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.

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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.

Updated AC 90-105A

FAA has published AC 90-105A – Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace (PDF available at the link).

AC90-105A

 

This update to the previous edition (published in 2009) contains many important changes for pilots who use GPS to navigate under IFR.

FAA is gradually adopting the concept of performance based navigation (PBN), which includes the old systems of area navigation (RNAV) and refines details of required navigation performance (RNP). For more details about these standards, see AIM Section 2. Performance−Based Navigation (PBN) and Area Navigation (RNAV).

Changes to Vectors-to-Final in Garmin GTN System 6.x

Garmin has released updated system software (version 6.11) for the GTN series of navigators. The software includes several new features. One of the changes, at least for day-to-day operations for typical general aviation pilots, involves the behavior of the vectors-to-final option (VTF) available when loading an approach.

To learn about and practice using the new features in GTN system 6.x, download the latest version of the free GTN 750 PC Trainer Lite from Garmin. The download includes updated manuals (PDFs) for the GTN series avionics that describe the new features in version 6.x.

The updated Pilot’s Guide for the new system software notes that “all waypoints along the final approach course, including waypoints before the FAF, are included in the flight plan.”

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As I noted in Avoiding the Vectors-to-Final Scramble, current versions of the system software for Garmin GNS and GTN units remove all fixes except the FAF and the MAP when you choose VTF:

When you load an approach into your IFR GPS box and choose Vectors-to-Final, the computer typically erases all fixes except the FAF and the MAP, making the snazzy moving map far less useful as an aide to situational awareness. Vectors-to-Final also may lead to a frenzy of knob turning and button pushing if ATC unexpectedly clears you to an IAF or IF instead of setting you up on a heading to intercept the magic magenta extended centerline that Vectors-to-Final draws on your screen.

A note in AIM 5-4-6 Approach Clearance recognizes this issue:

Selection of “Vectors-to-Final” or “Vectors” option for an instrument approach may prevent approach fixes located outside of the FAF from being loaded into an RNAV system. Therefore, the selection of these options is discouraged due to increased workload for pilots to reprogram the navigation system. (AIM 5-4-6)

For that reason, like many instructors, I’ve long recommended against using VTF, especially because ATC can clear an RNAV-capable aircraft direct to an IF or to a fix between the IF and the FAF on any approach (again, see AIM 5-4-6).

For more information, see also Flying Instrument Approaches without Activating the Approach here at my blog.

The change in behavior in GTN units updated to system 6.x may change that recommendation, at least when flying some approaches.

Example: Flying the New VTF

Consider the RNAV (GPS) Y RWY 16R approach at Paine Field (KPAE) north of Seattle, home of the Boeing wide-body aircraft factory that produces the 747, 767, 777, and 787 models. It’s a typical RNAV approach.

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If you fly the approach with the current system software for a Garmin GNS or GTN navigator, selecting the VTF option removes all of the fixes except for ITIPE (the FAF) and RW16R (the MAP). The map shows a magenta line extending from the MAP, through the FAF, and out along the final approach course north of the runway. If ATC clears you to EYWOK (an IF/IAF), you must reload the procedure and choose EYWOK as the transition (or ask for a new clearance).

If you choose VTF in an updated GTN navigator, however, the new system software includes all of the fixes along the final approach course, from EYWOK to the MAP at the runway threshold. The FAF, in this case ITIPE, becomes the active waypoint in your flight plan.

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And the map shows a magenta line extending from ITIPE out to EYWOK, providing a reference as ATC vectors you to intercept the final approach course.

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At this point, I’m still waiting for Garmin to release the new GTN system software and have it installed on my GTN 750. But my tests with the Garmin training software suggest that VTF may become a useful feature when flying some approaches.

If you’re flying with current system software or with a GNS-series unit such as GNS 530 or GNS 430, however, you should follow the recommendation in the AIM and in Avoiding the Vectors-to-Final Scramble to help you stay ahead of the airplane—and your avionics–when flying approaches.

For more information, see also Flying Instrument Approaches without Activating the Approach here at my blog.

Changes to Flight Plans with Procedures in GTN System Software 6.x

Garmin has released updated system software (version 6.11) for the GTN series of navigators. The software includes several new features. One of the most important changes, at least for day-to-day operations for typical general aviation pilots, is how loading (or activating procedures) affects departure and destination airports in flight plans (routes).

To learn about and practice using the new features, download the latest version of the free GTN 750 PC Trainer Lite from Garmin. The download includes updated manuals (PDFs) for the GTN series avionics that describe the new features in version 6.x.

I have experimented with how the new system software in the free GTN 750 PC Trainer Lite available from Garmin, and the following examples illustrate the changes and offer suggestions to help you adapt your personal techniques for using a GTN-series navigator in the cockpit. In particular, I offer suggestions for displaying information about your destination airport (frequencies, current weather, and so forth).

To learn about the new ad-hoc hold feature in the updated software, see Flying Ad-Hoc Holds with a GTN 750 here at my blog.

Basics of the Change

First, here’s a note in the updated Pilot’s Guide for the GTN 750 that describes how software version 6.x changes flight plans (routes) when you load an approach (or, it turns out, a departure procedure).

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Now let’s look at how this change affects when and how you load and fly a typical instrument approach.

A Typical IFR Flight Plan

Suppose you plan to fly from Boeing Field (KBFI) in Seattle, WA to Spokane International Airport (KGEG) in eastern Washington. Here’s a route across the Cascades that I often fly in my normally aspirated Beechcraft A36.

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Note that the first and last waypoints in the flight plan are the departure airport (KBFI) and destination (KGEG). ATC typically assigns a SID when departing Boeing Field. When runway 13R is in use for IFR departures, your clearance includes the KENT7 (or the current version) SID, which you load as follows.

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Note that after you load the departure, KBFI no longer appears as a waypoint in your current flight plan. The first waypoint in the flight plan is now the runway ((RW13R), which is the first fix in the KENT7 SID. The IDs of the departure and destination airports, however, remain in the title of the Active Flight Plan.

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Here’s the first tip. If you use your GTN navigator to retrieve frequencies and other information about your departure airport, collect that data before you load a departure procedure.

Now assume that you have departed KBFI, followed the SID and ATC vectors to join V2, and proceeded to a point west of Spokane where you are preparing for the arrival and approach at KGEG, say the RNAV (GPS) RWY 21 Y approach.

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Given that you’re approaching KGEG from the west, ZOOMR is good fix to choose, at least initially, as the transition for the approach. ATC will probably provide vectors, but with all the fixes from the west now in the flight plan, it’s easy to accept a clearance direct to any of the fixes or legs along the path to the final approach segment.

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Notice that after you load the approach, the GTN removes KGEG from your active flight plan—unless the active leg of your flight plan includes the airport. Versions of the system software prior to 6.x always added the approach name and fixes for an approach below the destination airport.

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A Logical Change?

The change in behavior in version 6.x may disrupt your habits at first. But it also may reduce the potential for errors when you load and fly an approach (or DP) under typical circumstances.

The new behavior provides a seamless transition from waypoints in en route section of your flight plan to fixes in an approach. You no longer have to scroll below the destination airport in the active flight plan list to select an initial fix or to activate a leg of the approach you’ve loaded into the GTN.

A Change in Tactics?

The new behavior described above may lead you to change your basic technique for loading an approach.

I have long advocated loading procedures as early as possible—even before taking off if the destination is nearby—to reduce your workload during busy phases of flight. The new behavior in GTN software version 6.x, however, suggests a change in tactics, at least under some circumstances.

If you can determine well in advance which approach you prefer to fly—in-cockpit weather can give you an early alert about which runway is likely to be in use long before you can receive the ATIS or AWOS (that is, the one-minute weather at a non-towered airport)—then loading the approach you prefer or reasonably expect to fly is still a good idea. Just take a moment before you load the procedure to retrieve and note frequencies and other details about your destination airport from the GTN.

Pilots arriving or departing an uncontrolled airport that has automated weather broadcast capability (ASOS/AWSS/AWOS) should monitor the broadcast frequency, advise the controller that they have the “one−minute weather” and state intentions prior to operating within the Class B, Class C, Class D, or Class E surface areas. (AIM 4-4-6)

ONE-MINUTE WEATHER− The most recent one minute updated weather broadcast received by a pilot from an uncontrolled airport ASOS/AWSS/AWOS. (P/C Glossary)

If you prefer to wait until you are closer to the airport, or if ATC clears you direct to the airport or issues vectors before initiating an approach clearance, you can delay loading the approach.

If you wait until the active leg of your flight plan includes the destination airport, the GTN adds the approach below the destination airport, just as it did prior to version 6.x.

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Or, as shown below, you can load a procedure early and then add the destination airport to the bottom of your current flight plan, so that the airport is still available as a reference and to provide easy access to the information about the airport in the GTN’s database. Here I’ve added KGEG below GANGS, the MAHP for the RNAV (GPS) RWY 21 Y approach. It’s easy, as before version 6.x, to touch the airport ID and then select Waypoint Info.

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Add an Alternate?

The change in version 6.x also simplifies adding an alternate to your flight plan.

Suppose the weather at KGEG is close to minimums as you begin your arrival. Adding an alternate airport to your flight plan before you miss the approach could reduce your workload during a critical phase of flight.

Here I’ve added Walla Walla, (KALW) as my alternate after the MAHP at GANGS.

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Now I can quickly retrieve information about KALW and even load an approach as soon as I get a new clearance from ATC.

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This technique would also be handy during training flights, when you fly several approaches, either to the same airport or close-by fields.

Other Methods for Retrieving Airport Information

If you prefer not to fuss with the way version 6.x handles airports in flight plans that include procedures, you can still retrieve information about airports from the GTN’s database, even if your departure and destination airports are no longer in your active flight plan.

For example, touch the map, scroll to display an airport, and touch an airport symbol. Touch Waypoint Info to display details (frequencies, current weather, runways, NOTAMs, and so forth) about the airport.

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You can also use the Nearest Airport feature (available from the Home screen) to gain quick access to details about your destination—provided you’re not too far away.

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Or you can use the various search option in the GTN to find an airport and retrieve information about it.

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More to Come

I’ll have more to say about the updated system software after I’ve had it installed in my airplane and explored the new features on test flights. Stay tuned.

List of Next VORs to be Decommisioned

FAA has published a list of the next VORs to be decommissioned as part of its plan to establish a minimum operational network (MON) of the ground-based navigation aids. The list is part of a news item at AOPA that explains the process.

Most of the 35 VORs on this list are in the eastern two-thirds of the continental U.S. Only one, ECA, is in the West, near Stockton, CA.

You can find more background the FAA’s plan to decommission VORs  at BruceAir, here.

 

New Edition of Instrument Procedures Handbook (FAA-H-8083-16A)

The FAA has published the 2015 edition of the Instrument Procedures Handbook (FAA-H-8083-16A). You can download the PDF from the FAA website here.

If you use ForeFlight on an iPad, the new edition should be the ForeFlight section of the Documents feature.

IPH-Cover

Here’s the summary of changes from the document:

This handbook supersedes FAA-H-8083-16, Instrument Procedures Handbook dated 2014, and contains substantial changes, updates, and reorganization. It must be thoroughly reviewed.

Chapter 1

  • This Chapter contains updated information and reorganization of important concepts and principles related to obstacle avoidance and departure planning. The presentation retains the same logical order as earlier versions, and includes updated graphics for clarity.
  • The section related to Surface Movement Guidance and Control System contains significant revisions to better reflect advancements in the way the system operates, as well as the Advisory Circulars published related to the subject.
  • The section related to Diverse Vector Areas (DVAs) contains significant revision reflecting policy changes.
  • Several subject matter areas and graphics discussed in this Chapter contain changes made in order to better align with updates and changes made to the Airman’s Information Manual (AIM).
  • Various editorial and graphics issues were addressed revised as appropriate.

Chapter 2

  • This Chapter contains various updates to Sectors and Altitudes, as well as various editorial changes throughout.
  • Several graphics were updated or changed as appropriate.

Chapter 3

This Chapter was updated with various editorial and graphics changes as appropriate

Chapter 4

  • This Chapter contains a significant number of changes and updates specific to the subject of Approaches:
  • Changed internet references related to on-line flight planning and filing.
  • Updated verbiage and information regarding Vertical Descent Angles (VDAs) and Visual Descent Points (VDPs).
  • Revised verbiage and illustration related to GLS approaches and associated minimums.
  • Added discussion regarding alerting functions that are part of the Performance-Based Navigation concept and associated systems.
  • Addressed changes to RNP approach naming convention issues.
  • Hot and cold weather altimetry limitations and their associated FAA-directed procedure implementation changes were addressed and discussed.
  • New information related to Terminal Arrival Areas (TAAs) was presented and discussed. This information now aligns with advances in the subject matter presented in the AIM.
  • Several updates were made regarding RNAV and GPS-based approaches in general, under several sub-sections. Associated graphics and illustrations updated.
  • Multiple changes were made to the section discussing ILS and parallel ILS approaches.
  • Several editorial and graphics issues were addressed as appropriate. While significant information was updated for this version, there are multiple policy changes pending that will be further changed or discussed in subsequent versions of this Handbook.

Chapter 5

  • This Chapter contains several editorial and graphics updates as deemed appropriate (fixed browser links, etc).

Chapter 6

  • This Chapter contains several editorial and graphics updates as deemed appropriate (fixed browser links, etc).

Chapter 7

  • This Chapter remains “Helicopter Instrument Procedures”and contains updated illustrations and graphics pertinent to information discussed within the Chapter.

Appendices

  • The Appendices in remain intact in this version. There are information and policy changes pending that, due to time constraints, will be addressed in subsequent versions of this Handbook.

Organizing Approach Charts and Checklists

My IFR students have asked about the system I use for organizing frequently-used approach charts and checklists, especially when flying aircraft with small cockpits. Although I use an iPad and have electronic charts in the G500/GTN750 avionics in the cockpit of the Bonanza, I still keep printed copies of the current charts for the airports that I use frequently, both as backup and for convenience when I fly with students and customers.

ChartProtector_0364

I use 5.5 x 8.5 (kneeboard size) Avery 77004 sheet protectors or Staples Item 616224 ($4.81 for 25) to organize and hold approach charts and checklists. These sheet holders work with printed FAA charts or Jeppesen plates.

You can quickly print sets of charts for airports by using the features at AOPA Airports. You can also capture and then print portions of IFR en route and VFR charts at SkyVector.com.

Staples® 5-1/2

You can use Staples Item 453599 ($7.79 for 66 tabs) or the equivalent to attach and label tabs to help you organize checklists and charts.

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