
[Federal Register Volume 77, Number 162 (Tuesday, August 21, 2012)]
[Proposed Rules]
[Pages 50420-50425]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-20464]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 91, 97, 121, 125, 129, and 135

[Docket No. FAA-2011-1082]


Proposed Provision of Navigation Services for the Next Generation 
Air Transportation System (NextGen) Transition to Performance-Based 
Navigation (PBN); Disposition of Comments

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed policy; disposition of comments.

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SUMMARY: On December 15, 2011, the FAA published a Federal Register 
Notice (76 FR 77939) requesting comments on the FAA's plans for 
providing PBN services, and particularly the transition from the 
current Very High Frequency Omnidirectional Ranges (VOR) and other 
legacy navigation aids (NAVAIDS) to Area Navigation (RNAV)-based 
airspace and procedures. This action responds to the public comments 
the FAA received.

ADDRESSES: You may review the public docket for this notice (Docket No. 
FAA-2011-1082) at the Docket Management Facility at DOT Headquarters in 
Room W12-140 of the West Building Ground Floor at 1200 New Jersey 
Avenue SE., Washington, DC 20590-0001 between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays. You may also review the public 
docket on the Internet at http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Mr. Greg Joyner, AJM-324, Program 
Management Organization, Navigation Program Engineering, Federal 
Aviation Administration, 800 Independence Avenue SW., Washington DC 
20591: telephone 202-493-5721.

SUPPLEMENTARY INFORMATION:

Summary of the December 15, 2011 FRN

    The FAA sought comments on the proposed transition of the U.S. 
National Airspace System (NAS) navigation infrastructure to enable PBN 
as part of the NextGen. The FAA plans to transition from defining 
airways, routes and procedures using VOR and other legacy NAVAIDs, to a 
NAS based on RNAV everywhere and Required Navigation Performance (RNP) 
where beneficial. RNAV and RNP capabilities will primarily be enabled 
by the Global Positioning System (GPS) and the Wide Area Augmentation 
System (WAAS). The FAA plans to retain an optimized network of Distance 
Measuring Equipment (DME) facilities and a Minimum Operational Network 
(MON) of VOR facilities to ensure safety and support continued 
operations in high and low altitude en route airspace over the 
Conterminous United States (CONUS) and in terminal airspace at the Core 
30 airports. The FAA is also conducting research on non-GPS based 
Alternate Positioning, Navigation and Timing (APNT) solutions that 
would enable further reduction of VORs below that of the MON.
    In addition, the FAA plans to satisfy any new requirements for 
Category I (CAT I) instrument landing operations with WAAS Localizer 
Performance with Vertical guidance (LPV) procedures. A network of 
existing Instrument Landing Systems (ILSs) will be sustained to provide 
alternative approach and landing capabilities to support continued 
recovery and dispatch of aircraft during GPS outages.
    This transition is consistent with the FAA's NextGen Implementation 
Plan (NGIP), NAS Enterprise Architecture (NASEA), and other 
documentation. More information is available on the

[[Page 50421]]

FAA's NextGen Web site at http://www.faa.gov/nextgen and the NASEA Web 
site at https://nasea.faa.gov.

Discussion of Comments Received

Summary

    The FAA received 330 comments on the FRN. Commenters include 
aircraft manufacturers, airline operators, individuals, and 
associations representing users, airports and several federal, state 
and local government organizations. Most comments were supportive of 
the evolution of the NAS to an RNAV based system, but a significant 
number of commenters were concerned about reliance on GPS and WAAS 
related to possible impacts of interference or disruption, as well as 
the requirements and costs of avionics. A number of commenters were 
concerned about loss of approach services at specific airports in the 
event of discontinuation of service from specific VOR facilities. A 
substantial number of the comments (185) received were from individuals 
concerned about noise and environmental impact in the New York 
metropolitan area. Some reflected concerns about aircraft emissions and 
flight paths used by helicopters. These comments have been forwarded to 
the FAA Eastern Region for action.

Discussion

    The FAA has reviewed all the comments received in response to the 
FRN and plans to proceed with the strategy as outlined in the FRN. The 
FAA is developing an initial VOR MON Plan, which will be publicly 
available when it is sufficiently matured. Development of this Plan 
will harmonize with development of a national Concept of Operations 
(CONOPS) supporting navigation and positioning in the NAS as it evolves 
from conventional navigation to PBN. When completed, this CONOPS will 
also be publicly available.
    As part of the coordination process, the FAA plans to develop a 
schedule showing the requisite activities associated with the 
discontinuance of VOR services. These activities will include timely 
notification for individual facilities and airspace and procedure 
redesign.
    Comment #1: Several commenters (International Air Traffic 
Association (IATA), Boeing Commercial Airplanes, National Association 
of State Aviation Officials (NASAO), Aircraft Owners and Pilots 
Association (AOPA), Department of Defense (DoD), and Airlines For 
America (A4A)) expressed interest in being included in the working 
group that the FRN indicated would be formed to complete the details of 
VOR discontinuance. Some airlines commented that they would like to be 
consulted on the policy.
    FAA Response: The FAA will convene a working group that will engage 
aviation industry stakeholders and other members of the public for 
input once the Program has reached a sufficient level of maturity 
conducive to working group.
    Comment #2: NASAO commented that planning the transition to NextGen 
PBN well in advance would be beneficial to the FAA and the state 
government aviation agencies.
    FAA Response: The FAA's VOR MON plan is proceeding to support 
transition to NextGen PBN in accordance with the NASEA. The NGIP, FRN 
and NASEA, all publicly available via FAA Web sites, are integral to 
the transition of the NAS to PBN operations.
    Comment #3: The Nebraska Department of Aviation (DoA) recommended 
that VORs remain available as a viable means for air navigation while 
the services to support NextGen PBN be provided for users that can 
obtain benefits from them during a transition.
    FAA Response: The VOR MON will remain in place during the PBN 
transition.
    Comment #4: Nebraska state-owned VORs, similar to the FAA inventory 
of Second Generation VORs, are maintained by the State, who reports 
there have been no problems with support cost or availability of parts.
    FAA Response: VOR facilities not owned or operated by the FAA are 
not being considered for discontinuance.
    Comment #5: Operators that fly outside the United States desired 
clarification on the GNSS reference to be used.
    FAA Response: The FRN used the terms GPS and WAAS, the specific 
U.S. implementations of the GNSS and Space Based Augmentation System 
(SBAS) described in ICAO Annex 10. Other countries have, or are 
building systems that implement these standards, such as Europe's GNSS 
(Galileo) and SBAS (European Geostationary Navigation Overlay Service 
(EGNOS)). Since the U.S. does not make regulatory determinations on 
navigation systems allowed in other countries, the U.S. cannot 
authorize use of GPS in other countries. The FAA is responsible for 
determining which services are adequate for operations in the U.S. NAS, 
and has, to date, only approved the use of the U.S. GPS and WAAS, and 
Russia's Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) on a 
supplemental basis. The U.S. is working with other GNSS providers to 
assure that their signals may be used to improve performance in the 
U.S. when those signals become available. Plans for navigation services 
will continue to use specific references (e.g., GPS and WAAS) and 
policies will be updated as additional constellations are approved for 
use in the U.S. The ability of avionics to use different GNSS 
constellations and services depends both on the authorized equipment 
available for specific aircraft and the type of systems the operators 
decided with which to equip their aircrafts. It also depends on what 
avionics manufacturers decide to develop. FAA's plans for navigation 
services will continue to use the ``GPS'' and ``WAAS'' terms so that it 
is clear that the U.S. is referring to U.S. systems/services for the 
U.S. NAS. Text describing this reasoning will be included in future 
documents to help ensure clarity.
    Comment #6: Some users stated that they either will not equip with 
GPS avionics or will not be flying in airspace that requires ADS-B. The 
Nebraska DoA stated that many pilots and users do not plan to equip 
aircraft with GPS and that instructors will still require students to 
learn VOR navigation.
    FAA Response: Pilots may continue to use VORs that remain in the 
MON or fly under Visual Flight Rules (VFR) in non-ADS-B airspace. 
Instructors will still teach VOR navigation.
    Comment #7: Operators and some aircraft and equipment manufacturers 
stated that they did not intend to equip with WAAS because (1) WAAS 
service is not provided in many parts of the world outside the United 
States, and (2) many air carrier aircraft are equipped with avionics 
that allow at least RNAV, if not some level of RNP, and they do not 
believe WAAS provides benefits commensurate with the added complexity 
and cost involved with equipage.
    FAA Response: WAAS avionics (Technical Standard Order (TSO)-C145/
146) with suitable other avionics, such as Flight Management Systems 
(FMS) support LPV and Lateral Navigation/Vertical Navigation (LNAV/
VNAV) terminal procedures and lower minima instrument approaches that 
are not available to users equipped with non-augmented GPS (TSO-C129 
and C196) avionics. Pilots may continue to use non-augmented GPS or 
other RNAV capabilities as described in FAA advisory circulars AC 90-
100, AC 90-101, AC 90-105, AC 90-107 and other directives.
    Comment #8: Federal Express stated that the FRN described 
implementation of PBN based on GPS and WAAS

[[Page 50422]]

backed up by a minimum network of VORs and DMEs, which it stated would 
require equipage of aircraft with avionics that is not offered by major 
airline airframe manufacturers.
    FAA Response: While the FAA intends to reduce the VOR 
infrastructure to a MON, it will maintain an optimized DME network to 
support RNAV operations throughout the NAS. In the NextGen timeframe, 
an optimized DME network could be used to support APNT.
    Comment #9: The DoD was concerned about discontinuation of service 
from all types of ground based navigation aids. The concept and 
planning described in the FRN does not contemplate discontinuation of 
service from all ground based navigation aids. It describes the 
considerations for determining the discontinuation of service by VOR 
ground based navigation aids. Where the VOR functionality is collocated 
with DME or DME and UHF azimuth equipment (which is the Tactical Air 
Navigation or TACAN), the FRN only addresses the VOR service and not 
these other services.
    FAA Response: The MON described in the FRN is a network of VORs 
only, and does not include TACAN. Retention of DMEs and the DME 
function provided via TACAN is desirable because of the large 
proportion of the air carrier fleet that uses DME/DME or DME/DME/
Inertial Reference Unit (IRU) for RNAV. Any national discontinuation of 
DME or TACAN service is separate from the VOR MON, not a part of this 
activity, and not contemplated in the near future.
    Comment #10: Some organizations (IATA, United Air Lines, FedEx, 
Honeywell, Thales, and A4A) expressed concern about the future of ILSs 
and other vertically guided approaches, in particular at 14 CFR Part 
139 airports serving air carriers.
    FAA Response: The FAA has no current plans to remove ILSs, but most 
new vertically guided approach requirements using Facilities and 
Equipment funding will be fulfilled with LPV approaches. ILS can 
continue to be approved under Airport Improvement Program (AIP) 
funding. While LPVs will receive increasing emphasis for projects 
funded under the AIP, the needs of users for ILS equipment will be 
considered in the determination of the types of approach navigation 
installed under the AIP. It is envisioned that many air carrier runways 
at major airports will continue to be supported by ILS (in addition to 
LPV). Additionally, the FAA plans to continue to develop LNAV/VNAV 
approaches, which can be flown by GPS-equipped aircraft with barometric 
vertical navigation and by WAAS-equipped aircraft to qualified runways 
used by air carrier aircraft. RNP approaches will be developed where 
beneficial, and GLS approaches will be developed as appropriate at 
airports with access to GBAS equipment.
APNT
    The FAA's NextGen Alternate PNT (APNT) program ensures that 
alternate PNT services will be available to support flight operations, 
maintain safety, minimize economic impacts from GPS outages within the 
NAS and support air transportation's timing needs. APNT will be an 
alternative for all users. Avionics equipage is a major consideration. 
APNT requirements will be met with the optimum use of existing 
avionics. The current plan is for APNT equipage to be optional.
    Comment #11: The airline industry voiced support for an increase in 
DME to provide additional coverage for DME-DME navigation provided by 
modern Flight Management Systems (FMS).
    FAA Response: The FAA concurs. Current planning is for 
implementation of the new DME sites beginning in 2014. The FAA goal is 
to have complete DME-DME coverage enroute at FL 180 and above 
throughout CONUS and in the terminal area of large airports in the 
CONUS.
    Comment #12: The airline industry was concerned about a statement 
in the FRN that seemed to indicate that WAAS was required for ADS-B.
    FAA Response: WAAS is not required for ADS-B. Other methods of 
meeting the performance requirements are being investigated. ADS-B 
implementation in international operations will require use of 
regionally or globally available services.
    Comment #13: IATA stated implementation of any new technology 
should be driven by coordinated operational requirements of 
stakeholders. The International Civil Aviation Organization PBN Manual 
(Document 9613) was cited by IATA in describing the steps that must be 
followed in implementing PBN, and states the FAA may not have followed 
the described process. IATA then related the plan described in the FRN 
to the ADS-B Out regulations at 14 CFR 91.225 and 91.227 and the 
implied SBAS mandate and provides comments on the implementation and 
the requirements that it states are very different from European 
requirements to obtain the same performance with simpler equipage. IATA 
states they do not support use of any SBAS systems such as WAAS and 
desires to be consulted on revision of the VOR MON and alternate 
positioning, navigation and timing and systems, such as eLORAN, Galileo 
and others. IATA does not support the use of LPV approaches as a 
universal solution and requires an adequate number of precision 
approaches be maintained to provide capacity without GNSS. IATA states 
GBAS and Baro VNAV approaches should be published to complement LPV 
approaches at airports used by international carriers. IATA does not 
want PBN levels to be specified that require augmentation unless they 
are operationally required.
    FAA Response: FAA will engage stakeholders via the working group in 
implementing the MON. PBN transition strategy is currently being 
developed within the FAA. The FAA will not mandate WAAS. PBN can be 
achieved by multiple means, such as DME/DME and ILS. GBAS is currently 
in the Research & Development phase.
    Comment #14: Boeing Commercial Airplanes was concerned about the 
interpretation text for the operational requirements for two 
independent systems (reference 14 CFR 121.349, 125.203, 129.17 and 
135.165). Specifically, they questioned the statement that the 
requirements for a second navigation system apply to the entire set of 
equipment needed to achieve the navigation capability, not just the 
individual components. They are concerned that this statement could be 
interpreted as requiring dual independent navigation computers. 
Additionally, they state that existing, certified multi-sensor 
navigation systems under AC 20-130A can meet the proposed policy 
requirements.
    FAA Response: The text does not imply the need for dual independent 
navigation computers. The text instead emphasizes the need for 
independence of the navigation systems and their components to ensure 
that there will be no potential single point of failure or event that 
could cause the loss of the ability to navigate along the intended 
route or proceed safely to a suitable diversion airport. The 
interpretation of this requirement as applied to an aircraft approved 
for multi-sensor navigation and equipped with a single FMS is that the 
aircraft must maintain an ability to navigate or proceed safely in the 
event that any one component of the navigation system fails, including 
the FMS. Retaining an FMS-independent VOR capability would satisfy the 
requirement, even as the NAS is transitioned to the MON. This 
interpretation corresponds to the advisory wording in AC 20-130A.

[[Page 50423]]

    Comment #15: The Maryland Aviation Administration (MAA) expressed 
concern about current GPS equipage rates.
    FAA Response: Though approximately 19 percent of all general 
aviation aircraft are equipped with aviation-qualified GPS, most 
aircraft that actually file IFR flight plans are typically equipped 
with GPS. Specifically, more than 72% of aircraft that filed at least 
two IFR flight plans in 2011 filed with an equipment code indicating 
they had IFR GPS receivers on board. Of aircraft that filed more than 
100 IFR flight plans in a year the rate was above 97%. While it may be 
the case that a significant number of aircraft flying VFR are not 
equipped with GPS, the purpose of the VOR system is to provide 
navigation for aircraft flying IFR, not VFR. VFR traffic is permitted 
to use hand-held and non-IFR certified GPS equipment for situational 
awareness as an aid to navigation and often use pilotage and dead 
reckoning navigation. While the VORs retained in the MON will support 
VFR aircraft operations, their purpose is clearly to support those 
aircraft operating under IFR.
    Comment #16: Two commenters (the Nebraska DoA and Thales) were 
concerned over the impact that a reduction in VORs would have on 
training and training requirements.
    FAA Response: The current training standards for the FAA emphasize 
VORs as the primary navigation source. The transition to NextGen will 
require that the FAA shift emphasis from VOR navigation to satellite-
based navigation by changing training syllabi and the PTS. However, 
some emphasis will need to remain on VOR and ILS to ensure that pilots 
can navigate using these systems in the event of a GPS outage. These 
considerations will be included in the FAA's plan for discontinuance of 
VORs. Additionally, transfer of FAA-owned VORs not selected to be in 
the MON to operation under non-Federal ownership for training may be 
considered on a case-by-case basis.
    Comment #17: The Nebraska DoA and Thales were also concerned with 
airport infrastructure requirements resulting from development of RNAV 
or RNP approaches.
    FAA Response: FAA airport infrastructure requirements resulting 
from instrument approaches are published in FAA Advisory Circular 150/
5300-13. Because airport infrastructure upgrades may be required for 
the attainment of lowest instrument approach minima, collaboration with 
local and state officials will be accomplished during the approach 
development process. For example, development of an LPV approach could 
not be accomplished if the required runway length were not available. 
However, if a decision was made in collaboration with local and state 
officials, to extend the runway, then an LPV could be reconsidered.
    Comment #18: United Air Lines and GE Aviation expressed concern on 
the use of GPS approach capability by air carriers at alternate 
airports.
    FAA Response: Current FAA policy allows operators of aircraft 
equipped with WAAS to plan for RNAV (GPS) approaches to the LNAV line 
of minima at their alternate. Furthermore, the FAA is currently 
investigating what requirements will be necessary to allow un-augmented 
GPS (TSO-C129/-C129a, TSO-C196/-C196a) equipped aircraft to plan for 
RNAV (GPS) or RNAV (RNP) approaches at alternate airports.
    Comment #19: Several commenters expressed concern that the 
navigation transition strategy as outlined in the FRN is indirectly 
requiring certain types of equipage, specifically GPS or WAAS equipage.
    FAA Response: The FAA is committed to the use of performance-based 
operations in the NAS. They remain the optimal way to both enable 
technological advances while maintaining safety, efficiency and 
consistency. Therefore, it is not the intention of the FAA to limit 
operational approvals to specific technologies or to force retrofit 
navigation solutions on current operators with legacy equipment. VOR 
navigation will continue to be a viable option for airspace users for 
the near future. Once the FAA completes implementation of the VOR MON, 
VOR navigation will still serve the NAS, albeit in a less robust 
fashion than today. Early publication of transition considerations and 
planning will allow users to consider long-term equipage strategies for 
their aircraft. Operators are encouraged to continue to seek approvals 
for the use of navigation equipment that was emphasized in the FRN, 
e.g. DME/DME/IRU, GPS, and WAAS. The FAA will continue to work with 
industry to advance new technologies not yet matured, e.g., GBAS and 
APNT. Additionally, the FAA will continue to work with our 
international partners on global strategies for multi-constellation/
multi-frequency GNSS solutions.
    Comment #20: AOPA and the National Business Aviation Association 
(NBAA) both expressed support for direct routing and avoiding excessive 
implementation of additional T and Q routes.
    FAA Response: In the NextGen environment, T and Q routes increase 
capacity and efficiency while maintaining safety by minimizing impact 
to air traffic control. T and Q routes allow controllers to safely 
manage air traffic during peak periods and to ensure predictable 
transitions between busy traffic areas. T and Q routes overlaid on 
existing airways defined by VORs could mitigate potential impacts to 
the discontinuance of VOR navigation services.
    Comment #21: Comments from military and general aviation expressed 
interest in participating in VOR discontinuation planning.
    FAA Response: As stated in the FRN, ``The FAA will convene a 
working group that will develop a candidate list of VORs for 
discontinuance using relevant operational, safety, cost and economic 
criteria. As part of the process, this working group will engage 
aviation industry stakeholders and other members of the public for 
input.'' Detailed planning for the implementation of the MON is still 
under development. As the program planning process is further 
developed, the FAA will solicit input from government and industry 
stakeholders before the VORs selected for the MON are finalized.
    Comment #22: Several commenters (MAA, Boeing Commercial Airplanes, 
United Air Lines, AOPA, Thales and DoD) indicated that an overall plan 
is necessary and requested more detail on the MON. MAA commented that 
without a national plan for discontinuation, the removal of specific 
VORs from service might be premature. They believed that several VORs 
in Maryland are currently planned for discontinuance and they suggested 
that the discontinuation of specific facilities should be considered on 
both a regional and national level using analysis to identify costs and 
benefits in a more holistic manner to make the consideration of 
facilities objective and consistent.
    FAA Response: The FAA has not developed a final list of VORs that 
will be included in the MON. The FAA is developing objective criteria, 
which will be applied consistently both nationally and regionally to 
help identify those VOR facilities that will remain operational. A 
specific overall national CONOPS and discontinuance plan are being 
developed to support this effort. The draft CONOPS and draft 
discontinuance plan will be presented to stakeholders, and the FAA will

[[Page 50424]]

engage stakeholders in the discontinuance process.
    Comment #23: Military and airline industry commenters expressed 
concern with the FAA plan to establish the VOR MON by January 1, 2020.
    FAA Response: This date coincides with the January 1, 2020 mandate 
for ADS-B equipage. Once aircraft are equipped with ADS-B, it is 
assumed that they will be equipped with GPS as well, since currently 
GPS is the only known position source that can satisfy the NIC/NAC/SIL 
requirements of ADS-B. At that time, the VOR MON will serve as the 
required GPS backup for non DME-DME equipped aircraft in the event of a 
GPS outage. By January 1, 2020, the VOR MON will provide sufficient VOR 
coverage to enable aircraft to fly VOR-to-VOR either through the GPS 
outage or to a safe landing.
    Comment #24: A number of operators, service providers and equipment 
manufacturers were concerned about the level of reliance on GPS 
expressed in the FRN in light of possible interference with the GPS 
service. Interference on a regular basis from government testing and 
training was specifically identified, as was possible widespread 
interference from licensed operators as well as unintentional 
interference from a variety of human and natural sources. There remains 
a concern among users that GPS is susceptible to interference and VORs 
should remain as a cost effective reliable means of navigation.
    FAA Response: U.S. National policy recognizes the vulnerability of 
GPS signals, from both human and natural sources, and requires 
operations reliant on GPS position, navigation, and timing (PNT) for 
safety, security, or significant economic benefit to have sufficient 
backups in place. The FAA has operated and will continue to operate 
GPS-independent systems to fulfill this requirement, such as ILS, DME, 
and VOR. As the NAS transitions to NextGen, there is also a requirement 
to move from conventional facility based navigation to point-to-point 
navigation using PBN, a role that the airways supported by VORs cannot 
support. The FAA will continue to operate a subset of the current VOR 
facilities in a MON to support those aircraft not equipped with GPS-
independent RNAV capability, while developing an RNAV-capable APNT 
system to fulfill this role in the future. DoD Interference with GPS: 
The FAA recognizes the need for DoD elements as part of their mission 
to operate and conduct training in a GPS-denied environment. Both the 
FAA and DoD are committed to working together to ensure that the DoD 
mission will not impact the FAA's mission to operate a safe and 
efficient NAS. DoD GPS interference testing is fully coordinated with 
the FAA and prior to testing, the FAA issues a Notice to Airmen (NOTAM) 
that describes the potential extent of interference and the timeframe 
in which it might occur. During testing the FAA maintains direct 
communications with DoD at all times and can have tests suspended in 
the event of any impact to NAS operations. Today, aircraft with non-GPS 
RNAV avionics are not impacted by this interference, and in the future, 
all APNT-equipped aircraft will similarly be unaffected.
    Comment #25: Comments were received relative to several specific 
VORs with reasons for their specific retention. In the case of the 
Wichita, KS VOR (ICT), it was stated that the facility is needed for 
testing and airworthiness demonstration of new manufactured aircraft by 
a number of companies in the area.
    FAA Response: While a VOR signal is necessary for this activity, it 
is not necessary that the service be provided by a FAA owned VOR, whose 
purpose under the MON will be to ensure safe operations in the event of 
a GPS outage. A non-Federal VOR, owned by an airport authority, state 
instrumentality or private entity could also perform this function. In 
cases where individuals/organizations have an interest in maintaining a 
specific VOR service, the VOR could be transferred to and operated 
under agreement with the FAA as a non-federal facility.
    Comment #26: Thales expressed a concern over how the VOR MON will 
support non-GPS aircraft and GPS aircraft during GPS interference if a 
key MON VOR is down for maintenance.
    FAA Response: In determining the VORs that will make up the MON, 
consideration will be given to the availability and continuity of 
navigation service expected from each facility. The VOR MON's purpose, 
a non-PBN backup in the event of a GPS outage, will be considered in 
making this determination. An element of this consideration will be the 
availability of non-GPS dependent surveillance services that would 
allow air traffic to provide services in the event of both a GPS and 
individual VOR service outage. Additionally, the equipage rate of IFR 
traffic with IFR GPS is significant and expected to be near 100% as we 
approach the year 2020 ADS-B mandate. While possible to fly IFR using 
the VOR MON, the increased distance of the VOR-only route as compared 
to using RNAV navigation will likely be highly undesirable. This will 
further drive GPS equipage.
    Comment #27: The DoD stated concern on the cost of transition 
versus benefits for their fleet of aircraft.
    FAA Response: The NAS' transition to NextGen is a national 
priority, in which the FAA plays an important role in concert with 
other Federal agencies and the aviation community. The transition to 
PBN as enabling capability for NextGen is a key part of the NGIP. 
Additionally, the considerations of the military in transitioning a 
14,600 aircraft fleet and operating practices to RNAV/RNP stated in 
comments to the public docket appear to include the notion that TACAN 
services from VORTAC facilities will be terminated when VOR service is 
discontinued. This is not the case. The military also desires the FAA 
to retain VOR and TACAN service for specific enroute and terminal 
locations and procedures as the military aircraft fleet equipage and 
operating procedures evolve.
    The FAA notes that there is historic precedent for the transition 
to a single national system--specifically the establishment of VORs and 
associated airways, DME, and ILS in the 1950s. At that time the 
military did not want to equip with VOR or ILS in tactical aircraft due 
to weight and space constraints, stating that Non-Directional Beacons 
(NDB) and four course ranges for enroute navigation and ground 
controlled approach (GCA) for landing was sufficient pending 
implementation of TACAN. The military also wanted to evolve to use 
TACAN because of weight/size and operational advantages over VOR and to 
include their implementation of DME, rather than the civil DME 
standard. The civil community, particularly airlines, wanted VOR for 
improved accuracy and usability over four course ranges and NDBs with 
ILS for approaches. In the end the NDBs and four course ranges were 
retained until military aircraft and operating practices transitioned 
to TACAN, the military DME standard was adopted for all DMEs and ILS 
was standardized for approaches, though the military continued GCA 
approaches, particularly for tactical aircraft.
    The transition to RNAV/RNP may be undertaken economically for 
military aviation by retaining TACAN as a system, discontinuing only 
specific facilities on an individual basis; incorporating military use 
considerations for identifying VOR service for discontinuation in 
enroute and terminal environments; designating special use airspace and 
other military usage features with RNAV references as well as TACAN or 
VOR rho/theta and

[[Page 50425]]

distance references; and retaining ILS at current sites with 
installation of new ILSs by military where needed in lieu of LP and 
LPV.
* * * * *

    Issued in Washington, DC, on August 14, 2012.
Lansine Toure,
Acting Manager, Navigation Programs.
[FR Doc. 2012-20464 Filed 8-20-12; 8:45 am]
BILLING CODE 4910-13-P


