Critical Differences with “+V”

Bruce:

“You’re right to ask. At first glance, these glidepaths look the same, but they very much are not.

If your IFR-approved GPS navigator is WAAS-capable (and most units made in the last 20 years are) you’ll see vertical guidance on almost every RNAV (GPS) approach.

Unless you fly a turboprop or jet with an FMS, approved vertical guidance on an RNAV approach usually means an LPV glidepath that leads to a DA. It works like an ILS glideslope on a 3D, precision approach that keeps you clear of obstructions down to a DA, where you either continue visually or go missed. When approved vertical guidance is available, you’ll see LPV annunciated on your PFD and navigator. On most systems, the glidepath marker is a diamond, like the ILS glideslope symbol, but the LPV indicator is magenta, not green.

Advisory glidepaths are labeled +V in approach titles and electronic panel displays, and they’re available on most 2D, nonprecision approaches to help you fly smooth, constant-angle descents to a minimum descent altitude. Often, +V glidepaths intersect the MDA at a visual descent point, or VDP, where you can continue on the glidepath below the MDA—if and only if—the runway environment is in sight, and you can avoid any obstacles in the path to the threshold.

Unfortunately, our avionics don’t always help us recognize the vital distinction between approved vertical guidance to a DA and +V advisory guidance to an MDA.

First, our PFDs usually display the same magenta diamond markers to show both approved and advisory vertical guidance. Maybe that will change someday, but for now it’s your responsibility to understand the guidance that you’re following.

Second, MDAs are typically higher above ground than DAs. This can suggest that it’s fine to follow the glidepath lower before deciding to go missed. In fact, you must decide to go missed slightly before you reach the MDA, because you can’t go below that hard deck unless you can safely avoid all obstacles visually. (When flying to a DA, you can dip slightly lower if you decide to go missed at that point and begin to climb.)

The final key point to understand is that autopilots don’t distinguish between approved and advisory glidepaths. Unless you intervene, they will blindly follow vertical guidance all the way to the touchdown zone. That’s a critical limitation if obstacles lurk below the MDA between the final approach fix and the threshold. And if the approach has only +V guidance, there are reasons. Obstacles are at the top of the list.

So when you see a glidepath symbol, always brief the limitations associated with the +V and LPV labels. Then confirm and verbally call out the LPV or +V annunciation as a last check before you cross the final approach fix.”

Join instructor and IFR Focus contributing author Bruce Williams for a free live webinar, Thursday, Jul 9, 2026 3:00 PM – 4:00 PM as he explains the three primary types of vertical guidance used on today’s IFR approaches. Register Now