United States General Accounting Office
GAO Testimony
Before the Subcommittee on Aviation, Committee on
Transportation and Infrastructure, House of
Representatives
For Release on Delivery
expected at
9:30 a.m.
NATIONAL AIRSPACE
Wednesday
October 1, 1997 SYSTEM
Observations on the Wide
Area Augmentation System
Statement of Gerald L. Dillingham
Associate Director, Transportation Issues
Resources, Community, and Economic
Development Division
GAO/T-RCED-98-12
Mr. Chairman and Members of the Subcommittee:
We are pleased to be here today to discuss the Federal Aviation
Administration’s (FAA) Wide Area Augmentation System (WAAS) program.
FAA is planning a transition from a ground-based civil air navigation system
to a satellite-based system using signals generated by the Department of
Defense’s Global Positioning System (GPS). However, GPS, designed for
military purposes, does not satisfy civil air navigation requirements such
as the one requiring that the system be available virtually all of the time.
FAA is acquiring WAAS—a network of equipment on the ground and in
space—to enhance GPS so that the system can meet civil aviation
requirements. Satellite-based navigation, using GPS/WAAS, is expected to
improve the safety of flight operations, allow the fuel-efficient routing of
aircraft, increase airport and airspace capacity to meet future air traffic
demands, and enable FAA to phase out its costly network of ground-based
navigation aids. By providing positioning information, GPS/WAAS is also
expected to benefit the operators of other modes of transportation and
other types of users.
The purpose of our testimony today, which is based on ongoing work
requested by your Subcommittee, is to aid congressional oversight by
providing insights into the cost, schedule, and technical issues that have
drawn considerable attention to the WAAS program. Specifically, our
testimony will discuss: (1) the likelihood of WAAS’ satisfying key
performance requirements within current program cost and schedule
estimates; (2) the importance of avoiding delays in FAA’s timetable for
shutting down (decommissioning) ground-based navigation aids; and
(3) the potential impact of cost increases and decommissioning delays on
the benefit-cost analysis for the WAAS program.
In summary
• While the developers of WAAS and outside experts are confident that WAAS
is likely to satisfy most key performance requirements within current
program cost and schedule estimates, some concerns are worth noting.
Specifically, FAA may use additional augmentations and make procedural
changes for aircraft landings if WAAS is not able to deliver the level of
service provided by existing ground-based landing systems. Also, FAA may
add more space-based equipment to meet performance requirements. FAA
expects to make decisions on these matters by late 1998 and late 2000,
respectively. If the space-based equipment is added, program costs would
grow between $71 million and $192 million above the current total
Page 1 GAO/T-RCED-98-12
program cost estimate of $2.4 billion. The program’s schedule can be
expected to slip if arrangements are not made immediately to put this
equipment in space.
• To realize the full cost savings from WAAS, FAA will need to avoid delays in
decommissioning its ground-based network of navigation aids. FAA
estimates that it incurs costs of $166 million annually to maintain this
ground-based network. FAA’s plans—which envision complete
decommissioning of the network by 2010—presume that the full WAAS will
become operational (commissioned) in 2001 and that the aviation industry
will install the necessary equipment in its aircraft during the remainder of
that decade. However, the planned decommissioning could be delayed if
the WAAS program’s schedule slips or if safety and economic benefits, such
as an aircraft’s ability to take advantage of more fuel-efficient routes, are
not sufficient to cause the industry to switch to satellite-based navigation
technology by the end of the next decade.
• Cost increases and decommissioning delays, if they occur, would reduce
the net benefits of the WAAS program, but program benefits would still
outweigh costs. FAA’s July 1997 benefit-cost analysis found that benefits
were (1) more than five times greater than costs when passenger time
savings were included and all aircraft gained savings from shorter flights,
and (2) more than two times greater than costs when passenger time
savings were excluded and 30 percent of all aircraft gained savings from
shorter flights. Additional analyses done at our request, using pessimistic
cost and decommissioning assumptions, found that the WAAS program’s
benefits are still significantly greater than the costs. However, if the
ground-based navigation network is not decommissioned or must remain
in place much longer than expected, the net benefits from WAAS would be
substantially reduced.
In the 1980s, FAA began considering how a satellite-based navigation
Background system could eventually replace the ground-based system that had long
provided navigation guidance to aviation. In August 1995, after years of
study and research, FAA contracted with Wilcox Electric to develop WAAS.
However, because of concerns about the contractor’s performance, FAA
terminated the contract in April 1996. In May 1996, the agency entered into
an interim contract with Hughes Aircraft. The interim contract with
Hughes was subsequently expanded and became final in October 1996.
Under the terms of the WAAS development contract, Hughes will deliver an
initial operational capability (Phase 1 WAAS) to FAA by April 1, 1999. The
original date written into the Wilcox contract was December 1997. Phase 1
Page 2 GAO/T-RCED-98-12
WAAS will be able to support the navigation of aircraft throughout the
continental United States for all phases of flight through Category I
precision approaches.1 However, the Phase 1 system will not have
sufficient redundancy to continue operations in the event of equipment
failures and will have to be backed up by FAA’s current ground-based
system. FAA expects to conclude the operational testing of Phase 1 WAAS in
June 1999 and to commission the system by July 15, 1999. To make WAAS
capable of serving as a “sole means” navigation system throughout the
United States,2 FAA plans to expand the system in Phases 2 and 3 of the
contract. The Phase 3, or full, WAAS is scheduled to be delivered by
October 2001 and commissioned in early 2002.
Our August 1997 report on WAAS to this Subcommittee and others provided
details on the history of FAA’s cost estimates for WAAS. We found that
although FAA knew that the facilities and equipment costs for WAAS could
exceed $900 million, the agency presented to the Congress a figure that
was some $400 million lower.3 In September 1997, FAA estimated the total
life cycle cost of the WAAS program to be $2.4 billion. Of this amount, about
$900 million is for facilities and equipment and $1.5 billion is for
operations and maintenance through the year 2016.
Accuracy, integrity, and availability are the major performance
requirements for GPS/WAAS. Accuracy is defined as the degree of
conformance of an aircraft’s position as calculated using GPS/WAAS to its
true position. Integrity is the ability to provide timely warnings when the
GPS/WAAS is providing erroneous information and thus should not be used
for navigation. Availability is the probability that at any given time
GPS/WAAS will meet the accuracy and integrity requirements for a specific
phase of flight.4
1
FAA currently categorizes landing systems according to their ability to safely guide an aircraft to a
runway. A Category I precision landing system provides safe vertical guidance to an aircraft as it
descends to a height of not less than 200 feet with runway visibility of at least 1,800 feet.
2
A “sole means” navigation system must, for a given operation or phase of flight, allow the aircraft to
meet all navigation system performance requirements, without having another navigation system on
board the aircraft.
3
See National Airspace System: Questions Concerning FAA’s Wide Area Augmentation System
(GAO/RCED-97-219R, Aug. 7, 1997). Past GAO reports and testimonies on the augmentation of GPS are
listed at the end of this document.
4
Continuity and service volume are also considered major requirements. However, because they are
derived from the accuracy, integrity, and availability requirements, we did not focus on them
separately in our analysis. Continuity is the probability that the GPS/WAAS signal will meet accuracy
and integrity requirements continuously for a specified period. Service volume is the area of coverage
for which the GPS/WAAS signal will meet availability requirements.
Page 3 GAO/T-RCED-98-12
WAAS is a system comprising a network of ground stations and
geostationary (GEO) communications satellites.
• Reference stations (up to 54 sites) on the ground will serve as the primary
data collection sites for WAAS. These stations receive data from GPS and GEO
satellites.
• Master stations (up to 8 sites) on the ground will process data from the
reference stations to determine and verify corrections for each GPS
satellite. These stations also validate the transmitted corrections.
• Ground earth stations (up to 8 sites) will, among other things, receive WAAS
message data from the master stations, and transmit and validate the
message to the GEO satellites.
• GEO satellites will transmit wide-area accuracy corrections and integrity
messages to aircraft and also serve as additional sources of signals similar
to GPS signals.
• The ground communications system will transmit information among the
reference stations, master stations, and ground stations.
For pilots to use GPS/WAAS for navigation, their aircraft must be equipped
with receivers that process the information carried by the GPS and GEO
signals. The receivers will enable the pilots to determine the time and their
aircrafts’ three-dimensional position (latitude, longitude, and altitude).
While system developers and outside experts have confidence that WAAS
Concerns Exist About can achieve most key performance requirements within current cost and
Whether WAAS Can schedule estimates, four concerns are worth noting:5 (1) the ability of WAAS
Satisfy Performance to provide the level of service for precision approaches provided by
existing ground-based systems; (2) the ability of computers to process the
Requirements Within large quantities of GPS/WAAS data within a few seconds; (3) the vulnerability
Budget and on of GPS/WAAS signals to interference; and (4) the need for additional
satellites to achieve the availability requirement.
Schedule
Regarding the first concern, it is uncertain whether WAAS can meet the
requirement that the GPS/WAAS signal be available for precision approaches
all but about 11 hours per year. Under current definitions based on
ground-based navigation technology, a Category I system provides a level
of service that allows aircraft to descend to an altitude (height) of not less
than 200 feet when visibility is at least 1,800 feet. If WAAS cannot meet this
requirement, FAA may incur additional costs to install local area
5
See app. I for additional information on achievability of requirements.
Page 4 GAO/T-RCED-98-12
augmentation systems at more airports than expected.6 The agency may
also change the procedures by which pilots can make precision
approaches. One procedural option under consideration is that FAA would
require pilots to visually recognize additional approach markings before
completing a landing. A decision is expected on any needed procedural
changes by late 1998.
A second concern is the integrity requirement that calls for the system to
sound an alarm within 5.2 seconds when it receives hazardously
misleading information, such as a correction that is wrong and would
result in an aircraft operator being placed in a dangerous situation. The
large volume of data that must be processed within a few seconds to meet
this requirement is beyond the capabilities of computer data processors
that are commercially available. However, FAA is testing newly developed
processors and is confident that they will meet the agency’s needs.
A third concern exists about the possibility that the GPS/WAAS signal could
prove vulnerable to unintentional or intentional radiofrequency
interference that could affect the signal’s availability or accuracy and,
ultimately, flight safety. These vulnerabilities are common to ground- and
satellite-based navigation aids. Because GPS broadcasts its signal at a very
low power level, its signal is somewhat more vulnerable to interference.
FAA expects to complete a vulnerability assessment for WAAS in
October 1997. Once the assessment is completed, countermeasures, if
needed, would be identified. Because of the sensitivity of this issue, we
cannot go into details in this public hearing. FAA has stated that it will offer
a private briefing for the Subcommittee.
A fourth concern is whether FAA may have to add more GEO satellites to
meet the availability requirement. FAA requires that GPS/WAAS be available
virtually 100 percent of the time—all but about 5 minutes a year—for the
phases of flight leading up to precision approaches. Although FAA
originally thought it could meet this requirement by using four
geostationary communications satellites, the agency may need five or six.
If so, FAA could continue using one or two of the GEO satellites currently in
space or obtain others. FAA intends to decide on the need for additional
satellites by late 2000. Even with the added satellites, there may be
isolated areas of air space, such as the far northern and western areas of
Alaska, where the requirements may not be met. In such areas, according
to FAA officials, FAA intends to use ground-based systems or local area
6
Local area augmentation systems enhance GPS to provide precision approaches under the most
stringent conditions.
Page 5 GAO/T-RCED-98-12
augmentation systems to provide a level of service that is at least equal to
what is provided today.
The addition of one or two GEO satellites would increase the program cost
beyond the current estimate of $2.4 billion. FAA expects that adding one or
two GEO satellites would cost between $71 million and $192 million over
the WAAS life cycle (2001-2016).7
FAA faces a very tight time frame for putting the GEO satellites in space. FAA
intends to work with the Defense Department to begin the acquisition
process this month, but it typically takes 4 years to acquire, launch, and
check out a GEO satellite. Given FAA’s October 2001 milestone for the
delivery of the full WAAS, any delays in putting the GEO satellites in space
could cause the WAAS program’s schedule to slip.
To get the full cost savings from WAAS, FAA will need to decommission its
Full Cost Savings ground-based network of navigation aids, which now costs the agency
From WAAS Tied to $166 million annually to maintain. FAA’s plan presumes that both its
FAA’s current ground-based system and the new satellite-based system will be in
place from the time that the full, Phase 3 WAAS is commissioned until the
Decommissioning of decommissioning of the ground-based network is completed in 2010.8 FAA’s
Ground-Based System plan recognizes that a critical factor in the transition will be the
widespread installation by commercial and general aviation operators of
GPS/WAAS avionics aboard their aircraft.
FAA believes that the safety and economic benefits of GPS/WAAS will
motivate aircraft operators to install GPS/WAAS avionics in the 5- to 6-year
period after the services become available in 2001. The safety
improvements include the vertical guidance WAAS will give aircraft during
approach and landing at airports where no precision approach capability
currently exists. This guidance enables aircraft to follow a smooth glide
path safely to the runway. Other benefits include the cost savings that
aircraft operators could realize by using one type of navigation equipment
in the cockpit for all phases of flight and by flying more direct,
fuel-efficient routes. FAA also expects that when it begins decommissioning
ground-based navigation aids, aircraft that are not equipped with GPS/WAAS
avionics will have to fly less direct routes and will have limits on the
precision approach options available to them. As a result, there will be
added incentives for aircraft operators to switch to satellite technology.
7
Program costs are presented in then-year dollars.
8
FAA’s Plan for Transition to GPS-Based Navigation and Landing Guidance (July 1996).
Page 6 GAO/T-RCED-98-12
Nevertheless, FAA’s plans could be impeded if the WAAS program’s schedule
slips or if safety and economic benefits are not sufficient to cause the
aviation industry to switch quickly to satellite technology. As already
discussed, the primary concern about whether the WAAS requirements can
be achieved on time is the potential for delays in putting the
communications satellites in space.
Economic considerations, however, could cause commercial and general
aviation aircraft operators to switch to GPS/WAAS avionics more slowly than
FAA envisioned in its Transition Plan. According to the U.S. GPS Industry
Council, the typical GPS receiver used by large commercial aircraft costs
between $20,000 and $50,000, and the typical GPS receiver used by smaller
general aviation aircraft capable of flying when visibility is limited costs
between $5,000 and $15,000. Database changes needed to keep the
receivers up to date now cost $70 to $100 a month. Expenses for installing
the equipment and training the pilots to use it would be additional.
Airlines already recognize the value of GPS/WAAS for determining the
position of aircraft flying over the oceans, where no ground-based
navigation aids exist, and have been installing GPS receivers for that
purpose. For flights over the continental United States, the airlines’
interest is not so clear cut. Responding to our questions, the organization
representing the airlines, the Air Transport Association, wrote that
“Airspace users must have a compelling reason to change from their current ground-based
avionics to space-based avionics. Simply stating that the technology is better is not enough.
There must be real operational benefits for changing or the equipment will have to [be]
mandated. Otherwise, avionics change will be extremely slow.”
The organization representing general aviation, the Aircraft Owners and
Pilots Association, has argued that the present cost of GPS/WAAS avionics,
including the cost of maintaining a current database, is not affordable for
all segments of the general aviation community. Representatives of the
Association told us that FAA’s plan for decommissioning by 2010 would be
realistic if (1) FAA provides routes that are more direct, (2) more
inexpensive avionics are available, (3) FAA places a high priority on
certifying approach procedures where none currently exist,
(4) inexpensive database updates for GPS receivers can be obtained
electronically from FAA, and (5) FAA does not require aircraft operators to
incur the added expense of carrying redundant (dual) GPS/WAAS receivers.
Page 7 GAO/T-RCED-98-12
FAA is currently working with industry to resolve these concerns. Even if
the Association’s concerns are satisfied, however, FAA could still face a
slower-than-expected conversion to GPS/WAAS avionics if individual aircraft
operators do not conclude that the benefits of installing the new
navigation equipment outweigh their costs. FAA would then have to make a
difficult choice—either slow down its decommissioning of ground-based
navigation aids or, in effect, require conversion by proceeding with
decommissioning as planned.
In making investment decisions, FAA conducts benefit-cost analyses to
Cost Increases and determine if the benefits to be derived from acquiring new equipment
Delays in outweigh the costs. In the case of WAAS, the benefits to the government
Decommissioning include the cost savings from reduced maintenance of the existing,
ground-based network of navigation aids and the avoidance of capital
Reduce Net Benefits expenditures for replacing those aids. The benefits to aircraft
of WAAS, but Benefits operators—the users of the system—include the reduction in
accident-related costs (from death, injury, and property damage) because
Still Exceed Costs WAAS landing signals would be available at airports that currently lack
precision landing capability. Operators could also realize “direct route”
savings that result from the shorter flight times on restructured, more
direct routes that aircraft can fly using GPS/WAAS. The costs include the life
cycle costs for WAAS facilities and equipment as well as operations and
maintenance.
Despite differing assumptions used in calculating benefit-cost ratios, FAA’s
analyses dating back to 1994 have always found WAAS to be a
cost-beneficial investment—that is, the benefits clearly exceeded the
costs, resulting in benefit-cost ratios in excess of 1.9 The most recent 1997
analysis found (1) a 5.2 ratio of benefits to costs when passenger time
savings were included in the direct route benefits and all aircraft would
gain a savings of 1 minute per flight from shorter routes, and (2) a 2.2 ratio
when passenger time savings were excluded and 30 percent of all aircraft
would gain a savings of 1 minute per flight.10 When these two cases were
evaluated in dollar terms, the net benefits of WAAS were $5.3 billion and
9
Although WAAS will benefit nonaviation users, these benefits were not included in FAA’s analysis. If
these additional benefits were included, the benefit-cost ratio would increase.
10
Cost-Benefit Analysis of the Wide Area Augmentation System (draft), July 1997.
Page 8 GAO/T-RCED-98-12
$1.5 billion, respectively.11 (See app. II for details on FAA’s benefit-cost
analyses for the WAAS program in 1994, 1996, and 1997.)
To understand the impact of the potential cost increases and
decommissioning delays previously discussed, we requested that FAA’s
support contractor perform alternative runs of the benefit-cost analysis.12
FAA’s 1997 analysis served as the base case for comparison purposes. One
pessimistic scenario that we requested made the following alternative
assumptions from the base case: (1) the development cost of the primary
WAAS contract would increase by 15 percent, (2) the leasing costs for
communications satellites would increase by 50 percent, and (3) the
decommissioning of the ground-based navigation aids would be delayed by
5 years.
Using these assumptions, the contractor’s analysis found that the
benefit-cost ratio would be 4.6 when passenger time savings were included
and all aircraft gained savings from shorter flights and 1.7 when passenger
time savings were excluded and 30 percent of all aircraft gained savings
from shorter flights. In dollar terms, net benefits declined
substantially—about $490 million—when going from the base case to the
pessimistic scenario. When scenarios were run using the three
assumptions in turn, the analysis showed that the decommissioning delay
of 5 years caused about $370 million of the decline in net benefits. The
cost increases for contract development and satellite leasing contributed
the remainder. We also asked for a run with a more pessimistic scenario in
which the contract development and satellite leasing costs would increase
by the same amount but ground-based navigation aids would never be
decommissioned. In this case, the decline in net benefits totaled about
$700 million.
Ultimately, even when pessimistic assumptions were used, the analysis
found that the benefits of the WAAS program still clearly outweighed its
costs. However, delays in decommissioning or the retention of
ground-based navigation aids would cause substantial decreases in the net
benefits of the WAAS program.
11
As an alternative to the benefit-cost ratio, where the present value of benefits are divided by the
present value of costs, analysts sometimes calculate the present value of net benefits. This value is
equal to the present value of benefits minus the present value of costs. When using alternative
assumptions for calculating benefits and costs, the present value of net benefits can be a useful tool
for making comparisons.
12
While we did not perform an extensive review of the contractor’s model used to calculate
benefit-cost ratios, the model appeared to be reasonably constructed. For example, future benefits and
costs were discounted appropriately.
Page 9 GAO/T-RCED-98-12
We received comments on a draft of this testimony from officials of the
Agency Comments Department of Transportation and FAA, including FAA’s Deputy Program
Manager of the GPS Integrated Product Team and the WAAS Program
Manager. These officials expressed general agreement with the findings of
the testimony, considered it well-balanced, and provided clarifying and
technical suggestions, which we incorporated as appropriate.
Mr. Chairman, this concludes our statement. I would be happy to answer
any questions that you or other Members of the Subcommittee may have.
Page 10 GAO/T-RCED-98-12
Page 11 GAO/T-RCED-98-12
Appendix I
Achievability of WAAS Performance
Requirements
Phase 3 WAAS requirements Remarks
Availability: Probability that the system will provide an accurate and continuous
navigation signal for each phase of flight
En route through nonprecision approach: FAA may need to add one or two GEO
99.999% availability (i.e., unavailable less satellites to the four it planned to procure.
than 5 minutes a year) Also, FAA is investigating the optimal
placement of GEO satellites in orbit. But in
isolated areas such as the far northern and
western areas of Alaska the requirement
may not be met.
Precision approach: 99.9% available (i.e., FAA may field up to 54 ground stations,
unavailable 11 hours a year) and Canada and Mexico may field up to
21. Between late 1998 and mid-1999, FAA
will determine how many ground stations
are needed based on system test results.
FAA may be required to make changes to
approach procedures to meet this
requirement.
Accuracy: Percentage of time that an aircraft’s GPS position is within a given
distance of the aircraft’s true position
En route through nonprecision approach: No major concerns have been raised by
Within 100 meters 95% of the time—During system developers or outside parties
periods when this standard cannot be met about these requirements because the
(up to a cumulative 72 minutes a day), existing GPS already guarantees this level
system safety will be guaranteed by a of performance. Feasibility testing at FAA’s
proposed 2-mile horizontal protection limit. National Satellite Test Bed (NSTB) has
validated that these requirements have
Within 500 meters 99.999% of the been met. FAA will revalidate whether the
time—During periods when this standard WAAS software and hardware will achieve
cannot be met (up to a cumulative 6 these requirements.
seconds a day), system safety will be
guaranteed by a proposed 2-mile horizontal
protection limit.
Precision approach: Within 7.6 meters No major concerns have been raised by
95% of the time—During periods when this system developers or outside parties
standard cannot be met (up to a cumulative about this requirement. FAA’s NSTB has
72 minutes a day), system safety will be achieved this level of accuracy. During
guaranteed by a proposed 63-foot WAAS software and hardware testing, FAA
horizontal and vertical protection limit. will validate that this requirement can be
met.
(continued)
Page 12 GAO/T-RCED-98-12
Appendix I
Achievability of WAAS Performance
Requirements
Phase 3 WAAS requirements Remarks
Integrity: Ability of the system to provide users with timely warnings about
erroneous information
Probability that the system will not detect hazardously misleading information
En route through nonprecision approach: No major concerns have been raised by
1 chance in 10 million during 1 hour of system developers and outside parties
system operation about these requirements. FAA plans to
acquire safety-certified equipment and
Precision approach: 1 chance in 400 software, and during hardware and
million per approach (an approach is the software testing also plans to collect and
final 2-1/2 minutes of flight) analyze data to provide increased
assurance that the requirements will be
met.
Maximum number of seconds elapsed before an alarm sounds
En route through nonprecision approach: The feasibility of meeting the 5.2-second
8 seconds requirement (and, therefore, the 8-second
requirement) has been demonstrated at
Precision approach: 5.2 seconds FAA’s NSTB. But as WAAS processes
more data, its ability to meet the
requirement may decline. FAA’s present
analysis shows that the requirement is
being marginally satisfied. FAA is looking
at faster processing equipment to
accommodate the expected increase in
data.
Continuity: Probability that service will continue to be available for a specified
period
En route through nonprecision approach: FAA may need to add one or two GEO
1 chance in 100 million per hour of flight satellites to the four it planned to procure
operations that the accuracy requirement or it may have to relax the requirement.
will not be met Experts believe relaxing the requirement
may be possible, but FAA has to
determine the impact on safety if, in the
event of a catastrophic loss of both GPS
and WAAS, air traffic controllers might
have to rely on radar to separate and
direct aircraft.
En route through nonprecision approach: No major concerns have been raised by
1 chance in 100,000 per hour of flight system developers or outside parties
operations that the integrity requirement will because existing aircraft systems have
not be met demonstrated this ability. During testing,
FAA will review contractor data to validate
that the integrity requirement can be met.
Precision approach: Per approach, 1 No major concerns have been raised by
chance in 550,000 that the accuracy and system developers or outside parties
integrity requirements will not be met (an about this requirement on the basis of the
approach is the final 2-1/2 minutes of flight) preliminary analysis. But because of the
volume of data needed to validate
compliance with this requirement, FAA is
gathering additional data and exploring
alternative methods for validating that the
requirement can be met.
(continued)
Page 13 GAO/T-RCED-98-12
Appendix I
Achievability of WAAS Performance
Requirements
Phase 3 WAAS requirements Remarks
Service volume: The air space in which all other performance requirements must be
met
En route through nonprecision approach: FAA may need to add one or two GEO
The continental United States, Alaska, satellites to the four it planned to procure.
Hawaii, the Caribbean, the Gulf of Mexico, Also, FAA is investigating the optimal
and major portions of the Atlantic and the placement of GEO satellites in orbit. But in
Pacific isolated areas such as eastern Canada
and oceanic airspace the requirement may
not be met.
Precision approach: The continental United FAA may field up to 54 ground stations,
States, Alaska, Hawaii, and Puerto Rico and Canada and Mexico may field up to
21. Between late 1998 and mid-1999, FAA
will determine how many ground stations
are needed based on system test results.
FAA may be required to make changes to
approach procedures to meet this
requirement.
Page 14 GAO/T-RCED-98-12
Appendix II
Results of FAA’s Benefit-Cost Analyses,
1994, 1996, and 1997
The results of FAA’s benefit-cost analyses of the WAAS program in 1994,
1996, and 1997 are summarized in table II-1. On the benefit side, benefits to
the government accrue from the reduced maintenance of the existing,
ground-based network of navigation aids and the avoidance of capital
expenditures for replacing these aids. Benefits to users—the aircraft
operators—fall into five categories:
• Efficiency benefits derive from having precision landing capability at
airports where it does not now exist.
• Avionics cost savings reflect how GPS/WAAS will enable users to reduce
the proliferation of avionics equipment in their cockpits.
• Fuel savings reflect the use of less fuel to fly aircraft that carry less
avionics equipment.
• Safety benefits stem from the reduction in accident-related costs (death,
injury, and property damage) because of the availability of WAAS landing
signals at airports that presently lack a precision landing capability.
• Direct route savings result from the shorter flight times associated with
restructured, more direct routes that aircraft can fly.
Table II-1: FAA’s Analysis of Benefits
and Costs for WAAS Project, 1994, Dollars in millions
1996, and 1997 1997 1997
1994 1996 High Low
Benefits
Government 1,385 943 754 754
User
Efficiency 1,051 768 286 148
Avionics 1,312 1,109 546 546
Fuel 98 95 13 13
Safety 560 1,384 624 624
Direct Route 5,489 4,299 637
Total 4,406 9,789 6,521 2,722
Costs
R&D, F&E 540 540
O&M 720 720
Total 1,081 1,051 1,260 1,260
Benefit-Cost Ratio 4.1 9.3 5.2 2.2
Source: Federal Aviation Administration.
Page 15 GAO/T-RCED-98-12
Appendix II
Results of FAA’s Benefit-Cost Analyses,
1994, 1996, and 1997
FAA’s 1997 benefit-cost analysis took a more conservative approach than
previous versions of the model in estimating the benefit-cost ratio. That is,
compared with the previous analyses, the assumptions underlying the
current study increased the expected costs of WAAS and simultaneously
reduced the expected benefits, which resulted in a lower benefit-cost ratio
than found in the previous versions of the study. The higher total costs in
the 1997 version were largely due to the inclusion of the costs of
decommissioning land-based navigation systems that were not included in
any earlier versions of the study. On the benefit side, several changes in
key assumptions led to reduced expected benefits including (1) a shorter
life cycle for the project, (2) a reduction in the assumed “saved” costs from
phasing out ground-based navigation systems,13 (3) a reduction in
estimated safety benefits based on the use of the more recent accident
data,14 and (4) a reduction in the expected flight time savings resulting
from more direct routes.
13
Specifically, the analyst assumed that old equipment would have been replaced at a slower rate so
that savings from not having to replace that equipment were reduced.
14
In previous versions of the study, older data on accident rates were used. Since rates of accidents
have been declining with time, use of the most recent data reduced the expected safety benefits from
WAAS.
Page 16 GAO/T-RCED-98-12
Page 17 GAO/T-RCED-98-12
Page 18 GAO/T-RCED-98-12
Page 19 GAO/T-RCED-98-12
Related GAO Products
National Airspace System: Questions Concerning FAA’s Wide Area
Augmentation System (GAO/RCED-97-219R, Aug. 7, 1997).
Air Traffic Control: Improved Cost Information Needed to Make Billion
Dollar Modernization Investment Decisions (GAO/AIMD-97-20, Jan. 22, 1997).
Global Positioning System Augmentations (GAO/RCED-96-74R, Feb. 6, 1996).
National Airspace System: Assessment of FAA’s Efforts to Augment the
Global Positioning System (GAO/T-RCED-95-219, June 8, 1995).
Air Traffic Control: Status of FAA’s Modernization Program
(GAO/RCED-95-175FS, May 26, 1995).
Aviation Research: Perspectives on FAA’s Efforts to Develop New
Technology (GAO/T-RCED-95-193, May 16, 1995).
National Airspace System: Comprehensive FAA Plan for Global Positioning
System Is Needed (GAO/RCED-95-26, May 10, 1995).
Global Positioning Technology: Opportunities for Greater Federal Agency
Joint Development and Use (GAO/RCED-94-280, Sept. 28, 1994).
Airspace System: Emerging Technologies May Offer Alternatives to the
Instrument Landing System (GAO/RCED-93-33, Nov. 13, 1992).
(341525) Page 20 GAO/T-RCED-98-12
Ordering Information
The first copy of each GAO report and testimony is free.
Additional copies are $2 each. Orders should be sent to the
following address, accompanied by a check or money order
made out to the Superintendent of Documents, when
necessary. VISA and MasterCard credit cards are accepted, also.
Orders for 100 or more copies to be mailed to a single address
are discounted 25 percent.
Orders by mail:
U.S. General Accounting Office
P.O. Box 37050
Washington, DC 20013
or visit:
Room 1100
700 4th St. NW (corner of 4th and G Sts. NW)
U.S. General Accounting Office
Washington, DC
Orders may also be placed by calling (202) 512-6000
or by using fax number (202) 512-6061, or TDD (202) 512-2537.
Each day, GAO issues a list of newly available reports and
testimony. To receive facsimile copies of the daily list or any
list from the past 30 days, please call (202) 512-6000 using a
touchtone phone. A recorded menu will provide information on
how to obtain these lists.
For information on how to access GAO reports on the INTERNET,
send an e-mail message with "info" in the body to:
info@www.gao.gov
or visit GAO’s World Wide Web Home Page at:
http://www.gao.gov
PRINTED ON RECYCLED PAPER
United States Bulk Rate
General Accounting Office Postage & Fees Paid
Washington, D.C. 20548-0001 GAO
Permit No. G100
Official Business
Penalty for Private Use $300
Address Correction Requested
National Airspace System: Observations on the Wide Area Augmentation System
Published by the Government Accountability Office on 1997-10-01.
Below is a raw (and likely hideous) rendition of the original report. (PDF)