Setting a Course v. Vectors to Final

I am not a fan of the vectors to final (VTF) option when loading instrument approaches in GPS navigators like the Garmin GNS and GTN series avionics.

As a general rule, avoid the vectors (vectors-to-final) option

Even with recent improvements to how the Garmin GTN series boxes handle VTF, it’s usually best to choose an initial fix (IF) or initial approach fix (IAF) based on the direction from which you’re arriving in the terminal environment, and then, depending on your clearance from ATC, activate a leg of the procedure or proceed direct to an IF or IAF. See the example at KMWH below.

Choosing a transition (IF) when loading an approach.

For more information about VTF, see Avoiding the Vectors-to-Final Scramble, Changes to Vectors-to-Final in Garmin GTN System 6.x, and Flying Instrument Approaches without Activating the Approach.

Occasionally, however, you may encounter an approach such as the ILS or LOC RWY 14 at Boeing Field (KBFI) (chart below).

Video of the approach described in this discussion

Knowing how to use a handy technique that straddles the line between the VTF and setting a specific course (a variation on OBS mode) can help you smoothly join the final approach course. Bear with me for a somewhat convoluted explanation.

For more information about setting a specific course to a fix and the OBS feature, search for Direct To and OBS in the pilot guide for the avionics you use.

ILS or LOC RWY 14R at KBFI

The plan view for this approach shows two key fixes along the localizer: ISOGE and TOGAE.

Plan view

TOGAE is step-down fix with a crossing restriction and a GS intercept altitude at 1600 (the beginning of the final approach segment when you fly the full ILS with glideslope). TOGAE also serves as the FAF when you fly the LOC-only version of the procedure.

In theory, Seattle Approach could vector you to join the localizer a few miles outside TOGAE (within the approach gate; see the Instrument Procedures Handbook and the P/C Glossary).

APPROACH GATE− An imaginary point used within ATC as a basis for vectoring aircraft to the final approach course. The gate will be established along the final approach course 1 mile from the final approach fix on the side away from the airport and will be no closer than 5 miles from the landing threshold.

Definition of approach gate in the P/C Glossary

The approach also chart shows ISOGE, a fix 9 nm from the ruwnay, as an IF/IAF. (You will never fly the depicted hold/course reversal anchored at ISOGE.)

And ISOGE appears in the list of transitions when you load this approach in a GPS navigator such as a Garmin GTN 750.

If you choose either Vectors or ISOGE, the fix appears in the flight plan.

If you activate VTF for this approach, the GTN draws an extended centerline from TOGAE (the FAF) out along in the localizer course. You loose ISOGE as a reference.

VTF leaves ISOGE in the flight plan, but all distance and ETE information references TOGAE.

If you activate the approach with ISOGE as the transition, the navigator draws a magenta line from your present position to ISOGE, and if you hand-fly that course or put the autopilot in NAV mode, you will head directly to that fix.

But Seattle Approach always issues a series of vectors to sequence you into the flow of traffic for KBFI and to avoid conflicts (wake turbulence and otherwise) with airliners aiming for nearby KSEA. Regardless of the direction from which you’re arriving, ATC places you on the localizer at least a few miles outside of ISOGE.

In other words, you don’t want to go direct to ISOGE, and it’s helpful to have a reference to the localizer course as ATC vectors you into the flow.

For example, I recently flew the ILS from the area near Arlington, WA (KAWO) northeast of Seattle (video here).

Radar vectors KAWO-KBFI to the ILS or LOC RWY 14R

This typical routing from the northeast involves a long vector on a southwest heading to intercept the localizer. Even if you have the navaid tuned, you may not be able to identify it and confirm its appearance on the CDI until you are almost on top of the course. If ATC is busy or if you’re flying a fast airplane, it’s easy to blow through the localizer or be tempted to make an aggressive turn to capture it when you get the final vector from ATC.

Here’s the “trick” to help you fly a smooth intercept. It involves setting a specific course direct to a fix–in other words, it’s similar to using OBS mode:

  • If you’re using the autopilot, make sure you’re in HDG mode to follow vectors from ATC.
  • Because you’re flying vectors to join the localizer, confirm that you’re showing “green needles” on the HSI or CDI used to fly the ILS. You don’t need GPS guidance from this point on.
  • Load the approach with ISOGE as the transition (i.e., as the first fix in the procedure).
  • Confirm the list of fixes in the flight plan.
  • Select ISOGE and choose direct-to.
  • In the direct-to window, enter the course inbound to ISOGE along the localizer–135 degrees.
  • On the map, you’ll see a magenta line extending to ISOGE along the course 135 degrees–in effect, an extension of the localizer.

Here’s how that sequence looks using a GTN 750:

ISOGE selected as the transition (initial fix). ISOGE is the current direct-to fix–the approach is activated.
The GTN 750 shows guidance direct to ISOGE. But ATC is vectoring you to join the final approach course at a point outside ISOGE.

To draw an extension of the localizer from ISOGE, select ISOGE again, choose Direct-To, and enter the course 135.

Setting a specific course to ISOGE.
The GTN draws a course of 135 to ISOGE, in effect, an extension of the localizer.

Now you can monitor your progress toward the final approach course and prepare for the turn onto the localizer, even if you’re not currently receiving the signal or showing a flyable localizer CDI.

Joining the localizer.

As you join the localizer and then pass ISOGE, the GTN sequences to the next fix in the approach, TOGAE. If you used OBS mode to set a course to ISOGE, the GTN would suspend waypoint sequencing past ISOGE, but setting a direct-to course preserves that feature.

On the ILS approaching TOGAE.

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.