Historically, navigation systems have depended on

time. This was clearly demonstrated by the sailing of

Harrisons chronometer on HMS Deptford in 1761,

to prove that the instrument allowed navigators for

the first time to determine longitude accurately and

reliably. Because of this relationship between navigation and time, the time-keeping community has

always had a keen interest in the use of navigation

systems for the distribution of time. Even today, the

heart of the GPS rests on a highly evolved clock technology. Unlike navigators, who need four GPS satellites by which to determine their position, timekeepers, who know their position, need only one satellite

to determine time. Observations of a single satellite also allow timekeepers to remotely synchronize clocks around the world.

 This article summarizes the result of a recent study, which showed that the GPS Wide Area

Augmentation System (WAAS), once fully operational, should provide a very stable, continuously-available timing signal. It should also allow the development of more economical

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.

The WAAS is one of the most recent developments in the evolution of navigation systems.

While it is similar to other differential GPS systems in concept, the WAAS gives the Federal

Aviation Administration (FAA) and air navigation a significantly higher level of performance

than other differential GPS (DGPS) systems. Because of the augmentation methods utilized

by the WAAS, it provides not only improved accuracy, but also increased availability, integrity, and continuity of service. It does this by continually monitoring GPS transmissions from

WAAS Reference Stations (WRSs) and by transmitting an augmented message from several

geostationary communications satellites (GEOs). The WAAS is currently in its early stages of

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

reasonably expect improved levels of precision and accuracy as the system matures.

Time and the WAAS

 Figure 1 schematically depicts the WAAS process, as it will be once fully implemented.

The basic unit is the WAAS Reference Equipment (WRE), consisting of a cesium beam frequency standard, a 12-channel, dual-frequency WAAS-GPS receiver, and a wide- and a narrow-band GPS receiver. Each WRE continuously tracks as many GPS satellites and GEOs as

it is able to acquire.

In this issue:

Using WAAS for precise

timing............................1

WAAS increases aviation

safety benefits of the

Capstone Program in

Alaska...........................3

Independent Review

Board backs WAAS......4

LAAS GIP explained....4

Procedures Development

Initiatives......................5

Salt Lake City prepares

for increased air traffic

during 2002 Winter

Olympic Games............7

Interregional airspace

redesigns offer potential

benefits to users............7

Unique capabilities of

vertical flight aircraft are

aided by development of

new helicopter GPS

approach procedures.....8

Industry Corner: GAME

model benefits from GPSbased instrument

approaches....................9

Worldwide adoption of

Satellite Navigation.....10

US and Mexico cooperate to expand future

WAAS coverage..........11

GPS in India................12

From Time to Time

by W.J. Klepczynski, GPS TAC/WAAS Team (AND-730)

 Ed Powers, United States Naval Observatory

 Rob Douglas, National Research Council of Canada

 Pat Fenton, NOVAtel
 Each WRS contains three identical WREs. This redundancy ensures that each WRS will continue to provide data

to its WMS in the event that one of the WREs fails. Each

WRS, in turn, transmits the data it obtains to two WAAS

Master Stations (WMS), which form the WAAS navigation

message and WAAS Network Time (WNT). The message

contains information on satellite orbits, the current state of

the ionosphere, timing information, and system health. Each

WMS passes the navigation message to each of, initially, two

Geostationary Uplink Stations (GUSs), which upload it to

the two Phase 1 GEOs which then transmit it to the user.

WAAS Master Stations

 Once per second, all WRSs transmit all their data to all

WMSs, which then perform the functions of correction processing, 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 transmissions 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 corrections 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 contribute to the WRE measurements that a WMS corrections

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 controls the synchronization of the WAAS navigation 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 provided by the U.S. Naval Observatory (USNO),

and transmits the offsets as part of the WAAS

navigation message.

Status of WAAS Time-keeping

 Data collection commenced at USNO on October 6, 1999.

Every 15 seconds, GPS and Atlantic Ocean Region-West

(AOR-W) WAAS GEO satellites make pseudorange and carrier-phase measurements. All of the broadcast data from the

satellites are now collected for postprocessing.

Time Transfer Capabilities

 Fig. 2 illustrates the computed difference between USNO

and GPS system time. We included this difference as a common denominator benchmark process. Most GPS timing receivers today use this observable to provide time reference

information. Note that selective availability (SA) caused most

of the 43-nanosecond standard deviation. On May 1, 2000,

the U.S. Department of Defense (DoD) turned off this inten2
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 System (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 signal will be available continuously.

 Such a signal provides some unusual capabilities for the

timekeeping community. It should allow the development of

more economical timing systems utilizing its signals. Cheaper

crystals can now be used in systems that rely on atomic standards as their flywheel while they continuously integrate GPS

time or UTC using only one geostationary satellite. A user

will be able to instantly detect any pathological behavior in a

system providing time by comparing signals with another visible GEO. With GPS, one has to wait to see whether the

transients are due to anomalous clock behavior in a satellite.

The WAAS, on the other hand, provides an immediate redundancy check to anyone who is within the footprint of its

two transmitting geostationary satellites. This can be used as

an extremely robust check for many timed systems.

Based on an article originally published in the May 2001 issue

of GPS World, Eugene Oregon.

 Safety, capacity, and efficiency continue to be a concern for members of the

FAAs Alaska Region where airplane accidents are a daily reality. The avionics

package offered by the Capstone Program

addresses these challenges and offers solutions, and the key to this program is the

partnership formed by the FAA and the

Alaskan aviation industry.

 The Capstone Program, named for its

combination of a range of concepts and

3

New Technology Benefits Region

with High Safety Risks

by Jim Hebert, Capstone Liaison (Contract support for AND-500)

recommendations, recognizes the need to integrate emerging

technologies into the present airspace in order to resolve the

hurdles of the Alaskan environment. The initial Capstone

challenge focuses on aviation safety in the Southwest YukonKuskokwim (Y-K) and Southeast regions of Alaska. These

areas experience a significant number of mid-air collisions,

controlled flight into terrain, and weather related accidents.

The Capstone effort is working to provide ground infrastructure and avionics in order to address these problems as well as

to determine the operational benefits for commercial carrier

aircraft operating in these areas. Capstone has equipped up

to 90% of the aircraft operating in the Y-K and Southeast

regions of Alaska giving the program the ability to measure

the anticipated benefits. While Capstone is initially focusing

on these two geographic areas, the intention is to leave systems in place that provide a benefit and to expand these

ground systems to the rest of Alaska. Capstone technology is

being engineered so that it can be deployed to the rest of the

National Airspace System (NAS) as needed. The following

have been provided in the Y-K area and will migrate to the

Southeast in 2002:

· Data link weather and other flight information into the

cockpit

· A cockpit display that uses a terrain database to reduce

controlled flight into terrain

· Increased number of airports served

by GPS non-precision approaches

· Automated Weather Observing System (AWOS) to provide weather for

the GPS approaches

· Cockpit display of adjacent traffic

· Radar-like service using Automatic

Dependent Surveillance-Broadcast

(ADS-B)
The Wide Area Augmentation System (WAAS) has introduced area navigation (RNAV) routes in a region with no

existing infrastructure, and has increased aviation safety and

airspace capacity while decreasing the cost of the supporting

infrastructure and aircraft avionics equipment and systems.

WAAS, in conjunction with terrain and traffic avoidance data,

offers a practical evaluation that will validate the application

and functional capabilities of new technologies and enhance

the pilots ability to operate safely. As a result, the avionics

and ground infrastructure in the Southeast will provide this

user-identified useable Instrument Flight Rules (IFR) infrastructure. Narrow approaches into airports bordered by

sharply rising terrain will pose less of a threat. Environments

with weather patterns that have restricted or even prevented

flight due to the route structure will also be more accessible.

 On April 10, 2001, the FAA publicly released the report of the WAAS

Independent Review Board (IRB),

which was chartered to review and

report to the FAA Administrator on system engineering efforts aimed at resolving the technical barriers that were preventing delivery of WAAS to the customer. The full Report

and accompanying Executive Summary can be viewed at http:/

/gps.faa.gov/Library/Documents/documents.htm#waas

Background

 The Wide Area Augmentation System was originally scheduled to achieve Initial Operational Capability in September

2000. In January of that year, however, FAA certification

specialists identified a problem with proving that the system

met the stringent integrity requirements specified for the system.

 Integrity is the ability of the system to provide timely warnings to users when it should not be used for navigation. For

WAAS, integrity means there can be a no greater than one in

ten million chance of hazardously misleading information

being transmitted to the user without the system notifying

the user within six seconds of its degraded status.

 To meet the challenge of establishing the parameters of the

integrity issue and developing the solution to the problem, in

February 2000 the FAA formed the WAAS Integrity Performance Panel (WIPP). Shortly thereafter, the FAA also chartered the WAAS IRB to review the WIPPs efforts and offer

additional technical and strategic advice concerning the

WAAS Program. The IRB was formed under the auspices of

the Institute for Defense Analyses (IDA) in Alexandria, VA

to report directly to the Administrator. Its membership is

composed of senior scientists and managers from outside the

FAA.

IRB Report

 The IRB made a number of near, mid and long-term recommendations to improve the WAAS acquisition program.

In brief, the IRB validated the WIPPs approach to defining

the parameters of the integrity problem and its proposed solution to achieve an initial capability of Lateral Navigation/Vertical Navigation (LNAV/VNAV). It also supported the

WIPPs proposed path to achieve the follow-on GNSS Landing System (GLS) capability that will constitute full operational capability for WAAS. The IRB strongly supported the

continuance of the WIPP at least through commissioning of

the system.

 The IRB urged the FAA to make a stronger commitment

to the evolution of WAAS, considering how to exploit the

possible synergies among WAAS, the Local Area Augmentation System (LAAS) and the U.S. Coast Guards Differential

GPS (DGPS) augmentation system.

 The IRB also strongly urged the acquisition of an additional

geostationary satellite as soon as possible to mitigate the single

thread of failure that exists with the current two-satellite

INMARSAT III constellation. The IRB also pressed for the

immediate initiation of acquisition efforts aimed at achieving

the required end-state constellation of four satellites with

autonomous payloads supporting broadcast of three civil signals.

 The IRB has provided the FAA a valuable assessment of

where the FAA is and where it needs to go to make WAAS,

the cornerstone of its future navigation architecture, available to the aviation community as soon as possible. The IRB

will continue to provide analysis and advice at least through

2001.

 In March of this year, the New York Times published an

article discussing FedEx and the airlines expectations for the

ongoing Local Area Augmentation System (LAAS) activities

in Memphis. The article focussed on the FedEx / Memphis

activities but did not really expand on the complexity of the

Government Industry Partnership (GIP) driving the devel4

WAAS in Review: IRB Report

Released

by Hal Bell, WAAS Team Lead (AND-730)

The LAAS Government Industry

Partnership: A Complex Approach

to System Implementation

by Dieter Guenter, GPS-TAC/LAAS Team (AND-710)
opment and implementation of the LAAS. The New York

Times also made little mention of the other two GIP teams

and additional FAA activities, which are equally important

for the LAAS success story. The following article intends to

bring to light some of the other activities included in the LAAS

Government Industry Partnership.

 With the GIP, the FAA is pursuing an innovative approach

to overall LAAS system development, fielding, testing

and evaluation, and operational approval for public use. The GIP approach is a costsharing partnership between the government and industry. FAA (government)

is responsible for the development of the system specification, operational documentation,

technical support, and certification of the system while private companies (industry) provide

the funds to develop a LAAS Category I system.

Honeywell, Raytheon, and most recently, Airsys ATM, presently lead different industry teams, which are made up of airline/aircraft manufacturers, airports, and avionics manufacturers. As part of the FAA GIP program, these teams were

formed to start the development of the LAAS Category I system.

 LAAS has made tremendous progress due to the work of

all the GIP partners. Honeywell prototype ground systems

have been established at Chicago OHare, Midway, and Memphis. Raytheon is converting its SCAT I system into a prototype LAAS in Salt Lake City, and Rockwell Collins is working on the integration of LAAS into the aircraft avionics within

its multi-mode receiver (MMR). These activities and prototype installations provide the FAA and the GIP partners with

valuable insight into the development and implementation

of LAAS systems.

 The FAAs LAAS Product Team (AND-710) is directing

research, validation, and implementation of LAAS. The relatively small LAAS team, under the leadership of Steve Hodges,

is involved in all aspects of the GIP, coordinating implementation activities, leading the LAAS acquisition process and

further development of the LAAS Category II/III systems.

 The development efforts of LAAS are focused on two main

areas: ground equipment and avionics. Honeywell, Raytheon,

the FAA Technical Center, and the University of Oklahoma

have developed prototype ground systems. Installing such

prototype systems, however, is just one part of LAAS development. Stanford University, Ohio University and MITRE

continue to work in different areas of the LAAS ground facility development including Ephemeris, Signal-Quality and

Integrity Monitoring, Very High Frequency (VHF) Data Link

projects and Multipath modeling. These development efforts,

as well as validation of the requirements, are equally crucial

to the progress of the final system.

 On the airborne/avionics side of LAAS development, the

Navy/NAVAIR and the Technical Center both play a significant role. Using LAAS prototype ground systems both are

working towards implementing and validating LAAS airborne

receiver requirements and are teaming up with Rockwell

Collins on the LAAS multi-mode receiver.

 In addition to the technical development and validation of the LAAS ground system and avionics, the

LAAS team is working with the different FAA disciplines on installation and

operational issues for implementing

LAAS into the National Airspace System (NAS). FAAs Airways Facilities

and the Technical Center are working

on LAAS siting criteria (how and where to install

LAAS), which constitutes a major undertaking due

to the diversity of the system and the individual requirements

of each airport. Maintenance, training, and logistics issues

have to be identified and worked on as well.

 In order to utilize the LAAS signal, specific approach and

departure criteria and procedures need to be established to

fly LAAS approaches. Flight Standards develops and validates these criteria through flight tests in Oklahoma City with

the University of Oklahoma and in Atlantic City with the

Technical Center aircraft. Aviation System Standards (AVN)

develops LAAS approach procedures and establishes flight

inspection criteria for LAAS flight inspections. Other important factors include the coordination and training of Air Traffic

personnel and the development of LAAS NOTAM capabilities and specific LAAS air traffic monitor capabilities.

 All these activities have to be coordinated for the GIP teams

and their systems as well as for the FAA systems. Coordinated activities between the FAA Headquarters, the FAA

Regional Offices, Industry, and users are essential for the successful implementation of LAAS into the National Airspace

System.

 The National Airspace System (NAS) is in a period of unprecedented growth and change. Our national airspace comprises more than 29 million square miles and handles more

than 55,000 flights per day that use 12,300 instrument approach procedures. Since 1994, the number of instrument

procedures has grown by approximately 50%. Technology improvements, funding levels and other factors will impact the

course of the modernization strategy. In addition, global

5

GNSS Procedures Development

Initiatives

by Kelly McKee, GPS TAC/NAS Implementation Team (AND-710)
interoperability of technology and harmonization of procedures are essential for continuity of operations and avionics

investments. Aviation System Standards (AVN) has the responsibility for designing instrument approach and departure

procedures for the 21st Century NAS in accordance with Federal Aviation Regulations (FAR 97)

safety standards. A web site developed to assist people in understanding the procedure development process and providing a method for requesting new instrument procedures

can be found at http://

www.mmac.jccbi.gov/avn/iap/

iap_flow.html

 As an outgrowth of the general

context described above, the Federal

Aviation Administration (FAA) participates with the aviation industry

on the Commercial Aviation Safety

Team (CAST) to reduce accidents,

incidents, and delays. One of the

efforts of CAST was to form a subgroup to work on precision-like approach implementation. This subgroup has generated a plan with a

series of actions for different FAA

organizations, including AVN.

AVNs strategy is effectively integrated with the (FAA) NAS Architecture and National Airspace Redesign initiative. The AVN strategy also addresses industries request to fully utilize ground,

aircraft, and space- based navigation systems for improved

safety, capacity, and operational flexibility. The AVN organization has produced a plan that addresses the CASTs direction toward a 21st Century precision landing system. The AVN

plan provides a broad framework of flight procedure production options that are linked to specific funding requirements

and provides the opportunity for the FAA to effectively and

efficiently deliver the improved safety benefits desired by the

CAST. The CAST AVN Implementation Plan can be viewed

or downloaded at http://www.mmac.jccbi.gov/avn/home/documents/cast.doc.

 The CAST Plan makes several references to area navigation (RNAV), lateral navigation (LNAV), and vertical navigation (VNAV). RNAV is a method of navigation that permits aircraft operation on any desired course within the limits

of a self-contained system capability. Many systems also provide vertical guidance. The Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS)

will expand the availability of LNAV/VNAV instrument approach opportunities to lower weather minimums. To foster

and support full and optimum integration of RNAV into the

NAS, the FAA has developed a new charting format for

RNAV Standard Instrument Approach Procedures (SIAPS).

This new format maximizes the information available to the

pilot for the safe and efficient conduct of the instrument procedure.

 Vertical guidance is provided as

a linear deviation from the desired

track defined by a line joining two

waypoints with specified altitudes,

or as a vertical angle from a specified waypoint. Computed positive

vertical guidance is based on barometric, satellite elevation, or other

approved systems. The desired

vertical path may be pilot selectable or may be determined by the

VNAV computer with computations based on the altitudes associated with successive waypoints.

These instrument approach procedures provide separate minima for

LNAV and LNAV/VNAV. The

LNAV/VNAV procedure and the

LNAV procedure are designed

with different obstruction criteria.

The flight inspection of RNAV

procedures evaluates the soundness of the procedures in accordance with FAA Order 8200.1A,

Section 214, and identifies any deficiencies in the procedure.

Approach safety and flyability are evaluated as a non-precision approach with and without vertical guidance. The final

segment of the flight inspection may require repeated flights

for obstacle verification/evaluation.

 The AVN production plan schedules and prioritizes procedure development through 2007. The production schedule specifies a what by when schedule that enables the aviation industry to plan for the introduction of new instrument

approach procedures. In addition, the AVN production schedule is prioritized based upon risk assessment and contains a

matrix that displays the priority as directed by the CAST, i.e.

first priority Part 139 runways, second priority runways 5,000

feet or longer, and third priority paved public use runways less

than 5,000 feet. The plan takes into consideration the available safety risk factors to mitigate accident rates at airports by

using National Transportation Safety Board (NTSB) accident

data. This production plan also supports Safer Skies objectives.

 The first two fiscal years (2001  2002) of the production

6
plan contain specific information about the type of procedure

that will be published at an identified airport and runway end

during each quarter of the year. Beginning in the third year

(2003), the schedule identifies the airport and runway end

that will be published during the year without a quarterly commitment. The production schedule for the remaining years

(2004-2007) contains information on the airport that will be

addressed during that fiscal year. The schedule will be a rolling schedule whereby specific information on airport runway ends and quarterly publication plans will be available for

a continuous two-year period. It is anticipated that the production schedule will be revised every six months, facilitating

industry input and assuring that the agency is as responsive as

it can be with the resources that are available.

 AVN has developed a comprehensive website that allows

the flying community to access information about the instrument flight procedure production schedule. The website contains general information about the process of flight procedure production, the current FAA production schedule based

upon agency resource commitments, and options for private

investment in instrument flight procedure production. Available on the web-site, on a quarterly basis, will be a listing of

vertical descent angle (VDA) additions as they are completed

and also the accomplishment of renaming the GPS procedures. Finally, the site offers a listing of contacts. You can

access the site at: http://www.mmac.jccbi.gov/avn/iap/

 The AVN production schedule considers the visual glideslope indicator (VGSI) installation plans of the Airway Facilities organization. Updated information on the adjustment/

alignment of the VGSI angles will also be available on the

production schedule web-site.

 AVN 100 faces many challenges with the resources available. Although the CAST plan is prioritized based on safety

benefits, procedure development continues at all airports in

the NAS. As of July 2000, AVN has added Vertical Descent

Angles (VDAs) to non-precision approaches at 60% of Part

139 airports, 40% of non-Part 139 airport with runways 5000

ft or greater, and less then 10% at all other runways less than

5000 ft. As the number of procedures increase, so does the

amount of resources allocated to the maintenance of these

procedures.

 AVN, in conjunction with other organizations, continues

daily support of the CAST initiatives. The initial group of

airports selected for airport surveys, procedure development,

and implementation are just the beginning, as time goes on,

numerous new airports will be added to the list. Procedure

development will continue and eventually, almost all airports

will have GPS approaches available. Support of this longterm program is imperative as the program continues to grow

and expand. We invite you to visit our websites and let us

know what you think.

 The complex flight environment of the Salt Lake City Airport terminal area is overly congested and can pose a significant

challenge to VFR pilots. One of

the busiest air traffic environments in the nation, Salt Lake City Airport is situated in a

valley with high mountainous terrain to the east and west. In

preparation of the 2002 Winter Olympic Games next February, the Air Traffic Control facility is also preparing for a substantial increase of both Instrument Flight Rules (IFR) and

VFR air traffic in the region.

 Two Air Traffic divisions have recently taken a significant

step in providing for safer flight in the Salt Lake City area by

instituting the use of VFR Waypoints. VFR Waypoints are

predetermined geographical coordinates, determined by the

Global Positioning System (GPS) and designed to enhance

pilot situational awareness, enhance safety, reduce airspace

deviations, and increase Air Traffic Control efficiency.

 The VFR Waypoint program was developed to aid VFR

pilots in navigating into, out of, through, or around terminal

airspace areas, special use airspace (SUA), or other areas where

VFR navigational assistance is deemed prudent. The

Waypoints are graphically displayed on the April 19,2001 edition of the Salt Lake City VFR Terminal Area Chart (TAC)

and are either associated with a VFR Reporting Point, or as a

stand-alone Waypoint.

 The charting of the VFR Waypoints is a big step in improving VFR flight and airspace efficiency. The FAA has also

published VFR Waypoints on VFR TACs at Kansas City, Missouri on November 20, 2000, and Houston, Texas, on March

22, 2001. The benefits to Kansas City are similar to those of

Salt Lake City and enable VFR pilots to safely navigate around

Class B airspace. The Houston TAC application provides

GPS Waypoints to assist pilots in navigating through the Class

B airspace by ensuring the correct identification of the flight

corridor. The publication of these Waypoints is part of the

FAAs commitment to being a good service provider to the

flying public and supporting safe VFR flying.

7

2002 Winter Games: Salt Lake

City Uses GPS to Prepare Airspace for Increased Traffic

by Brian Durham (ANM -520) and Paul Ewing (ATP-104) for NAS

Implementation Team (AND-710)
 The FAA has aggressively pursued development of new

instrument flight rules (IFR) applications of the Global Positioning System (GPS) for civil helicopter operations, which

include Emergency Medical Service (EMS) operations.

 Facilitating EMS operations to hospital heliports has offered the FAA a unique set of challenges when compared to

standard IFR operations into airports. Hospitals are necessarily located within cities,

which are, by nature, obstacle rich environments. The necessary land to convert a typical VFR heliport into an IFR facility rarely

exists, and obstacles would penetrate into the

shallower IFR heliport airspace surfaces.

Relocating the hospital heliport is rarely a

solution as its mission is to deliver patients

to the trauma services of an emergency room as quickly as

possible.

 FAA standards and orders provide for helicopter point-in-space GPS instrument approach procedures to non-IFR heliports. The

standards facilitate IFR operations into VFR

heliports with special visual-segment criteria

for the transition from an IFR approach to a

VFR ground infrastructure. While these FAA

efforts permit greater capability for EMS helicopters to complete missions, safety of flight

for EMS helicopters is also enhanced by sole

reliance on VFR during periods of reduced visibility. The

Flight Standards Service is presently in the

process of developing new heliport departure

criteria for departing VFR heliports under

IFR conditions.

 In 1998, as part of the solution necessary

for meeting the helicopter industrys unique

needs, Flight Standards Service Flight Technologies and Procedures Division (AFS-400)

and Aviation System Standards (AVN-1)

entered into agreement to participate in a

cooperative effort with Satellite Technology Implementation

L.L.C (STI) for non-federally developed helicopter GPS approach procedures. Interim Policy, Letters of Agreement, and

Letters of Authorization, allow for STI developed approach

procedures to be submitted to AVN for Quality Control (QC)

and flight inspection, and authorize STI to perform Flight

8

GPS Supports Unique Helicopter

Capabilities for Emergency Medical Flights

by Mike Webb, ARINC/NAS Implementation Team (AND-710)

Standards and Flight Procedures Office (FPO) coordination in the Regions. Under this program there have been

107 industry funded Special Helicopter GPS approaches developed to hospitals and 25 more are under development.

Applications of these procedures at private locations

throughout the country have given populations living in remote areas access to trauma services during the crucial

golden hour.

 Additionally, in preparation of the availability of the Wide

Area Augmentation System (WAAS) to augment GPS, the

FAAs William J. Hughes Technical Center has collected data

for WAAS helicopter precision instrument approaches to

heliports. These data are currently being analyzed for incorporation into FAA procedures criteria.

These criteria should be in place when

WAAS is commissioned for IFR use. The

Technical Center is also collecting data on

GPS lateral navigation and barometric altimeter-aided vertical navigation (LNAV/

VNAV) approach capability to heliports.

This will permit the use of existing navigation equipment and aircraft avionics to fly

a vertical path to a decision altitude (DA), reducing the

risk of controlled flight into terrain (CFIT).

 The importance of this work cannot be

overestimated. The FAA and industry

have long touted the unique capabilities

of the helicopter. Operations to airport

runways seldom call upon these capabilities. Operations to heliports, by definition,

demand them. Through this research, the

FAA is pushing the envelope to quantify

these unique capabilities.

The FAA regional Flight Standards and

Air Traffic staffs have been aggressively working to assist

helicopter operators in creating private, low

altitude GPS enroute infrastructures, a recommendation supported by the FAA Safer

Skies Program. In California, the Western

Pacific Region recently approved 8 STI developed approaches to hospital helipads

and the first helicopter GPS enroute system. This system will greatly increase the

use of IFR for EMS operations in northern

California. It will also effectively reduce

minimum enroute altitudes for REACH Air Ambulance

helicopter operations by 50% thereby improving their availability to provide healthcare for local communities in a four

county area in Northern California. The RNAV routes are

the end result of many months of collaboration and coordi-
nation between the various entities in the FAA and STI.

Three different air traffic control facilities are involved in providing services: Oakland ARTCC, Sacramento Terminal Radar Approach Control (TRACON), and Bay TRACON. STI

developed the routes by using interim criteria provided by

the Flight Procedures Standards Branch (AFS-420) and policy

from AFS-400. Quality control reviews and flight inspections were completed by AVN prior to final approval by the

FAA. The Western-Pacific Regional Headquarters (AWP),

including the AWP-Airspace Branch and Operations Branch,

the Los Angeles FPO and the AWP AWO to mention just a

few involved in making these new GPS routes a reality. STI is

currently involved with Erlanger Medical Center, of Chattanooga, Tennessee, and has developed six special GPS-based

RNAV routes servicing 17 special helicopter GPS approaches

located in Tennessee, Georgia, and North Carolina.

 The helicopter has emerged as a solution for point-to-point

air transportation, and EMS helicopters are a proven means

of transporting trauma patients between medical facilities.

Historically, the EMS was rooted in air transportation designed

to service airports and lacked the capability for inter-heliport

and airport-heliport all-weather air transportation. With the

implementation of GPS, an integrated EMS system offers reliable and cost-effective solutions for providing accessible care

for populations over a large area. The key to this network lies

in establishing affordable, safe instrument approaches using

the availability of GPS for low altitude enroute navigation

and landing guidance.

 Though small in number compared to other segments of

the aviation industry, EMS operators have developed in response to improving emergency healthcare for a larger segment of society, while keeping medical costs down. GPS is an

integral component in the evolution of this segment of the

national healthcare system.

 One of the principal objectives of WAAS is to improve

safety by providing instrument approaches with vertical guidance to almost all instrument capable runways in the U.S.

Another important consideration, especially for users, is the

airport access benefits that will accrue from WAAS approaches. Airport access can be measured by the height

above touchdown (HAT) and the visibility minimum for an

instrument approach to a runway end.

 It has been difficult, however, to estimate what the airport access benefits would be for the thousands of airports

and runways in the U.S. The FAA (AVN-100 in Oklahoma

City) currently develops instrument approaches, but the

process can take weeks for one runway end. Evaluating thousands of runway ends has just not been practical.

 MITRE has developed a computer-based tool that estimates the HAT and visibility minima for GPS instrument

approaches using electronic databases of terrain and obstacles. The model is called the GPS Approach Minima

Estimator (GAME). GAME uses criteria from the FAA

Terminal Instrument Procedures (TERPS) developed for

GPS approaches, but can be modified to use different criteria. The design of the model allows the evaluation of a large

number of runways, with subsequent analysis of the benefits

of a particular approach procedure.

 GAME is not intended to replace the procedure developers at AVN. To reduce development, processing, and

analysis time, GAME only evaluates a 5 nautical mile straight

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 approach path. Also, GAME

does not use all the data, such

as maps, that might be available to a human developer.

 However, initial validation

results comparing the HAT

from GAME to an existing

approach are promising. The

difference between GAME

GPS-Based Instrument Approaches Benefit Tool for

Estimating Airport Access

by Vince Massimini, MITRE Corporation

9

Industry Corner
estimates of the HAT for a GLS approach versus an existing ILS approach to the same

runway end have a median of zero and a 75th percentile of only 25 ft. Differences between a GAME estimate of HAT for an LNAV/VNAV approach and the HAT determined by AVN have a median of 12 ft, and a 75th percentile of 5 ft. Similarly, differences

between GAME and AVN HATs for LNAV have a median of 30 ft and a 75th percentile

of 2 ft.

 At present, GAME does not include considerations for airport infrastructure, which

can reduce visibility minima (e.g., with approach lights), increase visibility minima (e.g.,

runway surface composition), or even preclude a category of approach (e.g., runway length).

These capabilities, in addition to missed approach considerations, are presently being

incorporated into GAME.

 Preliminary results for over 5000 runway ends at over 1500 airports are already showing the relative airport access benefits of LNAV/VNAV and GLS approaches. When the

airport infrastructure and missed approach considerations are included, GAME will be

capable of estimating benefits for existing and future airport configurations.

 Another important use of GAME will be to investigate the effects of improved WAAS

performance on airport access. For example, if the WAAS Vertical Alert Limit (VAL)

can be reduced from 50 to 20 m, and if criteria are developed for approaches using the

new VAL, then GAME can estimate the airport access benefits of the reduced VAL.

 Contact Les Crane (703 883 7243; lescrane@mitre.org) or Vince Massimini (703 883

5893; svm@mitre.org) for more information on GAME.

 Interwoven within the FAAs mission is a strong emphasis and commitment to global

leadership. The FAA Research and Acquisitions Office (ARA) is a critical contributor

to the execution and success of this global leadership as it facilitates worldwide system

compatibility and interoperability of global implementation initiatives with those technologies being fielded for operational use in the U.S. National Airspace Systems (NAS).

 One of the technologies that has provided the most impact to international aviation is

the Global Positioning System (GPS). The number of countries adopting GPS at least as

a supplemental navigation aid has continued to grow at a healthy rate as the safety and

efficiency benefits of GPS become clearer to both service providers and the users.

 For instance, countries that currently have little or no ground-based navigation infrastructure are realizing the potential safety, efficiency, and economic benefits of using GPS

to provide an immediate navigation capability. This type of space-based service also is

beneficial to countries and regions that currently have to take extreme measures to safeguard ground-based navigation aids from hostile forces, tampering, or vandalism.

 The benefits from basic GPS are clearer than ever. However, many countries and

regions are already opting to take steps to progress beyond what the basic GPS constellation can provide. The FAA, represented by the International Research and Acquisition

Office (ASD-500) and the Satellite Navigation Product Teams (AND-710/730), is actively involved in providing support to these regional satellite navigation implementation efforts and initiatives that are gaining momentum around the globe.

 In North America, we have been working with our counterparts in Canada and Mexico

for several years on cooperation towards creating a North American satellite navigation

system based on WAAS and LAAS technologies. In March of this year, we brought three

Mexico National Satellite Test Bed (NSTB) reference stations on-line, and thus created

a true North American WAAS test bed capability (Canada already has three NSTB

reference stations). This newly formed architecture provides opportunities to conduct

10

Efficiencies for the

Future: Airport Redesign

Raises Airport Standards

by Bob Brekke, GPS TAC/NAS

Implementation Team (AND-710)

 With the National Airspace

Redesign, airspace changes are

underway across the United

States. Both the Western Pacific Region and the Southwest

Region are jointly undertaking

one of the newest airspace redesign projects, known as the

Northwest 2000 and Las Vegas

Four Cornerpost Plan, which

seeks to achieve the most efficient airspace possible for both

system-users and providers.

 This comprehensive airspace redesign plan, scheduled

for implementation in the fall

of 2001, integrates changes in

the airspace at the Albuquerque and Los Angeles Centers.

It also includes the Phoenix

and Las Vegas Terminal Radar

Approach Control

(TRACON) areas that serve

the Phoenix Sky Harbor International and Las Vegas

McCarran International Airports. Area navigation

(RNAV) arrival and departure

routings have been designed to

reduce delays, improve efficiency, and reduce complexity

while maintaining the highest

standards of safety and environmental sensitivity.

 Airspace studies have

shown that RNAV procedures

have the potential for a significant cost savings for systems

users. On a recent RNAV arrival-route test-flight into the

Phoenix Sky Harbor International Airport the aircraft

saved approximately four minutes of flight time and 300

pounds of fuel. Additional

benefits include increases in

flexibility, predictability, and

improved access to the National Airspace System.

Worldwide Adoption of Satellite Navigation

by David Burkholder, Office of International Research and Acquisition (ASD-500)
more advanced regional analyses on how a North American

WAAS can come to fruition.

 Latin America is taking monumental steps towards developing its own regional Global Navigation Satellite System

(GNSS) architecture. Brazil has initiated an extensive joint

project with the FAA to establish a prototype WAAS test bed

capability. This Brazilian Test Bed (BTB) should be operational this Fall and will also be a major component of a larger

effort to establish a prototype WAAS test bed capability for

the entire Latin American region. This Latin American test

bed will facilitate the development and implementation of an

operational WAAS/LAAS architecture for Latin America that

will be interoperable with the systems being fielded in the

U.S. NAS in order to create a

seamless Western

Hemisphere

SatNav system.

 The success of

the Latin American effort has already been recognized by other

regions and has

become a model

and template for

these regions to

begin a similar GNSS implementation project. The Asia Pacific region is following-up on previous decisions of the Asia

Pacific Economic Cooperation (APEC) Transportation Working Group and the International Civil Aviation Organization

(ICAO) Regional Office in Bangkok, Thailand to adopt a similar GNSS work project for the creation of a GNSS augmentation test bed capability in South East Asia. Work on this

project is just getting underway so look for continued updates

in future editions of this newsletter.

 As you can see, the momentum of GPS and GPS augmentation implementation around the globe is reaching an alltime high. ASD-500 and AND-710/730 are right in the thick

of it and will continue to provide global leadership and assistance to the international community with the implementation of these technologies. As more regions adopt programs for advanced GPS implementation, we collectively inch closer to the original ICAO vision of a

seamless Global Navigation Satellite System

(GNSS). The momentum of this revolutionary

transition is just beginning to heat up.

WAAS Arrives in Mexico

by Tom Dehel, NSTB Lead Engineer (ACT-360)

 Mexican civil aviation officials, engineers, and pilots of

the FAA completed a flight test of Mexicos recently installed

National Satellite Testbed (NSTB) equipment. Sr. Oscar

Amable, Dirección General Adjunto Servicios a la

Navegación en el Espacio Aéreo Mexicano (SENEAM) and

several other Mexican officials flew on board the FAA 727

as it conducted multiple precision approaches into the airport at Mérida, Mexico. The test was conducted from March

20  March 25, 2001.

 The NSTB prototype WAAS system is functionally simi

lar to the WAAS and was used in the US for the WAAS

proof-of-concept. The NSTB is now primarily used to collect data to support WAAS testing in the US and to support

test efforts in areas outside the WAAS service volume. In

Mexico, US and Mexican officials are cooperating to expand the coverage of the NSTB, as a first step toward investigating the expansion of future WAAS coverage over

Mexico. Three NSTB reference stations were installed in

Mexico (Mazatlán, Mexico City, and Mérida), and communications lines were provided by Mexico to send the data to

the NSTB Master Station at the FAA Technical Center in

Atlantic City. The Mexican reference station data was used

along with 11 US and Canadian reference stations to generate the WAAS-like correction message, which was sent via

the same communication line back to Mérida, where the

corrections were broadcast to the aircraft in Mexico. The

total testing will include two more flight tests, as well as a

year of static data collection and analysis.

 One of the challenges facing the global use of WAAS systems is the difference in ionospheric conditions around the

globe, especially at the geomagnetic equator. Even in the

continental US, ionospheric storms could decrease WAAS

safety, and this threat has been specifically addressed by

WAAS with new monitoring algorithms. The NSTB master station software used in this test was provided by Stanford

University in the 1990s as part of research conducted on

the WAAS. In 2001, the NSTB/WAAS Technical Center

engineers coded software on a processor connected to the

output of the Stanford NSTB master station processor to

modify the output according to the latest available

ionosphere-monitoring algorithms. In addition to

the new software, this test was scheduled to

coincide with the worst expected ionospheric

conditions  near the equinox in a year of solar

maximum conditions.

11

Brazilian delegates training on a TRS
http://gps.faa.gov

12

 The testing in Mexico included over 40 precision approaches into Merida as well as

two enroute flights across Mexico in order to collect additional ionospheric data. Data

analyzed to date has shown that Mexico has similar ionospheric conditions to the continental US, and a similar response to ionospheric storms. Simultaneous data collected

from Antofagasta, Chile (which lies closer to the geomagnetic equator than Mexico),

however, show much more irregular ionospheric conditions. To continue research in

this area, the FAA is providing technical expertise to the Brazilian Testbed effort, continuing cooperative efforts with the Chilean Testbed efforts, and is planning to collect

additional flight data in the region affected by the geomagnetic equator near the time of

the next equinox, in October 2001.

 This test was possible because of the work of both the Mexican officials and engineers,

and the FAA officials, pilots, mechanics, and engineers  thanks to all!

We want your feedback. We encourage your questions, suggestions, and recommendations for

improvement. Please e-mail our editor at Ashley.ctr.brott@faa.gov.

Federal Aviation Administration

800 Independence Avenue, SW

Washington, DC 20591

 The FAA has an important

new partner in expanding the

use of CNS/ATM technology

in Asia. A recently signed

Memorandum of Cooperation

between the FAA and India

could lead to the development

of an interoperable Global

Navigation Satellite System,

using GPS and its augmentation systems to significantly enhance air traffic system safety

and efficiency of air carrier

operations in that region.

 An FAA/U.S. Trade Development Agency-sponsored

GPS workshop is scheduled for

later this summer in India to

provide Indian aviation officials with additional information about how to implement

GPS in their air traffic control

system.

FAA, India Agree to GPS

Cooperation

reprinted from the FAA Intercom,

May 2001