From Time to Time In this issue: by W.J. Klepczynski, GPS TAC/WAAS Team (AND-730) Using WAAS for precise Ed Powers, United States Naval Observatory timing...... 1 Rob Douglas, National Research Council of Canada Pat Fenton, NOVAtel WAAS increases aviation Historically, navigation systems have depended on safety benefits of the time. This was clearly demonstrated by the sailing of Capstone Program in Harrison’s chronometer on HMS Deptford in 1761, Alaska...... 3 to prove that the instrument allowed navigators for Independent Review the first time to determine longitude accurately and Board backs WAAS...... 4 reliably. Because of this relationship between navi- gation and time, the time-keeping community has LAAS GIP explained....4 always had a keen interest in the use of navigation systems for the distribution of time. Even today, the Procedures Development heart of the GPS rests on a highly evolved clock tech- Initiatives...... 5 nology. Unlike navigators, who need four GPS satel- lites by which to determine their position, timekeep- Salt Lake City prepares ers, who know their position, need only one satellite for increased air traffic to determine time. Observations of a single satellite also allow timekeepers to remotely syn- during 2002 Winter Olympic Games...... 7 chronize clocks around the world. This article summarizes the result of a recent study, which showed that the GPS Wide Area Interregional airspace Augmentation System (WAAS), once fully operational, should provide a very stable, con- redesigns offer potential tinuously-available timing signal. It should also allow the development of more economical benefits to users...... 7 timing systems utilizing its signals, the almost instantaneous detection of any pathological behavior in a system providing time, and an extremely robust check for many timed systems. Unique capabilities of The WAAS is one of the most recent developments in the evolution of navigation systems. vertical flight aircraft are While it is similar to other differential GPS systems in concept, the WAAS gives the Federal aided by development of Aviation Administration (FAA) and air navigation a significantly higher level of performance new helicopter GPS than other differential GPS (DGPS) systems. Because of the augmentation methods utilized approach procedures.....8 by the WAAS, it provides not only improved accuracy, but also increased availability, integ- Industry Corner: GAME rity, and continuity of service. It does this by continually monitoring GPS transmissions from model benefits from GPS- WAAS Reference Stations (WRSs) and by transmitting an augmented message from several based instrument geostationary communications satellites (GEOs). The WAAS is currently in its early stages of approaches...... 9 development. Current studies on the use of WAAS for time transfer and time distribution indicate that it is already at the level of the GPS Precise Positioning System (PPS). We can Worldwide adoption of reasonably expect improved levels of precision and accuracy as the system matures. Satellite Navigation.....10 Time and the WAAS US and Mexico cooper- Figure 1 schematically depicts the WAAS process, as it will be once fully implemented. ate to expand future The basic unit is the WAAS Reference Equipment (WRE), consisting of a cesium beam fre- WAAS coverage...... 11 quency standard, a 12-channel, dual-frequency WAAS-GPS receiver, and a wide- and a nar- GPS in India...... 12 row-band GPS receiver. Each WRE continuously tracks as many GPS satellites and GEOs as it is able to acquire. 2

processor receives and uses to form the WNT time scale. This time scale is then steered to GPS time with the same algorithm. Ground Uplink Stations (GUS) will each have a cesium clock, slaved to WNT. Once per day, the WMS will issue commands to steer the GUS clock in order to reduce any offset it may have from GPS time. The GUS clock con- trols the synchronization of the WAAS navi- gation message from the GEO.

WAAS Time Distribution As a secondary mission, the WAAS provides coordinated universal time (UTC). To this purpose, the WAAS compares WNT, which is synchronized to GPS time, with the UTC pro- vided by the U.S. Naval Observatory (USNO), and transmits the offsets as part of the WAAS navigation message.

Each WRS contains three identical WREs. This redun- Status of WAAS Time-keeping dancy ensures that each WRS will continue to provide data Data collection commenced at USNO on October 6, 1999. to its WMS in the event that one of the WREs fails. Each Every 15 seconds, GPS and Atlantic Ocean Region-West WRS, in turn, transmits the data it obtains to two WAAS (AOR-W) WAAS GEO satellites make pseudorange and car- Master Stations (WMS), which form the WAAS navigation rier-phase measurements. All of the broadcast data from the message and WAAS Network Time (WNT). The message satellites are now collected for postprocessing. contains information on satellite orbits, the current state of the ionosphere, timing information, and system health. Each Time Transfer Capabilities WMS passes the navigation message to each of, initially, two Fig. 2 illustrates the computed difference between USNO Geostationary Uplink Stations (GUSs), which upload it to and GPS system time. We included this difference as a com- the two Phase 1 GEOs which then transmit it to the user. mon denominator benchmark process. Most GPS timing re- ceivers today use this observable to provide time reference WAAS Master Stations information. Note that selective availability (SA) caused most Once per second, all WRSs transmit all their data to all of the 43-nanosecond standard deviation. On May 1, 2000, WMSs, which then perform the functions of correction pro- the U.S. Department of Defense (DoD) turned off this inten- cessing, satellite orbit determination, integrity determination, verification, validation, and WAAS message generation, and transmit a formatted 250-bit WAAS message to all GUSs.

WNT Time Scale In order for the WAAS signal to supplement the GPS navigation signals, the GEOs must synchronize their trans- missions with those from the GPS satellites. In other words, WAAS must be on GPS time. The reference for the WAAS is called WAAS Network Time (WNT). Measurements from all WREs at all WRSs are sent to each WMS. The correc- tions processor at each WMS employs a WNT algorithm to compute a potentially independent WNT time scale from the data received from the WRSs. All “good clocks” con- tribute to the WRE measurements that a WMS corrections 3

tional degradation and performance has since substantially improved. These results, at this early stage in the development of the WAAS, indicate the future promise of this technique for time transfer and time distribution.

Future Potential of SBAS The WAAS will contribute to the timing infrastructure of the U.S. by providing time within the National Airspace Sys- tem (NAS) for the recording of all events. It will also provide a very stable timing signal for the timekeeping community. Because the source remains at the same approximate point in the sky, a high-gain antenna can provide a very good signal to the stationary user. The offset of WNT from UTC will be transmitted within the WAAS navigation message. The sig- nal will be available continuously. recommendations, recognizes the need to integrate emerging Such a signal provides some unusual capabilities for the technologies into the present airspace in order to resolve the timekeeping community. It should allow the development of hurdles of the Alaskan environment. The initial Capstone more economical timing systems utilizing its signals. Cheaper challenge focuses on aviation safety in the Southwest Yukon- crystals can now be used in systems that rely on atomic stan- Kuskokwim (Y-K) and Southeast regions of Alaska. These dards as their flywheel while they continuously integrate GPS areas experience a significant number of mid-air collisions, time or UTC using only one geostationary satellite. A user controlled flight into terrain, and weather related accidents. will be able to instantly detect any pathological behavior in a The Capstone effort is working to provide ground infrastruc- system providing time by comparing signals with another vis- ture and avionics in order to address these problems as well as ible GEO. With GPS, one has to wait to see whether the to determine the operational benefits for commercial carrier transients are due to anomalous clock behavior in a satellite. aircraft operating in these areas. Capstone has equipped up The WAAS, on the other hand, provides an immediate re- to 90% of the aircraft operating in the Y-K and Southeast dundancy check to anyone who is within the footprint of its regions of Alaska giving the program the ability to measure two transmitting geostationary satellites. This can be used as the anticipated benefits. While Capstone is initially focusing an extremely robust check for many timed systems. on these two geographic areas, the intention is to leave sys- tems in place that provide a benefit and to expand these Based on an article originally published in the May 2001 issue ground systems to the rest of Alaska. Capstone technology is of GPS World, Eugene Oregon. being engineered so that it can be deployed to the rest of the National Airspace System (NAS) as needed. The following New Technology Benefits Region have been provided in the Y-K area and will migrate to the Southeast in 2002: with High Safety Risks · Data link weather and other flight information into the by Jim Hebert, Capstone Liaison (Contract support for AND-500) cockpit · A cockpit display that uses a terrain database to reduce Safety, capacity, and efficiency con- controlled flight into terrain tinue to be a concern for members of the · Increased number of airports served FAA’s Alaska Region where airplane ac- by GPS non-precision approaches cidents are a daily reality. The avionics · Automated Weather Observing Sys- package offered by the Capstone Program tem (AWOS) to provide weather for addresses these challenges and offers so- the GPS approaches lutions, and the key to this program is the · Cockpit display of adjacent traffic partnership formed by the FAA and the · Radar-like service using Automatic Alaskan aviation industry. Dependent Surveillance-Broadcast The Capstone Program, named for its (ADS-B) combination of a range of concepts and 4

The Wide Area Augmentation System (WAAS) has intro- WAAS Program. The IRB was formed under the auspices of duced area navigation (RNAV) routes in a region with no the Institute for Defense Analyses (IDA) in Alexandria, VA existing infrastructure, and has increased aviation safety and to report directly to the Administrator. Its membership is airspace capacity while decreasing the cost of the supporting composed of senior scientists and managers from outside the infrastructure and aircraft avionics equipment and systems. FAA. WAAS, in conjunction with terrain and traffic avoidance data, offers a practical evaluation that will validate the application IRB Report and functional capabilities of new technologies and enhance The IRB made a number of near, mid and long-term rec- the pilot’s ability to operate safely. As a result, the avionics ommendations to improve the WAAS acquisition program. and ground infrastructure in the Southeast will provide this In brief, the IRB validated the WIPP’s approach to defining user-identified “useable Instrument Flight Rules (IFR) infra- the parameters of the integrity problem and its proposed solu- structure.” Narrow approaches into airports bordered by tion to achieve an initial capability of Lateral Navigation/Ver- sharply rising terrain will pose less of a threat. Environments tical Navigation (LNAV/VNAV). It also supported the with weather patterns that have restricted or even prevented WIPP’s proposed path to achieve the follow-on GNSS Land- flight due to the route structure will also be more accessible. ing System (GLS) capability that will constitute full opera- tional capability for WAAS. The IRB strongly supported the continuance of the WIPP at least through commissioning of WAAS in Review: IRB Report the system. Released The IRB urged the FAA to make a stronger commitment by Hal Bell, WAAS Team Lead (AND-730) to the evolution of WAAS, considering how to exploit the possible synergies among WAAS, the Local Area Augmenta- On April 10, 2001, the FAA pub- tion System (LAAS) and the U.S. Coast Guard’s Differential licly released the report of the WAAS GPS (DGPS) augmentation system. Independent Review Board (IRB), The IRB also strongly urged the acquisition of an additional which was chartered to review and geostationary satellite as soon as possible to mitigate the single report to the FAA Administrator on system engineering ef- thread of failure that exists with the current two-satellite forts aimed at resolving the technical barriers that were pre- INMARSAT III constellation. The IRB also pressed for the venting delivery of WAAS to the customer. The full Report immediate initiation of acquisition efforts aimed at achieving and accompanying Executive Summary can be viewed at http:/ the required end-state constellation of four satellites with /gps.faa.gov/Library/Documents/documents.htm#waas autonomous payloads supporting broadcast of three civil sig- nals. Background The IRB has provided the FAA a valuable assessment of The Wide Area Augmentation System was originally sched- where the FAA is and where it needs to go to make WAAS, uled to achieve Initial Operational Capability in September the cornerstone of its future navigation architecture, avail- 2000. In January of that year, however, FAA certification able to the aviation community as soon as possible. The IRB specialists identified a problem with proving that the system will continue to provide analysis and advice at least through met the stringent integrity requirements specified for the sys- 2001. tem. Integrity is the ability of the system to provide timely warn- The LAAS Government Industry ings to users when it should not be used for navigation. For WAAS, integrity means there can be a no greater than one in Partnership: A Complex Approach ten million chance of hazardously misleading information to System Implementation being transmitted to the user without the system notifying by Dieter Guenter, GPS-TAC/LAAS Team (AND-710) the user within six seconds of its degraded status. To meet the challenge of establishing the parameters of the In March of this year, the New York Times published an integrity issue and developing the solution to the problem, in article discussing FedEx and the airlines’ expectations for the February 2000 the FAA formed the WAAS Integrity Perfor- ongoing Local Area Augmentation System (LAAS) activities mance Panel (WIPP). Shortly thereafter, the FAA also char- in Memphis. The article focussed on the FedEx / Memphis tered the WAAS IRB to review the WIPP’s efforts and offer activities but did not really expand on the complexity of the additional technical and strategic advice concerning the “Government Industry Partnership” (GIP) driving the devel- 5

opment and implementation of the LAAS. The New York to the progress of the final system. Times also made little mention of the other two GIP teams On the airborne/avionics side of LAAS development, the and additional FAA activities, which are equally important Navy/NAVAIR and the Technical Center both play a signifi- for the LAAS success story. The following article intends to cant role. Using LAAS prototype ground systems both are bring to light some of the other activities included in the LAAS working towards implementing and validating LAAS airborne Government Industry Partnership. receiver requirements and are teaming up with Rockwell With the GIP, the FAA is pursuing an innovative approach Collins on the LAAS multi-mode receiver. to overall LAAS system development, fielding, testing In addition to the technical development and valida- and evaluation, and operational approval for pub- tion of the LAAS ground system and avionics, the lic use. The GIP approach is a cost- LAAS team is working with the differ- sharing partnership between the gov- ent FAA disciplines on installation and ernment and industry. FAA (“government”) operational issues for implementing is responsible for the development of the sys- LAAS into the National Airspace Sys- tem specification, operational documentation, tem (NAS). FAA’s Airways Facilities technical support, and certification of the sys- and the Technical Center are working tem while private companies (“industry”) provide on LAAS siting criteria (how and where to install the funds to develop a LAAS Category I system. LAAS), which constitutes a major undertaking due Honeywell, Raytheon, and most recently, Airsys ATM, pres- to the diversity of the system and the individual requirements ently lead different industry teams, which are made up of air- of each airport. Maintenance, training, and logistics issues line/aircraft manufacturers, airports, and avionics manufac- have to be identified and worked on as well. turers. As part of the FAA GIP program, these teams were In order to utilize the LAAS signal, specific approach and formed to start the development of the LAAS Category I sys- departure criteria and procedures need to be established to tem. fly LAAS approaches. Flight Standards develops and vali- LAAS has made tremendous progress due to the work of dates these criteria through flight tests in Oklahoma City with all the GIP partners. Honeywell prototype ground systems the University of Oklahoma and in Atlantic City with the have been established at Chicago O’Hare, Midway, and Mem- Technical Center aircraft. Aviation System Standards (AVN) phis. Raytheon is converting its SCAT I system into a proto- develops LAAS approach procedures and establishes flight type LAAS in Salt Lake City, and Rockwell Collins is work- inspection criteria for LAAS flight inspections. Other impor- ing on the integration of LAAS into the aircraft avionics within tant factors include the coordination and training of Air Traffic its multi-mode receiver (MMR). These activities and proto- personnel and the development of LAAS NOTAM capabili- type installations provide the FAA and the GIP partners with ties and specific LAAS air traffic monitor capabilities. valuable insight into the development and implementation All these activities have to be coordinated for the GIP teams of LAAS systems. and their systems as well as for the FAA systems. Coordi- The FAA’s LAAS Product Team (AND-710) is directing nated activities between the FAA Headquarters, the FAA research, validation, and implementation of LAAS. The rela- Regional Offices, Industry, and users are essential for the suc- tively small LAAS team, under the leadership of Steve Hodges, cessful implementation of LAAS into the National Airspace is involved in all aspects of the GIP, coordinating implemen- System. tation activities, leading the LAAS acquisition process and further development of the LAAS Category II/III systems. GNSS Procedures Development The development efforts of LAAS are focused on two main Initiatives areas: ground equipment and avionics. Honeywell, Raytheon, the FAA Technical Center, and the University of Oklahoma by Kelly McKee, GPS TAC/NAS Implementation Team (AND-710) have developed prototype ground systems. Installing such The National Airspace System (NAS) is in a period of un- prototype systems, however, is just one part of LAAS devel- precedented growth and change. Our national airspace com- opment. Stanford University, Ohio University and MITRE prises more than 29 million square miles and handles more continue to work in different areas of the LAAS ground facil- than 55,000 flights per day that use 12,300 instrument ap- ity development including Ephemeris, Signal-Quality and proach procedures. Since 1994, the number of instrument Integrity Monitoring, Very High Frequency (VHF) Data Link procedures has grown by approximately 50%. Technology im- projects and Multipath modeling. These development efforts, provements, funding levels and other factors will impact the as well as validation of the requirements, are equally crucial course of the modernization strategy. In addition, global 6

interoperability of technology and harmonization of proce- proach opportunities to lower weather minimums. To foster dures are essential for continuity of operations and avionics and support full and optimum integration of RNAV into the investments. Aviation System Standards (AVN) has the re- NAS, the FAA has developed a new charting format for sponsibility for designing instrument approach and departure RNAV Standard Instrument Approach Procedures (SIAPS). procedures for the 21st Century NAS in accordance with Fed- This new format maximizes the information available to the eral Aviation Regulations (FAR 97) pilot for the safe and efficient con- safety standards. A web site devel- duct of the instrument procedure. oped to assist people in understand- Vertical guidance is provided as ing the procedure development pro- a linear deviation from the desired cess and providing a method for re- track defined by a line joining two questing new instrument procedures waypoints with specified altitudes, can be found at http:// or as a vertical angle from a speci- www.mmac.jccbi.gov/avn/iap/ fied waypoint. Computed positive iap_flow.html vertical guidance is based on baro- As an outgrowth of the general metric, satellite elevation, or other context described above, the Federal approved systems. The desired Aviation Administration (FAA) par- vertical path may be pilot select- ticipates with the aviation industry able or may be determined by the on the Commercial Aviation Safety VNAV computer with computa- Team (CAST) to reduce accidents, tions based on the altitudes asso- incidents, and delays. One of the ciated with successive waypoints. efforts of CAST was to form a sub- These instrument approach proce- group to work on precision-like ap- dures provide separate minima for proach implementation. This sub- LNAV and LNAV/VNAV. The group has generated a plan with a LNAV/VNAV procedure and the series of actions for different FAA LNAV procedure are designed organizations, including AVN. with different obstruction criteria. AVN’s strategy is effectively inte- The flight inspection of RNAV grated with the (FAA) NAS Archi- procedures evaluates the sound- tecture and National Airspace Re- ness of the procedures in accor- design initiative. The AVN strat- dance with FAA Order 8200.1A, egy also addresses industries’ request to fully utilize ground, Section 214, and identifies any deficiencies in the procedure. aircraft, and space- based navigation systems for improved Approach safety and flyability are evaluated as a non-preci- safety, capacity, and operational flexibility. The AVN organi- sion approach with and without vertical guidance. The final zation has produced a plan that addresses the CAST’s direc- segment of the flight inspection may require repeated flights tion toward a 21st Century precision landing system. The AVN for obstacle verification/evaluation. plan provides a broad framework of flight procedure produc- The AVN production plan schedules and prioritizes pro- tion options that are linked to specific funding requirements cedure development through 2007. The production sched- and provides the opportunity for the FAA to effectively and ule specifies a “what by when schedule” that enables the avia- efficiently deliver the improved safety benefits desired by the tion industry to plan for the introduction of new instrument CAST. The CAST AVN Implementation Plan can be viewed approach procedures. In addition, the AVN production sched- or downloaded at http://www.mmac.jccbi.gov/avn/home/docu- ule is prioritized based upon risk assessment and contains a ments/cast.doc. matrix that displays the priority as directed by the CAST, i.e. The CAST Plan makes several references to area naviga- first priority Part 139 runways, second priority runways 5,000 tion (RNAV), lateral navigation (LNAV), and vertical navi- feet or longer, and third priority paved public use runways less gation (VNAV). RNAV is a method of navigation that per- than 5,000 feet. The plan takes into consideration the avail- mits aircraft operation on any desired course within the limits able safety risk factors to mitigate accident rates at airports by of a self-contained system capability. Many systems also pro- using National Transportation Safety Board (NTSB) accident vide vertical guidance. The Wide Area Augmentation Sys- data. This production plan also supports Safer Skies objectives. tem (WAAS) and Local Area Augmentation System (LAAS) The first two fiscal years (2001 – 2002) of the production will expand the availability of LNAV/VNAV instrument ap- 7

plan contain specific information about the type of procedure and expand. We invite you to visit our websites and let us that will be published at an identified airport and runway end know what you think. during each quarter of the year. Beginning in the third year (2003), the schedule identifies the airport and runway end 2002 Winter Games: Salt Lake that will be published during the year without a quarterly com- mitment. The production schedule for the remaining years City Uses GPS to Prepare Air- (2004-2007) contains information on the airport that will be space for Increased Traffic addressed during that fiscal year. The schedule will be a “roll- by Brian Durham (ANM -520) and Paul Ewing (ATP-104) for NAS ing schedule” whereby specific information on airport run- Implementation Team (AND-710) way ends and quarterly publication plans will be available for a continuous two-year period. It is anticipated that the pro- The complex flight environ- duction schedule will be revised every six months, facilitating ment of the Salt Lake City Air- industry input and assuring that the agency is as responsive as port terminal area is overly con- it can be with the resources that are available. gested and can pose a significant AVN has developed a comprehensive website that allows challenge to VFR pilots. One of the flying community to access information about the instru- the busiest air traffic environ- ment flight procedure production schedule. The website con- ments in the nation, Salt Lake City Airport is situated in a tains general information about the process of flight proce- valley with high mountainous terrain to the east and west. In dure production, the current FAA production schedule based preparation of the 2002 Winter Olympic Games next Febru- upon agency resource commitments, and options for private ary, the Air Traffic Control facility is also preparing for a sub- investment in instrument flight procedure production. Avail- stantial increase of both Instrument Flight Rules (IFR) and able on the web-site, on a quarterly basis, will be a listing of VFR air traffic in the region. vertical descent angle (VDA) additions as they are completed Two Air Traffic divisions have recently taken a significant and also the accomplishment of renaming the GPS proce- step in providing for safer flight in the Salt Lake City area by dures. Finally, the site offers a listing of contacts. You can instituting the use of VFR Waypoints. VFR Waypoints are access the site at: http://www.mmac.jccbi.gov/avn/iap/ predetermined geographical coordinates, determined by the The AVN production schedule considers the visual glide- Global Positioning System (GPS) and designed to enhance slope indicator (VGSI) installation plans of the Airway Fa- pilot situational awareness, enhance safety, reduce airspace cilities organization. Updated information on the adjustment/ deviations, and increase Air Traffic Control efficiency. alignment of the VGSI angles will also be available on the The VFR Waypoint program was developed to aid VFR production schedule web-site. pilots in navigating into, out of, through, or around terminal AVN 100 faces many challenges with the resources avail- airspace areas, special use airspace (SUA), or other areas where able. Although the CAST plan is prioritized based on safety VFR navigational assistance is deemed prudent. The benefits, procedure development continues at all airports in Waypoints are graphically displayed on the April 19, 2001 edi- the NAS. As of July 2000, AVN has added Vertical Descent tion of the Salt Lake City VFR Terminal Area Chart (TAC) Angles (VDAs) to non-precision approaches at 60% of Part and are either associated with a VFR Reporting Point, or as a 139 airports, 40% of non-Part 139 airport with runways 5000 stand-alone Waypoint. ft or greater, and less then 10% at all other runways less than The charting of the VFR Waypoints is a big step in improv- 5000 ft. As the number of procedures increase, so does the ing VFR flight and airspace efficiency. The FAA has also amount of resources allocated to the maintenance of these published VFR Waypoints on VFR TACs at Kansas City, Mis- procedures. souri on November 20, 2000, and Houston, Texas, on March AVN, in conjunction with other organizations, continues 22, 2001. The benefits to Kansas City are similar to those of daily support of the CAST initiatives. The initial group of Salt Lake City and enable VFR pilots to safely navigate around airports selected for airport surveys, procedure development, Class B airspace. The Houston TAC application provides and implementation are just the beginning, as time goes on, GPS Waypoints to assist pilots in navigating through the Class numerous new airports will be added to the list. Procedure B airspace by ensuring the correct identification of the flight development will continue and eventually, almost all airports corridor. The publication of these Waypoints is part of the will have GPS approaches available. Support of this long- FAA’s commitment to being a good service provider to the term program is imperative as the program continues to grow flying public and supporting safe VFR flying. 8

GPS Supports Unique Helicopter Standards and Flight Procedures Office (FPO) coordina- tion in the Regions. Under this program there have been Capabilities for Emergency Medi- 107 industry funded Special Helicopter GPS approaches de- cal Flights veloped to hospitals and 25 more are under development. Applications of these procedures at private locations by Mike Webb, ARINC/NAS Implementation Team (AND-710) throughout the country have given populations living in re- mote areas access to trauma services during the crucial The FAA has aggressively pursued development of new “golden hour”. instrument flight rules (IFR) applications of the Global Posi- Additionally, in preparation of the availability of the Wide tioning System (GPS) for civil helicopter operations, which Area Augmentation System (WAAS) to augment GPS, the include Emergency Medical Service (EMS) operations. FAA’s William J. Hughes Technical Center has collected data Facilitating EMS operations to hospital heliports has of- for WAAS helicopter precision instrument approaches to fered the FAA a unique set of challenges when compared to heliports. These data are currently being analyzed for in- standard IFR operations into airports. Hos- corporation into FAA procedures criteria. pitals are necessarily located within cities, These criteria should be in place when which are, by nature, obstacle rich environ- WAAS is commissioned for IFR use. The ments. The necessary land to convert a typi- Technical Center is also collecting data on cal VFR heliport into an IFR facility rarely GPS lateral navigation and barometric al- exists, and obstacles would penetrate into the timeter-aided vertical navigation (LNAV/ shallower IFR heliport airspace surfaces. VNAV) approach capability to heliports. Relocating the hospital heliport is rarely a This will permit the use of existing naviga- solution as its mission is to deliver patients tion equipment and aircraft avionics to fly to the trauma services of an emergency room as quickly as a vertical path to a decision altitude (DA), reducing the possible. risk of controlled flight into terrain (CFIT). FAA standards and orders provide for he- The importance of this work cannot be licopter point-in-space GPS instrument ap- overestimated. The FAA and industry proach procedures to non-IFR heliports. The have long touted the unique capabilities standards facilitate IFR operations into VFR of the helicopter. Operations to airport heliports with special visual-segment criteria runways seldom call upon these capabili- for the transition from an IFR approach to a ties. Operations to heliports, by definition, VFR ground infrastructure. While these FAA demand them. Through this research, the efforts permit greater capability for EMS he- FAA is pushing the envelope to quantify licopters to complete missions, safety of flight these unique capabilities. for EMS helicopters is also enhanced by sole The FAA regional Flight Standards and reliance on VFR during periods of reduced visibility. The Air Traffic staffs have been aggressively working to assist Flight Standards Service is presently in the helicopter operators in creating private, low process of developing new heliport departure altitude GPS enroute infrastructures, a rec- criteria for departing VFR heliports under ommendation supported by the FAA Safer IFR conditions. Skies Program. In California, the Western In 1998, as part of the solution necessary Pacific Region recently approved 8 STI de- for meeting the helicopter industry’s unique veloped approaches to hospital helipads needs, Flight Standard’s Service Flight Tech- and the first helicopter GPS enroute sys- nologies and Procedures Division (AFS-400) tem. This system will greatly increase the and Aviation System Standards (AVN-1) use of IFR for EMS operations in northern entered into agreement to participate in a California. It will also effectively reduce cooperative effort with Satellite Technology Implementation minimum enroute altitudes for REACH Air Ambulance L.L.C (STI) for non-federally developed helicopter GPS ap- helicopter operations by 50% thereby improving their avail- proach procedures. Interim Policy, Letters of Agreement, and ability to provide healthcare for local communities in a four Letters of Authorization, allow for STI developed approach county area in Northern California. The RNAV routes are procedures to be submitted to AVN for Quality Control (QC) the end result of many months of collaboration and coordi- and flight inspection, and authorize STI to perform Flight 9

nation between the various entities in the FAA and STI. Three different air traffic control facilities are involved in pro- GPS-Based Instrument Ap- viding services: Oakland ARTCC, Sacramento Terminal Ra- proaches Benefit Tool for dar Approach Control (TRACON), and Bay TRACON. STI Estimating Airport Access developed the routes by using interim criteria provided by by Vince Massimini, MITRE Corporation the Flight Procedures Standards Branch (AFS-420) and policy Industry Corner from AFS-400. Quality control reviews and flight inspec- One of the principal objectives of WAAS is to improve tions were completed by AVN prior to final approval by the safety by providing instrument approaches with vertical guid- FAA. The Western-Pacific Regional Headquarters (AWP), ance to almost all instrument capable runways in the U.S. including the AWP-Airspace Branch and Operations Branch, Another important consideration, especially for users, is the the Los Angeles FPO and the AWP AWO to mention just a airport access benefits that will accrue from WAAS ap- few involved in making these new GPS routes a reality. STI is proaches. Airport access can be measured by the height currently involved with Erlanger Medical Center, of Chatta- above touchdown (HAT) and the visibility minimum for an nooga, Tennessee, and has developed six special GPS-based instrument approach to a runway end. RNAV routes servicing 17 special helicopter GPS approaches It has been difficult, however, to estimate what the air- located in Tennessee, Georgia, and North Carolina. port access benefits would be for the thousands of airports The helicopter has emerged as a solution for point-to-point and runways in the U.S. The FAA (AVN-100 in Oklahoma air transportation, and EMS helicopters are a proven means City) currently develops instrument approaches, but the of transporting trauma patients between medical facilities. process can take weeks for one runway end. Evaluating thou- Historically, the EMS was rooted in air transportation designed sands of runway ends has just not been practical. to service airports and lacked the capability for inter-heliport MITRE has developed a computer-based tool that esti- and airport-heliport all-weather air transportation. With the mates the HAT and visibility minima for GPS instrument implementation of GPS, an integrated EMS system offers re- approaches using electronic databases of terrain and ob- liable and cost-effective solutions for providing accessible care stacles. The model is called the GPS Approach Minima for populations over a large area. The key to this network lies Estimator (GAME). GAME uses criteria from the FAA in establishing affordable, safe instrument approaches using Terminal Instrument Procedures (TERPS) developed for the availability of GPS for low altitude enroute navigation GPS approaches, but can be modified to use different crite- and landing guidance. ria. The design of the model allows the evaluation of a large Though small in number compared to other segments of number of runways, with subsequent analysis of the benefits the aviation industry, EMS operators have developed in re- of a particular approach procedure. sponse to improving emergency healthcare for a larger seg- GAME is not intended to replace the procedure devel- ment of society, while keeping medical costs down. GPS is an opers at AVN. To reduce development, processing, and integral component in the evolution of this segment of the analysis time, GAME only evaluates a 5 nautical mile straight national healthcare system. in final segment. The model does not attempt to optimize for terrain and obstacles, as would a human developer, nor does it consider increased minima that might result from obstacles in the missed ap- proach path. Also, GAME does not use all the data, such as maps, that might be avail- able to a human developer. However, initial validation results comparing the HAT from GAME to an existing approach are promising. The difference between GAME 10

estimates of the HAT for a GLS approach versus an existing ILS approach to the same Efficiencies for the runway end have a median of zero and a 75th percentile of only 25 ft. Differences be- Future: Airport Redesign tween a GAME estimate of HAT for an LNAV/VNAV approach and the HAT deter- Raises Airport Standards mined by AVN have a median of 12 ft, and a 75th percentile of 5 ft. Similarly, differences by Bob Brekke, GPS TAC/NAS th Implementation Team (AND-710) between GAME and AVN HATs for LNAV have a median of 30 ft and a 75 percentile With the National Airspace of 2 ft. Redesign, airspace changes are At present, GAME does not include considerations for airport infrastructure, which underway across the United can reduce visibility minima (e.g., with approach lights), increase visibility minima (e.g., States. Both the Western Pa- runway surface composition), or even preclude a category of approach (e.g., runway length). cific Region and the Southwest These capabilities, in addition to missed approach considerations, are presently being Region are jointly undertaking incorporated into GAME. one of the newest airspace re- Preliminary results for over 5000 runway ends at over 1500 airports are already show- design projects, known as the ing the relative airport access benefits of LNAV/VNAV and GLS approaches. When the Northwest 2000 and Las Vegas airport infrastructure and missed approach considerations are included, GAME will be Four Cornerpost Plan, which capable of estimating benefits for existing and future airport configurations. seeks to achieve the most effi- cient airspace possible for both Another important use of GAME will be to investigate the effects of improved WAAS system-users and providers. performance on airport access. For example, if the WAAS Vertical Alert Limit (VAL) This comprehensive air- can be reduced from 50 to 20 m, and if criteria are developed for approaches using the space redesign plan, scheduled new VAL, then GAME can estimate the airport access benefits of the reduced VAL. for implementation in the fall Contact Les Crane (703 883 7243; [email protected]) or Vince Massimini (703 883 of 2001, integrates changes in 5893; [email protected]) for more information on GAME. the airspace at the Albuquer- que and Los Angeles Centers. It also includes the Phoenix Worldwide Adoption of Satellite Navigation and Las Vegas Terminal Radar by David Burkholder, Office of International Research and Acquisition (ASD-500) Approach Control Interwoven within the FAA’s mission is a strong emphasis and commitment to “global (TRACON) areas that serve leadership.” The FAA Research and Acquisitions Office (ARA) is a critical contributor the Phoenix Sky Harbor Inter- to the execution and success of this global leadership as it facilitates worldwide system national and Las Vegas McCarran International Air- compatibility and interoperability of global implementation initiatives with those tech- ports. Area navigation nologies being fielded for operational use in the U.S. National Airspace Systems (NAS). (RNAV) arrival and departure One of the technologies that has provided the most impact to international aviation is routings have been designed to the Global Positioning System (GPS). The number of countries adopting GPS at least as reduce delays, improve effi- a supplemental navigation aid has continued to grow at a healthy rate as the safety and ciency, and reduce complexity efficiency benefits of GPS become clearer to both service providers and the users. while maintaining the highest For instance, countries that currently have little or no ground-based navigation infra- standards of safety and envi- structure are realizing the potential safety, efficiency, and economic benefits of using GPS ronmental sensitivity. to provide an immediate navigation capability. This type of space-based service also is Airspace studies have beneficial to countries and regions that currently have to take extreme measures to safe- shown that RNAV procedures guard ground-based navigation aids from hostile forces, tampering, or vandalism. have the potential for a signifi- The benefits from basic GPS are clearer than ever. However, many countries and cant cost savings for systems users. On a recent RNAV ar- regions are already opting to take steps to progress beyond what the basic GPS constella- rival-route test-flight into the tion can provide. The FAA, represented by the International Research and Acquisition Phoenix Sky Harbor Interna- Office (ASD-500) and the Satellite Navigation Product Teams (AND-710/730), is ac- tional Airport the aircraft tively involved in providing support to these regional satellite navigation implementa- saved approximately four min- tion efforts and initiatives that are gaining momentum around the globe. utes of flight time and 300 In North America, we have been working with our counterparts in Canada and Mexico pounds of fuel. Additional for several years on cooperation towards creating a North American satellite navigation benefits include increases in system based on WAAS and LAAS technologies. In March of this year, we brought three flexibility, predictability, and Mexico National Satellite Test Bed (NSTB) reference stations on-line, and thus created improved access to the Na- a true North American WAAS test bed capability (Canada already has three NSTB tional Airspace System. reference stations). This newly formed architecture provides opportunities to conduct 11

more advanced regional analyses on how a North American WAAS can come to fruition. WAAS Arrives in Mexico Latin America is taking monumental steps towards devel- by Tom Dehel, NSTB Lead Engineer (ACT-360) oping its own regional Global Navigation Satellite System Mexican civil aviation officials, engineers, and pilots of (GNSS) architecture. Brazil has initiated an extensive joint the FAA completed a flight test of Mexico’s recently installed project with the FAA to establish a prototype WAAS test bed National Satellite Testbed (NSTB) equipment. Sr. Oscar capability. This Brazilian Test Bed (BTB) should be opera- Amable, Dirección General Adjunto Servicios a la tional this Fall and will also be a major component of a larger Navegación en el Espacio Aéreo Mexicano (SENEAM) and effort to establish a prototype WAAS test bed capability for several other Mexican officials flew on board the FAA 727 the entire Latin American region. This Latin American test as it conducted multiple precision approaches into the air- bed will facilitate the development and implementation of an port at Mérida, Mexico. The test was conducted from March operational WAAS/LAAS architecture for Latin America that 20 – March 25, 2001. will be interoperable with the systems being fielded in the The NSTB prototype WAAS system is functionally simi U.S. NAS in or- lar to the WAAS and was used in the US for the WAAS der to create a proof-of-concept. The NSTB is now primarily used to col- seamless Western lect data to support WAAS testing in the US and to support Hemisphere test efforts in areas outside the WAAS service volume. In SatNav system. Mexico, US and Mexican officials are cooperating to ex- The success of pand the coverage of the NSTB, as a first step toward inves- the Latin Ameri- tigating the expansion of future WAAS coverage over can effort has al- Mexico. Three NSTB reference stations were installed in ready been rec- Mexico (Mazatlán, Mexico City, and Mérida), and commu- ognized by other nications lines were provided by Mexico to send the data to regions and has the NSTB Master Station at the FAA Technical Center in become a model Atlantic City. The Mexican reference station data was used and template for along with 11 US and Canadian reference stations to gener- Brazilian delegates training on a TRS these regions to ate the WAAS-like correction message, which was sent via begin a similar GNSS implementation project. The Asia Pa- the same communication line back to Mérida, where the cific region is following-up on previous decisions of the Asia corrections were broadcast to the aircraft in Mexico. The Pacific Economic Cooperation (APEC) Transportation Work- total testing will include two more flight tests, as well as a ing Group and the International Civil Aviation Organization year of static data collection and analysis. (ICAO) Regional Office in Bangkok, Thailand to adopt a simi- One of the challenges facing the global use of WAAS sys- lar GNSS work project for the creation of a GNSS augmenta- tems is the difference in ionospheric conditions around the tion test bed capability in South East Asia. Work on this globe, especially at the geomagnetic equator. Even in the project is just getting underway so look for continued updates continental US, ionospheric storms could decrease WAAS in future editions of this newsletter. safety, and this threat has been specifically addressed by As you can see, the momentum of GPS and GPS augmen- WAAS with new monitoring algorithms. The NSTB mas- tation implementation around the globe is reaching an all- ter station software used in this test was provided by Stanford time high. ASD-500 and AND-710/730 are right in the thick University in the 1990’s as part of research conducted on of it and will continue to provide global leadership and assis- the WAAS. In 2001, the NSTB/WAAS Technical Center tance to the international community with the implemen- engineers coded software on a processor connected to the tation of these technologies. As more regions adopt pro- output of the Stanford NSTB master station processor to grams for advanced GPS implementation, we collec- modify the output according to the latest available tively inch closer to the original ICAO vision of a ionosphere-monitoring algorithms. In addition to seamless Global Navigation Satellite System the new software, this test was scheduled to (GNSS). The momentum of this revolutionary coincide with the worst expected ionospheric transition is just beginning to heat up. conditions – near the equinox in a year of solar maximum conditions. 12

The testing in Mexico included over 40 precision approaches into Merida as well as FAA, India Agree to GPS two enroute flights across Mexico in order to collect additional ionospheric data. Data Cooperation analyzed to date has shown that Mexico has similar ionospheric conditions to the conti- reprinted from the FAA Intercom, May 2001 nental US, and a similar response to ionospheric storms. Simultaneous data collected from Antofagasta, Chile (which lies closer to the geomagnetic equator than Mexico), The FAA has an important however, show much more irregular ionospheric conditions. To continue research in new partner in expanding the use of CNS/ATM technology this area, the FAA is providing technical expertise to the Brazilian Testbed effort, con- in Asia. A recently signed tinuing cooperative efforts with the Chilean Testbed efforts, and is planning to collect Memorandum of Cooperation additional flight data in the region affected by the geomagnetic equator near the time of between the FAA and India the next equinox, in October 2001. could lead to the development This test was possible because of the work of both the Mexican officials and engineers, of an interoperable Global and the FAA officials, pilots, mechanics, and engineers – thanks to all! Navigation Satellite System, using GPS and its augmenta- tion systems to significantly en- hance air traffic system safety and efficiency of air carrier operations in that region. An FAA/U.S. Trade Devel- opment Agency-sponsored GPS workshop is scheduled for later this summer in India to provide Indian aviation offi- cials with additional informa- http://gps.faa.gov tion about how to implement GPS in their air traffic control system.

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