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Today’s National Airspace System (NAS) consists of acomplex collection of facilities, systems, equipment,procedures, and airports operated by thousands of peo-ple to provide a safe and efficient flying environment.The NAS includes:

• More than 750 air traffic control (ATC) facilitieswith associated systems and equipment to provideradar and communication service.

• Volumes of procedural and safety information nec-essary for users to operate in the system and forFAA employees to effectively provide essentialservices.

• More than 18,000 airports capable of accommo-dating an array of aircraft operations, many ofwhich support instrument flight rules (IFR) depar-tures and arrivals.

• Approximately 4,500 air navigation facilities.

• Approximately 48,000 FAA employees who pro-vide air traffic control, flight service, security,field maintenance, certification, systems acquisi-tions, and a variety of other services.

• Approximately 13,000 instrument flight proce-dures, including over 1,000 Instrument LandingSystem (ILS) procedures, over 1,700 nondirec-tional beacon (NDB) procedures, over 2,700 VHFomnidirectional range (VOR) procedures, andover 3,500 global positioning system/area naviga-tion procedures (GPS/RNAV).

• Procedures such as microwave landing system(MLS), localizer (LOC), localizer type directionalaid (LDA), simplified directional facility (SDF),charted visual flight procedures, departure proce-dures (DPs), and standard terminal arrivals(STARs).

• Approximately 2,153,326 instrument approachesannually, of which 36 percent are air carrier, 27percent air taxi, 33 percent general aviation, and 4percent military.

• Approximately 49,409,000 instrument operationslogged by FAA towers annually.

America’s aviation industry is projecting continuedincreases in business, recreation, and personal travel.Airlines in the United States (U.S.) expect to carry twiceas many passengers by the year 2015 as they do today.[Figure 1-1]

Figure 1-1. IFR Operations in the NAS.

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BRIEF HISTORY OF THE NATIONAL AIRSPACE SYSTEMAbout two decades after the introduction of poweredflight, aviation industry leaders believed that the air-plane would not reach its full commercial potential with-out federal action to improve and maintain safetystandards. 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 inregulating civil aviation. The act charged the Secretaryof Commerce with fostering air commerce, issuing andenforcing air traffic rules, licensing pilots, certifying air-craft, establishing airways, and operating and maintain-ing aids to air navigation. As commercial flyingincreased, the Bureau of Air Commerce—a division ofthe Department of Commerce—encouraged a group ofairlines to establish the first three centers for providingair traffic control (ATC) along the airways. In 1936, thebureau took over the centers and began to expand theATC system. [Figure 1-2] The pioneer air traffic con-trollers used maps, blackboards, and mental calculationsto ensure the safe separation of aircraft traveling alongdesignated routes between cities.

Figure 1-2. ATC System Expansion.

On the eve of America’s entry into World War II, theCivil Aeronautics Administration (CAA)—charged withthe responsibility for ATC, airman and aircraft certifi-cation, safety enforcement, and airway development—expanded its role to cover takeoff and landing

operations at airports. Later, the addition of radar helpedcontrollers to keep abreast of the postwar boom in com-mercial air transportation.

The introduction of jet airliners, followed by a series ofmidair collisions, instigated the passage of the FederalAviation Act of 1958, which transferred CAA functionsto the FAA (then the Federal Aviation Agency). The actentrusted safety rulemaking to the FAA, which also heldthe sole responsibility for developing and maintaining acommon civil-military system of air navigation and airtraffic control. In 1967, the new Department ofTransportation (DOT) combined major federal trans-portation responsibilities, including the FAA (now theFederal Aviation Administration) and a new NationalTransportation Safety Board (NTSB).

By the mid-1970s, the FAA had achieved a semi-auto-mated ATC system based on a marriage of radar andcomputer technology. By automating certain routinetasks, the system allowed controllers to concentratemore efficiently on the task of providing aircraft separa-tion. Data appearing directly on the controllers’ scopes

provided the identity, alti-tude, and groundspeed of air-craft carrying radar beacons.Despite its effectiveness, thissystem required continuousenhancement to keep pacewith the increased air trafficof the late 1970s, due in partto the competitive environ-ment created by airlinederegulation.

To meet the challenge oftraffic growth, the FAAunveiled the NAS Plan inJanuary 1982. The new plancalled for more advancedsystems for en route and ter-minal ATC, modernizedflight service stations, andimprovements in ground-to-air surveillance and commu-nication. Continued ATCmodernization under theNAS Plan included suchsteps as the implementationof Host Computer Systems(completed in 1988) that

were able to accommodate new programs needed for thefuture. [Figure 1-3]

In February 1991, the FAA replaced the NAS Plan withthe more comprehensive Capital Investment Plan (CIP),which outlined a program for further enhancement of theATC system, including higher levels of automation as well

1946

1970-2000

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as new radar, communications, and weather forecastingsystems. One of the CIP’s programs currently underway isthe deployment of new Terminal Doppler Weather Radarsystems able to warn pilots and controllers of meteorologi-cal hazards. The FAA is also placing a high priority onspeeding the application of the GPS satellite technology tocivil aeronautics. Another notable ongoing program isencouraging progress toward the implementation ofFree Flight, a concept aimed at increasing the efficiencyof high-altitude operations.

NATIONAL AIRSPACE SYSTEM PLANSFAA planners efforts to devise a broad strategy toaddress capacity issues resulted in the OperationalEvolution Plan (OEP)the FAA’s commitment to meetthe air transportation needs of the U.S. for the next tenyears.

To wage a coordinated strategy, OEP executives met withrepresentatives from the entire aviation community—including airlines, airports, aircraft manufacturers, serviceproviders, pilots, controllers, and passengers. They agreedon 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 expandcapacity, decrease delays, andimprove efficiency while main-taining safety and security. Withreliance on the strategic support ofthe aviation community, the OEP

is limited in scope, and only containsprograms to be accomplished between2001 and 2010. Programs may movefaster, but the OEP sets the minimumschedule. Considered a living docu-ment that matures over time, theOEP is continually updated as deci-sions are made, risks are identifiedand mitigated, or new solutions tooperational problems are discoveredthrough research.

An important contributor to FAAplans is the Terminal AreaOperations Aviation RulemakingCommittee (TAOARC). The objec-tives and scope of TAOARC are toprovide a forum for the U.S. aviationcommunity to discuss and resolveissues, provide direction for U.S.

flight operations criteria, and produce U.S. consensuspositions for global harmonization.

The general goal of the committee is to develop a meansto implement improvements in terminal area operationsthat address safety, capacity, and efficiency objectives, astasked, that are consistent with international implemen-tation. In the context of this committee, terminal areameans the airspace that services arrival, departure, andairport ground operations. This committee provides aforum for the FAA, other government entities, andaffected members of the aviation community to discussissues and to develop resolutions and processes to facil-itate the evolution of safe and efficient terminal areaoperations.

Current efforts associated with NAS modernizationcome with the realization that all phases must be inte-grated. The evolution to an updated NAS must be wellorchestrated and balanced with the resources available.Current plans for NAS modernization focus on three keycategories:

• Upgrading the infrastructure.

• Providing new safety features.

• Introducing new efficiency-oriented capabilitiesinto the existing system.

Figure 1-3. National AirspaceSystem Plan.

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It is crucial that our NAS equipment is protected, as lostradar or communications signals can slow the flow ofaircraft to a busy city, which in turn, could cause delaysthroughout the entire region, and possibly, the wholecountry.

The second category for modernization activitiesfocuses on upgrades concerning safety. Although wecannot control the weather, it has a big impact on theNAS. Fog in San Francisco, snow in Denver, thunder-storms in Kansas, wind in Chicago; all of these reducethe safety and capacity of the NAS. Nevertheless, greatstrides are being made in our ability to predict theweather. Controllers are receiving better informationabout winds and storms, and pilots are receiving betterinformation before they take offall of which makesflying safer. [Figure 1-4]

Another cornerstone of the FAA’s future is improvednavigational information available in the cockpit. As theuse of GPS becomes more widely accepted, the WideArea Augmentation System (WAAS) will supplementGPS navigation and provide pilots improved accuracyand availability, which increases safety of flight. Due tothe precise navigation service it provides, WAAS alsoenables improvements in efficiency by providing accessto more runways in poor weather.

Moreover, the Local Area Augmentation System(LAAS) is being developed to provide even betteraccuracy than GPS with WAAS. LAAS will providelocalized service for final approaches in poor weatherconditions at major airports. This additional naviga-tional accuracy will be available in the cockpit andwill be used for other system enhancements. Moreinformation about WAAS and LAAS is contained inChapters 5 and 6.

The Automatic Dependent Surveillance (ADS) sys-tem, currently being evaluated by the FAA and severalairlines, enables the aircraft to automatically transmitits location to various receivers. This broadcast mode,

commonly referred to as ADS-B, is a signal that canbe received by other properly equipped aircraft andground receiver stations, which in turn feed theautomation system accurate aircraft position informa-tion. This more accurate information will be used toimprove the efficiency of the system—the third cate-gory of modernization goals.

Other key efficiency improvements are found in thedeployment of new tools designed to assist the con-troller. For example, most commercial aircraftalready have equipment to send their GPS positionsautomatically to receiver stations over the ocean. Thiskey enhancement is necessary for all aircraft operat-ing in oceanic airspace and allows more efficient useof airspace. Another move is toward improving textand graphical message exchange, which is the ulti-mate goal of the Controller Pilot Data LinkCommunications (CPDLC) Program.

In the en route domain, the Display SystemReplacement (DSR), along with the Host/OceanicComputer System Replacement (HOCSR) andEunomia projects, are the platforms and infrastruc-ture for the future. These provide new displays to thecontrollers, upgrade the computers to accept futuretools, and provide modern surveillance and flightdata processing capabilities. For CPDLC to workeffectively, it must be integrated with the en routecontroller’s workstation.

RNAV PLANSDesigning routes and airspace to reduce conflictsbetween arrival and departure flows can be as simple asadding extra routes or as comprehensive as a full redesignin which multiple airports are jointly optimized. Newstrategies are in place for taking advantage of existingstructures to departing aircraft through congested transi-tion airspace. In other cases, RNAV procedures are usedto develop new routes that reduce flow complexity bypermitting aircraft to fly optimum routes with minimalcontroller intervention. These new routes spread the flow

Figure 1-4. Improved Safety of Flight.

1 This figure includes the four crashes of September 11, 2001. Because the crashes of September 11, 2001 were the results of terroristactivity, those crashes are included in the totals for scheduled U.S. airline accidents and fatalities, but are not used for the purpose of acci-dent rate computation. The accident rate of .317 per 100,000 departures is determined from the remaining 32 accidents in 2001.

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across the terminal and transition airspace so aircraft canbe separated with optimal lateral distances and altitudes inand around the terminal area. In some cases, the additionof new routes alone is not sufficient, and redesign of exist-ing routes and flows are required. Benefits are multipliedwhen airspace surrounding more than one airport (e.g., ina metropolitan area) can be jointly optimized.

SYSTEM SAFETYAlthough hoping to decrease delays, improve systemcapacity, and modernize facilities, the ultimate goal of theNAS Plan is to improve system safety. If statistics are anyindication, the beneficial effect of the implementation ofthe plan may already be underway as aviation safetyseems to have increased in recent years. The FAA hasmade particular emphasis to not only reduce the numberof accidents in general, but also to make strides in curtail-ing controlled flight into terrain (CFIT) and runway incur-sions as well as continue approach and landing accidentreduction (ALAR).

The term CFIT defines an accident in which a fullyqualified and certificated crew flies a properly workingairplane into the ground, water, or obstacles with noapparent awareness by the pilots. A runway incursion isdefined as any occurrence at an airport involving an air-craft, vehicle, person, or object on the ground that createsa collision hazard or results in a loss of separation with anaircraft taking off, attempting to take off, landing, orattempting to land. The term ALAR applies to an accidentthat occurs during a visual approach, during an instrumentapproach after passing the intermediate approach fix

(IF), or during the landing maneuver. This term alsoapplies to accidents occurring when circling or whenbeginning a missed approach procedure.

ACCIDENT RATESThe NTSB released airline accident rate statistics for2001 that showed a decline from the previous year.Thirty-six accidents1 on U.S. scheduled airlines wererecorded in 2001, resulting in .317 accidents per100,000 departures. These numbers represent a decreasefrom 2000, when 51 accidents were reported for a rateof .463 accidents per 100,000 departures.

Accident rates for both scheduled and non-scheduled 14CFR part 135 services also decreased in 2001. Thescheduled service rate shrank from 1.965 accidents per100,000 departures in 2000 to 1.407 in 2001. Forunscheduled, on-demand air taxis, the rate decreasedfrom 2.28 to 2.12 per 100,000 flight hours.

Despite reporting fewer accidents in 2001, the accident ratefor general aviation aircraft increased slightly from 6.33accidents per 100,000 flight hours in 2000 to 6.56 accidentsin 2001. General aviation was the only category of air trans-portation to report an increase in its accident rate.

Among the top priorities for accident prevention areCFIT and ALAR. Pilots can decrease exposure to aCFIT accident by identifying risk factors and remediesprior to flight. [Figure 1-5] Additional actions on theCFIT reduction front include equipping aircraft with

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. CFITReduction.

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state-of-the art terrain awareness and warning systems(TAWS), sometimes referred to as enhanced groundproximity warning systems (EGPWS). This measurealone has been assessed to contribute to at least a 90percent reduction in CFIT accidents. The total U.S.commercial fleet (excluding cargo planes) is planned tobe retrofitted with TAWS by the end of March 2005.

Added training for aircrews and controllers is part ofthe campaign to safeguard against CFIT, as well asmaking greater use of approaches with vertical guid-ance which use a constant angle descent path to therunway. This measure offers nearly a 70 percent poten-tial reduction. Another CFIT action plan involves acheck of ground-based radars to ensure that their mini-mum safe altitude warning (MSAW) feature functionscorrectly.

Like CFIT, the ALAR campaign features a menu ofactions, three of which involve crew training, altitudeawareness policies checklists, and smart alerting tech-nology. These three alone offer a potential 20 to 25percent reduction in approach and landing accidents.Officials representing Safer Skies—a ten-year col-laborative effort between the FAA and the airlineindustry—believe that the combination of CFIT andALAR interventions will offer more than a 45 per-cent reduction in accidents.

RUNWAY INCURSION STATISTICSWhile it is difficult to eliminate runway incursions, tech-nology offers the means for both controllers and flightcrews to create situational awareness of runway incur-sions in sufficient time to prevent accidents.Consequently, the FAA is taking actions that will identifyand implement technology solutions, in conjunction withtraining and procedural evaluation and changes, toreduce runway accidents. Recently established pro-grams that address runway incursions center on iden-tifying the potential severity of an incursion andreducing the likelihood of incursions through training,technology, communications, procedures, airportsigns/marking/lighting, data analysis, and developinglocal solutions. The FAA’s initiatives include:

• Promoting aviation community participation inrunway safety activities and solutions.

• Appointing nine regional Runway Safety ProgramManagers.

• Providing training, education, and awareness forpilots, controllers, and vehicle operators.

• Publishing an advisory circular for airport surfaceoperations.

• Increasing the visibility of runway hold line mark-ings.

• Reviewing pilot-controller phraseology.

• Providing foreign air carrier pilot training, educa-tion, and awareness.

• Requiring all pilot checks, certifications, and flightreviews to incorporate performance evaluations ofground operations and test for knowledge.

• Increasing runway incursion action team site visits.

• Deploying high-technology operational systemssuch as the Airport Surface Detection Equipment-3 (ASDE-3), Airport Movement Area SafetySystem (AMASS), and Airport Surface DetectionEquipment-X (ASDE-X).

• Evaluating direct warning capability to flightcrews using cockpit display avionics for both largeand small aircraft operators.

Runway incursion statistics compiled for the first half of2001 show that there were 243 runway incursions, twoless than the same time in 2000. Of these, 48 percent wereCategory D (little or no risk of collision), 38 percent wereCategory C (there is ample time and distance to avoid apotential collision), 8 percent were Category B (there is asignificant potential for collision), and 6 percent wereCategory A (collision avoidable only when extremeaction is taken). The good news is that, when comparingthe severity distribution of the combined totals of the lastthree years, the 2001 percentages have decreased inCategories A, B, and C.

SYSTEM CAPACITYOn the user side, there are more than 616,000 activepilots operating over 280,000 commercial, regional,general aviation, and military aircraft. That equates to4,000 to 6,000 aircraft operating in the NAS during peakperiods. Figure 1-6 depicts over 5,000 aircraft operatingat the same time in the U.S. shown on this Air TrafficControl System Command Center (ATCSCC) screen.

TAKEOFFS AND LANDINGSAccording to the General Aviation Manufacturer’sAssociation (GAMA) statistics for 2000, operations atgeneral aviation (GA) airports with FAA control tow-ers totaled over 27 millionapproximately 50,000aircraft operations per day. Aircraft landings anddepartures have increased steadily with more than11.5 million2 reported for 2001. These figures do noteven include operations at airports that do not have acontrol tower. Despite these numbers, user demandson the NAS are quickly exceeding the resourcesrequired to fulfill them. Delays for the period of

2 Source: BTS publication “Air Carrier Industry Scheduled Service TRAFFIC statistics.

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January through June 2000 were almost 13.6 percenthigher than in 1999. In June alone, delays increased 20percent. Delays for May, June, and July 2000 totaledmore than 86,684, a 6.8 percent increase over the previ-ous year. This clear illustration of the NAS’s growingpains provides the FAA with verification that moderniza-tion efforts currently underway are well justified.Nothing short of the integrated, systematic, cooperative,and comprehensive approach spelled out by the OEP canbring the NAS to the safety and efficiency standards thatthe flying public demands.

AIR TRAFFIC CONTROL SYSTEM COMMAND CENTER The task of managing the flow of air traffic within theNAS is assigned to the Air Traffic Control SystemCommand Center (ATCSCC). Headquartered inHerndon, Virginia, the ATCSCC has been operationalsince 1994 and is located in one of the largest andmost sophisticated facilities of its kind. The ATCSCCregulates air traffic at a national level when weather,equipment, runway closures, or other conditions placestress on the NAS. In these instances, traffic manage-ment specialists at the ATCSCC take action to modifytraffic 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 con-gestion and maximize the overall use of the NAS,thereby ensuring safe and efficient air travel within theU.S. For example, if severe weather, military operations,runway closures, special events, or other factors affectair traffic for a particular region or airport, the ATCSCCmobilizes its resources and various agency personnel toanalyze, coordinate, and reroute (if necessary) traffic tofoster maximum efficiency and utilization of the NAS.

The ATCSCC directs the operation of the traffic man-agement (TM) system to provide a safe, orderly, andexpeditious flow of traffic while minimizing delays.TM is apportioned into traffic management units(TMUs), which monitor and balance traffic flowswithin their areas of responsibility in accordancewith TM directives. TMUs help to ensure systemefficiency and effectiveness without compromisingsafety, by providing the ATCSCC with advancenotice of planned outages and runway closures thatwill impact the air traffic system, such as NAVAIDand radar shutdowns, runway closures, equipment

Figure 1-6. System Capacity.

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and computer malfunctions, and procedural changes.[Figure 1-7]

HOW THE SYSTEM COMPONENTS WORK TOGETHERThe NAS comprises the common network of U.S. air-space, air navigation facilities, equipment, services, air-ports and landing areas, aeronautical charts, informationand services, rules and regulations, procedures, techni-cal information, manpower, and material. Included aresystem components shared jointly with the military. Theunderlying demand for air commercepeople’s desireto travel for business and pleasure and to ship cargo byairgrows with the economy independent of the capac-ity or performance of the NAS. As the economy grows,more and more people want to fly, whether the systemcan handle it or not. Another typerealizeddemandrefers to flight plans filed by the airlines andother airspace users to access the system. Realizeddemand is moderated by the airline’s understanding ofthe number of flights that can be accommodated withoutencountering unacceptable delay, and is limited by thecapacity for the system.

USERSAccording to a 2000 MITRE report, between 1998 and1999, commercial traffic grew at 4.6 percent, using up muchof the capacity reserves in the system. The 2002 FAAACEPlan showed 695.7 million passenger enplanements in2000, while also verifying the impact of 9-11 with only682.5 million passenger enplanements for 2001 which is theequivalent of a 1.8 percent decrease in passenger traffic. A

steady growth rate (near 3 percent per year) is predicted toresume in 2003, with projected passenger enplanementsreaching the previous 2002 forecast of 740 million in 2005,or a 3 year delay in previous estimates. Likewise, the previ-ous forecast that passenger enplanements would reach 1 bil-lion by 2010, is now forecast for that level to be reached by2013. Even at the lower growth rate, the system is nearingthe point of saturation, with limited ability to grow unlessmajor changes are brought about.

Adding to the growth challenge, users of the NAS cover awide spectrum in pilot skill and experience, aircraft types,and air traffic service demands, creating a challenge to theNAS to provide a variety of services that accommodate alltypes of traffic. NAS users range from professional airline,commuter, and corporate pilots to single-engine pistonpilots, as well as owner-operators of personal jets to militaryjet fighter trainees.

AIRLINESThough commercial air carrier aircraft traditionallymake up less than 5 percent of the civil aviation fleet,they account for about 30 percent of the hours flown andalmost half of the total IFR hours flown in civil avia-tion3. Commercial air carriers are the most homogenouscategory of airspace users, although there are some dif-ferences between U.S. trunk carriers (major airlines) andregional airlines (commuters) in terms of demand forATC services. Generally, U.S. carriers operate large,high performance airplanes that cruise at altitudes above18,000 feet. Conducted exclusively under IFR, airlineflights follow established schedules and operate in and

out of larger and better-equipped airports. Interminal areas, however,they share airspace andfacilities with all types oftraffic and must competefor airport access withother users. Airline pilotsare highly proficient andthoroughly familiar withthe rules and proceduresunder which they mustoperate.

Some airlines are lookingtoward the use of largeraircraft, such as the 555-passenger Airbus A380,with the potential toreduce airway and termi-nal congestion by trans-porting more people infewer aircraft. This isespecially valuable atmajor hub airports,

SEA

PDX

SFOSJC

LAX

SAN

LAS

SLC

PHX

DEN

DFW

IAH

MCISTL

MEM

BNA

IND

ATL

TPAMCO

FLLMIA

CLT RDU

CVG

IADDCA

BWICLE

DTW

PITTEB

EWRPHL

LGAJFK

BOS

ORD

MDW

MSP

Figure 1-7. A real-time Airport Status page displayed on the ATCSCC web site(www.fly.faa.gov/flyFAA/index.html) provides general airport condition status. Though not flight spe-cific, 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 toorange locations is being delayed at the departure point. Red airports are experiencing taxi or air-borne holding delays greater than 45 minutes. Blue indicates closed airports.

3 Source: FAA Statistical Handbook of Aviation

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where the number of operations exceeds capacity at certaintimes of day. On the other hand, the proliferation of largeraircraft also requires changes to terminals (e.g., double-decker jetways and better passenger throughput), rethinkingof rescue and fire-fighting strategies, taxi-way filet changes,and perhaps stronger runways and taxiways.

Commuter airlines also follow established schedules andare flown by professional pilots. Commuters characteristi-cally operate smaller and lower performance aircraft inairspace that must often be shared by GAaircraft, includingvisual flight rules (VFR) traffic. As commuter operationshave grown in volume, they have created extra demands onthe airport and ATC systems. At one end, they use hubairports along with other commercial carriers, which con-tributes to growing congestion at major air traffic hubs.IFR-equipped and operating under IFR like other air carri-ers, commuter aircraft cannot be used to full advantageunless the airport at the other end of the flight, typically asmall community airport, also is capable of IFR operation.Thus, the growth of commuter air service has created pres-sure for additional instrument approach procedures andcontrol facilities at smaller airports. Agrowing trend amongthe major airlines is the proliferation of regional jets (RJs).RJs are replacing turboprop aircraft and they are welcomedby some observers as saviors of high-quality jet aircraftservice to small communities. RJs are likely to be a regularfeature of the airline industry for a long time becausepassengers and airlines overwhelmingly prefer RJs toturboprop service. From the passengers’ perspective, theyare far more comfortable; and from the airlines’ point ofview, they are more profitable. Thus, within a few years,most regional air traffic in the continental U.S. will be byjet, with turboprops filling a smaller role.

In 1997, the FAA’s research, development, and engi-neering armthe Center for Advanced AviationSystems Development (CAASD)investigated theunderlying operational and economic environmentsof RJs on the ATC system. The study demonstratedtwo distinct trends: (1) growing airspace and airportcongestion was exacerbated by the rapid growth of RJtraffic, and (2) potential airport infrastructure limita-tions may constrain airline business. During thespring and summer of 2000, the FAA, CAASD, majorairlines, and others focused on finding mitigatingstrategies to address airline congestion. With morethan 500 RJs in use—and double that expected overthe next few years—the success of these efforts iscritical if growth in the regional airline industry is tobe sustained. [Figure 1-8]

CORPORATE AND FRACTIONALSThough technically considered under the GA umbrella,the increasing use of sophisticated, IFR-equipped aircraftby businesses and corporations has created a niche of itsown. By using larger high performance airplanes andequipping them with the latest avionics, the business por-tion of the GA fleet has created demands for ATC services

that more closely resemble commercial operators than thepredominately VFR general aviation fleet.

GENERAL AVIATIONThe tendency of GA aircraft owners at the upper end ofthe spectrum to upgrade the performance and avionicsof their aircraft increases the demand for IFR servicesand for terminal airspace at airports. In response, theFAA has increased the extent of controlled airspace andimproved ATC facilities at major airports. The safety ofmixing IFR and VFR traffic is a major concern, but theimposition of measures to separate and control bothtypes of traffic creates more restrictions on airspace useand raises the level of aircraft equipage and pilot qualifi-cation necessary for access.

MILITARYFrom an operational point of view, military flight activi-ties comprise a subsystem that must be fully integratedwithin NAS. However, military aviation has uniquerequirements that often are different from civil aviationusers. The military’s need for designated training areasand low-level routes located near their bases sometimesconflicts with civilian users who need to detour aroundthese areas. In coordinating the development of ATCsystems and services for the armed forces, the FAA ischallenged to achieve a maximum degree of compatibil-ity between civil and military aviation objectives.

ATC FACILITIESFAA figures show that the NAS includes more than18,300 airports, 21 ARTCCs, 197 TRACON facilities,over 460 air traffic control towers (ATCTs), 75 flightservice stations (FSSs), and approximately 4,500 air nav-igation facilities. Several thousand pieces of maintainableequipment including radar, communications switches,

On Hand + Firm Orders + Options

Others

USANWAUAL

AAL

COA

DAL

2,500

2,000

1,500

1,000

500

0

Num

ber

of R

J A

ircra

ft

*Data current as of August 2000

Figure 1-8. Regional Jets in the Fleet. As this chart suggests,while there are only about 500 RJs in the combined U.S. com-mercial airline fleet today, the major airlines have some 750RJs on order, with options for another 1,250. As the CAASD’sRJ studies demonstrate, this dramatic change from the hand-ful of RJs that were in operation only five years ago has majorimplications for the NAS today and in the immediate future.

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ground-based navigation aids, computer displays, andradios are used in NAS operations, and NAS compo-nents represent billions of dollars in investments by thegovernment. Additionally, the aviation industry hasinvested significantly in ground facilities and avionicssystems designed to use the NAS. Approximately48,000 FAA employees provide air traffic control, flightservice, security, field maintenance, certification, sys-tem acquisition, and other essential services.

Differing levels of ATC facilities vary in their structureand purpose. Traffic management at the national level isled by the Command Center, which essentially “owns”all airspace. Regional Centers, in turn, sign Letters ofAgreement (LOAs) with various approach control facil-ities, delegating those facilities chunks of airspace inwhich that approach control facility has jurisdiction. Theapproach control facilities, in turn, sign LOAs with var-ious towers that are within that airspace, further delegat-ing airspace and responsibility. This ambiguity hascreated difficulties in communication between the localfacilities and the Command Center. However, a decen-tralized structure enables local flexibility and a tailoringof services to meet the needs of users at the local level.Improved communications between the CommandCenter and local facilities could support enhanced safetyand efficiency while maintaining both centralized anddecentralized aspects to the ATC system.

AIR ROUTE TRAFFIC CONTROL CENTERA Center’s primary function is to control and separateair traffic within a designated airspace, which may covermore than a 100,000 square miles, traverse over severalstates, and extends from the base of the underlying con-trolled airspace up to Flight Level (FL) 600. There are21 Centers located throughout the U.S., each of which isdivided into sectors. Controllers assigned to these sec-tors, which range from 50 to over 200 miles wide, guideaircraft toward their intended destination by way of vec-tors and/or airway assignment, routing aircraft aroundweather and other traffic. Centers employ 300 to 700 con-trollers, with more than 150 on duty during peak hours atthe busier facilities. A typical flight by a commercial air-liner is handled mostly by the Centers.

TERMINAL RADAR APPROACH CONTROLTerminal Radar Approach Control (TRACON) con-trollers work in dimly lit radar rooms located withinthe control tower complex or in a separate buildinglocated on or near the airport it serves. [Figure 1-9]Using radarscopes, these controllers typically workan area of airspace with a 50-mile radius and up to analtitude of 17,000 feet. This airspace is configured toprovide service to a primary airport, but may includeother airports that are within 50 miles of the radarservice area. Aircraft within this area are providedvectors to airports, around terrain, and weather, aswell as separation from other aircraft. Controllers in

TRACONs determine the arrival sequence for the con-trol tower’s designated airspace.

Figure 1-9.Terminal Radar Approach Control.

CONTROL TOWERControllers in this type of facility manage aircraft oper-ations on the ground and within specified airspacearound an airport. The number of controllers in thetower varies with the size of the airport. Small generalaviation airports typically have three or four controllers,while larger international airports can have up to fifteencontrollers talking to aircraft, processing flight plans,and coordinating air traffic flow. Tower controllers man-age the ground movement of aircraft around the airportand ensure appropriate spacing between aircraft takingoff and landing. In addition, it is the responsibility of thecontrol tower to determine the landing sequencebetween aircraft under its control. Tower controllersissue a variety of instructions to pilots, from how toenter a pattern for landing to how to depart the airportfor their destination.

FLIGHT SERVICE STATIONSFlight Service Stations (FSSs) are air traffic facilitieswhich provide pilot briefings, en route communica-tions and VFR search and rescue services, assist lostaircraft and aircraft in emergency situations, relayATC clearances, originate Notices to Airmen, broad-cast aviation weather and NAS information, receiveand process IFR flight plans, and monitor navigationalaids (NAVAIDs). In addition, at selected locations,FSSs provide En route Flight Advisory Service (FlightWatch), take weather observations, issue airportadvisories, and advise Customs and Immigration oftransborder flights.

Pilot Briefers at FAA flight service stations render pre-flight, in-flight, and emergency assistance to all pilotson request. They give information about actual weatherconditions and forecasts for airports and flight paths,relay air traffic control instructions between controllersand pilots, assist pilots in emergency situations, andinitiate searches for missing or overdue aircraft. FSSs

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provide information to all airspace users, including themilitary.

FLIGHT PLANSPrior to flying in controlled airspace under IFR condi-tions or in Class A airspace, pilots are required to file aflight plan. IFR (as well as VFR) flight plans provideair traffic center computers with accurate and preciseroutes required for flight data processing (FDP4). Thecomputer knows every route (published and unpub-lished) and NAVAID, most intersections, and all air-ports, and can only process a flight plan if the proposedroutes and fixes connect properly. Center computersalso recognize preferred routes and know that forecastor real-time weather may change arrival routes.Centers and TRACONs now have a computer graphicthat 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 notoverlap in coverage or information with other Centers,so that flight requests not honored in one must berepeated in the next.

RELEASE TIMEATC uses an IFR release time5 in conjunction withtraffic management procedures to separate departingaircraft from other traffic. For example, when control-ling departures from an airport without a tower, thecontroller limits the departure release to one aircraft atany given time. Once that aircraft is airborne and radaridentified, then the following aircraft may be releasedfor departure, provided they meet the approved radarseparation (3 miles laterally or 1,000 feet vertically)when the second aircraft comes airborne. Controllersmust take aircraft performances into account whenreleasing successive departures, so that a B-747 HEAVYaircraft is not released immediately after a departingCessna 172. Besides releasing fast aircraft before slowones, another technique commonly used for successivedepartures is to have the first aircraft turn 30 to 40degrees from runway heading after departure, and thenhave the second aircraft depart on a SID or runway head-ing. Use of these techniques is common practice whenmaximizing airport traffic capacity.

EXPECT DEPARTURE CLEARANCE TIMEAnother tool that the FAA is implementing to increaseefficiency is the reduction of the standard ExpectDeparture Clearance Time6 (EDCT) requirement. TheFAA has drafted changes to augment and modify proce-dures contained in Ground Delay Programs (GDPs).Airlines may now update their departure times byarranging their flights’ priorities to meet the controlled

time of arrival. In order to evaluate the effectiveness ofthe new software and the airline-supplied data, theactual departure time parameter in relation to the EDCTis being reduced. This change will impact all flights(commercial and GA) operating to seven of the nation’sbusiest airports. Instead of the previous 25-minuteEDCT window (5 minutes prior and 20 minutes after theEDCT), the new requirement for GDP implementationis a 7-minute window, and aircraft are required to departwithin 3 minutes before or after their assignedControlled Time of Departure (CTD). Using reducedEDCT and other measures included in GDPs, ATC aimsat reducing the number of arrival slots issued to accom-modate degraded arrival capacity at an airport affectedby weather. The creation of departure or ground delaysis less costly and safer than airborne holding delays inthe airspace at the arrival airport.

MANAGING SAFETY AND CAPACITY

SYSTEM DESIGNThe CAASD is aiding in the evolution towards free flightwith its work in developing new procedures necessaryfor changing traffic patterns and aircraft with enhancedcapabilities, and also in identifying traffic flow con-straints that can be eliminated. This work supports theFAA’s Operational Evolution Plan in the near-term.Rapid changes in technology in the area of navigationperformance, including the change from ground-basedarea navigation systems, provide the foundation for avia-tion’s global evolution. This progress will be marked bycombining all elements of communication, navigation,and surveillance (CNS) with air traffic management(ATM) into tomorrow’s CNS/ATM based systems. Thefuture CNS/ATM operating environment will be basedon navigation defined by geographic waypointsexpressed in latitude and longitude since instrumentprocedures and flight routes will not require aircraft tooverfly ground-based navigation aids defining specificpoints. Concepts in CNS/ATM such as RNAV, GPS,and required navigation performance (RNP) providethe path for this transition.

APPLICATION OF AREA NAVIGATIONRNAV airways provide more direct routings than thecurrent VOR-based airway system, giving pilots easieraccess through terminal areas, while avoiding the cir-cuitous routings now common in many busy Class Bareas. RNAV airways are a critical component to thetransition from ground-based navigation systems to GPSnavigation. Once established and certified, RNAV routeswill help maintain the aircraft flow through busy termi-nals by segregating arrival or departure traffic away

4 FDP maintains a model of the route and other details for each aircraft.5 A release time is a departure restriction issued to a pilot by ATC, specifying the earliest and latest time an aircraft may depart.6 The runway release time assigned to an aircraft in a controlled departure time program and shown on the flight progress strip as an EDCT.

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from possibly interfering traffic flows. Further, RNAVprovides the potential for increasing airspace capacityboth en route and in the terminal area in several impor-tant ways. RNAV may allow controllers to:

• Assign routes without overflying NAVAIDs suchas VORs.

• Reduce the lateral separation between aircrafttracks.

• Lower altitude minimums on existing airwayswhere VOR performance (minimum receptionaltitude) requires higher minimums.

• Allow the continued use of existing airways wherethe NAVAID signal is no longer suitable for enroute navigation.

This means that the route structures can be modifiedquickly and easily to meet the changing requirementsof the user community. Shorter, simpler routes can evenbe designed to minimize environmental impact, whennecessary. In the future, higher levels of navigationaccuracy and integrity are anticipated, which shouldlead to the introduction of closely spaced parallelroutes. RNAV can be used in all phases of flight and,when implemented correctly, can result in:

• Improved situational awareness for the pilot.

• Reduced workloads for both controller and pilot.

• Reduced environmental impact from improvedroute and procedure designs.

• Reduced fuel consumption from shorter, moredirect routes.

For example, take the situation at PhiladelphiaInternational Airport, located in the middle of somehighly popular north-south traffic lanes carrying NewYork and Boston traffic to or from Washington, Atlanta,and Miami. Philadelphia’s position is right underneaththese flows. Chokepoints resulted from traffic departingPhiladelphia, needing to wait for a “hole” in the trafficabove into which they could merge. The CAASD helpedUSAir and Philadelphia airport officials establish a setof RNAV departure routes that do not interfere with theprevailing established traffic. Traffic heading north orsouth can join the established flows at a point furtherahead when higher altitudes and speeds have beenattained. Aircraft properly equipped to execute RNAVprocedural routes can exit the terminal area faster — apowerful inducement for aircraft operators to upgradetheir navigation equipment.

Another example of an RNAV departure is the PRYMETWO DEPARTURE from Washington Dulles

International. Notice in figure 1-10 the RNAV waypointsnot associated with VORs help free up the flow of IFRtraffic out of the airport by not funneling them to onepoint through a common NAVAID.

Figure 1-10. RNAV Departure Routes.

New RNAV routes were implemented through Class Bairspace at Charlotte, North Carolina. IFR overflightswere routinely re-routed around the Class B airspace byas much as 50 miles. Twelve new routes through theCharlotte airspace were provided for RNAV-capable air-craft to file flight plan equipment codes of /E, /F, or /G.

However, before the FAA can designate RNAV air-ways, the agency has to develop criteria, en routeprocedures, procedures for airway flight checks, andcreate new charting specifications. Moreover, it isessential that:

• Navigation infrastructure (i.e. the ground-basedand space-based navigation positioning systems)provides adequate coverage for the proposedroute/procedure.

• Navigation coordinate data meets InternationalCivil Aviation Organization (ICAO) accuracy and

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integrity requirements. This means that all thecoordinates published in the AeronauticalInformation Publication (AIP) and used in the air-craft navigation databases must be referenced toWGS 84, and the user must have the necessaryassurance that this data has not been corrupted orinadvertently modified.

• Airborne systems are certified for use on theRNAV routes and procedures.

• Flight crews have the necessary approval to oper-ate on the RNAV routes and procedures

REQUIRED NAVIGATION PERFORMANCERNP is a navigation system that provides a specified levelof accuracy defined by a lateral area of confined airspacein which an RNP certified aircraft operates. The contin-uing growth of aviation places increasing demands onairspace capacity and emphasizes the need for the best useof the available airspace. These factors, along with theaccuracy of modern aviation navigation systems and therequirement for increased operational efficiency in termsof direct routings and track-keeping accuracy, have

resulted in the concept of required navigation performance— a statement of the navigation performance accuracynecessary for operation within a defined airspace. RNPcan include both performance and functional require-ments, and is indicated by the RNP type. These standardsare intended for designers, manufacturers, and installers ofavionics equipment, as well as service providers and usersof these systems for global operations. The minimumaviation system performance specification (MASPS)provides guidance for the development of airspace andoperational procedures needed to obtain the benefits ofimproved navigation capability. [Figure 1-11]

The RNP type defines the total system error (TSE) thatis allowed in lateral and longitudinal dimensionswithin a particular airspace. The TSE, which takesaccount of navigation system errors (NSE), computa-tion errors, display errors and flight technical errors(FTE), must not exceed the specified RNP value for95% of the flight time on any part of any single flight.RNP combines the accuracy standards laid out in theICAO Manual (Doc 9613) with specific accuracyrequirements, as well as functional and performance

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.

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standards, for the RNAV system to realize a systemthat can meet future air traffic management require-ments. The functional criteria for RNP address theneed for the flight paths of participating aircraft to beboth predictable and repeatable to the declared levelsof accuracy. More information on RNP is contained insubsequent chapters.

The term RNP is also applied as a descriptor for air-space, routes, and procedures — including departures,arrivals, and instrument approach procedures (IAPs).The descriptor can apply to a unique approach proce-dure or to a large region of airspace. RNP applies tonavigation performance within a designated airspace,and includes the capability of both the available infra-structure (navigation aids) and the aircraft.

RNP type is used to specify navigation requirements forthe airspace. The following are ICAO RNP Types: RNP-1.0, RNP-4.0, RNP-5.0, and RNP-10.0. The requiredperformance is obtained through a combination of air-craft capability and the level of service provided by thecorresponding navigation infrastructure. From a broadperspective:

Aircraft Capability + Level of Service = Access

In this context, aircraft capability refers to the airwor-thiness certification and operational approval elements(including avionics, maintenance, database, humanfactors, pilot procedures, training, and other issues).The level of service element refers to the NAS infra-structure, including published routes, signal-in-spaceperformance and availability, and air traffic manage-ment. When considered collectively, these elementsresult in providing access. Access provides the desiredbenefit (airspace, procedures, routes of flight, etc.).

RNP levels are actual distances from the centerline ofthe flight path, which must be maintained for aircraftand obstacle separation. Although additional FAA rec-ognized RNP levels may be used for specific operations,the United States currently supports three standard RNPlevels:

• RNP 0.3 – Approach

• RNP 1.0 – Departure, Terminal

• RNP 2.0 – 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 that is required on the finalapproach segment of an instrument approach is anexample of this RNP level. At the present time, a 0.3RNP level is the lowest level used in normal RNAVoperations. Specific airlines, using special procedures,are approved to use RNP levels lower than RNP 0.3, but

those levels are used only in accordance with theirapproved OpsSpecs. For aircraft equipment to qualifyfor a specific RNP type, it must be able to maintain nav-igational accuracy to within 95 percent of the total flighttime.

GLOBAL POSITIONING SYSTEMThe FAA’s Global Positioning System (GPS) imple-mentation activities are dedicated to the adaptation ofthe NAS infrastructure to accept Satellite Navigation(SATNAV) technology through the management andcoordination of a variety of overlapping NAS imple-mentation projects. These projects fall under the projectareas listed below and represent different elements ofthe NAS infrastructure:

• Avionics Development − includes engineeringsupport and guidance in the development of cur-rent and future GPS avionics minimum opera-tional performance standards (MOPS), as well asFAA Technical Standard Orders (TSOs) andestablishes certification standards for avionicsinstallations.

• Flight Standards − includes activities related toinstrument procedure criteria research, design,testing, and standards publication. The shift fromground-based to space-based navigation sourceshas markedly shifted the paradigms used inobstacle clearance determination and standardsdevelopment. New GPS-based TerminalProcedures (TERPS) manuals are in use today asa result of this effort.

• Air Traffic − includes initiatives related to thedevelopment of GPS routes, phraseology, proce-dures, controller GPS training and GPS outagesimulations studies. GPS-based routes, devel-oped along the East Coast to help congestion inthe Northeast Corridor, direct GPS-basedCaribbean routes, and expansion of RNAVactivities are all results of SATNAV sponsoredimplementation projects.

• Procedure Development − includes the provisionof instrument procedure development and flightinspection of GPS-based routes and instrumentprocedures. Today over 3,500 GPS-based IAPshave been developed.

• Interference Identification and Mitigation −includes the development and fielding of airborne,ground, and portable interference detection sys-tems. These efforts are ongoing and critical toensuring the safe use of GPS in the NAS.

To use GPS, WAAS, and/or LAAS in the NAS, equip-ment suitable for aviation use (such as a GPS receiver,

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WAAS receiver, LAAS receiver, or multi-modalreceiver) must be designed, developed, and certified foruse. To ensure standardization and safety of this equip-ment, the FAA plays a key role in the development andworks closely with industry in this process. The avionicsdevelopment process results in safe, standardized SAT-NAV avionics, developed in concurrence with industry.Due to the growing popularity of SATNAV and potentialnew aviation applications, there are several types ofGPS-based receivers on the market, but only those thatpass through this certification process can be used asapproved navigation equipment under IFR conditions.Detailed information on GPS approach procedures isprovided in Chapter 5–Approach.

GPS-BASED HELICOPTER OPERATIONSAn excellent example of what can be accomplished toforge the future of helicopter IFR SATNAV is the syn-ergy between industry and the FAA displayed during thedevelopment of the Gulf of Mexico GPS grid systemand approaches. The cooperation displayed during thedevelopment of this infrastructure by the HelicopterSafety Advisory Council (HSAC), National Air TrafficControllers Association (NATCO), helicopter operators,and FAA Flight Standards Divisions, all workingtogether has attributed to its resounding success andaccomplishment in one year. The system provides boththe operational and cost saving features of flying directto a destination when offshore weather conditions dete-riorate below VFR, and an instant and accurate aircraftlocation capability that is invaluable for rescue opera-tions with lives at stake.

Another success story of the further expansion of hel-icopter IFR service is the FAA working with EMSoperators in the development of helicopter GPS non-precision instrument approach procedures and enroute criteria. As a result of this collaborative effort,EMS operators have been provided with more than200 EMS helicopter procedures to medical facilities.Before the first EMS operator (1997) invested in aGPS IFR network, they had flown 4,000 missions peryear, missing 1,300 missions (30%) per year due toweather. With the new procedures and the same num-ber of helicopters, the number of requests has grownto 10,000 but only 11% of those missions were notachieved due to weather. This provided an investmentpayback in less than one year with over 500 criticallyill patients transported in a two-year period.

The success of these operations can be attributed in largepart to the collaborative efforts of the helicopter indus-try and the FAA to establish criteria that will supportcurrent and future operations.

REDUCED VERTICAL SEPARATION MINIMUMSThe U.S. domestic reduced vertical separation mini-mums (RVSM)7 program is a key element of the OEP.RVSM capability reduces the vertical separation fromthe current 2,000-foot minimum to a 1,000-foot mini-mum above FL 290, which allows aircraft to fly a moreoptimal profile, thereby saving fuel while increasing air-space capacity. The FAA’s objective is to implementRVSM between FL 290 and FL 410 (inclusive) inDecember 2004 in the airspace of the contiguous 48states, Alaska, and in Gulf of Mexico airspace where theFAA provides air traffic services. The proposal is consid-ered to be a feasible option and the FAA is developing itsplans accordingly. The goal of domestic reduced verticalseparation minimums (DRVSM) is to achieve in domes-tic airspace those user and provider benefits inherent tooperations conducted at more optimum flight profilesand with increased airspace capacity. Full DRVSM willadd six additional usable altitudes above FL 290 to thoseavailable with current vertical separation minimums.DRVSM users will experience increased benefits nation-wide, similar to those already achieved in oceanic areaswhere RVSM is operational. In domestic airspace, how-ever, operational differences create unique challenges.Domestic U.S. airspace contains a wider variety of air-craft types, higher-density traffic, and an increased per-centage of climbing and descending traffic. This, inconjunction with an intricate route structure with numer-ous major crossing points, creates a more demandingenvironment for the implementation of RVSM than thatexperienced to this point. Nevertheless, experiencegained in oceanic implementations is being considered inthe DRVSM project. As airspace gets more congested,DRVSM provides the potential to reduce fuel burn anddeparture delays, and to increase flight level availability,airspace capacity, and controller flexibility.

FAA RADAR SYSTEMSThe FAA operates two basic radar systems; airportsurveillance radar (ASR) and air route surveillanceradar (ARSR). Both of these surveillance systems useprimary and secondary radar returns, as well assophisticated computers and software programsdesigned to give the controller additional information,such as aircraft speed and altitude.

AIRPORT SURVEILLANCE RADARThe direction and coordination of IFR traffic withinspecific terminal areas is delegated to airport surveil-lance radar (ASR) facilities. Approach and departurecontrol manage traffic at airports with ASR. This radarsystem is designed to provide relatively short-rangecoverage in the airport vicinity and to serve as an expe-ditious means of handling terminal area traffic. The

7 RVSM is 1,000 feet for approved aircraft operating between FL 290 and FL 410 inclusive.

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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 toensure safe separation of aircraft transitioning fromdeparture to cruise flight or from cruise to a landingapproach.

Most ASR facilities throughout the country use a formof automated radar terminal system (ARTS). This sys-tem has several different configurations that depend onthe computer equipment and software programsused. Usually the busiest terminals in the countryhave the most sophisticated computers and programs.The type of system installed is designated by a suffixof numbers and letters. For example, an ARTS-IIIAinstallation can detect, track, and predict primary, aswell as secondary, radar returns. [Figure 1-12]

On a controller’s radar screen, ARTS equipment auto-matically provides a continuous display of an aircraft’sposition, altitude, groundspeed, and other pertinent infor-mation. This information is updated continuously as theaircraft progresses through the terminal area. To gainmaximum benefit from the system, each aircraft in thearea must be equipped with a Mode C transponder andits associated altitude encoding altimeter, although this isnot an operational requirement. Direct altitude readoutseliminate the need for time consuming verbal communi-cation between controllers and pilots to verify altitude.This helps to increase the number of aircraft which maybe handled by one controller at a given time.

AIR ROUTE SURVEILLANCE RADARThe long-range radar equipment used in controlled air-space to manage traffic is the air route surveillance radar

(ARSR) system. There are approximately 100 ARSRfacilities to relay traffic information to radar controllersthroughout the country. Some of these facilities candetect only transponder-equipped aircraft and arereferred to as beacon-only sites. Each air route surveil-lance radar site can monitor aircraft flying within a 200-mile radius of the antenna, although some stations canmonitor aircraft as far away as 600 miles through theuse of remote sites.

The direction and coordination of IFR trafficin the U.S. is assigned to air route traffic con-trol centers (ARTCCs). These centers are theauthority for issuing IFR clearances andmanaging IFR traffic; however, they alsoprovide services to VFR pilots. Workloadpermitting, controllers will provide trafficadvisories and course guidance, or vectors, ifrequested.

PRECISION RUNWAY MONITORINGPrecision 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 independentapproaches to closely spaced parallel runways, PRM hasbeen operational at Minneapolis since 1997, and fouradditional implementations are planned8. Once put intooperation successfully, PRM enables ATC to improvethe airport arrival rate on IFR days to one that moreclosely approximates VFR days; which means fewerflight cancellations, less holding, and decreased diver-sions.

PRM not only maintains the current level of safety, butalso increases it by offering air traffic controllers amuch more accurate picture of the aircraft’s locationon final approach. Whereas current airport surveillanceradar used in a busy terminal area provides an updateto the controller every 4.8 seconds, PRM updates every

Figure 1-12. ARTS-III Radar Display.

8 PRM is planned for PHL, STL, JFK, and SFO. Other airports are under consideration.

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second, giving the controller significantly more time toreact to potential aircraft separation problems. Thecontroller also sees target trails that provide very accu-rate trend information. With PRM, it is immediatelyapparent when an aircraft starts to drift off the runwaycenterline and toward the non-transgression zone.PRM also predicts the aircraft track and provides auraland visual alarms when an aircraft is within 10 secondsof penetrating the non-transgression zone. The addi-tional controller staffing that comes along with PRM isanother major safety improvement. During PRM ses-sions, there is a separate controller monitoring eachfinal approach course and a coordinator managing theoverall situation.

PRM is an especially attractive technical solution for theairlines and business aircraft because it does not requireany additional aircraft equipment, only special trainingand qualifications. However, all aircraft in the approachstreams must be qualified to participate in PRM or thebenefits are quickly lost and controller workloadincreases significantly. The delay-reduction benefits ofPRM can only be fully realized if everyone participates.Operators that choose not to participate in PRM opera-tions when arriving at an airport where PRM operationsare underway can expect to be held until they can beaccommodated without disrupting the PRM arrivalstreams.

EQUIPMENT AND AVIONICSBy virtue of distance and time savings, minimizingtraffic congestion, and increasing airport and airwaycapacity, the implementation of RNAV routes, directrouting, RSVM, PRM, and other technological innova-tions would be advantageous for the current NAS.Some key components that are integral to the futuredevelopment and improvement of the NAS aredescribed below. However, equipment upgrades requirecapital outlays, which take time to penetrate the exist-ing fleet of aircraft and ATC facilities. In the upcomingyears while the equipment upgrade is taking place, ATCwill have to continue to accommodate the wide rangeof avionics used by pilots in the nation’s fleet.

ATC RADAR EQUIPMENTAll ARTCC radars in the conterminous U.S., as well asmost airport surveillance radars, have the capability tointerrogate Mode C and display altitude information tothe controller. However, there are a small number ofairport surveillance radars that are still two-dimensional(range and azimuth only); consequently, altitude infor-mation must be obtained from the pilot.

At some locations within the ATC environment,secondary only (no primary radar) gap filler radarsystems are used to give lower altitude radar cover-age between two larger radar systems, each ofwhich provides both primary and secondary radar

coverage. In the geographical areas serviced by sec-ondary radar only, aircraft without transponders cannotbe provided with radar service. Additionally, transpon-der-equipped aircraft cannot be provided with radar advi-sories concerning primary targets and weather.

An integral part of the air traffic control radar beaconsystem (ATCRBS) ground equipment is the decoder,which enables the controller to assign discrete transpon-der codes to each aircraft under his/her control.Assignments are made by the ARTCC computer on thebasis of the National Beacon Code Allocation Plan(NBCAP). There are 4096 aircraft transponder codes thatcan be assigned. An aircraft must be equipped withCivilian Mode A (or Military Mode 3) capabilities to beassigned a transponder code. Another function of thedecoder is that it is also designed to receive Mode Caltitude information from an aircraft so equipped. Thissystem converts aircraft altitude in 100-foot incrementsto coded digital information that is transmitted togetherwith Mode C framing pulses to the interrogating groundradar facility. The ident feature of the transponder causesthe transponder return to “blossom” for a few seconds onthe controller’s radarscope.

AUTOMATED RADAR TERMINAL SYSTEMMost medium-to-large radar facilities in the U.S. usesome form of automated radar terminal system (ARTS),which is the generic term for the functional capabilityafforded by several automated systems that differ infunctional capabilities and equipment. “ARTS” fol-lowed by a suffix Roman numeral denotes a specificsystem, with a subsequent letter that indicates a majormodification to that particular system. In general, theterminal controller depends on ARTS to display aircraftidentification, flight plan data, and other information inconjunction with the radar presentation. In addition toenhancing visualization of the air traffic situation,ARTS facilitates intra- and inter-facility transfers andthe coordination of flight information. Each ARTS levelhas the capabilities of communicating with other ARTStypes as well as with ARTCCs.

As the primary system used for terminal ATC in theU.S., ARTS had its origin in the mid-1960’s as ARTSI, or Atlanta ARTS and evolved to the ARTS II andARTS III configurations in the early to mid-1970’s.Later in the decade, the ARTS II and ARTS III config-urations were expanded and enhanced and renamedARTS IIA and ARTS IIIA respectively. The vastmajority of the terminal automation sites today remaineither IIA or IIIA configurations, except for about nineof the largest IIIA sites, which are ARTS IIIE candi-date systems. Selected ARTS IIIA/IIIE and ARTS IIAsites are scheduled to receive commercial off the shelf(COTS) hardware upgrades, which replace portions ofthe proprietary data processing system with standardoff-the-shelf hardware.

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STANDARD TERMINAL AUTOMATION REPLACEMENT SYSTEMIn Spring 2002, the FAAAdministrator announced opera-tional use of the first Standard Terminal AutomationReplacement System (STARS) in El Paso, Texas, anupgraded version that completely replaces the ARTS. FullSTARS consists of new digital, color displays and com-puter software and processors that can track 435 aircraftat one time, integrating six levels of weather informationand 16 radar feeds. The final version of STARS, sched-uled for installation in Philadelphia, will be able to look20 minutes into the future of a flight path while providingcontrollers with enhanced data blocks, including aircrafttype and flight number, as well as destination and flightpath information.

For the terminal area and many of the towers, STARS isthe key to the future, providing a solid foundation fornew capabilities. STARS were designed to provide thesoftware and hardware platform necessary to supportfuture air traffic control enhancements.

PRECISION APPROACH RADAR While ASR provides pilots with horizontal guidancefor instrument approaches via a ground-based radar,Precision Approach Radar (PAR) provides both hori-zontal and vertical guidance for a ground controlledapproach (GCA). In the U.S., PAR is mostly used bythe military. Radar equipment in some ATC facilitiesoperated by the FAA and/or the military services atjoint-use locations and military installations are usedto detect and display azimuth, elevation, and rangeof aircraft on the final approach course to a runway.This equipment may be used to monitor certain non-radar approaches, but it is primarily used to conducta precision instrument approach.

BRIGHT RADAR INDICATOR TERMINAL EQUIPMENTBright Radar Indicator Terminal Equipment (BRITE)provides radar capabilities to towers, a system withtremendous benefits for both pilots and controllers.Unlike traditional radar systems, BRITE is similar to atelevision screen in that it can be seen in daylight.BRITE was so successful that the FAA has installed thenew systems in towers, and even in some TRACONs.In fact, the invention of BRITE was so revolutionarythat it launched a new type of air traffic facility theTRACAB, which is a radar approach control facilitylocated in the tower cab of the primary airport, asopposed to a separate room.

In the many facilities without BRITE, the controllersuse strictly visual means to find and sequence traffic.Towers that do have BRITE may have one of severaldifferent types. Some have only a very crude displaythat gives a fuzzy picture of blips on a field of green,perhaps with the capability of displaying an extra slashon transponder-equipped targets and a larger slash

when a pilot hits the ident button. Next in sophistica-tion are BRITEs that have alphanumeric displays ofvarious types, ranging from transponder codes and alti-tude to the newest version, the DBRITE (digitalBRITE). A computer takes all the data from the pri-mary radar, the secondary radar (transponder informa-tion), and generates the alphanumeric data. DBRITEdigitizes the image, and then sends it all, in TV format,to a square display in the tower that provides an excel-lent presentation, regardless of how bright the ambientlight.

One of the most limiting factors in the use of the BRITEis 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 radarservice provided by an approach control or Center. Theprimary duty of tower controllers is to separate airplanesoperating on runways, which means controllers spendmost of their time looking out the window, not staring ata radar scope.

RADAR COVERAGEA full approach is a staple of instrument flying, yetsome pilots rarely, if ever, have to fly one other thanduring initial or recurrency or proficiency training,because a full approach usually is required only whenradar service is not available, and radar is available atmost larger and busier instrument airports. Pilots cometo expect radar vectors to final approach courses andthat ATC will keep an electronic eye on them all theway to a successful conclusion of every approach. Inaddition, most en route flights are tracked by radaralong their entire route in the 48 contiguous states,with essentially total radar coverage of all instrumentflight routes except in the mountainous West. Lack ofradar coverage may be due to terrain, cost, or physicallimitations.

New developing technologies, like ADS-B, may offerATC a method of accurately tracking aircraft in non-radar environments. ADS-B is a satellite-based airtraffic tracking system enabling pilots and air trafficcontrollers to share and display the same information.ADS-B relies on the Global Positioning System todetermine an aircraft’s position. The aircraft’s preciselocation, along with other data such as airspeed, alti-tude, and aircraft identification, then is instantlyrelayed via digital datalink to ground stations and otherequipped aircraft. Unlike radar, ADS-B works well atlow altitudes and in remote locations and mountainousterrain where little or no radar coverage exists.

COMMUNICATIONSMost air traffic control communications between pilotsand controllers today are conducted via voice. Each airtraffic controller uses a radio frequency different from theones used by surrounding controllers to communicate

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with the aircraft under his or her jurisdiction. With theincreased traffic, more and more controllers have beenadded to maintain safe separation between aircraft. Whilethis has not diminished safety, there is a limit to the num-ber of control sectors created in any given region to han-dle the traffic. The availability of radio frequencies forcontroller-pilot communications is one limiting factor.Some busy portions of the U.S., such as the Boston-Chicago-Washington triangle are reaching toward thelimit. Frequencies are congested and new frequenciesare not available, which limits traffic growth to thoseaircraft that can be safely handled.

DATA LINKThe CAASD is working with the FAA and the airlinesto define and test a controller-pilot data link communi-cation (CPDLC), which provides the capability toexchange information between air traffic controllersand flight crews through digital text instead of voicemessages. With CPDLC, communications between theground and the air would take less time, and wouldconvey more information (and more complex informa-tion) than by voice alone. Communications wouldbecome more accurate as up-linked information wouldbe collected, its accuracy established, and then dis-played for the pilot in a consistent fashion.

By using digital data messages to replace conventionalvoice communications (except during landing and depar-ture phases and in emergencies) CPDLC is forecast toincrease airspace capacity and reduce delays. Today theaverage pilot/controller voice exchange takes around 20seconds, compared to one or two seconds with CPDLC.In FAA simulations, air traffic controllers indicated thatCPDLC could increase their productivity by 40 percentwithout increasing workload. Airline cost/benefit studiesindicate average annual savings that are significant in theterminal and en route phases, due to CPDLC-relateddelay reductions.

CPDLC for routine ATC messages, initially offered inMiami Center, will be implemented via satellite at alloceanic sectors. Communications between aircraft andFAA oceanic facilities will be available through satellitedata link, high frequency data link (HFDL), or othersubnetworks, with voice via HF and satellite communi-cations remaining as backup. Eventually, the servicewill be expanded to include clearances for altitude,speed, heading, and route, with pilot initiated downlinkcapability added later.

MODE SThe first comprehensive proposal and design for theMode 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 Stransponders were made available before 1980. Then, atragic mid-air collision over California in 1986prompted a dramatic change. The accident that claimed

the lives of 67 passengers aboard the two planes andfifteen people on the ground was blamed on inadequateautomatic conflict alert systems and surveillanceequipment. A law enacted by Congress in 1987required all air carrier airplanes operating within U.S.airspace with more than 30 passenger seats to beequipped with Traffic Alert and Collision AvoidanceSystem (TCAS II) by December 1993. Airplanes with10 to 30 seats were required to employ TCAS I byDecember 1995.

Due to the congressional mandate, TCAS became apervasive system for air traffic control centers aroundthe world. Because TCAS uses Mode S as the standardair-ground communication datalink, the widespreadinternational use of TCAS has helped Mode S becomean integral part of air traffic control systems all overthe world. The datalink capacity of Mode S hasspawned the development of a number of differentservices that take advantage of the two-way linkbetween air and ground. By relying on the Mode Sdatalink, these services can be inexpensively deployedto serve both the commercial transport aircraft andgeneral aviation communities. Using Mode S makesnot only TCAS, but also other services available to thegeneral aviation community that were previouslyaccessible only to commercial aircraft. These ModeS-based technologies are described below.

TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEMThe Traffic Alert and Collision Avoidance System(TCAS) is designed to provide a set of electronic eyesso the pilot can maintain awareness of the traffic situa-tion in the vicinity of the aircraft. The TCAS system usesthree separate systems to plot the positions of nearbyaircraft. First, directional antennae that receive Mode Stransponder signals are used to provide a bearing toneighboring aircraft accurate to a few degrees ofbearing. Next, Mode C altitude broadcasts are used toplot the altitude of nearby aircraft. Finally, the timing ofthe Mode S interrogation/response protocol is measuredto ascertain the distance of an aircraft from the TCASaircraft. [Figure 1-13 on page 1-20]

TCAS I allows the pilot to see the relative position andvelocity of other transponder-equipped aircraft within a10 to 20-mile range. More importantly, TCAS I providesa warning when an aircraft in the vicinity gets too close.TCAS I does not provide instructions on how to maneu-ver in order to avoid the aircraft, but does supply impor-tant data with which the pilot uses to evade intrudingaircraft.

TCAS II provides pilots with airspace surveillance,intruder tracking, threat detection, and avoidancemaneuver generations. TCAS II is able to determine

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whether each aircraft is climbing, descending, or flyingstraight and level, and commands an evasive maneuver toeither climb or descend to avoid conflicting traffic. If bothplanes in conflict are equipped with TCAS II, then theevasive maneuvers are well coordinated via air-to-airtransmissions over the Mode S datalink, and the com-manded maneuvers do not cancel each other out.

TCAS and similar traffic avoidance systems providesafety independent of ATC and supplement andenhance ATC’s ability to prevent air-to-air collisions.Pilots currently use TCAS displays for collisionavoidance and oceanic station keeping (maintainingmiles-in-trail separation). TCAS technology improve-ments, currently in development, will enable aircraft toaccommodate reduced vertical separation above FL 290and the ability to track multiple targets at longer ranges.

TRAFFIC INFORMATION SERVICETraffic Information Service (TIS) provides many of thefunctions available in TCAS; but unlike TCAS, TIS is aground-based service available to all aircraft equippedwith Mode S transponders. TIS takes advantage of theMode S data link to communicate collision avoidanceinformation to aircraft. Information is presented to apilot in a cockpit display that shows traffic within 5nautical miles and a 1,200-foot altitude of other ModeS-equipped aircraft. The TIS system uses track reportsprovided by ground-based Mode S surveillance sys-tems to retrieve traffic information. Because it isavailable to all Mode S transponders, TIS offers aninexpensive alternative to TCAS. The increasingavailability of TIS makes collision avoidance technol-ogy more accessible to the general aviation community.

TERRAIN AWARENESS AND WARNING SYSTEMThe Terrain Awareness and Warning System (TAWS),an enhanced ground proximity warning capability isalso being installed in many aircraft. TAWS uses posi-tion data from a navigation system, like GPS, and adigital terrain database to display surrounding terrain.TAWS equipment is mandatory for all U.S registeredturbine powered airplanes manufactured after March2002 with six or more passenger seats. For airplanesmanufactured earlier, compliance is required by March2005. FAA and National Transportation Safety Board(NTSB) studies show that in 14 CFR part 91 aircraftwith six or more passengers, ground proximity warn-ing systems (GPWS) could have avoided 33 of the 44controlled flight into terrain (CFIT) accidents with 96fatalities, and enhanced GPWS (EGPWS) could haveavoided 42 of the 44 accidents with 126 fatalities.

GRAPHICAL WEATHER SERVICEThe Graphical Weather Service provides a graphicalrepresentation of weather information that is transmit-ted to aircraft and displayed on the cockpit display unit.The service is derived from ground-based Mode S sen-sors and offers information to all types of aircraft,regardless of the presence of on-board weather avoid-ance equipment. The general aviation community hasbeen very pro-active in evaluating this technology, asthey have already participated in field evaluations inMode S stations across the U.S.

AVIONICS AND INSTRUMENTATIONThe proliferation of advanced avionics and instrumen-tation has substantially increased the capabilities ofaircraft in the IFR environment.

FLIGHT MANAGEMENT SYSTEMA flight management system (FMS) is a flight computersystem that uses a large database to allow routes to bepreprogrammed and fed into the system by means of adata loader. The system is constantly updated withrespect to position accuracy by reference to conventionalnavigation aids, inertial reference system technology, orthe satellite global positioning system. The sophisticatedprogram and its associated database ensures that themost appropriate navigation aids or inputs are automat-ically selected during the information update cycle. Atypical FMS provides information for continuous auto-matic navigation, guidance, and aircraft performancemanagement, and includes a control display unit(CDU). [Figure 1-14]

ELECTRONIC FLIGHT INFORMATION SYSTEMThe electronic flight information system (EFIS) found inadvanced aircraft cockpits offer pilots a tremendousamount of information on a colorful, easy-to-read display.Glass cockpits are a vast improvement over the earliergeneration of instrumentation. The latest flat panel screens

Figure 1-13.Traffic Alert and Collision Avoidance System.

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are about half the size of the cathode-ray tube (CRT)screens first used for EFIS displays. [Figure 1-15]

Primary flight, navigation, and engine information arepresented on large display screens in front of the flightcrew. Flight management CDUs are located on the centerconsole. They provide data display and entry capabilitiesfor flight management functions. The display units gener-ate less heat, save space, weigh less, and require lesspower than traditional navigation systems. From a pilot’spoint of view, the information display system is not onlymore reliable than previous systems, but also uses

advanced liquid-crystal technology that allows displayedinformation to remain clearly visible in all conditions,including direct sunlight.

NAVIGATION SYSTEMS Navigation systems are the basis for pilots to get fromone place to another and know where they are and whatcourse to follow. Since the 1930s, aircraft have navi-gated by means of a set of ground-based NAVAIDs.Today, pilots have access to over 2,000 such NAVAIDswithin the continental U.S., but the system has itslimitations:

• Constrained to fly from one NAVAID to thenext, aircraft route planners need to identify abeacon-based path that closely resembles thepath the aircraft needs to take to get from originto destination. Such a path will always begreater in distance than a great circle routebetween the two points.

• Because the NAVAIDs are ground-based, navi-gation across the ocean is problematic, as isnavigation in some mountainous regions.

• NAVAIDs are also expensive to maintain.

Since the 1980s, aircraft systems have evolvedtowards the use of SATNAV. Based on the GPS satel-lite constellation, SATNAV provides better positioninformation than a ground-based beacon system.

Figure 1-14. FMS Control Display Unit. This depicts an aircraftestablished on the Atlantic City, NJ, RNAV (GPS) Rwy 13instrument approach procedure at the Atlantic CityInternational Airport, KACY. The aircraft is positioned at theintermediate fix UNAYY inbound on the 128 degree magneticcourse, 5.5 nautical miles from PBIGY, the final approach fix.

Figure 1-15. Airline Flight Deck Instrument Displays

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GPS is universal so there are no areas without satellitesignals. Moreover, a space-based system allows “off air-way” navigation so that the efficiencies in aircraft routedetermination can be exacted. SATNAV is revolutioniz-ing navigation for airlines and other aircraft ownersand operators. A drawback of the satellite system,though, is the integrity and availability of the signal,especially during electromagnetic and other eventsthat distort the Earth’s atmosphere. In addition, thesignal from space needs to be augmented, especiallyin traffic-dense terminal areas, to guarantee the neces-sary levels of accuracy and availability.

The CAASD is helping the navigation system of theU.S. to evolve toward a satellite-based system. TheCAASD analysts are providing the modeling necessaryto understand the effects of atmospheric phenomena onthe GPS signal from space, while the CAASD is provid-ing the architecture of the future navigation system andwriting the requirements (and computer algorithms) toensure the navigation system’s integrity. Moving towarda satellite-based navigation system allows aircraft todivorce themselves from the constraints of ground-based NAVAIDs and formulate and fly those routes thataircraft route planners deem most in line with their owncost objectives.

With the advent of SATNAV, there are a number ofapplications that can be piggybacked to increase capac-ity in the NAS. Enhanced navigation systems will becapable of “random navigation,” that is, capable oftreating any latitude-longitude point as a radio navi-gation fix, and being able to fly toward it with theaccuracy we see today, or better. New routes into andout of the terminal areas are being implemented thatare navigable by on-board systems. Properlyequipped aircraft are being segregated from other air-craft streams with the potential to increase volume atthe nation’s busy airports by keeping the arrival anddeparture queues full and fully operating.

The CAASD is working with the FAA to define thenation’s future navigation system architecture. By itself,the GPS satellite constellation is inadequate to serve allthe system’s needs. Augmentation of the GPS signal viaWAAS and LAAS are necessary parts of that new archi-tecture. The CAASD is developing the requirementsbased on the results of sophisticated models to ensure thesystem’s integrity, security, and availability.

SURVEILLANCE SYSTEMSSurveillance systems are set up to enable the ATC sys-tem to know the location of an aircraft and where it isheading. Position information from the surveillancesystem supports many different ATC functions. Aircraftpositions are displayed for controllers as they watchover the traffic to ensure that aircraft do not violate sep-aration criteria. In the current NAS, surveillance is

achieved through the use of long-range and terminalradars. Scanning the skies, these radars return azimuthand slant range for each aircraft that, when combinedwith the altitude of the aircraft broadcast to the groundvia a transceiver, is transformed mathematically into aposition. The system maintains a list of these positionsfor each aircraft over time, and this time history is usedto establish short-term intent and short-term conflictdetection. Radars are expensive to maintain, and posi-tion information interpolated from radars is not as goodas what the aircraft can obtain with SATNAV. ADS-Btechnology may provide the way to reduce the costs ofsurveillance for air traffic management purposes and toget the better position information to the ground.

New aircraft systems dependent on ADS-B could beused to enhance the capacity and throughput of thenation’s airports. Electronic flight following is oneexample: An aircraft equipped with ADS-B could beinstructed to follow another aircraft in the landing pat-tern, and the pilot could use the on-board displays orcomputer applications to do exactly that. This meansthat visual rules for landing at airports might be used inperiods where today the airport must shift to instrumentrules due to diminishing visibility. Visual capacities atairports are usually higher than instrument ones, and ifthe airport can operate longer under visual rules (andseparation distances), then the capacity of the airport ismaintained at a higher level longer. The CAASD isworking with the Cargo Airline Association and theFAA to investigate these and other applications of theADS-B technology.

OPERATIONAL TOOLSAirports are one of the main bottlenecks in the NAS,responsible for one third of the flight delays. It is widelyaccepted that the unconstrained increase in the numberof airports or runways may not wholly alleviate the con-gestion problem and, in fact, may create more problemsthan it solves. The aim of the FAA is to integrate appro-priate technologies, in support of the OEP vision, withthe aim of increasing airport throughput.

The airport is a complex system of systems and anyapproach to increasing capacity must take this intoaccount. Numerous recent developments contribute tothe overall solution, but their integration into a systemthat focuses on maintaining or increasing safety whileincreasing capacity remains a major challenge. The sup-porting technologies include new capabilities for the air-craft and ATC, as well as new strategies for improvingcommunication between pilots and ATC.

IFR SLOTSDuring peak traffic, ATC uses IFR slots to promote asmooth flow of traffic. This practice began during thelate 1960s, when five of the major airports (LaGuardiaAirport, Ronald Reagan National Airport, John F.

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Kennedy International Airport, Newark InternationalAirport, and Chicago O’Hare International Airport)were on the verge of saturation due to substantial flightdelays and airport congestion. To combat this, the FAAin 1968 proposed special air traffic rules to these fivehigh-density airports (the “high density rule”) thatrestricted the number of IFR takeoffs and landings ateach airport during certain hours of the day and providedfor the allocation of “slots” to carriers for each IFR land-ing or takeoff during a specific 30 or 60-minute period.A more recent FAA proposal offers an overhaul of theslot-reservation process for JFK, LaGuardia, andReagan National Airport that includes a move to a 72-hour reservation window and an online slot-reservationsystem.

The high density rule has been the focus of muchexamination over the last decade since under therestrictions, new entrants attempting to gain access tohigh density airports face difficulties entering themarket. Because slots are necessary at high densityairports, the modification or elimination of the highdensity rule could subsequently have an effect on thevalue of slots. Scarce slots hold a greater economicvalue than slots that are easier to come by.

The current slot restrictions imposed by the high densityrule has kept flight operations well below capacity,especially with the improvements in air traffic controltechnology. However, easing the restrictions imposedby the high density rule is likely to affect airport oper-ations. Travel delay time might be affected not only atthe airport that has had the high density restrictionslifted, but also at surrounding airports that share thesame airspace. On the other hand, easing the restric-tions on slots at high density airports should helpfacilitate international air travel and help increase thenumber of passengers that travel internationally.

Slot controls have become a way of limiting noise,since it caps the number of takeoffs and landings at anairport. Easing the restrictions on slots could be politi-cally difficult since local delegations at the affectedairports might not support such a move. Ways otherthan imposing restrictions on slots exist that coulddiminish the environmental impacts at airports andtheir surrounding areas. Safeguards, such as requiringthe quietest technology available of aircraft using slotsand frequent consultations with local residents, havebeen provided to ensure that the environmental con-cerns are addressed and solved.

GROUND DELAY PROGRAMBad weather often forces the reconfiguration of run-ways at an airport or mandates the use of IFR arrivaland departure procedures, reducing the number offlights per hour that are able to takeoff or land at theaffected airport. To accommodate the degraded arrival

capacity at the affected airport, the ATCSCC imposes aground delay program (GDP), which allocates areduced number of arrival slots to airlines at airportsduring time periods when demand exceeds capacity.The GDP suite of tools is used to keep congestion atan arrival airport at acceptable levels by issuingground delays to aircraft before departure, as grounddelays are less expensive and safer than in-flight hold-ing delays. The FAA started GDP prototype operationsin January 1998 at two airports and expanded the pro-gram to all commercial airports in the U.S. within 9months.

Ground Delay Program Enhancements (GDPE) signifi-cantly reduced delays due to compression—a process thatis run periodically throughout the duration of a GDP. Itreduces overall delays by identifying open arrival slotsdue to flight cancellations or delays and fills in the vacantslots by moving up operating flights that can use thoseslots. During the first 2 years of this program, almost90,000 hours of scheduled delays have been avoided dueto compression, resulting in cost savings to the airlineindustry of more than $150 million. GDPE also hasimproved the flow of air traffic into airports; improvedcompliance to controlled times of departure; improveddata quality and predictability; resulted in equity indelays across carriers; and often avoided the necessity toimplement FAA ground delay programs, which can bedisruptive to air carrier operations.

FLOW CONTROLATC provides IFR aircraft separation services for NASusers. Since the capabilities of IFR operators vary fromairlines operating hundreds of complex jet aircraft toprivate pilots in single engine, piston-powered air-planes, the ATC system must accommodate the leastsophisticated user. The lowest common denominator isthe individual controller speaking to a single pilot on aVHF voice radio channel. While this commonality isdesirable, it has led to a mindset where other opportuni-ties to interact with NAS users have gone undeveloped.The greatest numbers of operations at the 20 busiest aircarrier airports are commercial operators (airlines andcommuters) operating IFR with some form of ground-based operational control. Since not all IFR operationshave ground-based operational control, very little efforthas been expended in developing ATC and AirlineOperations Control Center (AOC) collaboration tech-niques, even though ground-based computer-to-com-puter links can provide great data transfer capacity.Until the relatively recent concept of Air TrafficControl-Traffic Flow Management (ATC-TFM), theprimary purpose of ATC was aircraft separation, andthe direct pilot-controller interaction was adequate tothe task. Effective and efficient traffic flow manage-ment now requires a new level of control that includesthe interaction of and information transfer among ATC,TFM, AOCs, and the cockpit. [Figure 1-16]

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Figure 1-16. Flow Control Restrictions.

As the first step in modernizing the traffic flow man-agement infrastructure, the FAA began reengineeringtraffic flow management software using commercialoff-the-shelf products. In FY 1996, the FAA andNASA collaborated on new traffic flow managementresearch and development efforts for the developmentof collaborative decision making tools that will enableFAA traffic flow managers to work cooperatively withairline personnel in responding to congested conditions.Additionally, the FAA provided a flight schedulingsoftware system to nine airlines.

LAND AND HOLD SHORT OPERATIONSMany older airports, including some of the most con-gested, have intersecting runways. Expanding the useof Land and Hold Short Operations (LAHSO) onintersecting runways is one of the ways to increase thenumber of arrivals and departures. Currently, LAHSOoperations are permitted only on dry runways underacceptable weather conditions and limited to airportswhere a clearance depends on what is happening onthe other runway, or where approved rejected landingprocedures are in place. A dependent procedure exam-ple is when a landing airplane is a minimum distancefrom the threshold and an airplane is departing anintersecting runway, the LAHSO clearance can beissued because even in the event of a rejected landing,separation is assured. It is always the pilot’s option toreject a LAHSO clearance.

Working with pilot organizations and industry groups,the FAA is developing new LAHSO procedures thatwill provide increased efficiency while maintainingsafety. These procedures will address issues such aswet runway conditions, mixed commercial and general

aviation operations, thefrequency of missed app-roaches, and multi-stoprunway locations. Afterevaluating the new proce-dures using independentcase studies, the revisedindependent LAHSO pro-cedures may be imple-mented in 2005.

SURFACE MOVEMENT GUIDANCE AND CONTROL SYSTEMTo enhance taxiing capabilities in low visibility condi-tions and reduce the potential for runway incursions,improvements have been made in signage, lighting, andmarkings. In addition to these improvements, airportshave implemented the Surface Movement Guidanceand Control System (SMGCS),9 a strategy that requiresa low visibility taxi plan for any airport with takeoff orlanding operations with less than 1,200 feet RVR visi-bility conditions. This plan affects both aircrew and air-port vehicle operators, as it specifically designates taxiroutes to and from the SMGCS runways and displaysthem on a SMGCS Low Visibility Taxi Route chart.SMGCS airports may have several or all of the follow-ing features:

• Stop bars consist of a row of red unidirectional,in-pavement lights installed along the holdingposition marking. When extinguished by the con-troller, they confirm clearance for the pilot or vehi-cle operator to enter the runway.

• Taxiway centerline lights, which work in con-junction with stop bars, are green in-pavementlights that guide ground traffic under low visibilityconditions and during darkness.

• Runway guard lights, either elevated or in-pave-ment, will be installed at all taxiways that provideaccess to an active runway. They consist of alter-nately flashing yellow lights, used to denote boththe presence of an active runway and identify thelocation of a runway holding position marking.

• Geographic position markings, used as holdpoints or for position reporting, enable ATC toverify the position of aircraft and vehicles. Thesecheckpoints or “pink spots” are outlined with ablack and white circle and designated with anumber, a letter, or both.

9 SMGCS, pronounced “SMIGS,” is the Surface Movement Guidance and Control System. SMGCS provides for guidance and control orregulation for facilities, information, and advice necessary for pilots of aircraft and drivers of ground vehicles to find their way on the airportduring low visibility operations and to keep the aircraft or vehicles on the surfaces or within the areas intended for their use. Low visibilityoperations for this system means reported conditions of RVR 1,200 or less.

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• Clearance bars consist of three yellow in-pave-ment lights used to denote holding positions foraircraft and vehicles. When used for hold points,they are co-located with geographic positionmarkings.

SMGCS is an increasingly important element in a seam-less, overall gate-to-gate management concept to ensuresafe, efficient air traffic operations. It is the ground-complement for arrival and departure management andthe en route components of free flight. The FAA has sup-ported several major research and development effortson SMGCS to develop solutions and prototype systemsthat support pilots and ATC in their control of aircraftground operations.

EXPECTATION OF ATCAircraft safety is based on the adherence to a set of rulesbased on established separation standards. Air trafficcontrollers follow established procedures based uponspecific routes to maintain the desired separationsneeded for safety. The current ATM system has an excel-lent safety record for aircraft operations. Use of the freeflight approachwhere aircraft operators select paths,altitudes, and speeds in real timecan maximize effi-ciency and minimize operating costs. New technologiesand enhanced aircraft capabilities necessitate changes inprocedures, an increase in the level of automation andcontrol in the cockpit and in the ground system, andmore human reliance on automated information process-ing, sophisticated displays, and faster data communica-tion.

DISSEMINATING AERONAUTICAL INFORMATIONThe system for disseminating aeronautical informa-tion is made up of two subsystems, the Airmen’sInformation System (AIS) and the Notice to Airman(NOTAM) System. The AIS consists of charts andpublications. The NOTAM system is a telecommuni-cation system and is discussed in later paragraphs.Aeronautical information disseminated through chartsand publications includes aeronautical charts depict-ing permanent baseline data and flight informationpublications outlining baseline data.

IFR aeronautical charts include en route high altitudeconterminous U.S., and en route low altitude contermi-nous U.S., plus Alaska charts and Pacific Charts.Additional charts include U.S. terminal procedures, con-sisting of departure procedures (DP’s), standard termi-nal arrivals (STAR’s), and standard instrument approachprocedures (SIAP’s).

Flight information publications outlining baseline datain 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 AeronauticalInformation Manual (AIM).

PUBLICATION CRITERIA The following conditions or categories of informationare forwarded to the National Flight Data Center(NFDC) for inclusion in flight information publicationsand aeronautical charts:

• NAVAID commissioning, decommissioning, out-ages, restrictions, frequency changes, changes inmonitoring status and monitoring facility used inthe NAS.

• Commissioning, decommissioning, and changesin hours of operation of FAA air traffic controlfacilities.

• Changes in hours of operations of surface areasand airspace.

• RCO and RCAG commissioning, decommission-ing, and changes in voice control or monitoringfacility.

• Weather reporting station commissioning, decom-missioning, failure, and nonavailability or unreli-able operations.

• Public airport commissioning, decommissioning,openings, closings, and abandonments and someairport operating area (AOA) changes.

• Aircraft Rescue & Fire Fighting (ARFF) capabil-ity, including restrictions to air carrier operations.

• Changes to runway identifiers, dimensions,threshold placements, and surface compositions.

• NAS lighting system commissioning, decommis-sioning, outages, and change in classification oroperation.

• IFR Area Charts.

A wide variety of additional flight information publica-tions are available. Electronic flight publicationsinclude electronic bulletin boards, the FAA home page,advisory circulars, the AC checklist, federal aviationregulations, the Federal Register, including the noticesof proposed rulemaking (NPRM). Printed publicationsinclude the Guide to Federal Aviation AdministrationPublications, which is intended to help pilots identifyand obtain other FAA publications, as well as aviation-related materials issued by other federal agencies. ThisGuide is published annually and is available at nocharge. To order, request the Guide by name and num-ber, FAA-APA-PG-13, from: DOT, M-443.2, General

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Services Section, 400 7th St. S.W., Washington, D.C.20590.

AERONAUTICAL CHARTSPilots can obtain most aeronautical charts and publica-tions produced by the FAA National AeronauticalCharting Office (NACO), by subscription or one-timesales through a network of FAA chart agents primarilylocated at or near major civil airports. Additionally,opportunities to purchase or download aeronautical pub-lications online are expanding, which provides pilotsquicker and more convenient access to the latest infor-mation. Civil aeronautical charts for the U.S. and its ter-ritories, and possessions are produced according to a56-day IFR chart cycle by NACO, which is part of theFAA’s Office of Aviation Systems Standards (AVN).Comparable IFR charts and publications are availablefrom commercial sources, including charted visual flightprocedures, airport qualification charts, etc.

Most charts and publications described in this Chaptercan be obtained by subscription or one time sales fromNACO. Public sales of charts and publications are alsoavailable through a network of FAA chart agents prima-rily located at or near major civil airports. A listing ofproducts and agents is printed in the free FAA catalog,Aeronautical Charts and Related Products (FAA StockNo. ACATSET). A link to obtain publications is accessi-ble through http://www.naco.faa.gov. Below is the con-tact information for NACO.

FAA, National Aeronautical Charting OfficeDistribution Division AVN-5306303 Ivy Lane, Suite 400Greenbelt, MD 20770

Telephone(301) 436-8301(800) 638-8972 toll free, U.S. onlyFAX(301) 436-6829E-mail9-AMC-Chartsales@faa.gov

Retail SalesSee Agent Listings Page

IFR charts are revised more fre-quently than VFR charts becausechart currency is critical for safeoperations. Selected NACO IFRcharts and products availableinclude IFR navigation charts,planning charts, supplementary

charts and publications, and digital products. IFRnavigation charts include the following:

• IFR En route Low Altitude Charts (Conterminous U.S. and Alaska): En route lowaltitude charts provide aeronautical informationfor navigation under IFR conditions below 18,000feet MSL. This four-color chart series includes air-ways; limits of controlled airspace; VHFNAVAIDs with frequency, identification, channel,geographic coordinates; airports with terminalair/ground communications; minimum en routeand obstruction clearance altitudes; airway dis-tances; reporting points; special use airspace; andmilitary training routes. Scales vary from 1 inch = 5NM to 1 inch = 20 NM. The size is 50 x 20 inchesfolded to 5 x 10 inches. The charts are revised every56 days. Area charts show congested terminal areasat a large scale. They are included with subscriptionsto any conterminous U.S. Set Low (Full set, East orWest sets). [Figure 1-17]

• IFR En route High Altitude Charts(Conterminous U.S. and Alaska): En route highaltitude charts are designed for navigation at orabove 18,000 feet MSL. This four-color chartseries includes the jet route structure; VHFNAVAIDs with frequency, identification, channel,geographic coordinates; selected airports; andreporting points. The chart scales vary from 1 inch= 45 NM to 1 inch = 18 NM. The size is 55 x 20inches folded to 5 x 10 inches. Revised every 56days. [Figure 1-18]

• U.S. Terminal Procedures Publication (TPP):TPPs are published in 20 loose-leaf or perfectbound volumes covering the conterminous U.S.,Puerto Rico, and the Virgin Islands. A ChangeNotice is published at the midpoint between revi-sions in bound volume format. [Figure 1-19]

Figure 1-17. En route Low Altitude Charts.

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• Instrument Approach Procedure (IAP) Charts:IAP charts portray the aeronautical data that isrequired to execute instrument approaches to air-ports. Each chart depicts the IAP, all related navi-gation data, communications information, and anairport sketch. Each procedure is designated for

use with a specific electronic navigational aid, suchas an ILS, VOR, NDB, RNAV, etc.

• Instrument Departure Procedure (DP)Charts: There are two types of departure proce-dures; Standard Instrument Departures (SIDs)and Obstacle Departure Procedures (ODPs).

Figure 1-18. En route High Altitude Charts.

Figure 1-19.Terminal Procedures Publication.

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SIDs will always be in a graphic format and aredesigned to assist ATC by expediting clearancedelivery and to facilitate transition between take-off and en route operations. ODPs are establishedto insure proper obstacle clearance and are eithertextual or graphic, depending on complexity.

• Standard Terminal Arrival (STAR) Charts:STAR charts are designed to expedite ATC arrivalprocedures and to facilitate transition between enroute and instrument approach operations. Theydepict preplanned IFR ATC arrival procedures ingraphic and textual form. Each STAR procedure ispresented as a separate chart and may serve eithera single airport or more than one airport in a givengeographic area.

• Airport Diagrams: Full page airport diagrams aredesigned to assist in the movement of ground traf-fic at locations with complex runway and taxiwayconfigurations and provide information for updat-ing geodetic position navigational systems aboardaircraft.

• Alaska Terminal Procedures Publication: Thispublication contains all terminal flight proceduresfor civil and military aviation in Alaska. Includedare IAP charts, DP charts, STAR charts, airport dia-grams, radar minimums, and supplementary sup-port data such as IFR alternate minimums, take-offminimums, rate of descent tables, rate of climbtables and inoperative components tables. The vol-ume is 5-3/8 x 8-1/4 inches top bound, and isrevised every 56 days with provisions for aTerminal Change Notice, as required.

• U.S. IFR/VFR Low Altitude Planning Chart:This chart is designed for preflight and en routeflight planning for IFR/VFR flights. Depictionincludes low altitude airways and mileage,NAVAIDs, airports, special use airspace, cities,time zones, major drainage, a directory of air-ports with their airspace classification, and amileage table showing great circle distancesbetween major airports. The chart scale is 1 inch= 47 NM/1:3,400,000, and is revised annually,available either folded or unfolded for wallmounting.

Supplementary charts and publications include:

• Airport/Facility Directory (A/FD): This sevenvolume booklet series contains data on airports,seaplane bases, heliports, NAVAIDs, communi-cations data, weather data sources, airspace,special notices, and operational procedures. Thecoverage includes the conterminous U.S., PuertoRico, and the Virgin Islands. The A/FD shows

data that cannot be readily depicted in graphicform; e.g., airport hours of operations, types offuel available, runway widths, lighting codes, etc.The A/FD also provides a means for pilots toupdate visual charts between edition dates, and ispublished every 56 days. The volumes are side-bound 5-3/8 x 8-1/4 inches.

• Supplement Alaska: This is a civil/military flightinformation publication issued by the FAA every56 days. This booklet is designed for use withappropriate IFR or VFR charts. The SupplementAlaska contains an airport/facility directory, air-port sketches, communications data, weather datasources, airspace, listing of navigational facili-ties, and special notices and procedures. The vol-ume is side-bound 5-3/8 x 8-1/4 inches.

• Chart Supplement Pacific: This supplement isdesigned for use with appropriate VFR or IFR enroute charts. Included in this booklet are the air-port/facility directory, communications data,weather data sources, airspace, navigational facili-ties, special notices, and Pacific area procedures.IAP charts, DP charts, STAR charts, airport dia-grams, radar minimums, and supporting data forthe Hawaiian and Pacific Islands are included. Themanual is published every 56 days. The volume isside-bound 5-3/8 x 8-1/4 inches.

• North Pacific Route Charts: These charts aredesigned for FAA controllers to monitortransoceanic flights. They show established inter-continental air routes, including reporting pointswith geographic positions. The Composite Chartscale is 1 inch = 164 NM/1:12,000,000. 48 x 41-1/2 inches. Area Chart scales are 1 inch = 95.9NM/1:7,000,000. The size is 52 x 40-1/2 inches.All charts shipped unfolded. The charts are revisedevery 56 days.

• North Atlantic Route Chart: Designed for FAAcontrollers to monitor transatlantic flights, thisfive-color chart shows oceanic control areas,coastal navigation aids, oceanic reporting points,and NAVAID geographic coordinates. The full sizechart 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: Abooklet designed to be used as a teaching aid andreference document. It describes the substantialamount of information provided on the FAA’saeronautical charts and publications. It includes

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explanations and illustrations of chart terms andsymbols organized by chart type.

• Airport/Facilities Directory (A/FD)

Digital products include:

• The NAVAID Digital Data File: This file containsa current listing of NAVAIDs that are compatiblewith the NAS. Updated every 56 days, the file con-tains all NAVAIDs including ILS and its compo-nents, in the U.S., Puerto Rico, and the VirginIslands plus bordering facilities in Canada,Mexico, and the Atlantic and Pacific areas. Thefile is available by subscription only, on a 3.5-inch,1.4 megabyte diskette.

• The Digital Obstacle File: This file describes allobstacles of interest to aviation users in the U.S.,with limited coverage of the Pacific, Caribbean,Canada, and Mexico. The obstacles are assignedunique numerical identifiers, accuracy codes, andlisted in order of ascending latitude within eachstate or area. The file is updated every 56 days, andis available on 3.5-inch, 1.4 megabyte diskettes.

• The Digital Aeronautical Chart Supplement(DACS): The DACS is a subset of the data providedto FAA controllers every 56 days. It reflects digi-tally what is shown on the en route high and lowcharts. The DACS is designed to be used with aero-nautical charts for flight planning purposes only. Itshould not be used as a substitute for a chart. TheDACS is available on two 3.5-inch diskettes, com-pressed format. The supplement is divided into thefollowing 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 AIRMENSince the NAS is continually evolving, Notices toAirmen (NOTAM) provide the most current essentialflight operation information available, not known suffi-ciently in advance to publicize in the most recent aero-nautical charts or A/FD. NOTAMs provide informationon airports and changes which affect the NAS that aretime critical and in particular are of concern to IFR oper-ations. Published FAA domestic/international NOTAMsare available by subscription and on the internet. EachNOTAM is classified as a NOTAM (D), a NOTAM (L),or an FDC NOTAM. [Figure 1-20]

A NOTAM (D) or distant NOTAM is given dissemina-tion beyond the area of responsibility of a FlightService Station (AFSS/FSS). Information is attached tohourly weather reports and is available at AFSSs/FSSs.AFSSs/FSSs accept NOTAMs from the following per-sonnel in their area of responsibility: Airport Manager,Airways Facility SMO, Flight Inspection, and AirTraffic. They are disseminated for all navigationalfacilities that are part of the U.S. NAS, all public useairports, seaplane bases, and heliports listed in theA/FD. The complete NOTAM (D) file is maintained ina computer database at the National Weather MessageSwitching Center (WMSC) in Atlanta, Georgia. Mostair traffic facilities, primarily AFSSs/FSSs, have

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 C AND RWY10L/28R); TWY P (BTNTWY C AND RWY10L/28R) - CLSD DLY1615-2200.

FDC NOTAM

FDC 2/9651 DFW FI/P DALLAS/FORT WORTH INTL, DALLAS/FORT WORTH, TXCORRECT U.S. 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 READ352 VICE 351.

Figure 1-20. NOTAM Examples.

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access to the entire database of NOTAM (D)s, whichremain available for the duration of their validity, oruntil published.

A NOTAM (L) or local NOTAM requires disseminationlocally, but does not qualify as NOTAM (D) information.These NOTAMs usually originate with the AirportManager and are issued by the FSS. A NOTAM (L) con-tains information such as taxiway closures, personneland equipment near or crossing runways, and airportrotating beacon and lighting aid outages. A separate fileof local NOTAMs is maintained at each FSS for facilitiesin the area. NOTAM (L) information for other FSS areasmust be specifically requested directly from the FSS thathas responsibility for the airport concerned.Airport/Facility Directory listings include the associatedFSS and NOTAM file identifiers. [Figure 1-21]

FDC NOTAMs are issued by the National Flight DataCenter (NFDC) and contain regulatory information suchas temporary flight restrictions or amendments to instru-ment approach procedures and other current aeronauti-cal charts. FDC NOTAMs are available through all airtraffic facilities with telecommunications access.Information for instrument charts is supplied byAviation System Standards (AVN) and much of theother FDC information is extracted from the NOTAM(D) System.

The Notices to Airmen Publication (NTAP) is pub-lished by Air Traffic Publications every 28 days andcontains all current NOTAM (D)s and FDC NOTAMs(except FDC NOTAMs for temporary flight restric-tions) available for publication. Federal airwaychanges, which are identified as Center AreaNOTAMs, are included with the NOTAM (D) listing.Published NOTAM (D) information is not providedduring pilot briefings unless requested. Data of a per-manent nature are sometimes printed in the NOTAMpublication as an interim step prior to publication onthe appropriate aeronautical chart or in the A/FD. TheNTAP is divided into four parts:

• Notices in part one are provided by the NationalFlight Data Center, and contain selected

NOTAMs that are expected to be in effect on theeffective date of the publication. This part isdivided 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 spe-cific airport/facility, i.e. flight advisories and restrictions.

• Part two contains revisions to minimum en routeIFR altitudes and changeover points.

• Part three, International, contains flight prohibi-tions, potential hostile situations, foreign notices,and oceanic airspace notices.

• Part four contains special notices and graphics per-taining to almost every aspect of aviation; such as,military training areas, large scale sporting events,air show information, and airport-specific infor-mation. Special traffic management programs(STMPs) are published in part four.

If you plan to fly internationally, you can benefit byaccessing Class I international ICAO System NOTAMs,that include additional information. These help you dif-ferentiate IFR vs VFR NOTAMs, assist pilots who arenot multilingual with a standardized format, and mayinclude a “Q” line, or qualifier line that allows comput-ers to read, recognize, and process NOTAM contentinformation.

NAVIGATION DATABASESThe FAA has committed resources to the developmentand distribution of a navigation database to be imple-mented and distributed over the next few years. To thisend, the FAA has sought to implement the use of GPSand WAAS to replace the current ground-based infra-structure within the NAS. A major hurdle for thiseffort is the cost of acquiring and updating the naviga-tion database, especially for pilot/owners who also

have to update their flightdeck with RNAV equipment.

The FAA has developed animplementation and develop-ment plan that will provideusers with data in acceptable,open-industry standard for usein GPS/RNAV systems. Theestablished aviation industrystandard database model,

Figure 1-21. NOTAM File Reference in A/FD.

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Aeronautical Radio, Incorporated (ARINC 424) for-mat, includes the essential information necessary forIFR flight in addition to those items necessary forbasic VFR navigation. As part of Phase I of theprocess, existing en route data is entered and verifiedin the ARINC 424 database while Phase II includesthe verification and population of the proceduralinformation. Ultimately, this will allow manufacturersthe ability to provide several options to consumers.One option would be to allow the end user to down-load the FAA database utilizing the hardware/software

interface, while another option allows database sub-scribers access not only to the FAA database but alsovalue-added data such as FBO/airport services, fuelcosts, or a plug-and-play database card. Essentiallythe new FAA database will fulfill requirements foroperations within the NAS while still providing theopportunity for private entities to build upon thebasic navigation database and provide users withadditional services when desired. Refer to AppendixA, Airborne Navigation Databases for more detailedinformation.

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