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AOPA raises concerns about FAA's transition plan for GPSAOPA raises concerns about FAA's transition plan for GPS

Mr. Michael Harrison
Federal Aviation Administration
800 Independence Avenue, SW
Washington, DC 20591

Re: Satellite Navigation Transition

Dear Mr. Harrison,

On behalf of over 384,000 members, the Aircraft Owners and Pilots Association (AOPA) submit the following comments in response to the draft Navigation and Landing Transition Strategy dated June 5, 2002. As requested, we have reviewed the strategy and submit the following insights.

It is disconcerting to AOPA that major decisions on the nation's navigation architecture and infrastructure are about to be made in less than 45 days. We understand that the Department of Transportation (DOT) has met with the modes to discuss issues of Global Positioning System (GPS) interference since September 2001 when a report by the VOLPE research center was released identifying GPS interference as an issue. From our perspective, aviation industry involvement began for the first time five weeks ago, not nearly enough time for adequate information collection, validation, and development of feedback. Additionally the discussion about decommissioning today's navigation infrastructure generates many concerns at AOPA. Should the focus remain on GPS and the changes necessary to mitigate interference, our concerns diminish.

AOPA has three primary concerns in regards to this transition strategy. First, the transition strategy fails to provide adequate time for a transition of all aircraft to satellite navigation. Additionally, despite Federal Aviation Administration (FAA) assertion, the infrastructure for the transition to satellite navigation (SATNAV) is not currently in place, nor will it be soon. This issue is compounded by the aggressive decommissioning schedule proposed for ground-based navigational aids. Lastly, the government needs to establish a visible, multi-agency GPS interference elimination "go team" with proven experience at identifying, searching, and terminating GPS interference.

AOPA's historical position on incentives for transition to SATNAV

Before discussing details of the transition strategy, it is important to understand the perspective from which these comments are written. For many years AOPA has consistently worked with the FAA advocating for incentives years before any changes in today's navigation infrastructure begins. Those incentives include:

  • Instrument landing system (ILS)-like approaches (known as GNSS landing system, or GLS), including the same minima as ILS but using the Wide Area Augmentation System (WAAS).
  • GLS approaches at every public airport runway end. While AOPA is aware that airport infrastructure and obstacles impact approach quality, satellite navigation and WAAS should enable every airport to have GLS approaches where the infrastructure is present and/or the obstacles removed.
  • Instrument flight rules (IFR) and visual flight rules (VFR) GPS routes through terminal and special-use airspace. This service enables increased access for general aviation pilots to transition airspace in an en-route fashion with increased efficiency.
  • Affordable navigation database updates.
  • Operational approval of portable GPS receivers for VFR operations including navigation in Class B and C airspace areas. If these portable systems include all information, approval to use the systems in lieu of today's combination of aeronautical charts and VHF omnirange (VOR).

AOPA challenges the current status of WAAS as outlined in the transition strategy

From the end-user perspective, WAAS is not available for IFR and will not be until December 2003, less than four years from fiscal year 2007 when the first VOR services are proposed for termination. A four-year transition to satellite navigation is unacceptable to general aviation. What is acceptable depends on the availability and quality of the satellite navigation incentives. AOPA disagrees with the assertion that major incentives will develop in the next 18 months. No GLS approaches (CAT I ILS minimums) will exist using WAAS without dual frequency receivers sometime after 2010. This change to the WAAS program may negatively impact transition incentives for general aviation. To what extent is unknown at this time, and it may not be known for several years of LPV approach availability. Re-equipage to dual-frequency GPS requires additional time, a factor not mentioned in the strategy for ILS decommissioning.

Once the incentives listed below exist or are nearing completion, AOPA believes that general aviation will begin the transition to satellite navigation. Until such a time, the use of today's ground-based navigation aids and unaugmented GPS to supplement VOR continues.

  1. WAAS approaches with LPV minima to every airport. Where an existing GPS or ground-based navaid approach exists at a runway end, every WAAS approach must have lower visibility and ceiling minimums. When WAAS becomes available for IFR, there will be less than 10 approaches that are optimized for WAAS (called LPV). At 500 approaches per year, it will take at least eight years to build out this critical piece of infrastructure. In order to minimize the transition time to satellite navigation, the FAA must accelerate the implementation of LPV. Understand that no WAAS-based approaches exist in the NAS now, so the membership cannot evaluate/plan their investment decisions and use of WAAS in lieu of ground-based navaid approaches or unaugmented GPS.
  2. Charted IFR and VFR RNAV routes through all Class B and many special-use airspace areas. There are no milestones/dates when published RNAV routes will be charted. The FAA has no written plan to implement this incentive.
  3. Response time to GPS interference events by a (yet to be formed) multi-agency GPS interference elimination "go team" has been demonstrated to be under six hours.
  4. Operational approval of WAAS receivers in general aviation aircraft for IFR operations in all phases of flight, including random-route RNAV in non-radar airspace.
  5. Operational approval of portable GPS receivers for VFR operations including navigation in Class B and C airspace areas. If these portable systems include all necessary information, approval to use the systems in lieu of today's combination of charts and portable VOR should be included.
  6. WAAS navigation equipment capable of LPV approaches is sold by at least three manufacturers and available to aircraft owners in avionics shops. Currently are no WAAS avionics certified, or available for purchase by general aviation aircraft owners. Some manufacturers indicate their GPS receivers are upgradeable to LPV capability. Others indicate they will introduce new products in the future. However, they are wisely waiting on the FAA's successful deployment of the WAAS prior to launching new avionics capabilities.
  7. Before any ILS is decommissioned, there needs to be an approach to the same runway with equal or better ceiling and visibility minimums usable with
  8. GPS/WAAS equipment as certified by the TSO C 145/146 version current the date of this letter.
  9. Ensure there is sufficient VOR coverage and secondary surveillance radar for single-engine GA aircraft to continue to take off, fly en route, and land under IMC during a GPS interference event.

Additional observations about the current status of satellite navigation in the National Airspace System

In addition to the concerns about WAAS and the lack of incentives available to general aviation, AOPA is concerned about the transition strategy's premise that the change in the ground infrastructure services can begin incomplete satellite navigation infrastructure, a poorly performing information dissemination process, and a fundamental lack of multi-departmental coordination of GPS interference events.

First of all, the FAA must understand that aircraft owners could consider investment in WAAS navigation equipment a high risk without a third geostationary WAAS satellite in space and operating. Loss of the WAAS system will severely impact general aviation operations, and the users must be given time to develop confidence in the system's availability and reliability. The threat of losing WAAS coverage (and receiver investment expenses) over major portions of the United States with a single satellite loss may be an issue to many general aviation pilots.

GPS interference information is disseminated poorly. If a notam is issued for GPS interference, it is sometimes issued as a local notam, reducing the broadcast to a very small geographic area. Pilots are unable to obtain local notam information prior to departure on most cross-country flights. User groups such as AOPA seldom, if ever, are called upon to utilize resources available to quickly and accurately broadcast such information to users.

The satellite navigation information dissemination system needs to be fixed. This includes broad notam dissemination, immediate notification to news media, flight service, and user organizations who can then re-broadcast the information quickly to many users. This improved system must be utilized several times before users can increase confidence in GPS interference notification. In the past, there have been extremely poor response times to interference events. The federal government must develop a multi-agency GPS interference elimination "go team" capable of eliminating interference extremely quickly.

AOPA position on the transition strategy

Given the current status of incentive availability and the additional issues identified above, we strongly object to any decision to decommission ground-based navaids as discussed in the transition strategy. AOPA supports the continuation of deadline-driven discussions/decisions on the initial operational capability of WAAS and the next steps to achieving GLS. Additional deadlines and milestones are also required for the development and publication of operational approvals to use WAAS, instrument approach procedures, and RNAV routes, and the development of incentives for manufacturers to use low-cost navigation databases.

AOPA recommends that the FAA immediately establish timelines/milestones for the improved response to GPS interference impacting civil aviation operations. The FAA must have in place all necessary memorandums and agreements, and interagency issues resolved and in place, before proclaiming that the ability to mitigate GPS interference exists. If general aviation is expected to transition to satellite navigation, the FAA should focus on maintaining confidence in the government's ability to identify, locate, and eliminate GPS interference in under six hours. This "anti GPS" team should be highly visible and publicly known. The presence of this team should be used as a deterrent itself.

While some parts of the document are well thought out, some parts are still clearly notional. For example, the strategy includes some operational contingencies, which generates many questions. In what airspace, and under what condition, is a backup capability required on board an aircraft? If required, does it need to be installed, or can it be portable? How will the use of temporary flight restrictions be effectively used in the manner prescribed? Will VFR operations navigating without GPS be impacted? If so, how? It is AOPA's position that continued discussion needs to occur before AOPA supports the further development or use of this strategy.

AOPA comments on loran

AOPA agrees with the FAA observation that loran is the best theoretical backup to satellite navigation. AOPA members continue to use loran in its present state (loran-C). It is AOPA's understanding that to utilize loran for a backup under IFR including approaches, that today's loran-C receivers will be rendered useless. AOPA encourages the FAA to continue researching loran and other systems that enable area navigation during GPS interference. This capability increases navigation capabilities and itself acts as a deterrent against intentionally jamming of GPS navigation equipment.

AOPA provides the above comments as they relate to the draft Navigation and Landing Transition Strategy of June 5, 2002. It is our desire to continue to work with the FAA and DOT as key infrastructure decisions are made. However, AOPA remains committed to general aviation, objecting to timelines and strategies that negatively impact operations in the United States. We look forward to continued dialogue during this difficult but important process.


Randy Kenagy
Director, Advanced Technology

June 11, 2002

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