Using G1000.  On RNav approach.  AP and VNav on and lining up for landing.

When do I hit the approach button? 

 

Edited November 11, 2025Nov 11 by Roy Warren

Never mind,  I've got it from YouTube.

In the real world, you’d almost certainly be vectored on to the approach, and given something like “turn heading 270, intercept the localizer, cleared for the ILS 30 approach.”

At that point I’d turn to the heading and push the APR button.  
 

In uncontrolled airspace, you’d self vector into it, and do the same.  
 

If it’s like my IRL plane, it won’t couple to an LPV approach, so we fly it in NAV and then VS mode for the glideslope.  

1 hour ago, ATRguy said:

If it’s like my IRL plane, it won’t couple to an LPV approach, so we fly it in NAV and then VS mode for the glideslope.  

That's the case for legacy systems and 1st gen G1000 (with no WAAS and therefore no LPV).  The Garmin G1000, G3X and GTN units will allow coupling to a RNAV GP.   The behaviour is similar to a coupled ILS but often with different minima and requirements.   For AP coupling, an advanced autopilot like the GFC500 or 700 will fly GPs fully coupled.

@Roy Warren

So the answer to your question is that, if it is a full RNAV LPV approach, you hit APPR after the final approach fix (the one before the Runway fix).    The FD/AP will then provide vertical guidance with a 'GP' annunciation (as opposed to a 'GS' annunciation for ILS).
 

RNAV (LNAV/VNAV) and RNAV (LNAV+V) approaches work differently though.  For the latter, the APPR button is not used, as the calculated vertical guidance is not to the same level of accuracy as with LPV.  If you want to fly these RNAV approaches coupled (or with FD guidance), you will usually remain in VNAV mode until minimums. (The altitude selector must also be dialled down to those minimums too - full RNAV LPV Glidepaths work just like an ILS and the altitude selector is disregarded once the LPV GP is captured).

Edited November 11, 2025Nov 11 by JYW

On 11/11/2025 at 10:13 AM, JYW said:

For the latter, the APPR button is not used, as the calculated vertical guidance is not to the same level of accuracy as with LPV.

I was told by a retired Learjet pilot, who also was a Learjet instructor for Flight Safety International, and works with the FAA in the design of instrument approaches, that there are differing opinions on the use of the APPR button with an LNAV + V approach.  His opinion is you can use the APPR  button with an LNAV+V approach. He said in part:

LNAV+V is a GPS derived lateral path using GPS, and SBAS if available.  However, it uses Baro-VNAV for vertical guidance.  That vertical guidance is advisory, in part because the Technical Standard Order (TSO) for Baro-VNAV guidance does not require a level of performance to prevent false and/or misleading information from being presented to the pilot.  That's because when using Baro-VNAV, the pilot is supposed to be referencing the barometric altimeter for minimum altitudes.  LNAV 's obstacle clearance surface (OCS) is a level surface, providing 250' of obstacle clearance in the final approach segment (in contrast, the OCS for a typical 3.00 degree GP slopes at 34:1).  No one cares how you get down to the MDA or any intervening stepdown altitudes.  You simply have to not go below these altitudes.  You can use VNAV, use VS, or basic PIT mode.
With LNAV+V, you can use APP mode.  In the Lear 35 with the GTNXi, that means NAV and GS.  You have to keep in mind that approaching the MDA or a stepdown altitude, the autopilot will ignore the altitude preselected set altitude and not level off.  If you flying Constant Descent Final Approach, which you should be doing with modern aircraft, you do not level at MDA anyway.  You set a derived decision altitude, which is typically no lower than MDA+50'.  I like to use MDA + 10% of the final segment vertical speed. When you get to your derived DA, if the runway is not insight, you execute a missed approach just like an ILS or RNAV to LPV or LNAV/VNAV.  All approaches are flown the same this way, and APP mode is used in all of these approaches. Treat all approaches the same, fly them the same, and you won't have any problems.  Being doing it this way for 25 years, in the Collins, Universal, and Garmin systems and a variety of jets.

The key take-away for me on this is you can use Approach Mode on a LNAV+V approach, but you are still responsible for not busting any of the stepdown altitudes or the MDA as indicated on your altimeter.

Edited November 13, 2025Nov 13 by ark

I engage it just before the FAF.

You can do it earlier and it will couple earlier most times. That's on an RNAV approach.

24 minutes ago, petejohno1 said:

I engage it just before the FAF.

You can do it earlier and it will couple earlier most times. That's on an RNAV approach.

I used it today G1000 and engaged APR before the final fix & it showed GP & the deviation diamond & tracked the approach

On 11/11/2025 at 11:13 AM, JYW said:

RNAV (LNAV/VNAV) and RNAV (LNAV+V) approaches work differently though.  For the latter, the APPR button is not used, as the calculated vertical guidance is not to the same level of accuracy as with LPV.  If you want to fly these RNAV approaches coupled (or with FD guidance), you will usually remain in VNAV mode until minimums.

This is the case with some avionics suites, but not with the Garmins. You would use the APPR button (arming GP) in all RNAV cases with vertical guidance (LNAV+V, LNAV/VNAV, LP+V, and LPV). VPTH will discontinue vertical guidance at the FAF.

When to arm GP (by pressing the APPR) button is a matter of pilot preference and situation. You can arm it any time after you have passed the IAF on the approach. Most commonly it is armed some time while enroute to the FAF.

Definitely do not wait until after passing the FAF to press APPR. Because VNAV guidance will discontinue at the FAF, you will level off and likely miss the GP; Garmins do not capture the GP from above (the above limit is very small, like 10-15 feet) so you will have to then dive to meet the GP to get GP to go from armed (in white) to active (in green).

Edited November 13, 2025Nov 13 by MattNischan

An interesting point (at least to me 🤔) is that when using approach mode with an LNAV+V approach, if when reaching the MDA you don't see the runway, you don't want to initiate the missed approach procedure until reaching the published LNAV MAP. It is not uncommon for the advisory GP to intersect the MDA well before the MAP, but as with any approach, initiating the missed approach "early" can be bad for your health.  

So this begs the question, if you don't have any ground contact during your approach, how will you know you have reached the MAP? Unless there is a convenient VOR, NDB, etc to help identify the MAP, you would need to time the approach from the FAF to the MAP even if flying an approach with advisory GP information. 

Edited November 13, 2025Nov 13 by ark

3 hours ago, ark said:

So this begs the question, if you don't have any ground contact during your approach, how will you know you have reached the MAP?

For approach procedures, for the case in which the MAP isn't just the runway fix, it will be a labeled fix in the procedure, so can be tracked as such and will appear in the list of approach legs (after the FAF).