I am going to do my CFII checkride in a few weeks and my DPE wants to do RNAV approaches to satisfy the Non-Precision and Precision approaches tasks on the PTS/ACS.

According with the Instrument ACS an RNAV (GPS) approach with LPV minimums can be used to satisfy the precision approach task as long at it has a DH lower than 300 ft. I don't have a problem with that, the airport has an LPV approach with LPV minimum of DH 250 ft.

Now for the non-precision approach, I am going to use the same approach but flying the LNAV minima. So my question, since I haven't flown LNAV minima since my IFR training, my question is: Can I fly the LNAV MDA even if the GPS annunciator is on LPV mode? I guess the answer is yes, so, is there any consideration when doing that?

And just for future applicants, an LPV approach with greater than 300 ft DH can be used to satisfy the Non-precision approach task on the ACS (instrument ACS page A-17).

  • $\begingroup$ Welcome to aviation.SE! LPV and LNAV/VNAV glideslopes aren't always the same so I'm not sure that it would be safe to do what you're describing. But I may have misunderstood your question, could you edit it to explain why you would want to that? If we understand the scenario then someone may be able to give a better answer. $\endgroup$ – Pondlife Aug 24 '20 at 17:40
  • $\begingroup$ Also, please specify if you are doing a practice approach under VFR, or if you have been cleared for an IFR approach. $\endgroup$ – Michael Hall Aug 24 '20 at 18:07
  • $\begingroup$ Thanks for your answer, I've just did it $\endgroup$ – Ivan Parra Aug 24 '20 at 19:03
  • $\begingroup$ Thanks for the clarification, that helps. It didn’t answer my VFR vs IFR question though. My answer would be that if VFR it shouldn’t matter. If IFR I would probably at least advise the controller if I planned to fly the LNAV approach, just so they wouldn’t be surprised by the ratcheting step down, but I’m interested in what others might say because I am still kind of new to GPS approaches. $\endgroup$ – Michael Hall Aug 24 '20 at 20:19
  • $\begingroup$ Yes, I don't know if it's going to be VFR or IFR. I guess it will be VFR and I am just going to simulate that I don't have LPV but LNAV, therefore descend to the MDA until the MAWP. Thanks $\endgroup$ – Ivan Parra Aug 24 '20 at 20:35

GPS approaches are designed for you to fall back to LNAV if a 'higher' precision option like LPV fails during the approach. Just like going from ILS to localizer only if the glideslope fails.

The Instrument Procedure Handbook p. 4-26 says:

Flying a WAAS LPV approach requires an aircraft with WAAS-LPV avionics. If for some reason the WAAS service becomes unavailable, all GPS or WAAS equipped aircraft can revert to the LNAV MDA and land safely using GPS only, which is available nearly 100 percent of the time.

So you can just ignore the vertical guidance and fly the LNAV step downs using lateral guidance only from the GPS, and your regular altimeter (not your GPS) to identify altitude.

If you haven't done it already (or recently), I'd suggest practicing it before your checkride to see how your avionics behave. You might get alerts that you have to ignore and they could be distracting. It would be best to get a feel for that ahead of time rather than experience it for the first time with an examiner sitting beside you.

You can also just check with your examiner in advance that they're comfortable with what you want to do.

  • $\begingroup$ Yes, I am going to do that, thanks! $\endgroup$ – Ivan Parra Aug 24 '20 at 22:57

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