Auto Pilot and Glideslope Glitch

[norcali.pilot]

Hey forum,

When flying the LOC 28L into KMRY (Monterey, CA), I had the autopilot fly the procedure turn(PT) from SNS using the FMS nav source. When I was done with the PT and was established on the localizer course inbound, I switched the nav source to LOC and enabled the APPR mode (APPR LOC 1 indicating). The aircraft captured and tracked the localizer just fine and a green glideslope diamond (not the advisory VNAV) appeared but did not provide descent guidance.

A few issues; the LOC 28L does not have a glideslope, whatever glideslope the LOC was sensing caused the aircraft to maintain altitude (6,200') during the entire approach and over the airport (I waited to see what it would do). I disabled advisory VNAV and tried switching autopilot modes to VS and PITCH, neither would change from GS. I also switched from APPR back to NAV mode (LOC indicated) but the autopilot was still tracking level on the 'glideslope'.

Disabling autopilot and re-selecting NAV (LOC indicated) and VS worked, but I feel like there is a better solution.

P3D V5 and King Air are all of the latest versions, nav database is current.

Thank you!

[Slayer]

Is it just this airport or do all LOC approaches do this? Payware ORBX I assume?

[norcali.pilot]

I have flown a few LOC-only IAP's. One that is an orbx scenery airport, one that is an airport within an orbx region but not a specifically modeled airport, and two airports outside of any orbx coverage. This glitch occurred at the two airports within orbx coverage and one of the non-orbx airports.

I plan on trying more LOC-only approaches when I return from a quick trip, this is just initial findings. LOC-only approaches are rare but I am hoping the resolution to this issue might help other possible issues.

Thanks again.

[Taguilo]

Hi,

I flew the KMRY LOC 28L and experienced the same. Checked and the aircraft was receiving a false GS signal which forced it to remain on the altitude. It seems to be a P3D scenery (NAV) issue. As you already detected, not all LOC only might be affected, probably many are though.
Unfortunately not much to do but fly it manually, following Advisory VNAV altitudes, as FGS follows default ILS/LOC signals.

Tomas

[Slayer]

You may have luck using the tools found here:

https://www.aero.sors.fr/navaids.html

[norcali.pilot]

Thanks for the reference Slayer. I was going to mention if the FMS uses the P3D database then I may be out of luck. I did use that tool to update as much of the default P3D database as I could but the page lists the ILS and runway updates as not released.

Separate question, on a few random GPS approaches (in the KA and the Avanti), the final approach segment is curved or " bends" to one side. Should I make an individual post concerning that?

Update: The ILS update did not resolve the issue, maybe sometime in the future it'll workout.

[Slayer]

I'm not sure about the curved segment I'll ask on discord and see if that is correct behavior

[norcali.pilot]

It occurs in the KA or Avanti when loading the RNAV GPS (Y) 28L into KMRY and RNAV GPS 12 into KEKA, both ORBX airports.

[Slayer]

The FMS uses navigraph data but AFAIK radio/ILS/VOR etc comes from the sim so it may be something with Navigraph data or that may be how our simulation displays a GPS approach.

[norcali.pilot]

That makes sense. The curved approach paths have been consistent across Navigraph updates and KA/Avanti versions and doesn't exist in other addons.