In this issue:

LAAS Contract Award and

Beyond...............................1

WAAS International

Expansion..........................2

LAAS - The Next

Step....................................2

FAA Alaska Capstone

Program..............................3

WAAS Helping to Solve

Worldwide Agriculture

Problems.............................6

LAAS Operational Applications Implementation On

Track..................................7

Geostationary Communications and Control Segment

(GCCS).............................8

WAAS Receivers...............8

LAAS Contract Award and Beyond

by Hazel Russell, GPS TAC/AND-710

The Federal Aviation Administration (FAA) moves forward

with a satellite landing system

to improve aircraft safety during airport approaches and

landings. On April 30, 2003,

the FAA awarded the Local

Area Augmentation System

(LAAS) Category I contract to

Honeywell International, Inc.

of Minneapolis, MN. LAAS

is a satellite navigation landing

system that enables pilots to guide planes safely into busy airports in bad weather. LAAS will

significantly enhance the safety and efficiency of air travel by increasing the accuracy, availability, continuity and integrity of the information received from the Global Positioning System

(GPS).

The contract, originally scheduled for an award last September, was restructured to minimize

the FAA’s financial exposure and reduce technical risks by separating the design and development phases. The current contract has three phases. Phase I, valued at $16.7 million, provides

for the software and hardware design. Phase II and III, with values totaling $340 million, are

contract options that cover the development and production of the system. If the Phase II

option of the contract is exercised, the operational Low Rate Initial Production (LRIP) LAAS

will be installed at airports in Juneau, Phoenix, Chicago, Memphis, Houston and Seattle. The

first system is scheduled to be operational by late 2006.

Following the contract award, the LAAS team participated in the Post Award Conference that

was held at Honeywell’s facility in Minnesota on May 14-16, 2003. The Contractor presented

its overall approach in meeting the Government’s requirements and both sides had an opportunity to talk. The Conference was a success and both teams are currently looking forward to

working together and providing LAAS to the National Airspace System (NAS). LAAS is expected to provide a significant improvement in aircraft and airport operations. LAAS Category

I precision landing provides a level of service in poor weather conditions down to a ceiling of

200 ft. and visibility of one-half mile. LAAS can be installed at some airports where conventional landing systems can’t be used because of space or radio frequency spectrum constraints.
2

A single LAAS will provide precision landing service for most

runways at an airport and will transmit approaches to each

equipped aircraft that would avoid obstacles, restricted airspace,

noise sensitive areas, or congested airspace.

WAAS International

Expansion

Ed Sigler, GPS TAC/AND-730

The FAA’s Wide Area Augmentation System (WAAS), once

commissioned into the National Airspace System this year,

is designed to provide position correction and integrity information to aviation and non-aviation users. The WAAS

will provide service across the United States using a series of

reference station (WRS) sites. WAAS interest is generating

from outside the U.S. due to the success of the WAAS program, coupled with the International Civil Aviation Organization (ICAO)’s desire to implement Satellite Based Augmentation Systems (SBAS) across the world.

The FAA will authorize the use of WAAS only within the

National Airspace System (NAS). However, the WAAS is

capable of providing service sufficient for LNAV/VNAV and

LPV approaches across large portions of Canada and Mexico

with the addition of minimal reference stations in those countries. Recently, the FAA began dialogue with officials from

Navigation Canada and SENEAM of Mexico to locate additional WRS sites in these countries.

WAAS Program Manager Dan Hanlon, WAAS Technical

Manager Leo Eldredge, and WAAS System Engineer Jeff

Auerbach, met with Canadian Officials in April 2003. The

FAA and Canadian officials drafted an agreement calling for

the placement of up to four WRS sites within Canada, which

would expand WAAS service across most of Canada. By

adding WRS sites in Canada, the FAA also improves WAAS

coverage and service levels across the northern U.S., particularly in New England.

Dan Hanlon, and technical and international representatives

from FAA Amy Johns, Dave Burkholder and Carey Fagan,

met with Mexican officials from SENEAM in Mexico City

on April 3, 2003. During these discussions, the FAA and

SENEAM arrived at a tentative relationship for the placement of five WRS sites within Mexico, expanding WAAS

coverage across nearly all of Mexico. Doing so would improve the FAA’s WAAS coverage and service levels within

the U.S. along the southwestern border. WAAS service extension to Mexico and Canada is expected to be complete by

2005.

FAA representatives Dan Salvano and Dan Hanlon, met with

Brazilian officials in April 2003. As most of Brazil and South

America receive the WAAS signals via Geostationary satellites, the information contained in these messages does not

provide for position corrections in these locations. Although

it is possible to modify the existing WAAS system to provide

correction information for South America, the complexity

and cost are prohibitive. With the assistance of the FAA, the

Brazilian government intends to install reference stations and

processing centers, based on WAAS technology, to provide

SBAS service across Brazil and other South American countries. The WAAS-based South American SBAS system is expected to be operational within the next few years.

LAAS -The Next Step

by Cedric D. Lewis, GPS TAC/AND-710

The FAA awarded a contract for the Category I Local Area

Augmentation System (LAAS) to Honeywell International

Inc. of Minneapolis, MN on April 30, 2003. The contract

provides for 10 Limited Rate Initial Production (LRIP) systems beginning in 2006. Four of the systems will be used for

test and evaluation, and training. The remaining six will be
3

installed at major commercial airports, each with a single LAAS

providing approach guidance for multiple runway ends. Aircarriers will use the six systems to assess operational benefits

while in daily revenue service.

The FAA plans to spend hundreds of millions of dollars to

replace the aging National Airspace System (NAS) infrastructure but it will be all for naught if the air-carriers do not utilize

the system. At the same time, the operators want to make

sure that there is an economic pay off for them before they

commit to equipping their aircraft. The air-carriers need to

establish and validate a business case by comparing the cost of

the aircraft receiver equipage and training with the economic

benefits of increased efficiency and fuel savings.

The FAA is working with “IBM Global Services” (formerly Price

Waterhouse Cooper) on a “LAAS Benefit Assessment”. The

IBM assessment will include maximum sponsor and stakeholder involvement. The assessment is in collaboration with

the Investment Analysis and Operational Research branch

(ASD-400) and the Regulation and Certification Group (AVR).

The LAAS benefit assessment results combined with the operational results, will assist the FAA in making a decision to

move forward with acquiring additional LAAS systems.

The activities associated with the development of Catagory I

LAAS are viewed as a “stepping-stone” to Category III. This is

especially true for integrity validation. Experience gained from

WAAS shows that the most challenging requirement for GPS

augmentation is integrity. Integrity is the assurance that there

are only rare occurrences when aircraft receive any hazardously

misleading information (HMI). It is specified as a probability

of 2x10-7 and 10-9 per approach for Category I and Category

III respectively. The other navigation parameters, availability,

continuity, and accuracy, are equally as important but deemed

easier to achieve. The FAA is continuing with Research and

Development (R&D) activities on Category III LAAS to define high-level system performance requirements and to mitigate critical technical risk areas. Standards are being developed through the Radio Technical Commission for Aeronautics (RTCA) and the International Civil Aviation Organization (ICAO) processes. Based on results of the Category II/III

R&D efforts, and the LAAS Benefit assessment, the FAA will

make a decision in 2005 on the feasibility of pursuing a Category 3, full-scale development and production contract.

In Summary, GPS is a quantum leap in aviation technology,

which is being exploited to improve safety and efficiency. The

business cases for both the LAAS users and the FAA are being structured. Category I LAAS is now under contract and

will soon be a reality. Research and development on Category II/III is moving the technology ahead as the FAA continues to refine and validate the requirements. The full economic benefits for the FAA will come when the FAA eliminates some of the ground-based navigation aids (navaids).

For the foreseeable future, however, a significant number of

navaids will be retained to provide a robust and redundant

navigational capability.

FAA Alaska Capstone

Program

by Don Streeter, FAA AFS-400

The Alaskan Region’s Capstone Program is an accelerated

effort to improve aviation safety and efficiency through installation of government-furnished Global Positioning System (GPS)-based avionics and data link communications

suites in commercial aircraft. Compatible ground systems,

equipment, and services will also be provided.

At the recent Joint Aviation Authority (JAA)/FAA Annual

Conference’s Communication Navigation Surveillance

(CNS)/ Air Traffic Management (ATM) Workshop, the

Capstone project was used as an example of the real-time
4

implementation of new technologies in CNS/ATM; and the

demonstration of benefits achievable through its implementation. The JAA noted in the out briefing, that while work

traditionally focused on CNS, today’s economic environment

requires evaluation of the ATM element and how CNS technologies benefit ATM.

The Alaska Capstone Program’s primary purpose is to decrease the number of aircraft accidents in Alaska. Data from

a current Capstone Safety Study indicates that the Capstone

Program is reducing accidents and fatalities in Alaska while

providing an implementation path for advanced CNS/ATM

capabilities in the National Airspace System. The advanced

capabilities will move us closer to “Free Flight” and resulting

safety, efficiency, and capacity benefits.

Some of the successes from the Capstone program include:

Phase I of the Capstone Program resulted in the installation

of IFR certified GPS navigation systems, multi-function displays that provide navigation, traffic, terrain, and weather

information, and data link communications capabilities. The

capabilities resulted in the first ever “radar-like” air traffic

services using automatic dependent surveillance-broadcast

[ADS-B] in Alaskan airspace on January 1, 2001.

• On April 4, 2000, Capstone-equipped aircraft were authorized to use Automatic Dependent Surveillance Broadcast (ADS-B) for "enhanced see and avoid" using a cockpit display of

traffic information.

• On January 1, 2001, the Capstone Program

efforts resulted in the Anchorage Center providing "radar-like" services for surveillance of ADS-B

equipped aircraft in non-radar airspace in Alaska.

• On March 13, 2003, FAA Administrator

Marion Blakey approved special Federal Aviation

Regulation (SFAR) No. 97. This special "Alaska"

rule authorizes properly trained pilots using Technical Standard Order C145a/C146a GPS and

Wide Area Augmentation System (WAAS) navigation systems to fly on air traffic routes at special (lower than usual) GPS Area Navigation

(RNAV) altitudes using certified and approved

GPS/WAAS avionics for navigation. Initial application of SFAR No. 97 in Southeast Alaska

has already created 41,000 feet of usable airspace

spread over 1,521 nautical miles of existing routes.

• On March 26, 2003, the FAA established guidance and requirements for the operational approval and use of GPS/WAAS RNAV systems as

the only means of navigation in Alaska airspace.

• On March 26, 2003, the Anchorage FAA Aircraft Certification Office issued a Supplemental

Type Certificate (STC) to Chelton Flight Systems

Inc., certifying the Chelton Flight Systems

FlightLogic electronic flight information systems

(EFIS) equipment to TSO C146a Class Gamma

1. This system complies with FAA Advisory Circular 20-138a for navigation using GPS and

WAAS for en route, terminal area, and non-precision approach operations (including "GPS" or

"GPS and RNAV" approaches). The installed system includes: an Integrated Display Unit that can

be configured as a Primary Flight Display or a

Multi-Function Display, up to two Air Data Computers, up to two GPS receivers, up to two Attitude and Heading Reference System units, and

an Analog Interface Unit with reversionary switching as needed.

• On March 31, 2003, L.A.B. Flying Service, the

first certified air carrier operator based in Juneau,

AK authorized by the FAA to conduct instrument

flight rules (IFR) RNAV operations using

Capstone Phase II EFIS avionics, departed from

Juneau in a Piper Seneca PA-34-200T on a round

trip to Sitka on V431 at 6,000 feet ending with

the approach to Sitka Runway 11. The aircraft

returned to Juneau via V428 at 6,000 feet with an

approach and landing at Juneau using the Runway 8 localizer type directional aid (LDA) approach. This IFR RNAV flight was conducted

under the authorization specified in SFAR No.

97 using certified GPS/WAAS systems as the only

means of en route navigation outside the operational service volume of ground-based navigation

aids.
5

Capstone Phase I Apollo MX-20 is a 6" Diagonal, color, Multifunction cockpit display in the custom map mode.

Capstone Phase I GX60 is a TSO C129(A1) certified GPS navigation and communication solution in a single two-inch package

Capstone Phase I Universal Access Transceiver (UAT) and

antenna is a radio datalink system supporting Automatic Dependent Surveillance Broadcast (ADS-B), Traffic Information Service

(TIS-B) and Flight Information Service (FIS-B).

Capstone Phase I resulted in the equipage of approximately

180 aircraft conducting scheduled and on-demand air carrier

operations in the Bethel and the Yukon-Kuskokwim Delta

area in western Alaska.

Capstone Phase II will equip approximately 200 aircraft [including 50 helicopters] with Capstone Phase II equipment in

southeast Alaska. Capstone Phase II also provides for implementation of an IFR RNAV infrastructure in southeast Alaska

using advanced navigation, communication, and surveillance

technologies and applications.

Capstone Phase II Chelton PFD and Navigation Display installed

in a Single Engine Cessna 172RG

The Capstone program is a dynamic program that includes

dedicated FAA and aviation professionals who are not only

working in partnership to develop criteria and requirements

for implementation of advanced CNS/ATM technology,

but are also working with appropriate FAA procedures, air

traffic,

Chelton PFD and Navigation Display in twin enginePiper Seneca

[PA-34-200T]

airways facilities, flight standards, aircraft certification, and

other lines of business to ensure that an IFR infrastructure is

in place to support the technology. The successes of the FAA

Alaska Program have become a catalyst for implementation

of advanced CNS/ATM technology in the National Airspace

System and throughout the world.

For additional information regarding the FAA Alaska
Capstone Program and associated technology the following

Internet web site should be helpful (www.alaska.faa.gov/

capstone).

For additional information or questions regarding this article,

please contact Don Streeter, FAA Flight Technologies and

Procedures Division (AFS-400), (202) 385-4567 or on email

at donald.w.streeter@faa.gov.

WAAS Helping To Solve

Worldwide Agricultural

Problems

by Eric Fly, GPS TAC

The worldwide agricultural community faces three great challenges: how to feed an ever-increasing world population, increase on-farm profits so farmers can keep their land, and

decrease the impact that modern agriculture can have on the

environment. To assist farmers in accomplishing these tasks,

an unlikely alliance has taken place.

The FAA has become a welcome partner in helping the agricultural industry meet and solve its challenges. FAA’s Wide

Area Augmentation System (WAAS), once considered just an

aviation tool, is becoming the very foundation for much of

the new technology being employed by the agricultural community today. Thanks to the FAA’s implementation of the

WAAS, agriculture has a powerful new Differential Global

Positioning System (DGPS) tool.

Before anyone in agriculture had heard of WAAS, the agricultural community was well on its way to creating new tools

and techniques to solve the problems facing a growing world.

These new agricultural tools range from new soil sampling

techniques, to yield monitors for combines, to variable rate

applicators for the accurate placement of fertilizer, chemicals

and seeds and many other new and exciting tools and techniques.

Each of these new tools holds the hope and promise that

agriculture could continue to feed a growing world using fewer

acres, while creating a cleaner environment. However, the

agriculture industry realized that many of these new tools and

techniques require accurate, reliable DGPS to provide repeat6

able field location. Furthermore, DGPS was an area of new

technology that only a few in the agriculture community were

comfortable with. The agricultural industry also realized that

the need for DGPS and its receiver in many cases doubled

the cost of this new equipment preventing many farmers from

adapting these tools and techniques.

Due to the prohibitive cost of these promising new tools from

1995 to 2000, they remained virtually unused. During this

time, many agricultural technology companies went out of

business waiting for the farm economy to embrace these new

technologies. Over this five-year period, the agriculture community tried using the USCG Beacon system and real-time

kinematic (RTK) base stations with little success. The only

reliable DGPS that was available during this time was

OmniStar’s L-Band signal, which helped to sustain what is

now known as the precision agriculture industry. OmniStar

also played a vital role in introducing and educating the agriculture industry to the world of satellite navigation. The long

awaited breakthrough came in 2000, when Northstar Technologies of Acton, MA introduced the agricultural industry

to the world of WAAS.

At last, the manufacturers and farmers involved in this new

precision agriculture industry saw an opportunity to greatly

reduce the cost of precision agriculture equipment by incorporating the new WAAS technology into their products. Almost at once, the agriculture industry showed the value that

the WAAS would bring to precision agriculture. A recent

study conducted by Dr. Jay T. Akridge of Purdue University

shows that in 2001, only 7.1 percent of United States farmers

were using yield monitors on combines compared to 17.2 percent in 2002.

Studies conducted by TVC, a Virginia based agricultural consulting firm, shows that the use of WAAS was and continues

to be a major contributing factor in this increase use of precision agriculture. TVC studies also show that around 20.5

percent of farmers in the United States are now involved with

precision agriculture and that over 230,000 farmers involved

in precision agriculture are reaping the benefits of WAAS.

One day, the number of WAAS users in agriculture will out

number those found in the aviation community. Today, every major company that manufactures precision agriculture

equipment offers WAAS as a DGPS option. Many companies are offering WAAS only receivers as standard equipment.
Through the use of precision agriculture, farmers are reporting yield increases from three percent to five percent in major

crops, such as corn, wheat and soybean helping to feed a growing world. Studies conducted by Agco Corporation and Silso

Research Institute in the U.K. have shown the ability to decrease nitrogen use in wheat as much as 33 percent by using

precision agriculture, thereby helping farmers protect the environment. U.S. farmers are showing net gains in on-farm

profits as much as $10 an acre by using these new tools and

technologies. Unlike five years ago, the precision agriculture

industry is spreading around the world. Much of this success

can be contributed to the FAA’s implementation of WAAS.

The agricultural industries in countries such as Argentina,

Brazil, Chile, Peru, Australia, the U.K., and Demark also seek

to use WAAS to bring about similar results. TVC estimated

that the value WAAS will bring to the U.S. agriculture community may reach well over $400 million in the next three

years. WAAS is truly becoming a worldwide agricultural utility.

LAAS Operational Applications Implementation On

Track

by Tracey Golden, GPS TAC/AND-720

The Local Area Augmentation System (LAAS) implementation remains on schedule with the continued meetings of the

Satellite Navigation User’s Group (SNUG) at airports selected

to receive initial Low Rate Initial Production (LRIP) systems.

Four of the six airport locations in Chicago, IL, Juneau, AK,

Memphis, TN, and Phoenix, AZ have held at least two meetings. The remaining sites in Houston, TX and Seattle, WA

have meetings planned in the coming months. The meetings

are designed to focus on identifying specific operational applications that can meet the unique terminal area demands of

each airport and establish operational test beds for the deployment of future systems.

In April 2003, America West Airlines hosted SNUG meetings

for LAAS implementation at Phoenix Sky Harbor International

Airport. The high interest level was indicated by the attendance of a broad cross section of airlines, manufacturers, airports, FAA Regional personnel, and air traffic controllers and

by the extensive number of questions. Users were primarily

concerned with issues pertaining to required navigation performance (RNP), avionics, and piloting. Some of the issues

included:

Because of the significant air traffic generated by corporate

and business jet activity, there is heavy interest for precision

service at satellite airports. The desire for LAAS capability to

improve minima at adjacent airports is directly aligned with the desire to create useful operational test beds. The FAA is seeking a lead organization to help develop a

linking study for remote broadcast to the

Scottsdale airport from the Sky Harbor location. Airlines expressed a need for a set

of precision approaches that will improve

noise reduction and lower minima that ILS will be unable to

deliver upon completion of the new Phoenix control tower.

In addition, precision guided departures and missed approaches complete a suite of precision tools that will make

efficient and safe use of shrinking terminal airspace.

 LAAS operational applications will develop slowly in Phoenix. Terminal area users favor an incremental approach beginning with the conversion of existing operational tracks to

LAAS guided applications. Current requirements to meet that

desire include:

 LAAS straight-ins at Sky Harbor requested by airlines.

 Cleaner (tighter RNP) arrivals and departures and guided

missed approaches.

 Applications that provide improved satellite airport service

and minima at Scottsdale (SDL), Goodyear (GYR), and Deer

Valley (DVT).

The meetings in Phoenix are representative of meetings held

at all airport sites selected as LAAS test beds. Although each

7

Display Requirements/Annunciations

Identification of LAAS Equipped Aircraft

Aircraft System Interface Activities

Controller/Pilot Training

Pilot Flight Technical Error (FTE)

RF Leg Implementation and Certification
airport has a unique operational environment, users express

similar concerns. Each site will find its own remedy and

method of employment for LAAS. For the remainder of fiscal

year 2003, AND-720 will be gathering information at each

site for LAAS Prototyping in hopes that they will all prove

LAAS’ ability to provide repeatable, reliable, and accurate terminal routing that enhances capacity, efficiency, safety, and

savings throughout the aviation industry.

Geostationary Communications and Control Segment

(GCCS)

by Bill Tisdale GPS TAC/AND-730

The FAA’s Wide Area Augmentation System (WAAS) consists

of space and terrestrial components that, once used with WAAS

certified avionics equipment, will provide major improvements

in the accuracy, reliability and safety of the Global Positioning

System (GPS). WAAS supports air navigation for all phases of

flight in the National Airspace System from departure through

en route and non-precision approaches.

The Geostationary Communications and Control Segment

(GCCS) is a key subsystem of the WAAS. The basic GCCS

element consists of a special navigation payload carried on a

commercial communications satellite, served by a dedicated

pair of geographically separated ground uplink stations (GUSs).

The FAA is actively planning to procure GCCS services from

two satellites and four GUSs. The terms of the GCCS contract provide the option for service from a total of three satellites.

The primary mission of the GCCS is to provide highly reliable signals-in-space (SIS) that are similar, but not identical to,

the existing GPS signals. One signal will broadcast on the

standard GPS L1 frequency, and the other on a new frequency

identified as L5. The GCCS SIS will include information in

compliance with GPS standards used to calculate a receiver’s

three-dimensional position and the exact time. In addition,

the GCCS SIS will incorporate information provided by the

WAAS that can be used to establish the integrity of the SIS

itself, and to facilitate corrections to the receiver’s calculated

position.

GCCS services will be provided entirely through a long-term

lease arrangement with prime contractor Lockheed Martin Air

Traffic Management (LMATM). The Government will fund

design and development activities, but will not procure or own

the equipment. A letter contract to initiate the development

and satellite payload efforts was issued to LMATM, on March

4, 2003. Members of LMATM’s team include the Raytheon

Co., The Boeing Company, and NovAtel Inc.

Selection of two initial providers for geo satellites and payloads is well under way. The initial Program Management

review and the Systems Requirements Review were held June

4 - 5, 2003. The Preliminary Design Review is scheduled for

August 2003. GCCS factory integration and test is planned

for May 2005. This will be followed by field tests, and subsequent integration into the WAAS.

WAAS Receivers

by Bob Beal, GPS TAC/AND-720

WAAS Procedures

In a previous SatNav News article (SatNav News, Volume 19,

April 2003, p.7), I wrote about the first Wide Area Augmentation System (WAAS) receivers to be certified for aviation use

and discussed the various WAAS receiver operational and functional classes.I described the WAAS receiver Gamma, Beta,

and Delta functional classes in conjunction with (1) the related operational classes and (2) the technical standard orders

under which WAAS receivers are certified. Since some of that

jargon may be a little arcane for many readers. The following

presents a more practical description of the receiver operational capabilities and why it may be important to understand

these capabilities when selecting a WAAS receiver. This article addresses the various approach classes, elaborates on the

UPSAT and Chelton receivers, and provides some insight into

the plans of some of the other potential WAAS receiver manufacturers.

Not all WAAS receivers are created equal. Whereas Beta,

Gamma, and Delta are terms that describe receiver configurations, the operational classes determine the operations those

receivers are certified to perform. Receivers that use just the

Global Positioning System (GPS) without WAAS augmentations can be used to fly procedures that do not require vertical

guidance. WAAS enables GPS to be used for vertical guid8
9

ance with added safety improvements. In the United States

there are basically three types of vertically guided approaches;

Lateral Navigation with Vertical Guidance (LNAV/VNAV),

Localizer Precision with Vertical Guidance (LPV), and Precision (Category I, II, and III).

When WAAS is commissioned, it will support LNAV/VNAV

and LPV approach procedures. In fact, LPV is a new procedure type being introduced into the National Airspace System

along with the introduction of WAAS. Not only will new LPV

procedures be developed, but virtually all of the existing GPSRNAV procedures will be upgraded to include LPV approach

minimums. WAAS will ultimately be able to support Category I precision approaches once the second civil broadcast

frequency is added to the GPS constellation.

How do the different procedure types and WAAS operational

classes relate? Figure 1 represents a vertical slice through these

three approach types viewed as if a pilot was flying into the

page. The yellow (cross-hatched) rectangle is the area that needs

to be protected for an LNAV/VNAV approach, the blue (solid)

for an LPV approach, and the red (vertical stripes) for a Category I precision approach..

Because of navigation system accuracy and integrity, for an

LNAV/VNAV approach, the procedure designer has to protect an area (at the missed approach point) that is ±556 meters

in the horizontal direction (either side of centerline) and ±50

meters in the vertical direction. Stated another way, the horizontal and vertical alert limits for an LNAV/VNAV approach

are 556 meters and 50 meters respectively (yellow area). For

an LPV procedure, the limits are ±40 meters in the horizontal

and ±50 meters in the vertical (blue area), and ±40 meters in

the horizontal and ±12 meters in the vertical for a Category I

precision approach (red area).

Figure 1 shows that a much greater area must be protected for

an LNAV/VNAV procedure than for an LPV procedure; likewise a larger area must be protected for an LPV procedure

than for a Category I precision approach. An LPV procedure

combines LNAV/VNAV vertical accuracy with precision approach horizontal accuracy requirements thereby greatly reducing the horizontal footprint of the LPV approach compared

to an LNAV/VNAV approach. This can substantially reduce

the number of obstacles that can interfere with the approach

procedure (i.e., penetrate the obstacle clearance surfaces) and

typically results in lower approach minimums for LPV procedures (as low as 250 feet).

Because LPV procedures are so similar to Category I precision

approach procedures, they use precision approach obstacle

clearance criteria. As a result, a receiver certified to fly an

LPV approach procedure must meet the same criteria as a receiver certified to fly a precision approach procedure. These

criteria are more stringent than the criteria for LNAV/VNAV

procedures (e.g., higher navigation solution update rates, higher

software integrity requirements, greater database integrity requirements, etc.). GPS receivers are built to less stringent standards than WAAS receivers; therefore GPS receivers that are

upgraded to meet WAAS certification requirements will typically be certified for LNAV/VNAV only. To achieve LPV certification requires significant improvements that are very difficult to meet through a GPS upgrade. Now let’s look at what

the various general aviation avionics manufacturers are doing.

WAAS Receiver Status

UPSAT was the first company to certify a WAAS receiver. The

UPSAT Apollo CNX80 is a new production receiver that can

meet all of the requirements needed for LPV certification,

including a 5 Hz navigation solution update rate. As shown

in Figure 2, the CNX80 integrates GPS/WAAS with a moving

UPSAT Apollo CNX80 WAAS Receiver

Figure 2

map, VHF communications, VHF Omnidirectional Range

WAAS Approach Type Comparison

Figure 1
10

(VOR) navigation, and Instrument Landing System (ILS) localizer and glide slope receivers. The CNX80 supports direct

routing, jet and victor airways, standard instrument approach

procedures, curved-path navigation, holding patterns, procedures turns, and standard instrument arrival and departure

procedures.

Chelton Flight Systems uses FreeFlight Systems’ GPS/WAAS

receiver in its synthetic vision Electronic Flight Information

System (EFIS). This GPS/WAAS receiver is a sensor only that

provides current position, velocity, and time information to

the Chelton EFIS. The EFIS provides the procedure database, navigation function, and pilot interface. As shown in

Figure 3, the Chelton EFIS incorporates Highway-in-the-Sky

(HITS) technology a series of 3-dimensional boxes along the

flight path that provide added pilot situational awareness. The

Chelton EFIS is the first navigation system to receive HITS

certification. The primary EFIS flight display combines pitotstatic information from an air data computer, attitude and

heading information from a solid-state 3-axis gyro, and position information from the WAAS sensor.

Chelton Fight Systems’ Synthetic Vision

Electronic Flight Information System

Figure 3

The Chelton EFIS was developed in conjunction with the

FAA’s Alaska Region under Phase II of its Capstone Program.

The goal of the Capstone program is to improve aviation safety

and efficiency through installation of next-generation government-furnished GPS-based avionics and data link communications suites in most commercial aircraft serving the southeastern Alaska region.

As noted, FreeFlight Systems developed the certified WAAS

sensor used in Chelton’s EFIS. This sensor was certified for

LNAV-only. FreeFlight Systems plans to upgrade that sensor

to support LNAV/VNAV in late 2003 and to support LPV in

mid-2004. FreeFlight Systems also plans to offer a new WAAS

receiver that will support LPV, as well as an LNAV/VNAV upgrade, to their existing 2101-series panel-mount GPS receiver.

Garmin plans to provide a WAAS upgrade to their 430/530-

eries GPS receivers in late 2004, but has no near-term plans to

produce a new WAAS receiver. As noted above, as a GPS upgrade, Garmin’s WAAS receivers will probably not support LPV

without an associated hardware modification to meet the 5 Hz

navigation solution update rate required for LPV. Bendix-King,

unlike Garmin, plans to introduce WAAS as a new product

rather than as an upgrade to their current line of GPS receivers. A Bendix-King WAAS receiver is expected in late 2004

and should support all WAAS procedure types. Bendix-King

has not ruled out an upgrade to their current GPS products.

Conclusion

Unlike most previous navigation systems, not all WAAS receivers are certified to perform the same operational procedures.

Depending on the level of certification, some WAAS receivers

may only be able to perform those operations (e.g., LNAV) already supported by GPS-alone, albeit with improved integrity

and accuracy. Some will support LNAV/VNAV-only, and others will support LNAV/VNAV and LPV. The user should be

aware of these differences, determine the needed level of performance, and then decide which receiver best meets those

needs. When buying a receiver it is important to understand

what you are buying. The information presented in this article

is always subject to change as the manufacturers reassess the

marketplace and their business plans. Much of this information was obtained on the web, while other information was

obtained directly from the vendors at air shows and other venues.

Federal Aviation Administration

800 Independence Avenue, SW

Washington, DC 20591

http://gps.faa.gov