Glideslope Failure on RNAV/LPV

Did a practice RNAV/LPV approach on Sunday and had a glideslope failure in the middle of the glidepath, at around 1000 ft AGL. 

Details:

- Entegra with 2xIFD440 and DFC90
- Flew standard RNAV GPS procedure to EDMS (Germany)
- Had a green LPV indication on both navigators (crossfill is activated)
- Flew by hand with FD ON
- Was exactly on virtual glidepath when Glideslope indicator on PFD diseappeared
- Two seconds later there was a yellow "glideslope not available" warning on the PFD for about 3 seconds
- Localizer indication stayed up and PFD said FD NAV APPR
- Green LPV indication stayed on on both IFDs, no warning on the IFDs
- 1 minute later the GS indicator came back and stayed on until landing

This video was started ten seconds after the GS indication failed. It comes up at 1:42 again.

https://youtu.be/tsv4ncGGYG4

Any idea what happened?

Do you mean the IFD logs? I can send those to you, although i got 2 exchange units from Bryan Kahl 3 weeks ago after the original ones took a long time to lock on to GPS. 

Edited by D-EACY - 21 Oct 2020 at 3:22am

Yes, I'm sure is was a momentary, localized event.  My guess is that the VPL from the GPS exceeded the VAL.  That could be confirmed by looking through the logs.  I would have expected the VDI on the MFD to be flagged instead of going away, though.

No, it will continue to display LPV, but the vertical deviation should be flagged.  It's like an ILS when the GS is out.

I looked through the EXP5000 Pilots Guide and you are correct that there was no mention of the "glideslope not available" message.  I did find that the description of the VDI said it is displayed when "GPS vertical deviation data has been received".  That's consistent with the behavior you documented.  Though admittedly undocumented, the yellow message provides further notification that vertical guidance is unavailable.