National Airspace System
FAA's Approach to Its New Communications System Appears Prudent, but Challenges Remain Gao ID: GAO-02-710 July 15, 2002The Federal Aviation Administration (FAA) provides air-ground voice and data communications for pilots and air traffic controllers to safely coordinate all flight operations, ground movement of aircraft at airports, and in-flight separation distances between aircraft. However, the anticipated growth in air traffic, coupled with FAA's efforts to reduce air traffic delays and introduce new air traffic services, will create a demand for additional channels of voice communications that FAA's current system cannot provide. FAA and the aviation industry agree that the existing communications system, even with enhancements, cannot meet aviation's expanding need for communications. To ensure that the technology it wants to use for Next Generation Air/Ground Communications (NEXCOM) will meet its future needs, FAA, in collaboration with the aviation industry, conducted a comparative analysis of numerous technologies, to assess each one's ability to meet technical requirements, minimize program risk, and meet the agency's schedule. However, before making a final decision on the technology for NEXCOM, FAA will need to efficiently address three major issues: whether the preferred technology is technically sound and will operate as intended, if the preferred technology and the equipment it requires can be certified as safe for use in the National Airspace System, and whether it is cost effective for users and the agency.
RecommendationsOur recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.
Director: Team: Phone:GAO-02-710, National Airspace System: FAA's Approach to Its New Communications System Appears Prudent, but Challenges Remain
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entitled 'National Airspace System: FAA's Approach to Its New
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Report to Congressional Requesters:
July 2002
GAO:
GAO-02-710
Contents:
Letter:
Results in Brief:
FAA‘s Planned Improvements Would Likely Expand the Life of Its Existing
Communications System but Would Not Meet Aviation Needs Beyond 2009:
To Help Ensure NEXCOM Will Meet Future Communications Needs, FAA Has
Collaborated with the Aviation Industry to Assess Alternative
Technologies:
FAA Needs to Resolve Three Key Issues Before It Can Make a Final
Decision on the Technology for NEXCOM:
Conclusions:
Recommendation:
Agency Comments:
Scope and Methodology:
Appendix I:
GAO Contacts and Staff Acknowledgments:
GAO Contacts:
Staff Acknowledgments:
Tables:
Table 1: FAA‘s Plans Provide for Additional Channel Assignments for
Voice Communications:
Table 2: Alternative Technologies and Reasons for Their Rejection:
Table 3: Major Milestones for Certifying VDL-3‘s Radio Equipment:
Figures:
Figure 1: Increasing Channel Capacity through Channel Splitting, 1966
through 1999, and the Proposed Future Use of VDL-3:
Figure 2: Relationship between the Demand for Assigning Channels for
Voice Communications and Increases in Air Traffic, 1977 through 2016:
Figure 3: FAA‘s Channel Assignments for Voice Communications, Actual,
and Projected, 1974 through 2009:
Figure 4: Effect of a Projected 2-Percent Annual Increase in Air
Traffic on FAA‘s Ability to Make New Channel Assignments for Voice
Communications, 2000 through 2015:
Figure 5: FAA‘s Planned Approach to Implement VDL-3:
Figure 6: FAA‘s Schedule to Implement Voice and Data Digital
Communications:
Abbreviations:
ACARS: Aircraft Communications Addressing and Reporting System:
FAA: Federal Aviation Administration:
GHz: gigahertz:
ICAO: International Civil Aviation Organization:
kHz: kilohertz:
MHz: megahertz:
NARC: NEXCOM Aviation Rulemaking Committee:
NASA: National Aeronautics and Space Administration:
NEXCOM: Next Generation Air/Ground Communications:
VHF: very high frequency:
VDL-2: Very High Frequency Digital Link Mode 2:
VDL-3: Very High Frequency Digital Link Mode 3:
VDL-4: Very High Frequency Digital Link Mode 4:
United States General Accounting Office:
Washington, DC 20548:
July 15, 2002:
The Honorable John L. Mica
Chairman
The Honorable William O. Lipinski
Ranking Democratic Member
Subcommittee on Aviation
Committee on Transportation and
Infrastructure
House of Representatives:
The Federal Aviation Administration (FAA) uses radios to provide air-
ground voice and data communications for pilots and air traffic
controllers to safely coordinate all flight operations--ground
movements of aircraft at airports, take-offs and landings, and
separation distances between aircraft as they cruise at high altitudes.
However, the anticipated growth in air traffic, coupled with FAA‘s
efforts to reduce air traffic delays and introduce new air traffic
services, will create a demand for additional channels for voice
communications that FAA‘s current system cannot provide. FAA is
implementing a new communications system to respond to this challenge
and also seeking to enhance its existing ability to transmit data to
provide more information to pilots, reduce errors in voice
communications, and better balance controllers‘ workload. Moreover, FAA
expects that its new system should be less susceptible to interference
from such sources as power lines and radio and television stations and
also improve security against unauthorized users. FAA is developing
products to use with its future integrated voice and data
communications system. FAA refers to the initiative to acquire this
system as Next Generation Air/Ground Communications (NEXCOM) and
estimates that its long-term funding commitment for this initiative
could reach $4 billion through fiscal year 2023.
Because voice and data communications are critical to air traffic
management, you asked us to determine (1) to what extent the existing
voice and data communications system used by FAA can effectively meet
its expected future needs, (2) what FAA has done to help ensure that
the technology it wants to use for NEXCOM will meet its future needs,
and (3) what major issues FAA needs to resolve before it can make a
final decision on the technology it wants to use for NEXCOM. To address
these objectives, among other things, we interviewed and analyzed data
and documentation from FAA program officials, experts in communications
from the Department of Defense and the National Aeronautics and Space
Administration, representatives of national and international aviation
groups, and officials representing FAA‘s controller and maintenance
workforces. We did not verify the data FAA provided or the results of
FAA‘s analysis.
Results in Brief:
FAA and the aviation industry agree that the existing communications
system, even with enhancements, cannot meet aviation‘s expanding need
for communications. FAA has identified 23 measures to improve its
existing voice communications system, which the agency and industry
believe will add several years to its useful life. However, they
believe that it will not meet aviation‘s future voice communications
needs beyond 2009, even with these improvements. Because FAA‘s current
system does not provide the capability for data link communications,
the agency is currently leasing this service from a commercial vendor.
However, even with planned improvements to this leased service, it will
not meet FAA‘s projected needs for sharing data between FAA facilities
and with aircraft operators. As FAA relies more on data communications,
in part to help alleviate voice congestion, this service cannot meet
the need to prioritize those messages that must be delivered
expeditiously.
To help ensure that the technology it wants to use for NEXCOM will meet
its future needs, FAA completed a comparative analysis of numerous
technologies, in collaboration with the aviation industry, to assess
each one‘s ability to meet technical requirements, minimize program
risk, and meet the agency‘s schedule. As a result of this analysis, in
March 1998, FAA selected Very High Frequency Digital Link Mode 3 (VDL-
3) as the technology it wanted to use for its future communications
needs. Although five other technologies, such as FAA‘s current voice
communications system coupled with a commercially available data link
communications system, offered some potential to satisfy a broad range
of future needs, each was rejected during the evaluation process. FAA
plans to implement its preferred technology for NEXCOM by using a
phased approach to help ensure that this technology can continue to
meet its future needs. In September 2001, an aviation industry panel
conditionally approved FAA‘s preferred technology.
However, before making a final decision to select the technology for
NEXCOM, FAA will need to effectively address three major issues:
whether the preferred technology is technically sound and will operate
as intended, if the preferred technology and the equipment it requires
can be certified as safe for use in the National Airspace System, and
whether it is cost effective for users and the agency. To evaluate the
technical and operational merits of the technology it wants to use, FAA
has scheduled a series of three system demonstrations to be completed
between October 2002 and October 2004. Using the preferred technology,
these tests will, among other things, demonstrate the integration of
voice and data communications and that the new equipment required for
NEXCOM is compatible with existing equipment. Moreover, these tests
will also demonstrate if this integrated system can be certified as
safe for aircraft operations. Because FAA plans to require aviation
users to buy new radios and other equipment to use with the technology
it selects for NEXCOM, FAA has begun to analyze the cost and benefits
of the technology it wants to use. Under FAA‘s current plans, the
agency is assuming a 30-year useful life for the NEXCOM technology it
wants to use. However, emerging technologies might shorten the useful
life and thus reduce the overall benefits. To help ensure that FAA‘s
final selection for NEXCOM is the most cost effective for the agency
and aviation users, we are recommending that, as part of its cost
benefit analysis before committing to a technology, FAA assess the
potential impact of emerging technologies in light of its requirements.
In commenting on a draft of this report, the Product Team Lead for Air/
Ground Voice Communications and officials from Spectrum Policy and
Management, FAA, indicated that they generally agreed with the facts
and recommendation. These officials and those from the National
Aeronautics and Space Administration provided a number of clarifying
comments, which we have incorporated where appropriate.
Background:
Air traffic controllers monitor and direct traffic in a designated
volume of airspace called a sector. Each sector requires a separate
channel assignment for controllers to communicate with aircraft flying
in that sector. As the amount of air traffic grows, the need for
additional sectors and channel assignments also increases. FAA‘s
present air-ground communications system operates in a worldwide, very
high frequency (VHF) band reserved for safety communications within the
118 to 137 megahertz (MHz) range.[Footnote 1] Within this range of
frequencies, FAA currently has 524 channels available for air traffic
services. During the past four decades, FAA has primarily been able to
meet the increased need for more channel capacity within this band by
periodically reducing the space between channels (a process known as
channel splitting). For example, in 1966, reducing the space between
channels from 100 kHz to 50 kHz doubled the number of channels. The
last channel split in 1977, from 50 kHz to 25 kHz, again doubled the
number of channels available. Each time FAA reduced this space, owners
of aircraft needed to purchase new radios to receive the benefits of
the increased number of channels. FAA can use or assign its 524
channels several times around the country (as long as channel
assignments are separated geographically to preclude frequency
interference). Through channel reuse, FAA can make up to 14,000 channel
assignments nationwide. While aviation literature often refers to
channel and channel assignments as frequency and frequency assignments,
throughout this report, we use the terms channel and channel
assignments.
Because the growth in air traffic during the past decade has created a
need for more communications channels since the 1977 split, FAA has
been increasingly concerned that the demand for channels would exceed
their availability, which would cause frequency congestion. FAA first
explored this issue at length at a 1990 International Civil Aviation
Organization (ICAO) conference,[Footnote 2] at which the ICAO member
countries addressed increasing congestion in the air traffic control
communications band and the especially acute problem in the U. S. and
Western Europe. Over the next 5 years, ICAO evaluated different
solutions that were proposed by the conference‘s participants. While
the Western European countries proposed further channel splitting to
increase capacity, FAA proposed a totally new air-ground communications
system. FAA‘s proposed technology, known as VDL-3, would be based on a
new integrated digital voice and data communications technology, which
would assign segments of a channel to users in milliseconds of time,
thereby allowing both voice and data to travel over the same channels
using one of the available time slots. Under the current system, each
channel is used exclusively and continuously for voice, so the air
traffic controller can communicate at all times with the aircraft. This
new technology could provide up to a fourfold increase in capacity
without channel splitting, thus meeting the demand for new voice
channels. VDL-3 digitizes a person‘s voice and sends it as encoded bits
of information, which is reassembled by the receiver. Moreover, this
technology could provide real-time data link on-board communications of
air traffic control messages and events.
Although ICAO adopted FAA‘s proposed digital air-ground communications
system VDL-3 in 1995 as its model for worldwide implementation, it also
approved standards allowing Western Europe, which was then experiencing
severe frequency congestion, to further reduce the spacing between
channels from 25 kHz to 8.33 kHz. While this action tripled the number
of channels available for assignment, it also resulted in the need for
aircraft flying in Western Europe to install new radios that are
capable of communicating over the 8.33 kHz channels. ICAO intended that
this reduction would be an interim measure until 2004, when FAA
estimated that the technology it had proposed would be operational.
However, FAA did not pursue developing VDL-3 in 1995, in part, because
its existing communications system still had available capacity to meet
near-term communications needs, and because the agency‘s need to
modernize its air traffic control system became an urgent priority. In
1998, FAA resumed developing VDL-3; however, the agency is not expected
to implement this technology until 2009. Figure 1 depicts how channel
splitting has increased channel capacity since 1966 and how FAA‘s
proposed use of VDL-3 will further increase channel capacity.
Figure 1: Increasing Channel Capacity through Channel
Splitting, 1966 through 1999, and the Proposed Future Use of VDL-3:
[See PDF for image]
Note: The distance between the vertical lines and horizontal lines--in
the case of VDL-3--represents the space between assigned channels.
Source: GAO‘s presentation of information provided by FAA.
[End of figure]
FAA‘s Planned Improvements Would Likely Expand the Life of Its Existing
Communications System but Would Not Meet Aviation Needs Beyond 2009:
FAA has identified 23 measures to improve its existing voice
communications system. While FAA and the U. S. aviation industry
generally believe that implementing all these measures would add
several years to the useful life of the existing system, they believe
it would not meet aviation‘s future voice communications needs beyond
2009. Because increases in air traffic create the need for more channel
assignments, the events of September 11, which have resulted in slower
than expected increases, might delay by a year or two when FAA starts
to encounter problems systemwide in providing new channel assignments.
Agency and industry representatives agree that it is not possible to
precisely predict when the existing system with its planned
improvements will no longer meet aviation‘s needs. As a result, FAA
plans to annually assess whether this system will be capable of meeting
the projected need for more channel assignments for at least 5 years
into the future. FAA plans to release the first of these annual
assessments in September 2002.
While the focus of FAA‘s efforts has been to meet aviation‘s need for
voice communications through 2009, FAA recognizes that its data
communications needs are evolving. The agency expects to increase its
use of data communications to help alleviate voice congestion and to
help controllers and pilots accurately exchange more information.
Because FAA‘s current system cannot do this, it has been leasing data
link services from ARINC.[Footnote 3] However, even with the planned
improvements, this service will not be able to meet FAA‘s projected
need for more data communications. As FAA relies more on data
communications, this leased system will not be able to meet the
agency‘s need to prioritize those messages that must be delivered
expeditiously. Recognizing that accurately projecting the growth in
aviation‘s need for data link communications beyond 15 years would be
difficult, FAA is designing a system to provide a sevenfold increase in
capacity to meet future needs.
FAA Does Not Have Enough Channels to Meet Aviation‘s Projected Need for
Voice Communications:
During the 1990s, several of FAA‘s studies found that, historically,
increases in air traffic were closely related to the growing need to
assign more channels for voice communications (see fig. 2).
Figure 2: Relationship between the Demand for Assigning
Channels for Voice Communications and Increases in Air Traffic, 1977
through 2016:
[See PDF for image]
Source: GAO‘s presentation of FAA‘s data.
[End of figure]
In its most recent study about the growing need for more channel
assignments for voice communications,[Footnote 4] FAA found that this
need had grown annually, on average, about 4 percent (about 300 new
channel assignments) since 1974 (see fig. 3). This growth paralleled
the increase in domestic air travel during that time frame. Despite the
recent downturn in air traffic resulting from a recession and the
September 11 terrorist attacks, FAA expects it to resume its historical
4-percent annual growth within a year or two. Currently, FAA‘s voice
communications system is limited to a maximum of 14,000 channel
assignments. Because increases in air traffic require more new channel
assignments, FAA expects that providing them in some metropolitan areas
will become increasingly difficult. If the system is left unchanged,
FAA has concluded that, as early as 2005, it could no longer fully
support aviation‘s need for voice communications and that in such high
traffic metropolitan areas as New York, Chicago, and Los Angeles the
need for additional assignments could be evident sooner.
Figure 3: FAA‘s Channel Assignments for Voice Communications,
Actual, and Projected, 1974 through 2009:
[See PDF for image]
Note: The Y-axis and graph line have been enlarged to show detail.
Source: GAO‘s presentation of FAA‘s data.
[End of figure]
Because FAA has delayed NEXCOM‘s implementation until 2009, the
agency‘s 23 planned improvement measures are designed to add
approximately 2,600 additional channel assignments for voice
communications. (See table 1.) FAA has classified these initiatives,
which involve a variety of technical, regulatory, and administrative
changes, according to how soon it expects to implement them. However,
FAA recognizes that there is no guarantee that all of these measures
can be implemented because some of them largely depend on gaining
agreement from other entities, such as other federal agencies and the
aviation community, and some may involve international coordination.
FAA also recognizes that the exact degree of improvement resulting from
the totality of these measures cannot be precisely projected and actual
test results could show less gain than anticipated. Many of these
initiatives involve reallocating channels being used for purposes other
than air traffic services and increasing FAA‘s flexibility to use
already assigned channels. For example, FAA is reviewing its policy for
assigning channels to such special events as air shows to determine if
fewer channels could be assigned to them so that channels could be used
for other purposes.
Table 1: FAA‘s Plans Provide for Additional Channel Assignments for
Voice Communications:
Year: 2003; Improvement measures: 15: Additional channel
assignments: 1,041.
Year: 2005; Improvement measures: 7; Additional channel
assignments: 1,574.
Year: 2009; Improvement measures: 1; Additional channel assignments:
[A].
Year: Total; Improvement measures: 23; Additional channel
assignments: 2,615.
[A] FAA is still studying the gains that this measure should achieve.
Source: GAO‘s analysis of FAA‘s data.
[End of table]
While it is not possible to predict exactly when FAA‘s existing voice
communications system will run out of available channel assignments,
agency and aviation representatives concur that, without the 23
improvement measures, the system will be strained to provide enough
channel assignments. According to a MITRE Corporation study completed
in 2000,[Footnote 5] even if the need for more channel assignments for
voice communications were to grow at 2 percent per year (instead of
FAA‘s projected growth of 4 percent per year), by 2005 or sooner, it
would be difficult for FAA to meet the need for air traffic
communications in major metropolitan areas. MITRE also projected that
the shortage of available channel assignments would become a nationwide
problem by 2015 or sooner.[Footnote 6] In 2000, FAA first encountered a
shortage problem when it had to reassign a channel from one location to
another that FAA viewed as a higher priority in the Cleveland area.
Figure 4 shows MITRE‘s analysis of how the projected demand for more
voice communications capacity will intensify if FAA does nothing to
improve this system.
Figure 4: Effect of a Projected 2-Percent Annual Increase in
Air Traffic on FAA‘s Ability to Make New Channel Assignments for Voice
Communications, 2000 through 2015:
[See PDF for image]
Note: Each circle represents where the demand for voice communications
capacity will inhibit FAA‘s ability to meet new air traffic needs.
Source: GAO‘s presentation of MITRE‘s analysis.
[End of figure]
FAA Does Not Have Enough Channels to Meet Aviation‘s Projected Need for
Data Communications:
Currently, FAA is leasing ARINC‘s Aircraft Communications Addressing
and Reporting System (ACARS) to provide data link communications that
are not time critical, such as forwarding clearances to pilots prior to
takeoff.[Footnote 7] Because this analog system is also reaching its
capacity to handle data link communications, FAA plans to use ARINC‘s
new digital data communications system, known as Very High Frequency
Digital Link Mode 2 (VDL-2) until 2009.[Footnote 8] By then, FAA
expects to use its VDL-3 system, which is being developed to integrate
voice and data communications, to meet aviation‘s needs for about 1,800
channel assignments for data communications over the next 15 years and
to prioritize messages that must be delivered expeditiously, which VDL-
2 cannot provide. Because FAA believes that aviation‘s need for data
communications cannot be realistically projected beyond 15 years, it is
designing a system to provide a sevenfold increase in capacity for data
communications, thereby providing what it believes is an excess
capacity that should meet aviation‘s future needs.
To Help Ensure NEXCOM Will Meet Future Communications Needs, FAA Has
Collaborated with the Aviation Industry to Assess Alternative
Technologies:
In consultation with stakeholders from the aviation industry, FAA
selected VDL-3 as the preferred solution to meet its future
communications needs. During the 1990s, FAA collaborated with its
stakeholders to analyze many different communications systems, as well
as variations of them, as potential candidates to replace its existing
communications system. As a result of these studies, FAA eliminated
several designs because they did not meet some of the fundamental needs
established for NEXCOM. For example, FAA found that Europe‘s Very High
Frequency Digital Link Mode 4 (VDL-4) technology was too early in
development to assess and that it would not provide voice
communications, FAA‘s most pressing need. Moreover, a vendor of VDL-4
recently told us that this technology still needed additional
development to meet FAA‘s communications needs and that the
international community had not yet validated it as a standard for air
traffic control communications, which could take at least an additional
3 years. In March 1998, FAA rated VDL-3 as the best of the six possible
technologies to meet its future communications needs and the most
likely to meet its schedule with the least risk. FAA found that VDL-3,
the international model for aviation communications, could:
* provide up to a maximum fourfold increase in channel capacity, but
the increase is estimated to be three to fourfold because of initial
deployment scenarios;
* transmit voice and data communications without interference;
* increase the level of security;
* provide voice and data communications to all users with minimal
equipment replacement;
* require no additional channel splitting, thereby reducing the need
for engineering changes; and:
* reduce the number of ground radios required by FAA because each radio
could accommodate up to four channels within the existing 25 kHz
channel spacing.
Although FAA and its stakeholders thought that each of the five other
technologies had some potential to satisfy a broad range of their
future needs, each was rejected during the 1998 evaluation process.
(See table 2.):
Table 2: Alternative Technologies and Reasons for Their Rejection:
Alternative: 25 kHz and VDL-2; Description: FAA‘s current analog voice
communications technology and a separate digital data technology that
ARINC is developing for aviation; Reason for rejection: Would not
provide the needed additional channels for voice communications because
the channels would need to be reassigned to communicate data.
Alternative: 8.33 kHz and VDL-2; Description: A system providing
additional channel capacity by reducing the space between channels by
using FAA‘s current analog voice communications technology and a
separate digital data technology that ARINC is developing for aviation;
Reason for rejection: --Could only double the number of voice channels;
--Could not resolve existing radio interference and loss of
communications issues and; --Would likely require a significant
increase in the number of ground radios.
Alternative: Cellular telecommunications; Description: A commercially
available digital technology that would need to be enhanced for air
traffic control; Reason for rejection: Significant technical challenges
would preclude meeting FAA‘s need to deploy an initial operational
system by 2005.
Alternative: Geostationary satellites; Description: A system whose
satellites maintain fixed positions at 22,000 miles above the earth;
Reason for rejection: Significant technical challenges would preclude
meeting FAA‘s need to deploy an initial operational system by 2005.
Alternative: Low-earth orbit or medium-earth orbit satellites;
Description: A system whose satellites can range from 200 to 500 miles
above the earth or a system from a few hundred to a few thousand miles
above the earth; Reason for rejection: Significant technical challenges
would preclude meeting FAA‘s need to deploy an initial operational
system by 2005.
Source: GAO‘s presentation of FAA‘s data.
[End of table]
Academia and other experts have concluded that FAA‘s rationale for
rejecting alternative technologies in 1998 remains valid today.
Specifically, the technical challenges facing these technologies have
not been sufficiently resolved to allow FAA to deploy an initial
operating system by 2005. For example, while satellite technology is
used to provide voice and data communications across the oceans and in
remote regions, it is expensive, it does not support the need for
direct aircraft-to-aircraft communications, and does not meet
international standards for air traffic control communications.
Representatives from the National Aeronautics and Space Administration
(NASA) told us that emerging technologies that could meet FAA‘s need
for voice and data communications could be developed and available by
2015. However, in further discussion with these representatives, they
indicated that while such technologies might be mature enough to
provide communications services, it may require additional time for
them to meet all of the requirements associated with air traffic
control safety systems. NASA officials commented that FAA initiated its
plans for its new communications system at the outset of the emerging
wireless technology explosion and was not able to assess and integrate
any of these emerging technologies into the NEXCOM architecture.
However, they noted that the telecommunications field is changing
rapidly, and FAA and the aviation industry will need to continually
assess their requirements and keep abreast of emerging technologies
that could better meet their future communications needs.
FAA‘s planned approach for NEXCOM is to implement VDL-3 in three
segments, as shown in figure 5. Currently, FAA‘s senior management has
only approved investments for the first segment.
Figure 5: FAA‘s Planned Approach to Implement VDL-3:
[See PDF for image]
Note: In segment 1, FAA plans to start deploying radios that can
operate in both the current analog and future digital modes because
voice communications will continue in the analog mode until 2009 when
FAA plans to start providing digital voice communications.
Source: GAO‘s presentation of FAA‘s plans.
[End of figure]
If FAA cannot demonstrate that VDL-3 can successfully integrate both
voice and data in a cost-effective manner, FAA plans to implement a
backup approach to meet the need for more channel capacity. FAA‘s
backup follows the Western European approach as follows:
* For analog voice communications, reduce the 25 kHz space between
channels to 8.33 kHz.
* For digital data communications, rely on a commercial vendor that is
developing a technology to support aviation‘s need for data, known as
VDL-2.
However, this approach remains a backup because it doubles, not
quadruples, voice channel capacity. Furthermore, it does not resolve
the issues of radio interference and loss of communications that now
confront FAA, nor does it meet all of the requirements for air traffic
control data link communications.
FAA Needs to Resolve Three Key Issues Before It Can Make a Final
Decision on the Technology for NEXCOM:
Before selecting VDL-3 as the technology for NEXCOM, FAA needs to
demonstrate the technical and operational merits of VDL-3, certify VDL-
3 as a ’safety critical system,“ and prove its cost-effectiveness to
the aviation industry. To help address these issues, the FAA
Administrator formed the NEXCOM Aviation Rulemaking Committee (NARC) in
2000.[Footnote 9] The NARC, composed of representatives from the
aviation industry and other groups, submitted its final report in
September 2001, which included recommendations to expedite the
resolution of technical and operational issues involving NEXCOM.
To demonstrate VDL-3‘s technical and operational merits, FAA has
scheduled a series of three tests of this technology, beginning in
October 2002 and ending in October 2004. The first test is designed to
demonstrate the quality of voice communications and the integration of
voice and data communications. A key component of the second test is to
demonstrate that new digital ground radios can work with new digital
aircraft equipment and other equipment in FAA‘s air traffic control
system.[Footnote 10] Finally, in the third test, FAA plans to validate
that VDL-3 can be certified as safe for aircraft operations. Moreover,
to make VDL-3 fully operational will require FAA and users to undertake
a phased installation of tens of thousands of new pieces of equipment.
In addition to FAA and users installing radios with new transmitters
and receivers, FAA would need to install new voice switches and
workstations. FAA also needs to ensure that all the new equipment
required for NEXCOM will be compatible with FAA‘s existing equipment,
especially the numerous types of voice switches as well as the local
and wide area networks. Therefore, FAA estimates that it will take 5
years following the successful conclusion of its demonstration tests
for it to install the new ground equipment, while the airlines install
new aircraft equipment. Figure 6 shows FAA‘s schedule to implement both
voice and data digital communications.
Figure 6: FAA‘s Schedule to Implement Voice and Data Digital
Communications:
[See PDF for image]
Note: FAA has yet to determine what services it will receive on VDL-2
after it implements VDL-3.
Source: FAA.
[End of figure]
Because communications are critical to ensuring safe aircraft
operations, FAA is developing a process to certify that VDL-3 and the
new equipment it requires could be used in the National Airspace
System. In April 2002, FAA‘s teams responsible for developing and
certifying VDL-3 drafted a memorandum of understanding that describes
their respective responsibilities. They agreed to maintain effective
communications among them as well as with the manufacturers developing
VDL-3 equipment. (See table 3 for the schedule for certifying the
radios that will be used with VDL-3.) To FAA‘s credit, the agency is
proactively seeking certification before making a final decision on
VDL-3.
Table 3: Major Milestones for Certifying VDL-3‘s Radio Equipment:
Date: September 2002; Milestone: Sign a final memorandum of
understanding..
Date: August 2003; Milestone: Publish guidelines for manufacturing FAA-
approved digital radios..
Date: August 2004; Milestone: Certify that the radios selected for
NEXCOM meet aviation‘s needs before the final October 2004
demonstration..
Source: GAO‘s presentation of information provided by FAA.
[End of table]
The issue of cost effectiveness was raised by the NARC because it
wanted FAA to fully analyze the airlines‘ transition to digital radios
before the agency requires their use. Convincing enough users to
purchase VDL-3 radios might be difficult because some air carriers had
recently bought 8.33 kHz radios for operation in Europe, and they would
not be eager to purchase additional equipment. As part of its cost-
benefit analysis, FAA is assuming a 30-year life cycle for NEXCOM;
however, changing requirements coupled with the rapidly changing
developments in telecommunications technology could reduce this life
cycle. Without analyzing the costs and benefits under different
confidence levels for other potential life cycles for NEXCOM while
considering the impact of changing requirements and the effects of
emerging technologies, FAA might find it more difficult to enlist the
continued support of the aviation community for NEXCOM. FAA plans to
begin analyzing the cost-effectiveness of NEXCOM in mid-2002, publish a
notice of proposed rulemaking by January 2004, complete its cost-
benefit analysis by mid-2004, and publish its final rulemaking by June
2005. FAA officials agreed that it is important to continually evaluate
the requirements of the future system and whether emerging technologies
could reduce VDL-3‘s cost-effectiveness prior to making the final
selection. Throughout its rulemaking process, program officials
stressed that they plan to continue involving all key FAA organizations
and the aviation industry.
Conclusions:
FAA‘s approach for selecting its NEXCOM technology appears prudent. The
FAA officials managing NEXCOM have worked with the aviation industry
and involved other key FAA organizations to help ensure that the
technical and operational, safety, and cost-effectiveness issues are
resolved in a timely manner. However, FAA is only in the early stages
of resolving these three issues, and the program‘s continued success
hinges on FAA‘s maintaining close collaboration with major
stakeholders. FAA‘s follow-through on the development of a
comprehensive cost-benefit analysis, which considers how changing
requirements and emerging technologies could affect the cost
effectiveness of VDL-3, will be key to this success. Otherwise, the
aviation community might not continue to support FAA in developing
NEXCOM, as they now do.
Recommendation:
To make the most informed decision in selecting the technology for
NEXCOM and continue to receive the support from the aviation community,
we recommend that the Secretary of Transportation direct the FAA
Administrator to assess whether the requirements for voice and data
communications have changed and the potential impact of emerging
technologies on VDL-3‘s useful life as part of its cost-effectiveness
analysis of NEXCOM.
Agency Comments:
We provided the Department of Transportation, the Department of
Defense, and the National Aeronautics and Space Administration with a
draft of this report for review and comment. The Department of Defense
provided no comments. The Product Team Lead for Air/Ground Voice
Communications and officials from Spectrum Policy and Management, FAA,
indicated that they generally agreed with the facts and recommendation.
These officials, along with those from the National Aeronautics and
Space Administration, provided a number of clarifying comments, which
we have incorporated where appropriate.
Scope and Methodology:
To determine the extent to which FAA‘s existing communications system
can effectively meet its future needs, we interviewed officials from
FAA‘s NEXCOM program office, the agency‘s spectrum management office,
union officials representing the air traffic controller and maintenance
technician workforces, representatives of the MITRE Corporation, and
members of the NARC, an advisory committee formed by FAA to help ensure
that NEXCOM meets the aviation industry‘s needs. We reviewed
documentation on the current status of FAA‘s existing air-ground
communications system as well as documentation on potential measures
FAA plans to take to increase the channel capacity of its existing
system.
To determine what FAA did to help ensure that its preferred technology
for NEXCOM will meet aviation‘s future needs, we interviewed officials
from FAA‘s NEXCOM program office; officials from the Department of
Defense, the National Aeronautics and Space Administration, and
Eurocontrol;[Footnote 11] an expert in satellite communications from
the University of Maryland; and contractors who offer VDL-2 and VDL-4
communications services. We reviewed documentation indicating to what
extent varying technologies could meet FAA‘s time frames for
implementing NEXCOM. We also reviewed documentation indicating how well
varying technologies could meet FAA‘s specifications for NEXCOM. We did
not perform an independent verification of the capabilities of these
technologies. Additionally, we reviewed studies performed by FAA in
collaboration with the U.S. aviation industry to assess alternative
technologies for NEXCOM that led the U.S. aviation community to endorse
FAA‘s decision to select VDL-3 as its preferred technology for NEXCOM.
To identify issues FAA needs to resolve before it can make a final
selection for NEXCOM‘s technology, we interviewed officials from FAA‘s
NEXCOM program office as well as members of the NARC. We also reviewed
NEXCOM program office documentation that prioritizes the program‘s
risks, assesses their potential impact on the program‘s cost and
schedule, and describes the status of FAA‘s efforts to mitigate those
risks. In addition, we reviewed the NARC‘s September 2001 report that
made recommendations to FAA for modernizing its air-ground
communications system. We conducted our review from September 2001
through May 2002, in accordance with generally accepted government
auditing standards.
We are sending copies of this report to interested Members of Congress;
the Secretary of Transportation; the Secretary of Defense; the
Administrator, National Aeronautics and Space Administration, and the
Administrator, FAA. We will also make copies available to others upon
request. In addition, the report will be available at no charge on the
GAO Web site at http://www.gao.gov.
If you or your staff have any questions about this report, please
contact me at (202) 512-3650. I can also be reached by E-mail at
dillinghamg@gao.gov. Key contributors are listed in appendix I.
Gerald L. Dillingham, Ph.D.
Director, Physical Infrastructure:
Signed by Gerald L. Dillingham:
GAO Contacts:
Appendix I: GAO Contacts and Staff Acknowledgments:
Gerald L. Dillingham (202) 512-3650
Belva M. Martin (202) 512-4285:
Staff Acknowledgments:
In addition to those individuals named above, Nabajyoti Barkakati,
Geraldine C. Beard, Jeanine M. Brady, Peter G. Maristch, and Madhav S.
Panwar made key contributions to this report.
FOOTNOTES
[1] Frequency is the number of waves traveling by a given point per
unit of time, in cycles per second, or hertz. Radio frequency is
usually measured in thousands of hertz or kilohertz (kHz), millions of
hertz or megahertz (MHz), and billions of hertz or gigahertz (GHz).
Because the range of consecutive frequencies makes up a band, the
greater the range of frequencies, the greater the bandwidth. In
addition to using this bandwidth for air traffic services, FAA uses it
for such other services as flight-testing and air shows. Other
organizations, such as the Department of Defense and commercial
airlines, also use it for flight-testing and airline operations.
[2] ICAO is a specialized agency of the United Nations that sets
international standards and regulations necessary for the safety,
security, and efficiency in all fields of civil aviation.
[3] ARINC coordinates radio frequencies for the airlines and is a
leader in providing air-ground communications worldwide.
[4] FAA‘s Radio Spectrum Plan for 2001-2010, which was issued on
September 30, 2001, does not reflect the impact of the terrorist
attacks of September 11.
[5] MITRE provides air traffic control, air traffic management, and
airport systems engineering support to FAA and civil aviation
authorities around the world.
[6] Due, in part, to the events of September 11, 2001, concerns also
exist about the adequacy of radio spectrum resources to enable public
safety agencies to communicate with one another.
[7] ACARS is an analog data link communications system designed
primarily for airlines‘ use.
[8] Analog radios rely on signals that use electric currents with
continuously variable voltages to reproduce data being transmitted.
Because an analog system transmits data by using variable voltages,
removing noise and wave distortions is very difficult. For this reason,
analog signals cannot perform high-quality data transmission. Because
digital radios rely on signals that use binary digits (0 and 1) to
transmit data, there is little interference. The resulting high-quality
transmission of data at high speeds is crucial for communications that
use computers because they use digital signals to process information.
[9] The NARC was composed of representatives from various
organizations, including the National Business Aviation Association;
American, Southwest, Northwest, and United Airlines; the Airline Pilots
Association; the Aircraft Owners and Pilots Association; the Department
of Defense; the National Air Traffic Controllers Association;
Professional Airways Systems Specialists; MITRE; the General Aviation
Manufacturers Association; and the Air Transport Association. FAA
chartered the NARC to review its previous work on cost, benefits, and
transition assumptions and to recommend appropriate actions. Moreover,
since some members of the U.S. aviation community knew that Western
Europe had chosen a different technology to meet its more pressing need
for additional channels for voice communications, they requested that
the NARC review both the U. S. and European systems.
[10] In July 2001, FAA awarded a contract for ground radios that can
operate in either the current analog mode or the future digital mode.
Likewise the radios being developed for aircraft will operate in both
modes, which will make them compatible with radios being used by the
Western European communications system.
[11] Eurocontrol is Europe‘s organization for managing air traffic.
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