed to minimize environmental impact.
Dozens of new RNAV routes have been designated, and
new ones are being added continuously. In order to designate RNAV airways, the FAA developed criteria, en
route procedures, procedures for airway flight checks,
and created new charting specifications. Some of the
considerations include:
• Navigation infrastructure (i.e., the ground-based
and space-based navigation positioning systems)
provides adequate coverage for the proposed
route/procedure.
• Navigation coordinate data meets International
Civil Aviation Organization (ICAO) accuracy and
integrity requirements. This means that all of the
coordinates published in the Aeronautical
Information Publication (AIP) and used in the aircraft navigation databases must be referenced to
WGS 84, and the user must have the necessary
assurance that this data has not been corrupted or
inadvertently modified.
• Airborne systems meet airworthiness performance
for use on the RNAV routes and procedures.
• Flight crews have the necessary approval to operate on the RNAV routes and procedures.
In the future, as aircraft achieve higher levels of navigation accuracy and integrity, closely spaced parallel
routes may be introduced, effectively multiplying the
number of available routes between terminal areas.
RNAV can be used in all phases of flight and, when
implemented correctly, results in:
• Improved situational awareness for the pilot.
• Reduced workloads for both controller and pilot.
• Reduced environmental impact from improved
route and procedure designs.
• Reduced fuel consumption from shorter, more
direct routes.
For example, take the situation at Philadelphia
International Airport, located in the middle of some
highly popular north-south traffic lanes carrying New
York and Boston traffic to or from Washington, Atlanta,
and Miami. Philadelphia¡¯s position is right underneath
these flows. Chokepoints resulted from traffic departing
Philadelphia, needing to wait for a ¡°hole¡± in the traffic
above into which they could merge. The CAASD helped
US Airways and Philadelphia airport officials establish a
set of RNAV departure routes that do not interfere with
the prevailing established traffic. Traffic heading north
or south can join the established flows at a point further
ahead when higher altitudes and speeds have been
attained. Aircraft properly equipped to execute RNAV
procedural routes can exit the terminal area faster ¡ª a
powerful inducement for aircraft operators to upgrade
their navigation equipment.
Another example of an RNAV departure is the PRYME
TWO DEPARTURE from Washington Dulles
International. Notice in Figure 1-10 the RNAV waypoints not associated with VORs help free up the flow of
IFR traffic out of the airport by not funneling them to
one point through a common NAVAID.
RNAV IFR TERMINAL TRANSITION ROUTES
The FAA is moving forward with an initiative to chart
RNAV terminal transition routes through busy airspace.
In 2001, some specific RNAV routes were implemented
through Charlotte¡¯s Class B airspace, allowing RNAVcapable aircraft to cross through the airspace instead of
Figure 1-10. RNAV Departure Routes.
1-13
using costly and time-consuming routing around the
Class B area. The original RNAV terminal transition
routes have evolved into RNAV IFR terminal transition
routes, or simply RITTRs.
Beginning in March 2005, with the publication of the
notice of proposed rulemaking (NPRM) for the
Charlotte, North Carolina, RITTRs, the FAA advanced
the process of establishing and charting the first
RITTRs on IFR en route low altitude charts. The five
new RITTRs through Charlotte's Class B airspace took
effect on September 1, 2005, making them available
for pilots to file on their IFR flight plans. Additional
RITTRs are planned for Cincinnati, Ohio, and
Jacksonville, Florida.
The RITTRs allow IFR overflights through the Class
B airspace for RNAV-capable aircraft. Without the
RITTRS, these aircraft would be routinely routed
around the Class B by as much as 50 miles.
REQUIRED NAVIGATION PERFORMANCE
The continuing growth of aviation places increasing
demands on airspace capacity and emphasizes the need
for the best use of the available airspace. These factors,
along with the accuracy of modern aviation navigation
systems and the requirement for increased operational
efficiency in terms of direct routings and track-keeping
accuracy, have resulted in the concept of required navigation performance¡ªa statement of the navigation
performance accuracy necessary for operation within a
defined airspace. Required Navigation Performance
(RNP) is a statement of the navigation performance
necessary for operation within a defined airspace. RNP
includes both performance and functional requirements, and is indicated by the RNP value. The RNP
value designates the lateral performance requirement
associated with a procedure. [Figure 1-11]
RNP includes a navigation specification including
requirements for on-board performance monitoring and
alerting. These functional and performance standards
allow the flight paths of participating aircraft to be both
predictable and repeatable to the declared levels of accuracy. More information on RNP is contained in subsequent chapters.
TERMINAL FINAL APPROACH
EN ROUTE
2.0 NM
1.0 NM
0.3 NM
2.0 NM
1.0 NM
0.3 NM
RNP 1.0 RNP 2.0 RNP 1.0 RNP 0.3
Departure Enroute Arrival Approach
Figure 1-11. Required Navigation Performance.
1-14
The term RNP is also applied as a descriptor for airspace, routes, and procedures ¡ª including departures,
arrivals, and instrument approach procedures (IAPs).
The descriptor can apply to a unique approach procedure
or to a large region of airspace. RNP applies to navigation
performance within a designated airspace, and includes
the capability of both the available infrastructure (navigation aids) and the aircraft. Washington National Airport
(KDCA) introduced the first RNP approach procedure in
September 2005. An example of an RNP approach chart
is shown in Figure 1-12.
Figure 1-12. RNP Approach Chart.
1-15
The RNP value designates the lateral performance
requirement associated with a procedure. The required
performance is obtained through a combination of aircraft capability and the level of service provided by the
corresponding navigation infrastructure. From a broad
perspective:
Aircraft Capability + Level of Service = Access
In this context, aircraft capability refers to the airworthiness certification and operational approval elements
(including avionics, maintenance, database, human
factors, pilot procedures, training, and other issues).
The level of service element refers to the NAS infrastructure, including published routes, signal-in-space
performance and availability, and air traffic management. When considered collectively, these elements
result in providing access. Access provides the desired
benefit (airspace, procedures, routes of flight, etc.).
A key feature of RNP is the concept of on-board monitoring and alerting. This means the navigation equipment is accurate enough to keep the aircraft in a specific
volume of airspace, which moves along with the aircraft.
The aircraft is expected to remain within this block of
airspace for at least 95 percent of the flight time.
Additional airspace outside the 95 percent area is provided for continuity and integrity, so that the combined
areas ensure aircraft containment 99.9 percent of the
time. RNP levels are actual distances from the centerline
of the flight path, which must be maintained for aircraft
and obstacle separation. Although additional FAA-recognized RNP levels may be used for specific operations,
the United States currently supports three standard RNP
levels:
• RNP 0.3 ¨C Approach
• RNP 1.0 ¨C Terminal
• RNP 2.0 ¨C Terminal and En Route
RNP 0.3 represents a distance of 0.3 nautical miles
(NM) either side of a specified flight path centerline.
The specific performance required on the final approach
segment of an instrument approach is an example of this
RNP level.
For international operations, the FAA and ICAO member states have led initiatives to apply RNP concepts to
oceanic routes. Here are the ICAO RNP levels supported
for international operations:
• RNP-1 ¨C European Precision RNAV (P-RNAV)
• RNP-4 ¨C Projected for oceanic/remote areas where
30 NM horizontal separation is applied
• RNP-5 ¨C European Basic RNAV (B-RNAV)
• RNP-10 ¨C Oceanic/remote areas where 50 NM lateral separation is applied
NOTE: Specific operational and equipment performance
requirements apply for P-RNAV and B-RNAV.
GLOBAL POSITIONING SYSTEM
The FAA¡¯s implementation activities of the Global
Positioning System (GPS) are dedicated to the adaptation of the NAS infrastructure to accept satellite navigation (SATNAV) technology through the management
and coordination of a variety of overlapping NAS
implementation projects. These projects fall under the
project areas listed below and represent different elements of the NAS infrastructure:
• Avionics Development − includes engineering
support and guidance in the development of
current and future GPS avionics minimum
operational performance standards (MOPS), as
well as FAA Technical Standard Orders (TSOs)
and establishes certification standards for
avionics installations.
• Flight Standards − includes activities related to
instrument procedure criteria research, design,
testing, and standards publication. The shift from
ground-based to space-based navigation sources
has markedly shifted the paradigms used in
obstacle clearance determination and standards
development. New GPS-based Terminal
Procedures (TERPS) manuals are in use today as
a result of this effort.
• Air Traffic − includes initiatives related to the
development of GPS routes, phraseology, procedures, controller GPS training and GPS outage
simulations studies. GPS-based routes, developed along the East Coast to help congestion in
the Northeast Corridor, direct GPS-based
Caribbean routes, and expansion of RNAV
activities are all results of SATNAV sponsored
implementation projects.
• Procedure Development − includes the provision
of instrument procedure development and flight
inspection of GPS-based routes and instrument
procedures. Today over 3,500 GPS-based IAPs
have been developed.
• Interference Identification and Mitigation −
includes the development and fielding of airborne,
ground, and portable interference detection systems. These efforts are ongoing and critical to
ensuring the safe use of GPS in the NAS.
1-16
To use GPS, WAAS, and/or LAAS in the NAS, equipment suitable for aviation use (such as a GPS receiver,
WAAS receiver, LAAS receiver, or multi-modal
receiver) must be designed, developed, and certified for
use. To ensure standardization and safety of this equipment, the FAA plays a key role in the development and
works closely with industry in this process. The avionics
development process results in safe, standardized SAT-
NAV avionics, developed in concurrence with industry.
Due to the growing popularity of SATNAV and potential
new aviation applications, there are several types of
GPS-based receivers on the market, but only those that
pass through this certification process can be used as
approved navigation equipment under IFR conditions.
Detailed information on GPS approach procedures is
provided in Chapter 5¨CApproach.
GPS-BASED HELICOPTER OPERATIONS
The synergy between industry and the FAA created during the development of the Gulf of Mexico GPS grid
system and approaches is an excellent example of what
can be accomplished to establish the future of helicopter
IFR SATNAV. The Helicopter Safety Advisory Council
(HSAC), National Air Traffic Controllers Association
(NATCA), helicopter operators, and FAA Flight
Standards Divisions all worked together to develop this
infrastructure. The system provides both the operational
and cost-saving features of flying direct to a destination
when offshore weather conditions deteriorate below
VFR and an instant and accurate aircraft location capability that is invaluable for rescue operations.
The expansion of helicopter IFR service for emergency
medical services (EMS) is another success story. The
FAA worked with EMS operators to develop helicopter
GPS nonprecision instrument approach procedures and
en route criteria. As a result of this collaborative effort,
EMS operators have been provided with hundreds of
EMS helicopter procedures to medical facilities. Before
the GPS IFR network, EMS helicopter pilots had been
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
detail later in this chapter.
AIR ROUTE SURVEILLANCE RADAR
The long-range radar equipment used in controlled airspace to manage traffic is the air route surveillance radar
(ARSR) system. There are approximately 100 ARSR
facilities to relay traffic information to radar controllers
throughout the country. Some of these facilities can
detect only transponder-equipped aircraft and are
referred to as beacon-only sites. Each air route surveillance radar site can monitor aircraft flying within a
200-mile radius of the antenna, although some stations
can monitor aircraft as far away as 600
miles through the use of remote sites.
The direction and coordination of IFR traffic in the U.S. is assigned to air route traffic
control centers (ARTCCs). These centers
are the authority for issuing IFR clearances
and managing IFR traffic; however, they
also provide services to VFR pilots.
Workload permitting, controllers will provide traffic advisories and course guidance,
or vectors, if requested.
PRECISION RUNWAY MONITORING
Precision runway monitor (PRM) is a high-update-rate
radar surveillance system that is being introduced at
selected capacity-constrained U.S. airports. Certified to
provide simultaneous independent approaches to closely
spaced parallel runways, PRM has been operational at
Minneapolis since 1997. ILS/PRM approaches are conducted at Philadelphia International Airport.
Simultaneous Offset Instrument Approach (SOIA)/PRM
operations are conducted at San Francisco International
and Cleveland Hopkins International Airports. Since the
number of PRM sites is increasing, the likelihood is
increasing that you may soon be operating at an airport
conducting closely spaced parallel approaches using
PRM. Furthermore, St. Louis Lambert International
Airport began SOIA/PRM operations in 2005, and
Atlanta Hartsfield International Airport will begin PRM
operations in 2006. PRM enables ATC to improve the
airport arrival rate on IFR days to one that more closely
approximates VFR days, which means fewer flight cancellations, less holding, and decreased diversions.
PRM not only maintains the current level of safety, but
also increases it by offering air traffic controllers a
much more accurate picture of the aircraft¡¯s location
on final approach. Whereas current airport surveillance
radar used in a busy terminal area provides an update
to the controller every 4.8 seconds, PRM updates every
second, giving the controller significantly more time to
react to potential aircraft separation problems. The
controller also sees target trails that provide very accurate trend information. With PRM, it is immediately
Figure 1-13. ARTS-III Radar Display.
apparent when an aircraft starts to drift off the runway
centerline and toward the non-transgression zone.
PRM also predicts the aircraft track and provides aural
and visual alarms when an aircraft is within 10 seconds
of penetrating the non-transgression zone. The additional controller staffing that comes along with PRM is
another major safety improvement. During PRM sessions, there is a separate controller monitoring each
final approach course and a coordinator managing the
overall situation.
PRM is an especially attractive technical solution for the
airlines and business aircraft because it does not require
any additional aircraft equipment, only special training
and qualifications. However, all aircraft in the approach
streams must be qualified to participate in PRM or the
benefits are quickly lost and controller workload
increases significantly. The delay-reduction benefits of
PRM can only be fully realized if everyone participates.
Operators that choose not to participate in PRM operations when arriving at an airport where PRM operations
are underway can expect to be held until they can be
accommodated without disrupting the PRM arrival
streams.
EQUIPMENT AND AVIONICS
By virtue of distance and time savings, minimizing
traffic congestion, and increasing airport and airway
capacity, the implementation of RNAV routes, direct
routing, RSVM, PRM, and other technological innovations would be advantageous for the current NAS.
Some key components that are integral to the future
development and improvement of the NAS are
described below. However, equipment upgrades require
capital outlays, which take time to penetrate the existing fleet of aircraft and ATC facilities. In the upcoming
years while the equipment upgrade is taking place, ATC
will have to continue to accommodate the wide range of
avionics used by pilots in the nation¡¯s fleet.
ATC RADAR EQUIPMENT
All ARTCC radars in the conterminous U.S., as well as
most airport surveillance radars, have the capability to
interrogate Mode C and display altitude information to
the controller. However, there are a small number of airport surveillance radars that are still two-dimensional
(range and azimuth only); consequently, altitude information must be obtained from the pilot.
At some locations within the ATC environment,
secondary only (no primary radar) gap filler radar
systems are used to give lower altitude radar coverage between two larger radar systems, each of
which provides both primary and secondary radar
coverage. In the geographical areas serviced by secondary radar only, aircraft without transponders cannot
be provided with radar service. Additionally, transponder-equipped aircraft cannot be provided with radar
advisories concerning primary targets and weather.
An integral part of the air traffic control radar beacon system (ATCRBS) ground equipment is the decoder, which
enables the controller to assign discrete transponder
codes to each aircraft under his/her control. Assignments
are made by the ARTCC computer on the basis of the
National Beacon Code Allocation Plan (NBCAP). There
are 4,096 aircraft transponder codes that can be assigned.
An aircraft must be equipped with Civilian Mode A (or
Military Mode 3) capabilities to be assigned a transponder code. Another function of the decoder is that it is also
designed to receive Mode C altitude information from
an aircraft so equipped. This system converts aircraft
altitude in 100-foot increments to coded digital information that is transmitted together with Mode C
framing pulses to the interrogating ground radar
facility. The ident feature of the transponder causes
the transponder return to ¡°blossom¡± for a few seconds on the controller¡¯s radarscope.
AUTOMATED RADAR TERMINAL SYSTEM
Most medium-to-large radar facilities in the U.S. use
some form of automated radar terminal system (ARTS),
which is the generic term for the functional capability
afforded by several automated systems that differ in
functional capabilities and equipment. ¡°ARTS¡± followed by a suffix Roman numeral denotes a specific
system, with a subsequent letter that indicates a major
modification to that particular system. In general, the
terminal controller depends on ARTS to display aircraft
identification, flight plan data, and other information in
conjunction with the radar presentation. In addition to
enhancing visualization of the air traffic situation,
ARTS facilitates intra- and inter-facility transfers and
the coordination of flight information. Each ARTS level
has the capabilities of communicating with other ARTS
types as well as with ARTCCs.
As the primary system used for terminal ATC in the
U.S., ARTS had its origin in the mid-1960¡¯s as ARTS
I, or Atlanta ARTS and evolved to the ARTS II and
ARTS III configurations in the early to mid-1970¡¯s.
Later in the decade, the ARTS II and ARTS III configurations were expanded and enhanced and renamed
ARTS IIA and ARTS IIIA respectively. The vast
majority of the terminal automation sites today remain
either IIA or IIIA configurations, except for about nine
of the largest IIIA sites, which are ARTS IIIE candidate systems. Selected ARTS IIIA/IIIE and ARTS IIA
sites are scheduled to receive commercial off the shelf
(COTS) hardware upgrades, which replace portions of
the proprietary data processing system with standard
off-the-shelf hardware.
STANDARD TERMINAL
AUTOMATION REPLACEMENT SYSTEM
The FAA has begun modernizing the computer equipment in the busiest terminal airspace areas. The newer
equipment is called STARS, for Standard Terminal
Automation Replacement System. The system's
improvements will enhance safety while reducing
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delays by increasing system reliability and lowering lifecycle operating and maintenance costs. STARS also will
accommodate the projected growth in air traffic and
provide a platform for new functions to support FAA
initiatives such as Free Flight. STARS offers many
advantages, including an open architecture and expansion capability that allow new software and capacity to
be added as needed to stay ahead of the growth in air
traffic. Under the first phase of terminal modernization, STARS is being deployed to 47 air traffic control
facilities. As of July 2005, 37 FAA and 22 Department
of Defense sites were fully operational with STARS.
The first phase is expected to be complete in fiscal year
2007. By then, STARS will be operational at 18 of the
FAA's 35 most critical, high-volume airports, which
together handle approximately 50 percent of air traffic.
STARS consists of new digital, color displays and
computer software and processors that can track 435
aircraft at one time, integrating six levels of weather
information and 16 radar feeds.
For the terminal area and many of the towers, STARS is
the key to the future, providing a solid foundation for
new capabilities. STARS was designed to provide the
software and hardware platform necessary to support
future air traffic control enhancements.
PRECISION APPROACH RADAR
While ASR provides pilots with horizontal guidance
for instrument approaches via a ground-based radar,
Precision Approach Radar (PAR) provides both horizontal and vertical guidance for a ground controlled
approach (GCA). In the U.S., PAR is mostly used by
the military. Radar equipment in some ATC facilities
operated by the FAA and/or the military services at
joint-use locations and military installations are used
to detect and display azimuth, elevation, and range of
aircraft on the final approach course to a runway.
This equipment may be used to monitor certain nonradar approaches, but it is primarily used to conduct
a precision instrument approach.
BRIGHT RADAR INDICATOR TERMINAL EQUIPMENT
Bright Radar Indicator Terminal Equipment (BRITE)
provides radar capabilities to towers, a system with
tremendous benefits for both pilots and controllers.
Unlike traditional radar systems, BRITE is similar to a
television screen in that it can be seen in daylight.
BRITE was so successful that the FAA has installed the
new systems in towers, and even in some TRACONs. In
fact, the invention of BRITE was so revolutionary that
it launched a new type of air traffic facility ⎯ the
TRACAB, which is a radar approach control facility
located in the tower cab of the primary airport, as
opposed to a separate room.
In the many facilities without BRITE, the controllers
use strictly visual means to find and sequence traffic.
Towers that do have BRITE may have one of several
different types. Some have only a very crude display
that gives a fuzzy picture of blips on a field of green,
perhaps with the capability of displaying an extra slash
on transponder-equipped targets and a larger slash
when a pilot hits the ident button. Next in sophistication are BRITEs that have alphanumeric displays of
various types, ranging from transponder codes and altitude to the newest version, the DBRITE (digital
BRITE). A computer takes all the data from the primary
radar, the secondary radar (transponder information), and
generates the alphanumeric data. DBRITE digitizes the
image, and then sends it all, in TV format, to a square display in the tower that provides an excellent presentation,
regardless of how bright the ambient light.
One of the most limiting factors in the use of the BRITE
is in the basic idea behind the use of radar in the tower.
The radar service provided by a tower controller is not,
nor was it ever intended to be, the same thing as radar
service provided by an approach control or Center. The
primary duty of tower controllers is to separate airplanes
operating on runways, which means controllers spend
most of their time looking out the window, not staring at
a radar scope.
RADAR COVERAGE
A full approach is a staple of instrument flying, yet
some pilots rarely, if ever, have to fly one other than
during initial or recurrency or proficiency training,
because a full approach usually is required only when
radar service is not available, and radar is available at
most larger and busier instrument airports. Pilots come
to expect radar vectors to final approach courses and
that ATC will keep an electronic eye on them all the
way to a successful conclusion of every approach. In
addition, most en route flights are tracked by radar
along their entire route in the 48 contiguous states,
with essentially total radar coverage of all instrument
flight routes except in the mountainous West. Lack of
radar coverage may be due to terrain, cost, or physical
limitations.
New developing technologies, like ADS-B, may offer
ATC a method of accurately tracking aircraft in nonradar environments. ADS-B is a satellite-based air
traffic tracking system enabling pilots and air traffic
controllers to share and display the same information.
ADS-B relies on the Global Positioning System (GPS)
to determine an aircraft¡¯s position. The aircraft¡¯s precise location, along with other data such as airspeed,
altitude, and aircraft identification, then is instantly
relayed via digital datalink to ground stations and other
equipped aircraft. Depending on the location of the
ground based transmitters (GBT), ADS-B has the
potential to work well at low altitudes, in remote locations, and mountainous terrain where little or no radar
coverage exists.
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COMMUNICATIONS
Most air traffic control communications between pilots
and controllers today are conducted via voice. Each air
traffic controller uses a radio frequency different from the
ones used by surrounding controllers to communicate
with the aircraft under his or her jurisdiction. With the
increased traffic, more and more controllers have been
added to maintain safe separation between aircraft. While
this has not diminished safety, there is a limit to the
number of control sectors created in any given region
to handle the traffic. The availability of radio frequencies
for controller-pilot communications is one limiting factor.
Some busy portions of the U.S., such as the Boston-
Chicago-Washington triangle are reaching toward the
limit. Frequencies are congested and new frequencies are
not available, which limits traffic growth to those aircraft
that can be safely handled.
DATA LINK
The CAASD is working with the FAA and the airlines
to define and test a controller-pilot data link communication (CPDLC), which provides the capability to
exchange information between air traffic controllers
and flight crews through digital text instead of voice
messages. With CPDLC, communications between the
ground and the air would take less time, and would
convey more information (and more complex information) than by voice alone. Communications would
become more accurate as up-linked information would
be collected, its accuracy established, and then displayed for the pilot in a consistent fashion.
By using digital data messages to replace conventional
voice communications (except during landing and departure phases and in emergencies) CPDLC is forecast to
increase airspace capacity and reduce delays. Today the
average pilot/controller voice exchange takes around 20
seconds, compared to one or two seconds with CPDLC.
In FAA simulations, air traffic controllers indicated that
CPDLC could increase their productivity by 40 percent
without increasing workload. Airline cost/benefit studies
indicate average annual savings that are significant in the
terminal and en route phases, due to CPDLC-related
delay reductions.
CPDLC for routine ATC messages, initially offered in
Miami Center, will be implemented via satellite at all
oceanic sectors. Communications between aircraft and
FAA oceanic facilities will be available through satellite
data link, high frequency data link (HFDL), or other
subnetworks, with voice via HF and satellite communications remaining as backup. Eventually, the service will
be expanded to include clearances for altitude, speed,
heading, and route, with pilot initiated downlink capability added later.
MODE S
The first comprehensive proposal and design for the
Mode S system was delivered to the FAA in 1975.
However, due to design and manufacturing setbacks,
few Mode S ground sensors and no commercial Mode S
transponders were made available before 1980. Then, a
tragic mid-air collision over California in 1986
prompted a dramatic change. The accident that claimed
the lives of 67 passengers aboard the two planes and
fifteen people on the ground was blamed on inadequate
automatic conflict alert systems and surveillance
equipment. A law enacted by Congress in 1987
required all air carrier airplanes operating within U.S.
airspace with more than 30 passenger seats to be
equipped with Traffic Alert and Collision Avoidance
System (TCAS II) by December 1993. Airplanes with
10 to 30 seats were required to employ TCAS I by
December 1995.
Due to the congressional mandate, TCAS II became a
pervasive system for air traffic control centers around
the world. Because TCAS II uses Mode S as the standard air-ground communication datalink, the widespread international use of TCAS II has helped Mode S
become an integral part of air traffic control systems
all over the world. The datalink capacity of Mode S has
spawned the development of a number of different
services that take advantage of the two-way link
between air and ground. By relying on the Mode S
datalink, these services can be inexpensively deployed
to serve both the commercial transport aircraft and
general aviation communities. Using Mode S makes
not only TCAS II, but also other services available to
the general aviation community that were previously
accessible only to commercial aircraft. These Mode
S-based technologies are described below.
TRAFFIC ALERT AND
COLLISION AVOIDANCE SYSTEM
The traffic alert and collision avoidance system (TCAS)
is designed to provide a set of electronic eyes so the pilot
can maintain awareness of the traffic situation in the
vicinity of the aircraft. The TCAS system uses three separate systems to plot the positions of nearby aircraft.
First, directional antennae that receive Mode S transponder signals are used to provide a bearing to neighboring
aircraft ⎯ accurate to a few degrees of bearing. Next,
Mode C altitude broadcasts are used to plot the altitude
of nearby aircraft. Finally, the timing of the Mode S
interrogation/response protocol is measured to ascertain
the distance of an aircraft from the TCAS aircraft.
TCAS I allows the pilot to see the relative position and
velocity of other transponder-equipped aircraft within a
10 to 20-mile range. [Figure 1-14] More importantly,
TCAS I provides a warning when an aircraft in the vicinity gets too close. TCAS I does not provide instructions
on how to maneuver in order to avoid the aircraft, but
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does supply important data with which the pilot uses to
evade intruding aircraft.
TCAS II provides pilots with airspace surveillance,
intruder tracking, threat detection, and avoidance
maneuver generations. TCAS II is able to determine
whether each aircraft is climbing, descending, or flying
straight and level, and commands an evasive maneuver to
either climb or descend to avoid conflicting traffic. If both
planes in conflict are equipped with TCAS II, then the
evasive maneuvers are well coordinated via air-to-air
transmissions over the Mode S datalink, and the commanded maneuvers do not cancel each other out.
TCAS and similar traffic avoidance systems provide
safety independent of ATC and supplement and enhance
ATC¡¯s ability to prevent air-to-air collisions. Pilots currently use TCAS displays for collision avoidance and
oceanic station keeping (maintaining miles-in-trail separation). Recent TCAS technology improvements enable
aircraft to accommodate reduced vertical separation
above FL 290 and the ability to track multiple targets at
longer ranges. The Airborne Collision Avoidance
System (ACAS) is an international ICAO standard that
is the same as the latest TCAS II, which is sometimes
called ¡°Change 7¡± or ¡°Version 7¡± in the United States.
ACAS has been mandated, based on varying criteria,
throughout much of the world.
TRAFFIC INFORMATION SERVICE
Traffic Information Service (TIS) provides many of the
functions available in TCAS; but unlike TCAS, TIS is
a ground-based service available to all aircraft
equipped with Mode S transponders. TIS takes advantage of the Mode S data link to communicate collision
avoidance information to aircraft. Information is pre-
sented to a pilot in a cockpit display that shows traffic
within 5 nautical miles and a 1,200-foot altitude of
other Mode S-equipped aircraft. The TIS system uses
track reports provided by ground-based Mode S surveillance systems to retrieve traffic information.
Because it is available to all Mode S transponders, TIS
offers an inexpensive alternative to TCAS. The increasing
availability of TIS makes collision avoidance technology
more accessible to the general aviation community.
Beginning in 2005, the use of Mode S TIS is being discontinued at some sites as the ground radar systems are
upgraded. In all, 23 sites are expected to lose TIS capability by 2012.
TERRAIN AWARENESS AND WARNING SYSTEM
The Terrain Awareness and Warning System (TAWS) is
an enhanced ground proximity warning capability being
installed in many aircraft. TAWS uses position data from
a navigation system, like GPS, and a digital terrain database to display surrounding terrain. TAWS equipment is
mandatory for all U.S registered turbine powered airplanes with six or more passenger seats. FAA and NTSB
studies have shown that a large majority of CFIT accidents could likely have been avoided had the aircraft
been equipped with enhanced ground proximity warning systems.
GRAPHICAL WEATHER SERVICE
The Graphical Weather Service provides a graphical representation of weather information that is transmitted to
aircraft and displayed on the cockpit display unit. The
service is derived from ground-based Mode S sensors
and offers information to all types of aircraft, regardless
of the presence of on-board weather avoidance equipment. The general aviation community has been very
pro-active in evaluating this technology, as they have
already participated in field evaluations in Mode S stations across the U.S. The service is provided through
one of two types of flight information services (FIS) systems. Broadcast only systems, called FIS-B, include a
ground- or space-based transmitter, an aircraft receiver,
and a portable or installed cockpit display device. They
allow pilots to passively collect weather and other operational data and to display that data at the appropriate
time. They can display graphical weather products such
as radar composite/mosaic images, temporary flight
restricted airspace and other NOTAMs. In addition to
graphical weather products, they can also show textual
information, such as Aviation Routine Weather Reports
(METARs)/Aviation Selected Special Weather Reports
(SPECIs) and Terminal Area Forecasts (TAFs).
Two-way FIS systems are request/reply systems, that is,
they permit the pilot to make specific requests for
weather and other operational information. An FIS service provider will then prepare a reply in response to that
specific request and transmit the product to that specific
aircraft for display in the cockpit.
Figure 1-14. Traffic Alert and Collision Avoidance System.
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AVIONICS AND INSTRUMENTATION
The proliferation of advanced avionics and instrumentation has substantially increased the capabilities of
aircraft in the IFR environment.
FLIGHT MANAGEMENT SYSTEM
A flight management system (FMS) is a flight computer
system that uses a large database to allow routes to be
preprogrammed and fed into the system by means of a
data loader. The system is constantly updated with
respect to position accuracy by reference to conventional
navigation aids, inertial reference system technology, or
the satellite global positioning system. The sophisticated
program and its associated database ensures that the
most appropriate navigation aids or inputs are automatically selected during the information update cycle. A
typical FMS provides information for continuous automatic navigation, guidance, and aircraft performance
management, and includes a control display unit
(CDU). [Figure 1-15]
ELECTRONIC FLIGHT
INFORMATION SYSTEM
The electronic flight information system (EFIS) found in
advanced aircraft cockpits offer pilots a tremendous
amount of information on a colorful, easy-to-read display.
Glass cockpits are a vast improvement over the earlier generation of instrumentation. [Figure 1-16]
Primary flight, navigation, and engine information are
presented on large display screens in front of the flight
crew. Flight management CDUs are located on the center
console. They provide data display and entry capabilities
for flight management functions. The display units generate less heat, save space, weigh less, and require less power
than traditional navigation systems. From a pilot¡¯s point of
view, the information display system is not only more
reliable than previous systems, but also uses advanced
liquid-crystal technology that allows displayed informa-
tion to remain clearly visible in all conditions, including
direct sunlight.
NAVIGATION SYSTEMS
Navigation systems are the basis for pilots to get from
one place to another and know where they are and what
course to follow. Since the 1930s, aircraft have navigated by means of a set of ground-based NAVAIDs.
Today, pilots have access to over 2,000 such NAVAIDs
within the continental U.S., but the system has its
limitations:
• Constrained to fly from one NAVAID to the
next, aircraft route planners need to identify a
beacon-based path that closely resembles the
path the aircraft needs to take to get from origin
to destination. Such a path will always be
greater in distance than a great circle route
between the two points.
• Because the NAVAIDs are ground-based, navigation across the ocean is problematic, as is
navigation in some mountainous regions.
• NAVAIDs are also expensive to maintain.
Since the 1980s, aircraft systems have evolved towards
the use of SATNAV. Based on the GPS satellite constellation, SATNAV may provide better position information
than a ground-based navigation system. GPS is universal
so there are no areas without satellite signals. Moreover, a
space-based system allows ¡°off airway¡± navigation so that
the efficiencies in aircraft route determination can be
exacted. SATNAV is revolutionizing navigation for airlines and other aircraft owners and operators. A drawback
of the satellite system, though, is the integrity and availability of the signal, especially during electromagnetic
and other events that distort the Earth¡¯s atmosphere. In
addition, the signal from space needs to be augmented,
especially in traffic-dense terminal areas, to guarantee the
necessary levels of accuracy and availability.
The CAASD is helping the navigation system of the
U.S. to evolve toward a satellite-based system. The
CAASD analysts are providing the modeling necessary
to understand the effects of atmospheric phenomena on
the GPS signal from space, while the CAASD is providing the architecture of the future navigation system and
writing the requirements (and computer algorithms) to
ensure the navigation system¡¯s integrity. Moving toward
a satellite-based navigation system allows aircraft to
divorce themselves from the constraints of ground-based
NAVAIDs and formulate and fly those routes that aircraft route planners deem most in line with their own
cost objectives.
With the advent of SATNAV, there are a number of
applications that can be piggybacked to increase capacity in the NAS. Enhanced navigation systems will be
capable of ¡°random navigation,¡± that is, capable of
Figure 1-15. FMS Control Display Unit. This depicts an aircraft
established on the Atlantic City, NJ, RNAV (GPS) Rwy 13
instrument approach procedure at the Atlantic City
International Airport, KACY. The aircraft is positioned at the
intermediate fix UNAYY inbound on the 128 degree magnetic
course, 5.5 nautical miles from PVIGY, the final approach fix.
treating any latitude-longitude point as a radio navigation fix, and being able to fly toward it with the
accuracy we see today, or better. New routes into and
out of the terminal areas are being implemented that
are navigable by on-board systems. Properly
equipped aircraft are being segregated from other aircraft streams with the potential to increase volume at
the nation¡¯s busy airports by keeping the arrival and
departure queues full and fully operating.
The CAASD is working with the FAA to define the
nation¡¯s future navigation system architecture. By itself,
the GPS satellite constellation is inadequate to serve all
the system¡¯s needs. Augmentation of the GPS signal via
WAAS and LAAS is a necessary part of that new architecture. The CAASD is developing the requirements
based on the results of sophisticated models to ensure the
system¡¯s integrity, security, and availability.
SURVEILLANCE SYSTEMS
Surveillance systems are set up to enable the ATC system to know the location of an aircraft and where it is
heading. Position information from the surveillance
system supports many different ATC functions. Aircraft
positions are displayed for controllers as they watch
over the traffic to ensure that aircraft do not violate separation criteria. In the current NAS, surveillance is
achieved through the use of long-range and terminal
radars. Scanning the skies, these radars return azimuth
and slant range for each aircraft that, when combined
with the altitude of the aircraft broadcast to the ground
via a transceiver, is transformed mathematically into a
position. The system maintains a list of these positions
for each aircraft over time, and this time history is used
to establish short-term intent and short-term conflict
detection. Radars are expensive to maintain, and position information interpolated from radars is not as good
as what the aircraft can obtain with SATNAV. ADS-B
technology may provide the way to reduce the costs of
surveillance for air traffic management purposes and to
get the better position information to the ground.
New aircraft systems dependent on ADS-B could be
used to enhance the capacity and throughput of the
nation¡¯s airports. Electronic flight following is one
example: An aircraft equipped with ADS-B could be
instructed to follow another aircraft in the landing pattern, and the pilot could use the on-board displays or
computer applications to do exactly that. This means
that visual rules for landing at airports might be used in
periods where today the airport must shift to instrument
rules due to diminishing visibility. Visual capacities at
airports are usually higher than instrument ones, and if
the airport can operate longer under visual rules (and
separation distances), then the capacity of the airport is
maintained at a higher level longer. The CAASD is
working with the Cargo Airline Association and the
Figure 1-16. Airline Flight Deck Instrument Displays
Primary Flight Displays (PFD) Navigation Displays (ND)
Engine Indicating and Crew
Alerting System (EICAS)
Multifunction Display (MFD)
Flight Management Control
Display Units (CDU)
Photo and graphic courtesy of Boeing
Commercial Airplane Group
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FAA to investigate these and other applications of the
ADS-B technology.
OPERATIONAL TOOLS
Airports are one of the main bottlenecks in the NAS,
responsible for one third of the flight delays. It is widely
accepted that the unconstrained increase in the number
of airports or runways may not wholly alleviate the congestion problem and, in fact, may create more problems
than it solves. The aim of the FAA is to integrate appropriate technologies, in support of the OEP vision, with
the aim of increasing airport throughput.
The airport is a complex system of systems and any
approach to increasing capacity must take this into
account. Numerous recent developments contribute to
the overall solution, but their integration into a system
that focuses on maintaining or increasing safety while
increasing capacity remains a major challenge. The
supporting technologies include new capabilities for
the aircraft and ATC, as well as new strategies for
improving communication between pilots and ATC.
IFR SLOTS
During peak traffic, ATC uses IFR slots to promote a
smooth flow of traffic. This practice began during the
late 1960s, when five of the major airports (LaGuardia
Airport, Ronald Reagan National Airport, John F.
Kennedy International Airport, Newark International
Airport, and Chicago O¡¯Hare International Airport)
were on the verge of saturation due to substantial flight
delays and airport congestion. To combat this, the FAA
in 1968 proposed special air traffic rules to these five
high-density airports (the ¡°high density rule¡±) that
restricted the number of IFR takeoffs and landings at
each airport during certain hours of the day and provided
for the allocation of ¡°slots¡± to carriers for each IFR landing or takeoff during a specific 30 or 60-minute period.
A more recent FAA proposal offers an overhaul of the
slot-reservation process for JFK, LaGuardia, and
Reagan National Airport that includes a move to a 72-
hour reservation window and an online slot-reservation
system.
The high density rule has been the focus of much
examination over the last decade since under the
restrictions, new entrants attempting to gain access to
high density airports face difficulties entering the
market. Because slots are necessary at high density
airports, the modification or elimination of the high
density rule could subsequently have an effect on the
value of slots. Scarce slots hold a greater economic
value than slots that are easier to come by.
The current slot restrictions imposed by the high density
rule has kept flight operations well below capacity,
especially with the improvements in air traffic control
technology. However, easing the restrictions imposed
by the high density rule is likely to affect airport oper-
ations. Travel delay time might be affected not only at
the airport that has had the high density restrictions
lifted, but also at surrounding airports that share the
same airspace. On the other hand, easing the restrictions on slots at high density airports should help
facilitate international air travel and help increase the
number of passengers that travel internationally.
Slot controls have become a way of limiting noise,
since it caps the number of takeoffs and landings at
an airport. Easing the restrictions on slots could be
politically difficult since local delegations at the
affected airports might not support such a move. Ways
other than imposing restrictions on slots exist that
could diminish the environmental impacts at airports
and their surrounding areas. Safeguards, such as
requiring the quietest technology available of aircraft
using slots and frequent consultations with local
residents, have been provided to ensure that the
environmental concerns are addressed and solved.
GROUND DELAY PROGRAM
Bad weather often forces the reconfiguration of runways at an airport or mandates the use of IFR arrival
and departure procedures, reducing the number of
flights per hour that are able to takeoff or land at the
affected airport. To accommodate the degraded arrival
capacity at the affected airport, the ATCSCC imposes a
ground delay program (GDP), which allocates a
reduced number of arrival slots to airlines at airports
during time periods when demand exceeds capacity.
The GDP suite of tools is used to keep congestion at an
arrival airport at acceptable levels by issuing ground
delays to aircraft before departure, as ground delays
are less expensive and safer than in-flight holding
delays. The FAA started GDP prototype operations in
January 1998 at two airports and expanded the program
to all commercial airports in the U.S. within nine
months.
Ground Delay Program Enhancements (GDPE) significantly reduced delays due to compression¡ªa process that
is run periodically throughout the duration of a GDP. It
reduces overall delays by identifying open arrival slots due
to flight cancellations or delays and fills in the vacant slots
by moving up operating flights that can use those slots.
During the first two years of this program, almost 90,000
hours of scheduled delays were avoided due to compression, resulting in cost savings to the airline industry of more
than $150 million. GDPE also has improved the flow of air
traffic into airports; improved compliance to controlled
times of departure; improved data quality and predictability; resulted in equity in delays across carriers; and often
avoided the necessity to implement FAA ground delay programs, which can be disruptive to air carrier operations.
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FLOW CONTROL
ATC provides IFR aircraft separation
services for NAS users. Since the
capabilities of IFR operators vary
from airlines operating hundreds of
complex jet aircraft to private pilots
in single engine, piston-powered airplanes, the ATC system must accommodate the least sophisticated user.
The lowest common denominator is
the individual controller speaking to
a single pilot on a VHF voice radio
channel. While this commonality is
desirable, it has led to a mindset
where other opportunities to interact
with NAS users have gone undeveloped. The greatest numbers of operations at the 20 busiest air carrier
airports are commercial operators (airlines and commuters) operating IFR with some form of ground-based
operational control. Since not all IFR operations have
ground-based operational control, very little effort has
been expended in developing ATC and Airline Operations
Control Center (AOC) collaboration techniques, even
though ground-based computer-to-computer links can
provide great data transfer capacity. Until the relatively
recent concept of Air Traffic Control-Traffic Flow
Management (ATC-TFM), the primary purpose of ATC
was aircraft separation, and the direct pilot-controller
interaction was adequate to the task. Effective and efficient traffic flow management now requires a new level of
control that includes the interaction of and information
transfer among ATC, TFM, AOCs, and the cockpit.
[Figure 1-17]
As the first step in modernizing the traffic flow management infrastructure, the FAA began reengineering
traffic flow management software using commercial
off-the-shelf products. In FY 1996, the FAA and
NASA collaborated on new traffic flow management
research and development efforts for the development
of collaborative decision making tools that will enable
FAA traffic flow managers to work cooperatively with
airline personnel in responding to congested conditions.
Additionally, the FAA provided a flight scheduling
software system to nine airlines.
LAND AND HOLD SHORT OPERATIONS
Many older airports, including some of the most congested, have intersecting runways. Expanding the use
of Land and Hold Short Operations (LAHSO) on
intersecting runways is one of the ways to increase the
number of arrivals and departures. Currently, LAHSO
operations are permitted only on dry runways under
acceptable weather conditions and limited to airports
where a clearance depends on what is happening on
the other runway, or where approved rejected landing
procedures are in place. A dependent procedure example is when a landing airplane is a minimum distance
from the threshold and an airplane is departing an
intersecting runway, the LAHSO clearance can be
issued because even in the event of a rejected landing,
separation is assured. It is always the pilot¡¯s option to
reject a LAHSO clearance.
Working with ICAO, pilot organizations, and industry
groups, the FAA is developing new LAHSO procedures
that will provide increased efficiency while maintaining
safety. These procedures will address issues such as wet
runway conditions, mixed commercial and general aviation operations, the frequency of missed approaches, and
multi-stop runway locations. After evaluating the new
procedures using independent case studies, the revised
independent LAHSO procedures may be implemented in
the near future.
SURFACE MOVEMENT GUIDANCE
AND CONTROL SYSTEM
To enhance taxiing capabilities in low visibility conditions and reduce the potential for runway incursions,
improvements have been made in signage, lighting, and
markings. In addition to these improvements, airports
have implemented the Surface Movement Guidance and
Control System (SMGCS),4
a strategy that requires a low
visibility taxi plan for any airport with takeoff or landing
operations with less than 1,200 feet RVR visibility conditions. This plan affects both aircrew and airport vehicle
operators, as it specifically designates taxi routes to and
from the SMGCS runways and displays them on a
SMGCS Low Visibility Taxi Route chart.
4
SMGCS, pronounced ¡°SMIGS,¡± is the Surface Movement Guidance and Control System. SMGCS provides for guidance and control or
regulation for facilities, information, and advice necessary for pilots of aircraft and drivers of ground vehicles to find their way on the airport
during low visibility operations and to keep the aircraft or vehicles on the surfaces or within the areas intended for their use. Low visibility
operations for this system means reported conditions of RVR 1,200 or less.
Figure 1-17. Flow Control
Restrictions.
SMGCS is an increasingly important element in a seamless, overall gate-to-gate management concept to ensure
safe, efficient air traffic operations. It is the ground-complement for arrival and departure management and the
en route components of free flight. The FAA has supported several major research and development efforts
on SMGCS to develop solutions and prototype systems
that support pilots and ATC in their control of aircraft
ground operations.
EXPECT CHANGES IN THE ATC SYSTEM
To maintain air safety, ATC expects all aircraft to adhere
to a set of rules based on established separation standards. Until recently, air traffic controllers followed
established procedures based upon specific routes to
maintain the desired separations needed for safety. This
system has an excellent safety record for aircraft operations. Because of increases in the number of flights, the
availability of more accurate and reliable technologies,
and the inherent limitations of the existing system, there
will be many changes in the near future. Use of the free
flight concept where aircraft operators select paths, altitudes, and speeds in real time can maximize efficiency
and minimize operating costs. New technologies and
enhanced aircraft capabilities necessitate changes in
procedures, an increase in the level of automation
and control in the cockpit and in the ground system,
and more human reliance on automated information
processing, sophisticated displays, and faster data
communication.
DISSEMINATING
AERONAUTICAL INFORMATION
The system for disseminating aeronautical information
is made up of two subsystems, the Airmen¡¯s Information
System (AIS) and the Notice to Airman (NOTAM)
System. The AIS consists of charts and publications.
The NOTAM system is a telecommunication system and
is discussed in later paragraphs. Aeronautical information disseminated through charts and publications
includes aeronautical charts depicting permanent baseline data and flight information publications outlining
baseline data.
IFR aeronautical charts include en route high altitude
conterminous U.S., and en route low altitude conterminous U.S., plus Alaska charts and Pacific Charts.
Additional charts include U.S. terminal procedures, consisting of departure procedures (DPs), standard terminal
arrivals (STARs), and standard instrument approach procedures (SIAPs).
Flight information publications outlining baseline data
in addition to the Notices to Airmen Publication (NTAP)
include the Airport/Facility Directory (A/FD), a Pacific
Chart Supplement, an Alaska Supplement, an Alaska
Terminal publication, and the Aeronautical Information
Manual (AIM).
PUBLICATION CRITERIA
The following conditions or categories of information
are forwarded to the National Flight Data Center
(NFDC) for inclusion in flight information publications
and aeronautical charts:
• NAVAID commissioning, decommissioning, outages, restrictions, frequency changes, changes in
monitoring status and monitoring facility used in
the NAS.
• Commissioning, decommissioning, and changes
in hours of operation of FAA air traffic control
facilities.
• Changes in hours of operations of surface areas
and airspace.
• RCO and RCAG commissioning, decommissioning, and changes in voice control or monitoring
facility.
• Weather reporting station commissioning,
decommissioning, failure, and nonavailability or
unreliable operations.
• Public airport commissioning, decommissioning,
openings, closings, abandonments, and some airport operating area (AOA) changes.
• Aircraft Rescue & Fire Fighting (ARFF) capability, including restrictions to air carrier operations.
• Changes to runway identifiers, dimensions, threshold placements, and surface compositions.
• NAS lighting system commissioning, decommissioning, outages, and change in classification or
operation.
• IFR Area Charts.
A wide variety of additional flight information publications are available online at the FAA website
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http://www.faa.gov and can be found with the ¡°Library¡±
link, and the tabs for both ¡°Education and Research¡± and
¡°Regulation and Policies.¡± Electronic flight publications
include electronic bulletin boards, advisory circulars,
the AC checklist, Federal Aviation Regulations, the
Federal Register, and notices of proposed rulemaking
(NPRM).
When planning a flight, you can obtain information on
the real-time status of the national airspace system by
accessing the Air Traffic Control System Command
Center¡¯s Operational Information System (OIS) at
http://www.fly.faa.gov/ois/. This data is updated every
five minutes, and contains useful information on closures, delays, and other aspects of the system.
AERONAUTICAL CHARTS
Pilots can obtain most aeronautical charts and publications produced by the FAA National Aeronautical
Charting Office (NACO). They are available by subscription or one-time sales through a network of FAA
chart agents primarily located at or near major civil airports. Additionally, opportunities to purchase or download aeronautical publications online are expanding,
which provides pilots quicker and more convenient
access to the latest information. Civil aeronautical charts
for the U.S. and its territories, and possessions are produced according to a 56-day IFR chart cycle by NACO,
which is part of the FAA¡¯s Technical Ops Aviation
Systems Standards (AJW-3). Comparable IFR charts
and publications are available from commercial sources,
including charted visual flight procedures, airport qualification charts, etc.
Most charts and publications described in this chapter
can be obtained by subscription or one-time sales from
NACO. Charts and publications are also available
through a network of FAA chart agents primarily
located at or near major civil airports. To order online,
use the ¡°Catalogs/Ordering Info¡± link at
http://www.naco.faa.gov. Below is the contact information for NACO.
FAA, National Aeronautical Charting Office
Distribution Division AJW-3550
10201 Good Luck Road
Glenn Dale, MD 20769-9700
Telephone
(301) 436-8301
(800) 638-8972 toll free, U.S. only FAX
(301) 436-6829
Email: 9-AMC-chartsales@faa.gov
IFR charts are revised more frequently than VFR charts
because chart currency is critical for safe operations.
Selected NACO IFR charts and products available
include IFR navigation charts, planning charts, supplementary charts and publications, and digital products.
IFR navigation charts include the following:
• IFR En route Low Altitude Charts
(Conterminous U.S. and Alaska): En route low
altitude charts provide aeronautical information
for navigation under IFR conditions below 18,000
feet MSL. This four-color chart series includes airways; limits of controlled airspace; VHF
NAVAIDs with frequency, identification, channel,
geographic coordinates; airports with terminal
air/ground communications; minimum en route
and obstruction clearance altitudes; airway distances; reporting points; special use airspace; and
military training routes. Scales vary from 1 inch = 5
NM to 1 inch = 20 NM. The size is 50 x 20 inches
folded to 5 x 10 inches. The charts are revised every
56 days. Area charts show congested terminal areas
at a large scale. They are included with subscriptions
to any conterminous U.S. Set Low (Full set, East or
West sets). [Figure 1-18]
Figure 1-18. En route Low Altitude Charts.
1-27
• IFR En route High Altitude Charts
(Conterminous U.S. and Alaska): En route high
altitude charts are designed for navigation at or
above 18,000 feet MSL. This four-color chart
series includes the jet route structure; VHF
NAVAIDs with frequency, identification, channel,
geographic coordinates; selected airports; and
reporting points. The chart scales vary from 1 inch
= 45 NM to 1 inch = 18 NM. The size is 55 x 20
inches folded to 5 x 10 inches. Revised every 56
days. [Figure 1-19 ]
• U.S. Terminal Procedures Publication (TPP)
TPPs are published in 20 loose-leaf or perfect
bound volumes covering the conterminous U.S.,
Puerto Rico, and the Virgin Islands. A Change
Notice is published at the midpoint between revisions in bound volume format. [Figure 1-20]
• Instrument Approach Procedure (IAP) Charts:
IAP charts portray the aeronautical data that is
required to execute instrument approaches to airports. Each chart depicts the IAP, all related navigation data, communications information, and
an airport sketch. Each procedure is designated
for use with a specific electronic navigational
aid, such as an ILS, VOR, NDB, RNAV, etc.
• Instrument Departure Procedure (DP) Charts:
There are two types of departure procedures;
Standard Instrument Departures (SIDs) and
Obstacle Departure Procedures (ODPs). SIDs
will always be in a graphic format and are
designed to assist ATC by expediting clearance
delivery and to facilitate transition between
takeoff and en route operations. ODPs are
established to ensure proper obstacle clearance
and are either textual or graphic, depending on
complexity.
• Standard Terminal Arrival (STAR) Charts:
STAR charts are designed to expedite ATC
arrival procedures and to facilitate transition
between en route and instrument approach
operations. They depict preplanned IFR ATC
arrival procedures in graphic and textual form.
Each STAR procedure is presented as a separate chart and may serve either a single airport
or more than one airport in a given geographic
area.
• Airport Diagrams: Full page airport diagrams
are designed to assist in the movement of
ground traffic at locations with complex runway and taxiway configurations and provide
information for updating geodetic position navigational systems aboard aircraft.
• Alaska Terminal Procedures Publication: This
publication contains all terminal flight procedures
for civil and military aviation in Alaska. Included are
IAP charts, DP charts, STAR charts, airport diagrams, radar minimums, and supplementary support
data such as IFR alternate minimums, take-off minimums, rate of descent tables, rate of climb tables,
and inoperative components tables. The volume is
5-3/8 x 8-1/4 inches top bound, and is revised every
56 days with provisions for a Terminal Change
Notice, as required.
Figure 1-19. En route High Altitude Charts.
1-28
1-29
• U.S. IFR/VFR Low Altitude Planning Chart:
This chart is designed for preflight and en route
flight planning for IFR/VFR flights. Depiction
includes low altitude airways and mileage,
NAVAIDs, airports, special use airspace, cities,
time zones, major drainage, a directory of airports with their airspace classification, and a
mileage table showing great circle distances
between major airports. The chart scale is 1 inch
= 47 NM/1:3,400,000, and is revised annually,
available either folded or unfolded for wall
mounting.
Supplementary charts and publications include:
• Airport/Facility Directory (A/FD): This seven
volume booklet series contains data on airports,
seaplane bases, heliports, NAVAIDs, communications data, weather data sources, airspace,
special notices, and operational procedures. The
coverage includes the conterminous U.S., Puerto
Rico, and the Virgin Islands. The A/FD shows
data that cannot be readily depicted in graphic
form; e.g., airport hours of operations, types of
fuel available, runway widths, lighting codes, etc.
The A/FD also provides a means for pilots to
update visual charts between edition dates, and is
published every 56 days. The volumes are sidebound 5-3/8 x 8-1/4 inches.
• Supplement Alaska: This is a civil/military flight
information publication issued by the FAA every
56 days. This booklet is designed for use with
appropriate IFR or VFR charts. The Supplement
Alaska contains an airport/facility directory, airport sketches, communications data, weather data
sources, airspace, listing of navigational facilities, and special notices and procedures. The
volume is side-bound 5-3/8 x 8-1/4 inches.
Figure 1-20. Terminal Procedures Publication.
• Chart Supplement Pacific: This supplement is
designed for use with appropriate VFR or IFR en
route charts. Included in this booklet are the airport/facility directory, communications data,
weather data sources, airspace, navigational facilities, special notices, and Pacific area procedures.
IAP charts, DP charts, STAR charts, airport diagrams, radar minimums, and supporting data for
the Hawaiian and Pacific Islands are included. The
manual is published every 56 days. The volume is
side-bound 5-3/8 x 8-1/4 inches.
• North Pacific Route Charts: These charts are
designed for FAA controllers to monitor
transoceanic flights. They show established intercontinental air routes, including reporting points
with geographic positions. The Composite Chart
scale is 1 inch = 164 NM/1:12,000,000. 48 x 41-
1/2 inches. Area Chart scales are 1 inch = 95.9
NM/1:7,000,000. The size is 52 x 40-1/2 inches.
All charts shipped unfolded. The charts are revised
every 56 days.
• North Atlantic Route Chart: Designed for FAA
controllers to monitor transatlantic flights, this
five-color chart shows oceanic control areas,
coastal navigation aids, oceanic reporting points,
and NAVAID geographic coordinates. The full size
chart scale is 1 inch = 113.1 NM/1:8,250,000,
shipped flat only. The half size chart scale is 1 inch
= 150.8 NM/1:11,000,000. The size is 29-3/4 x 20-
1/2 inches, shipped folded to 5 x 10 inches only,
and is revised every 56 weeks.
• FAA Aeronautical Chart User¡¯s Guide: This
publication is designed to be used as a teaching
aid and reference document. It describes the substantial amount of information provided on the
FAA¡¯s aeronautical charts and publications. It
includes explanations and illustrations of chart
terms and symbols organized by chart type. It is
available online at:
http://www.naco.faa.gov/index.asp?xml=naco/on
line/aero_guide
• Airport/Facility Directory (A/FD)
Digital products include:
• The NAVAID Digital Data File: This file contains
a current listing of NAVAIDs that are compatible
with the NAS. Updated every 56 days, the file
contains all NAVAIDs including ILS and its components, in the U.S., Puerto Rico, and the Virgin
Islands plus bordering facilities in Canada,
Mexico, and the Atlantic and Pacific areas. The
file is available by subscription only, on a 3.5-
inch, 1.4 megabyte diskette.
• The Digital Obstacle File: This file describes all
obstacles of interest to aviation users in the U.S.,
with limited coverage of the Pacific, Caribbean,
Canada, and Mexico. The obstacles are assigned
unique numerical identifiers, accuracy codes, and
listed in order of ascending latitude within each
state or area. The file is updated every 56 days, and
is available on 3.5-inch, 1.4 megabyte diskettes.
• The Digital Aeronautical Chart Supplement
(DACS): The DACS is a subset of the data provided
to FAA controllers every 56 days. It reflects digitally what is shown on the en route high and low
charts. The DACS is designed to be used with aeronautical charts for flight planning purposes only. It
should not be used as a substitute for a chart. The
DACS is available on two 3.5-inch diskettes, compressed format. The supplement is divided into the
following nine individual sections:
Section 1: High Altitude Airways, Conterminous U.S.
Section 2: Low Altitude Airways, Conterminous U.S.
Section 3: Selected Instrument Approach Procedure
NAVAID and Fix Data
Section 4: Military Training Routes
Section 5: Alaska, Hawaii, Puerto Rico, Bahamas, and
Selected Oceanic Routes
Section 6: STARs, Standard Terminal Arrivals
Section 7: DPs, Instrument Departure Procedures
Section 8: Preferred IFR Routes (low and high altitude)
Section 9: Air Route and Airport Surveillance Radar
Facilities
NOTICE TO AIRMEN
Since the NAS is continually evolving, Notices to
Airmen (NOTAM) provide the most current essential
flight operation information available, not known sufficiently in advance to publicize in the most recent
aeronautical charts or A/FD. NOTAMs provide information on airports and changes that affect the NAS that
are time critical and in particular are of concern to IFR
operations. Published FAA domestic/international
NOTAMs are available by subscription and on the
Internet. Each NOTAM is classified as a NOTAM (D),
a NOTAM (L), or an FDC NOTAM. [Figure 1-21]
1-30
A NOTAM (D) or distant NOTAM is given dissemination
beyond the area of responsibility of a Flight Service
Station (AFSS/FSS). Information is attached to hourly
weather reports and is available at AFSSs/FSSs.
AFSSs/FSSs accept NOTAMs from the following personnel in their area of responsibility: Airport Manager,
Airways Facility SMO, Flight Inspection, and Air Traffic.
They are disseminated for all navigational facilities that
are part of the U.S. NAS, all public use airports, seaplane
bases, and heliports listed in the A/FD. The complete
NOTAM (D) file is maintained in a computer database at
the National Weather Message Switching Center
(WMSC) in Atlanta, Georgia. Most air traffic facilities,
primarily AFSSs/FSSs, have access to the entire database
of NOTAM (D)s, which remain available for the duration
of their validity, or until published.
A NOTAM (L) or local NOTAM requires dissemination
locally, but does not qualify as NOTAM (D) information.
These NOTAMs usually originate with the Airport
Manager and are issued by the FSS/AFSS. A NOTAM (L)
contains information such as taxiway closures, personnel
and equipment near or crossing runways, and airport
rotating beacon and lighting aid outages. A separate file
of local NOTAMs is maintained at each FSS/AFSS for
facilities in the area. NOTAM (L) information for other
FSS/AFSS areas must be specifically requested directly
from the FSS/AFSS that has
responsibility for the airport
concerned. Airport/Facility
Directory listings include the
associated FSS/AFSS and
NOTAM file identifiers.
[Figure 1-22]
FDC NOTAMs are issued by
the National Flight Data
Center (NFDC) and contain
regulatory information such as
temporary flight restrictions or amendments to instrument approach procedures and other current aeronautical charts. FDC NOTAMs are available through all air
traffic facilities with telecommunications access.
Information for instrument charts is supplied by
Aviation System Standards (AVN) and much of the
other FDC information is extracted from the
NOTAM (D) System.
The Notices to Airmen Publication (NTAP) is published by Air Traffic Publications every 28 days and
contains all current NOTAM (D)s and FDC NOTAMs
(except FDC NOTAMs for temporary flight restrictions) available for publication. Federal airway
changes, which are identified as Center Area
NOTAMs, are included with the NOTAM (D) listing.
Published NOTAM (D) information is not provided
during pilot briefings unless requested. Data of a permanent nature are sometimes printed in the NOTAM
publication as an interim step prior to publication on
the appropriate aeronautical chart or in the A/FD. The
NTAP is divided into four parts:
• Notices in part one are provided by the National
Flight Data Center, and contain selected
NOTAMs that are expected to be in effect on the
NOTAM(D)
DEN 09/080 DEN 17L IS LLZ OTS WEF 0209141200-0210012359
NOTAM(L)
TWY C (BTN TWYS L/N); TWY N (BTN TWY AND RWY10L/28R); TWY P (BTN
TWY C AND RWY10L/28R) - CLSD DLY
1615-2200.
FDC NOTAM
FDC 2/9651 DFW FI/DALLAS/FORT WORTH INTL, DALLAS/FORT WORTH, TX
CORRECT TERMINAL PROCEDURES SOUTH CENTRAL (SC) VOL 2 OF 5.
EFFECTIVE 8 AUGUST 2002, PAGE 192.
CHANGE RADIAL FROM RANGER (FUZ) VORTAC TO EPOVE INT TO READ
352 VICE 351. 3
CH
35
EF
HAN
2
NGE
FECT
GE
CT
TIV
R
T U
VE
A
U.S
D
S.
A
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FW
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F P DALL
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001235
Figure 1-21. NOTAM Examples.
Figure 1-22. NOTAM File Reference in A/FD.
1-31
1-32
effective date of the publication. This part is
divided into three sections:
a. Airway NOTAMs reflecting airway changes
that fall within an ARTCC¡¯s airspace;
b. Airports/facilities, and procedural NOTAMs;
c. FDC general NOTAMs containing NOTAMs
that are general in nature and not tied to a specific airport/facility, i.e. flight advisories and
restrictions.
• Part two contains revisions to minimum en route
IFR altitudes and changeover points.
• Part three, International, contains flight prohibitions, potential hostile situations, foreign notices,
and oceanic airspace notices.
• Part four contains special notices and graphics pertaining to almost every aspect of aviation; such as,
military training areas, large scale sporting events,
air show information, and airport-specific information. Special traffic management programs
(STMPs) are published in part four.
If you plan to fly internationally, you can benefit by
accessing Class I international ICAO System NOTAMs,
that include additional information. These help you differentiate IFR versus VFR NOTAMs, assist pilots who
are not multilingual with a standardized format, and may
include a ¡°Q¡± line, or qualifier line that allows computers to read, recognize, and process NOTAM content
information.
NAVIGATION DATABASES
The FAA updates and distributes the National Flight
Database (NFD), a navigation database that is published
by NACO every 28 days. This helps pilots and aircraft
owners maintain current information in onboard navigation databases, such as those used in GPS and RNAV
equipment. Current data elements include airports and
heliports, VHF and NDB navigation aids, fixes/waypoints, airways, DPs, STARs, and GPS and RNAV
(GPS) standard instrument approach procedures
(SIAPs) with their associated minimum safe altitude
(MSA) data, runways for airports that have a SIAP
coded in the NFD, and special use airspace (SUA)
including military operation areas (MOA) and national
security areas (NSA).
Future data elements to be added are:
• Air Traffic Service (ATS) routes
• Class B, C, and D Airspace
• Terminal Navigation Aids
• ILS and LOC SIAPs with Localizer and
Glideslope records
• FIR/UIR Airspace
• Communication
Details about the NFD can be found at:
http://www.naco.faa.gov/index.asp?xml=naco/catalog/
charts/digital/nfd
The FAA has developed an implementation and development plan that will provide users with data in an
acceptable, open-industry standard for use in
GPS/RNAV systems. The established aviation industry
standard database model, Aeronautical Radio,
Incorporated (ARINC 424) format, includes the essential information necessary for IFR flight in addition to
those items necessary for basic VFR navigation.
Essentially the new FAA database will fulfill
requirements for operations within the NAS while
still providing the opportunity for private entities to
build upon the basic navigation database and provide users with additional services when desired.
Refer to Appendix A, Airborne Navigation
Databases for more detailed information.
As FAA and other government websites are continuously being changed and updated, be ready to use the
search feature to find the information or publications
you need.