Seeks Comments On Shift To RNAV, And RNP Navigation, LPV Approaches

The FAA has posted a plan to shift away from VOR navigation to a system using RNAV and RNP in the Federal Register, and is asking for public comments. The proposed transition of the U.S. National Airspace System (NAS) navigation infrastructure will enable performance-based navigation (PBN) as part of NextGen. The FAA plans to transition from defining airways, routes and procedures using VOR and other legacy NAVAIDs towards a NAS based on Area Navigation (RNAV) everywhere and Required Navigation Performance (RNP) where beneficial.

Such capabilities will be enabled largely by GPS and WAAS. The FAA says it plans to retain an optimized network of Distance Measuring Equipment (DME) stations and a minimum operational network (MON) of VOR stations to ensure safety and continuous operations for high and low altitude en route airspace over the conterminous US (CONUS) and terminal operations at the Core 30 airports. The FAA is also conducting research on Alternate Positioning, Navigation and Timing (APNT) solutions that would enable further reduction of VORs below the MON.

In addition, the FAA plans to satisfy any new requirements for Category I instrument operations with WAAS localizer performance with vertical guidance (LPV) procedures. A network of existing Instrument Landing Systems (ILS) would be sustained to provide alternative approach and landing capabilities to continue recovery and dispatch of aircraft during GPS outages.

This transition would be consistent with the FAA's NextGen Implementation Plan (NGIP), NAS Enterprise Architecture (EA), and other documentation.

FAA regulations addressing the operational requirements to carry navigation equipment in aircraft are set forth in 14 CFR parts 91, 121, 125, 129, and 135. Operators should be familiar with their specific requirements. Equipment is considered suitable if it has been demonstrated to provide the accuracy, integrity and reliability for the operation and the necessary radionavigation service is provided for the planned route of flight. For conventional ground-based routes and procedures, suitable equipment can be directly inferred from the type of procedure (e.g., a VOR receiver would be suitable for operation on a Jet Route).

Unaugmented GPS is capable of providing the accuracy and integrity required by the FAA's ADS-B Out regulations (14 CFR 91.225 and 91.227) that were effective August 31, 2010 and have a compliance date of January 1, 2020. However, at this time, WAAS augmentation is the only service that provides the 99.9 percent availability (equivalent to radar) needed for ADS-B. Operators that equip with other position sources, such as Receiver Autonomous Integrity Monitoring (RAIM) based GPS, may experience periods of unavailability that limit their access to the airspace. The FAA expects that positioning from GPS combined with future positioning sources such as the L5 GPS signal and/or other GNSS signals, and GPS tightly integrated with inertial navigation systems, will also provide 99.9 percent availability.

The FAA is conducting research on APNT for service beyond 2020. The FAA will consider, in consultation with the users, whether the MON may be further reduced after an APNT solution is selected and available. The FAA is also evaluating the use of the Ground-Based Augmentation System (GBAS) in addition to ILS to provide Category II/III approach services.

Interested parties are invited to provide comments on the proposal. Comments that provide the factual basis supporting the views and suggestions presented would be particularly helpful in developing reasoned decisions on the proposal.

Comments must be received on or before March 7, 2012.

FMI: http://www.faa.gov/nextgen