Loss of LPV on an RNAV approach

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Scottman

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Scottman
I was on a VFR practice RNAV approach the other day when I lost LPV after the FAF. At that point I just flew it as an LNAV approach and used the LNAV MDA. I wasn't in actual IMC and needed to return the plane, so I just continued. But wondering if that is legal to just continue on course if you lose LPV for some reason. At this airport (KTOA) the only difference is MDA vs DA. Thoughts?
 
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I think that’s a possible question on the IR written test (I’m taking it tomorrow).

From what I’ve learned, it’s legal to use a less precise GPS mode, if you lose WAAS or RAIM.

I believe you need to advise ATC of the loss of capability/malfunction?
 
Scottman said:
I was on a VFR practice RNAV approach the other day when I lost LPV after the FAF. At that point I just flew it as an LNAV approach and used the LNAV MDA. I wasn't in actual IMC and needed to return the plane, so I just continued. But wondering if that is legal to just continue on course if you lose LPV for some reason. At this airport (KTOA) the only difference is MDA vs DA. Thoughts?
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Flying to the DA in that circumstance is a no, no and could kill you, I think you knew that. If you know the MDA you can fly it as a non precision and continue. If it messes you up, go missed and regroup. That's what I was taught.
 
As long as you have not descended below any step-down fixes for the LNAV approach, and you have a valid LNAV integrity annunciation, you can continue as the LNAV non-precision approach. You should always check the integrity annunciator prior to starting the approach to see what you have. If LPV is not annunciated you will not have reliable vertical guidance. On the G5s it is obvious because you don't get a vertical CDI unless the LPV integrity is met.

I had the vertical guidance board on my GNS430W fail in flight before I had G5s, and the LPV annunciator would not light, and the vertical CDI flagged. The horizontal guidance was sufficient to do a plain LNAV approach. Took me a while to figure out why I could never get the LPVs to activate.
 
Unless it is the rare LPV only approach, you can fly the step downs and LNAV minimums. You are also required to report it.
 
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