Garmin issued Service Alert 26027 on March 12, 2026, addressing a potential misuse risk involving advisory vertical guidance (+V) on non-precision approaches across affected Garmin retrofit and OEM avionics systems.
Many Garmin systems display a +V glidepath on LNAV and LP approaches. The guidance supports a stabilized continuous descent final approach (CDFA) and is genuinely useful—but Garmin is clear that +V is advisory only. It does not provide obstacle or terrain clearance assurance, does not change approach classification, and does not alter published minima.
One operational note in the alert stands out: When coupled to +V in Approach Mode, the autopilot will not automatically stop the descent at the MDA. The barometric altimeter remains the primary reference for all altitude restrictions. Descent below MDA still requires meeting the conditions of 14 CFR 91.175—meaning the required visual references must be in sight—regardless of where the glidepath indicator sits.
Garmin also highlights temperature compensation as an important consideration. In cold-weather operations, barometric errors increase, and non-precision approaches are already one of the least forgiving environments for altitude deviations.
The alert applies to any Garmin system capable of displaying or coupling to +V guidance. If you’re flying non-precision approaches with automation in the loop, it’s worth a read. We’ll take a deeper operational look at +V guidance, CDFA technique, and potential automation traps in an upcoming issue of The Instrument Aviator.
So I like to practice instrument procedures a lot in nice weather, so there aren’t any “surprises” when I’m in the soup. I was flying a “vectors to final” approach on my Garmin box a few weeks ago and +V “vertical guidance” popped up on the display. I was no where near the final approach course and there was zero (0) protection from terrain or obstacles.
Good one.
I started flying these +V approaches about 20 years ago. What may help some readers is the geometry behind the trap.
The +V logic in the box builds a constant-angle descent from the FAF to the TCH, so it looks and feels like a normal landing glidepath. In many cases, if that path were extended, it would reach the runway near the aiming point area, roughly 1,000 feet past the threshold.
That is what makes it feel so natural in the cockpit. But the published LNAV procedure protects only to the MDA. The box keeps generating the descent, and if coupled the autopilot will keep following it.
Below MDA, the protected instrument segment does not continue unless the pilot has the required visual references, the flight visibility meets minimums, and the airplane is in position for a normal landing under 14 CFR 91.175.
Being able to plan and execute a constant descent angle approach from an Initial Approach Fix without automation is a very satifying and useful skill. Knowing what your automation is doing and how, is critical in maintaining situational awareness to avoid suprises and expsure to unexpected risk.
Four people died at SBS, because they used +V below the MDA.
The takeaways from this are:
Using this feature on a check ride can cost you the check ride if you blow through the step down altitudes while remaining on the +V.
last but not least, thanks to Garmin for verifying this matter.
The advisory glideslope appears most prominently in my installation (430W) on the LP approaches into my airport (two) and one nearby. The LP MDAs differ from the LNAV’s by only 20 feet; on US procedures the difference is usually less than 100 feet.
When flying these procedures I am careful not to arm the approach, which I only do when LPV minimums are published. I remind students that when they arm an approach they have opted for a collision course with the ground.
True for any approach with vertical guidance, including ILS. Is it that different from leveling at MDA?
I fully understand this guidance is advisory only and the pilot is still responsible to maintain minimum descent altitudes. However, as a retired systems engineer (and a few other things), I find it very troubling that Garmin would provide descent guidance that intersects terrain anywhere other than at a runway. Particularly, when their devices have terrain data readily available. I find that to be a very bizarre design choice.
I need to dig deeper into Smart Glide now as I thought it provided terrain avoidance, but maybe in an engine out situation Smart Glide will also fly into terrain prior to reaching an airport assuming an airport is within gliding distance.
I am no fan of lawsuits, but if I was on a jury and heard that a navigation device would actually provide guidance into terrain that wasn’t a runway, I’d be hard pressed to accept that as a reasonable engineering design choice and the manufacturer of such equipment would lose my vote.
Those are excellent points Voyager. What you have described is exactly why a pilot needs to understand what the automation is doing. And, by automation I mean anything that is not only doing but thinking for the pilot. Blindly engaging a VPath function is putting yourself at the mercy of all the HF errors that may be latent in the programming, display and integration of each. Pilot flying also means pilot thinking.
But remember, +V is not technically a V-Nav because it will not stop the descent at a selected altitude as a v-nav would. +V functions more like a glide path because it goes all the way to granite on the planet. Again, it’s very important to know and define whether you have captured a V-Nav, a glide slope or a glide path.
I agree 100%, but that doesn’t change the fact that Garmin has a serious flaw in its advisory glide path implementation.
I agree 100%. It’s troubling that this has just been raised.
This is anything but new. They’ve been around since 2003 when the G1000 came out or maybe sooner in the GNS 430W. You need WAAS for any GPS approach.
I don’t know what HF means, but they are nanoscopic compared to hitting a tree.
I find it hard to believe that anyone especially Garmin and Jeppesen could possibly allow to be published any thing that would fly you into the ground other than to a runway. Appears to be setting up for a crash. How can this help pilots be better pilots?? Makes you wonder if rest of stuff is safe.
You must understand what +V can and cannot do. It’s published in the Garmin manuals, clearly. Neither Garmin nor Jeppesen is negligent. The pilot is expected to be informed.
You are right but why publish something that the autopilot will take you to ground before airport?? Lately I was doing a RNAV (NOT RNAVW) with two other high time instrument pilots one a CFII and a glide path came up autopilot wanted to follow (I have used many old autopilots if there are four places to turn AP off that is first thing you want about autopilot and hand fly) I turned AP off and flew the approach. By the way we were in the clouds. Younger and newer pilots are using the auto pilot taught to follow the magenta line let us help them be safer not set up to follow line into terrain. I have bet my life on approach plates many times .
I have no idea of what he was talking about. Every approach has an MDA or DA. It’s on the pilot to pickle the AP off if you’re using one. Or you do it manually. This isn’t anything new. If it’s a circling approach, it has a circling MDA.
You’ve probably heard the term “children of the magenta.” Students are going to take the easiest way to get the job done. Same for licensed pilots. Some airlines encourage maximum use of the AP to save fuel. When one pilot crabbed about diminishing pilot skills, the answer he got was, “This is not a flying club.” Huh.
Interestingly, airline pilots who use the AP from takeoff to landing make a strong case for single-pilot Part 121 aircraft.
Approach charts are rigorously built to TERPS standards. You are only betting your life if they are not flown as charted. We fly those charts every day. I never thought I was betting my life, provided the appropriate chart was properly flown.
~Fred
+V takes you to from FAF to TCH but you’ll reach LNAV minimums long before that. All approaches with vertical guidance will fly you straight into the ground unless you stop them. The best indicator will be when sequencing stops at the MAP and asks you if you want to fly the miss. You can set the minimum, but it’s advisory only and doesn’t change a thing in the box.
Remember that +V is not a glide path. If an obstacle pokes into the pseudo glide path, you’re dead. As noted above, the line is straight from FAF to TCH. Obstacles are not considered. When they say “advisory” this is what they mean.
Step down fixes on ground-based approaches mean obstructions in the path over which you must fly. It might be wise to pass up a +V if even one stepdown is present on a VOR approach to your chosen runway.
Yes, all approaches with vertical guidance will take you into the ground, but at a RUNWAY. That is why I specifically said that in my original post. I don’t think ANY vertical guidance, be it advisory (glide path) or approach procedure (glide slope) should ever intersect terrain other than at the RUNWAY. That is simply poor design and is an accident designed to happen as it did in this case.
I checked and Garmin’s Smart Glide, which is also advisory, states that it factors in terrain and obstacles in providing guidance to an airport in range if such an airport exists. Do you think it would be acceptable in your opinion for Smart Glide to fly you into a mountain between your present position and an airport since it is only advisory guidance?
There should never be any electronic vertical guidance that intersects with terrain or obstacles other than the runway. That is in fact a crash just waiting to happen. There is a lot to know in aviation, especially avionics. I once long ago took a check ride with the FAA and the examiner seemed to assume that Lnav +V was useable on a non-precision approach because the vertical indicator was working and +V was annunciated. At the time, we both assumed (never assume anything) that it was the same vertical guidance as the full LPV approach.