An ILS that Requires GPS

You can still fly IFR in the U.S. without an IFR-approved GNSS (i.e., GPS), but being “slant G” (/G in the soon-to-be obsolete FAA domestic flight plan format) increasingly offers advantages, even if you fly only conventional procedures based on ground navaids. And sometimes an IFR-approved GNSS is required to fly even an ILS.

Consider the ILS Z OR LOC Z RWY 16R approach at Reno/Tahoe International Airport (KRNO). This procedure is not an Authorization Required approach–RNP doesn’t appear in the title, and you won’t find that restrictive note on the chart. (For more information about RNP procedures, see RNP Procedures and Typical Part 91 Pilots.)

KRNO-ILSorLOCZRwy16R

But the equipment required notes for this ILS approach include “RNAV-1 GPS required.”

KRNO-ILSorLOCZRwy16R-notes
A review of the plan view and missed approach track show why GPS is necessary to fly this procedure.

KRNO-ILSorLOCZRwy16R-Plan

First, you need GPS to fly transitions from most of initial fixes, which are RNAV waypoints marked by a star symbol.

RNAV-Waypoint-Symbol

Only LIBGE, directly north of the runway, is a non-RNAV IAF.

For example, HOBOA, KLOCK, BELBE, and WINRZ are all RNAV waypoints that serve as IAFs or IFs. Now, NORCAL Approach might provide vectors to the final approach course, but if you want to fly this procedure you should be prepared for a clearance direct to one of those fixes (see Avoiding the Vectors-to-Final Scramble).

Note also that entire missed approach track requires use of GNSS.

Two of the transitions are of special note. The “arcs” that begin at ZONBI and SLABS are radius-to-fix (RF) legs that are part of the transitions that begin at HOBOA and KLOCK. Each of those fixes is distinguished by the notes “RNP-1 GPS REQD” and “RF REQD.”

The first note means that your GPS must meet the RNP 1 standard, which is used for terminal procedures such as SIDs and STARs, the initial phases of approaches, and missed-approach segments. (For more information about RNP, see RNP Procedures and Typical Part 91 Pilots.)

Until recently, RF legs were included only in Authorization Required (AR) procedures. But as I explained in Garmin GTN Avionics and RF Legs, certain RF legs are now available if you have an appropriate GNSS navigator, updated system software, an electronic HSI, and other equipment. Some limitations on flying such RFs also apply, as described in that earlier post.

Suppose that you choose the less intimidating ILS X or LOC X RWY 16R to the same runway. A review of the notes and the plan view shows that even this conventional-looking ILS also requires RNAV 1 GPS, both to fly the transition from WINRZ and the missed approach track.

KRNO-ILSorLOCXRwy16R.jpg

 

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FAA Proposes Cuts to Circling Approach Minimums

The FAA has announced the early stages of plan to evaluate and then cut the number of circling minimums published for instrument approaches. According to a notice in the Federal Register on October 6, 2017:

In early 2015, the FAA requested the RTCA’s Tactical Operations Committee (TOC) with providing feedback and recommendations on criteria and processes for cancelling instrument flight procedures. Among the many recommendations provided by the TOC were criteria on how to identify circling procedures that would qualify as candidates for cancellation. As of the beginning of 2017, there are approximately 12,000 IAPs in publication, and there were nearly 10,600 circling lines of minima. Circling procedures account for approximately one-third of all lines of minima in the NAS.

In its continued effort to right-size the NAS through optimization and elimination of redundant and unnecessary IAPs, the FAA proposes the following criteria to guide the identification and selection of appropriate circling procedures to be considered for cancellation…

Proposed Policy

All circling procedures will continue to be reviewed through the established IAP periodic review process.As part of that review process, the FAA is proposing that each circling procedure would be evaluated against the following questions:

—Is this the only IAP at the airport?

—Is this procedure a designated MON airport procedure?

—If multiple IAPs serve a single runway end, is this the lowest circling minima for that runway? Note: If the RNAV circling minima is not the lowest, but is within 50′ of the lowest, the FAA would give the RNAV preference.

—Would cancellation result in removal of circling minima from all conventional NAVAID procedures at an airport? Note: If circling minima exists for multiple Conventional NAVAID procedures, preference would be to retain ILS circling minima.

—Would cancellation result in all circling minima being removed from all airports within 20 NMs?

—Will removal eliminate lowest landing minima to an individual runway?

The following questions are applicable only to circling-only procedures:

—Does this circling-only procedure exist because of high terrain or an obstacle that makes a straight-in procedure unfeasible or which would result in the straight-in minimums being higher than the circling minima?

—Is this circling-only procedure (1) at an airport where not all runway ends have a straight-in IAP, and (2) does it have a Final Approach Course not aligned within 45 degrees of a runway which has a straight-in IAP?

Further consideration for cancellation under this policy would be terminated if any of the aforementioned questions are answered in the affirmative. If all questions are answered in the negative, the procedure would be processed as described in the following paragraph.

FAA Changing Notes on Instrument Charts

The FAA is gradually changing notes on instrument procedure charts (SIDs, STARs, and approaches) to consolidate and clarify equipment required and PBN-related information.

AOPA has published a detailed summary with background on the changes here.

The AOPA summary also includes tables that can help pilots who use Garmin equipment understand the capabilities of the avionics installed in their aircraft.

 

FAA Releases List of VORs to be Shut Down

FAA has published a list of 308 VORs that it plans to shut down in phases by 2025. The notice in the Federal Register appeared on July 26, 2016. The notice includes a list of VORs that the FAA wants to decommission.

This document provides the discontinuance selection criteria and candidate list of VOR Navigational Aids (NAVAIDs) targeted for discontinuance as part of the VOR MON Implementation Program and United States (U.S.) National Airspace System (NAS) Efficient Streamline Services Initiative. Additionally, this policy addresses the regulatory processes the FAA plans to follow to discontinue VORs.

For background on the FAA’s plans, see Latest Info on VOR Shutdowns here at BruceAir. Note that under this plan, only about one-third of the existing network of VORs will be decommissioned.

According to the FAA notice:

The following criteria were used by the FAA to determine which VORs would be retained as a part of the MON:

— Retain VORs to perform Instrument Landing System (ILS), Localizer (LOC), or VOR approaches supporting MON airports at suitable destinations within 100 NM of any location within the CONUS. Selected approaches would not require Automatic Direction Finder (ADF), Distance Measuring Equipment (DME), Radar, or GPS.Show citation box

— Retain VORs to support international oceanic arrival routes.

— Retain VORs to provide coverage at and above 5,000 ft AGL.

— Retain most VORs in the Western U.S. Mountainous Area (WUSMA), specifically those anchoring Victor airways through high elevation terrain.

— Retain VORs required for military use.

— VORs outside of the CONUS were not considered for discontinuance under the VOR MON Implementation Program.

The following considerations were used to supplement the VOR MON criteria above:

— Only FAA owned/operated VORs were considered for discontinuance.

— Co-located DME and Tactical Air Navigation (TACAN) systems will generally be retained when the VOR service is terminated.

— Co-located communication services relocated or reconfigured to continue transmitting their services.

According to the FAA notice:

The FAA remains committed to the plan to retain an optimized network of VOR NAVAIDs. The MON will enable pilots to revert from Performance Based Navigation (PBN) to conventional navigation for approach, terminal and en route operations in the event of a GPS outage…

The VOR MON is designed to enable aircraft, having lost Global Navigation Satellite System (GNSS) service, to revert to conventional navigation procedures. The VOR MON is further designed to allow aircraft to proceed to a MON airport where an ILS or VOR approach procedure can be flown without the necessity of GPS, DME, ADF, or Surveillance. Of course, any airport with a suitable instrument approach may be used for landing, but the VOR MON assures that at least one airport will be within 100 NM.

Use of IFR GPS on Conventional Approaches

FAA has published an update to the AIM, effective 26 May 2016, and it includes a big change if you have an IFR-approved GPS [i.e., a “suitable navigation system” as defined in AC 20-138 and AIM 1-2-3 (b).]

Now, if you fly a conventional approach based on a VOR or NDB (but not a localizer), you can fly the procedure entirely with the GPS, provided you can monitor (using a separate CDI or a bearing pointer) the VOR or NDB facility specified for the approach.

The new language is in section 1−2−3. Use of Suitable Area Navigation (RNAV) Systems on Conventional Procedures and Routes.

The summary of changes to this AIM update notes that:

This change allows for the use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure (IAP) based on a VOR, TACAN, or NDB signal. The underlying NAVAID must be operational and monitored for the final segment course alignment.

The new text in the AIM is in paragraph 5 of AIM 1-2-3:

5. Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.

This change is the result of a discussion at the Aeronautical Charting Forum in 2014.

Garmin GTN Avionics and RF Legs

The release of updated operating software for Garmin GTN-series avionics brings new capabilities to many typical general aviation pilots who fly under IFR. One of the new features is the ability to fly curved radius-to-fix (RF) legs on some instrument approaches.

image.png

Until recently, RF legs were published only on so-called RNP procedures with authorization required (AR) restrictions (for more information, see AIM 5−4−18: RNP AR Instrument Approach Procedures). But FAA has started publishing some approaches with RF legs (like the example above) that are not designated as RNP AR procedures. And, with some limitations, pilots who fly aircraft equipped with GTN-series avionics should be able to fly the RF legs used as transitions/feeder routes on those approaches. (Note that so far, these approaches don’t require RF capability–conventional transitions/feeder routes and/or radar vectors are also available.)

For more information about RF legs, see RNP Procedures and Typical Part 91 Pilots and Garmin Radius to Fix Leg Project Report here at BruceAir. For additional background on GPS navigation and RNP procedures, see also Updated AC 90-105A.

The revised STC for the GTN series (document 190-01007-A5) notes that:

GPS/SBAS TSO-C146c Class 3 Operation
…The Garmin GNSS navigation system complies with the equipment requirements of AC 90-105 and meets the equipment performance and functional requirements to conduct RNP terminal departure and arrival procedures and RNP approach procedures including procedures with RF legs subject to the limitations herein [emphasis added].

Sections 2.12 RF Legs and 2.13.1 RNP 1.0 RF Leg Types of the STC add the following information:

2.12 RF Legs
This STC does not grant operational approval for RF leg navigation for those operators requiring operational approval. Additional FAA approval may be required for those aircraft intending to use the GTN as a means to provide RNP 1 navigation in accordance with FAA Advisory Circular AC 90-105. [Note that per AC 90-105A, domestic Part 91 operations do not require additional approval–only Part 91 subpart K operations and commercial operations need LOAs or the equivalent FAA approval.]

The following limitations apply to procedures with RF legs:

  • Aircraft is limited to 180 KIAS while on the RF leg
  • RF legs are limited to RNP 1 procedures. RNP AR and RNP <1 are not approved
  • Primary navigation guidance on RF legs must be shown on an EHSI indicator with auto-slew capability turned ON
  • GTN Moving Map, EHSI Map, or Distance to Next Waypoint information must be displayed to the pilot during the RF leg when flying without the aid of the autopilot or flight director.
  • The active waypoint must be displayed in the pilot’s primary field of view…

2.13.1 RNP 1.0 RF Leg Types
AC 90-105 states that procedures with RF legs must be flown using either a flight director or coupled to the autopilot.

This STC has demonstrated acceptable crew workload and Flight Technical Error for hand flown procedures with RF legs when the GTN installation complies with limitation set forth in Section 2.12 of this document. It is recommended to couple the autopilot for RF procedures, if available, but it is not required to do so. See section 4.5 of this manual to determine if this capability is supported in this installation.

At present, only a few non-AR approaches with RF legs meet the criteria in the STC and AC 90-105A. But RF legs could become more common on “standard” procedures to provide paths that offer better noise abatement, reduce airspace conflicts, and improve ATC efficiency, and pilots flying with GTN avionics (or similar navigators offered by other manufacturers) will be able to fly those procedures.

Latest Update on VOR Decommissioning Program

The latest update from FAA on its plans to decommission VORs includes the following details:

  • Decommission approximately 30% (308) of the current 957 VORs by 2025
  • 74 VORs will be shut down during phase 1 (FY2016 through FY2020)
  • Another 234 VORs will be decommissioned during phase 2 (FY2021 – FY2025)
  • Of the 308 VORs to be shut down, 15 will be in the West, 162 in the central U.S., and 131 in the East.
  • 649 VORs will remain in operation after 2025, forming the minimum operational network (MON).

The goals established for the MON include allowing pilots to:

  • Revert from PBN to conventional navigation in the event of a Global Positioning System (GPS) outage;
  • Tune and identify a VOR at an altitude of 5,000 feet or higher;
  • Navigate using VOR procedures through a GPS outage area;
  • Navigate to a MON airport within 100 nautical miles to fly an Instrument Landing System (ILS) or VOR instrument approach without Distance Measuring Equipment (DME), Automatic Direction Finder (ADF), surveillance, or GPS; and
  • Navigate along VOR Airways especially in mountainous terrain where surveillance services are not available and Minimum En Route Altitudes (MEAs) offer lower altitude selection for options in icing conditions.

Progress will be slow initially. Only 5 VORs are to be shut down by September 2016. Another 4 navaids will be decommissioned by September 2017, followed by 4 more through September 2018. In 2019, FAA plans to shut down an additional 25 VORs, followed by 36 more in 2020.

Phase 2 begins in FY2021. A total of 234 VORs will be shut down through 2025.

You can read more details about the MON plan in the minutes of the 15-02 meeting of the Aeronautical Charting Forum.