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.
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.
For more information about VTF, see Avoiding the Vectors-to-Final Scramble, Changes to Vectors-to-Final in Garmin GTN System 6.x, Flying Instrument Approaches without Activating the Approach, and Joining a Localizer from Afar.
Occasionally, however, you may encounter an approach such as the ILS or LOC RWY 14R at Boeing Field (KBFI) (chart below).
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.
The plan view for this approach shows two key fixes along the localizer: ISOGE and TOGAE.
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. But you loose ISOGE as a reference.
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).
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.
(For another demonstration of this technique, see the video below.)
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:
To draw an extension of the localizer from ISOGE, select ISOGE again, choose Direct-To, and enter the course 135.
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.
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.
BruceAir, LLC 
Thanks for a great explanation here. A couple of questions:
1. Can you share how this compares to what the G1000 normally draws as far as extended runway centerline goes (which would mirror the final approach course non LDA/SDA approaches)?
2. In G1000 – any tips on flying GPS towards an ILS or VOR procedure (maybe localizer or a hold off a radial). In particular the sequence in prepping for the green needles flying is to fly GPS based on ATC, then switch to greens and follow the needles. In prepping for it though you want to get the course right, and to do that you to switch your CDI mode to the VOR/LOC. However, if you’re flying GPS autopilot nav mode and switch the CDI to VOR so you can set the course/bearing, autopilot disconnects or reverts to roll mode. The closest trick I’ve found is to sink the heading bug, put the AP in HDG mode, switch CDI to VOR/LOC mode (greens) – do what I need to do to get the OBS/course bearings set, then switch back the CDI to GPS to continue to the fix, then put AP back in NAV mode from HDG mode to do more magenta flying until we have to switch to greens for the approach.
Any easier ways?
As a general rule, I recommend switching the AP to HDG mode when you’re loading procedures, editing a flight plan (at least the legs close to where you’re flying), or need to set up as you describe. I keep the HDG bug synced to the current heading except, for example, when I’m inbound to an airport VFR. Then I set the HDG bug to the runway I intend to use.
The same logic for loading and flying procedures, using OBS mode, etc. applies across all Garmin products from the GNS series through the G1000 and GTN and newer boxes. If you switch nav sources (i.e., change the CDI on the HSI), the AP drops out of NAV mode. That’s to make sure you are set up to fly the correct course. If you load an ILS or LOC procedure and tune the LOC frequency, the course automatically slews to the inbound course. You should verify that, of course. If you are flying a VOR procedure, you must set the proper inbound course.
If you’re using GPS during the initial phases of an approach, you can accomplish the steps you describe early in the approach process so that you’re not making last-minute changes as you capture the final approach course. Switching momentarily to HDG mode while you confirm course selections, etc. won’t disturb your track as you fly, for example, a feeder route, track outbound for a course reversal, etc.
Thanks for the great explanation.
Happen to know on the 750, how you can identify the VDP on a VOR approach?
It will say the distance from the runway, after the last waypoint, but not from the VOR which the VDP is based on for a VOR approach.
Just  curious
Same issue I’ve seen for a 750 and 430, 530w for a localizer approach, after you get to the last waypoint it will say the distance from the runway, but a lot of localizers are based off a VOR DME distance to determine the VDP.
Thanks
VDPs are not in the database and are not fixes in the list of fixes shown in a GPS flight plan page (see the AIM for more details). Depending on the charts you use, you can easily determine your distance relative to a VDP by noting the distances shown in the profile view, e.g., using the threshold waypoint as a reference. See, for example, the VOR RWY 35 approach at KOLM. The profile view on a FAA chart shows the VDP is defined by the 2.5 nm DME fix from the OLM VOR. But the profile also shows that the VDP is 1.8 nm from the threshold. As you fly the final approach course, you can watch the distance to the threshold decrease on the flight plan page, which shows the threshold as a fix.
Bruce, fantastic article, thank you. Im stumped – how would you perform this same task for a GPS approach, inbound to the IAF? I’ve found the GTN 750/650 automatically sequences to the NEXT leg after the IAF when the above technique is used on a GPS app (different from an ILS/LOC). For example, this afternoon I was asked to intercept the inbound course to SOCLO for the RNAV GPS 11 at BVS; I’m sure you’re familiar with the procedure. I did not want to hold, and wanted to keep SOCLO & ENSEW in the flight plan in order to mind step-down altitudes. Each time I selected direct SOCLO, and entered an inbound course of 110, the GTN activated the leg from SOCLO to ENSEW, instead of drawing a magenta line into SOCLO as desired. Thanks!
I just tried that approach in the Garmin PC Trainer Suite (https://www8.garmin.com/support/download_details.jsp?id=12373). I began the procedure at CANDL, with that fix set as the “transition,” and I set a direct-to course of 110 to SOCLO. The GTN 750 behaved as expected, and the G500 TXi showed a magenta line extension from SOCLO along the 110 course. When I reached SOCLO, the GTN sequenced to ENSEW as expected.
Where did you begin the approach? What did you load as a transition? Try flying the procedure in the trainer from different starting locations.
Thanks Bruce; I think you’ve helped me narrow the issue – I believe it is concerned with the selected IAF in the GTN, and the holding pattern at the IAF. I was approaching SOCLO from the south, somewhat near ISLND, but not on that transition. I selected SOCLO as the IAF in the GTN, then removed the hold. I then selected a direct-to course to SOCLO of 110, and the GTN activated the subsequent leg (SOCLO – ENSEW), as opposed to drawing a magenta line into that fix like your example of the extended LOC course into ISOGE at BFI.
I had the same issue earlier yesterday when approaching YAYUB on the RNAV GPS-A to 0S9. I had JIGEB selected as the transition, Whidbey cleared me direct to YAYUB, then subsequently provided vectors to intercept the course inbound to YAYUB for the straight-in, so as to avoid a turn in holding at YAYUB. After deleting the hold, the GTN would not permit a magenta line to be drawn on the inbound course (with my technique). It would, in both instances, permit direct-to navigation to SOCLO & YAYUB, which is what I ended up doing, and was cleared for, in both cases. But, it brought up the question in my mind, regardless…
Experimenting with the PC trainer suite is a great idea to sort this out. I’m away from home with only my iPad this weekend but will download and experiment when back at my PC.
Thanks! Grateful for your thoughts…
As a general guideline, I recommend selecting an initial fix as far out as possible given the direction from which you’re arriving, even if neither you nor ATC expects you to join the approach there. That technique preserves your options for later proceeding direct to a fix or activating a leg. The issue here may be that SOCLO is coded as dual-purpose fix because it anchors a HILPT that is required in some circumstances. And if you are on the airport side of SOCLO (i.e., east of the fix) when you set the direct-to course, the behavior you describe will happen. Experiment with the Garmin PC Trainer vector yourself outside of SOCLO so that you will intercept the 110 course northwest of the fix.