Hi, I’m using the latest developer version of the FBW A320NX (not the custom version). And I’ve tried a few RNAV approaches and I keep flying over the runway at the last altitude I set to intercept the glide slope. It’s doing the correct horizontal guidance but not vertical. 

Ive watched A320 Sim Pilot’s video (on YouTube) and can’t figure out what I might be doing wrong. The approach is in the MCDU, it goes to that phase automatically on approach, I hit APPR on the AP, but it doesn’t start descending. 

Any help or suggestions would be greatly appreciated. Thanks!

arm the approach mode?

46 minutes ago, Mike S KPDX said:

arm the approach mode?

Yeah, thanks... the approach phase is active in the MCDU and I hit the APPR button on the AP to arm the approach mode... I don't know what else I could be missing.  Unless RNAV is just flaky.

Maybe I've missed a major development, but I wasn't aware that that branch of the FBW32NX was capable of following or calculating a VNAV path yet, and as such wouldn't be able to provide or follow vertical guidance on an RNAV approach.  I know it'll follow an ILS glideslope, but am not aware of it being able to do a full RNAV approach with vertical guidance, only lateral.  I haven't flown the FBW all that much, been waiting for the VNAV autopilot logic to be implemented, so I could be WAY off here.

45 minutes ago, cmorg said:

Maybe I've missed a major development, but I wasn't aware that that branch of the FBW32NX was capable of following or calculating a VNAV path yet, and as such wouldn't be able to provide or follow vertical guidance on an RNAV approach.  I know it'll follow an ILS glideslope, but am not aware of it being able to do a full RNAV approach with vertical guidance, only lateral.  I haven't flown the FBW all that much, been waiting for the VNAV autopilot logic to be implemented, so I could be WAY off here.

Hmm... Maybe that's it. I wonder if only the custom build with their new AP will support VNAV?  I'll look into it a bit more.

Most RNAV approaches are considered non-precision and no not use the glide slope. You would require VNAV, however it is not modelled (yet) in any of the FBW a320 versions.

John

25 minutes ago, Virtual-Chris said:

Hmm... Maybe that's it. I wonder if only the custom build with their new AP will support VNAV?  I'll look into it a bit more.

VNAV is not modelled yet...from their discord it's still  a long time away before we will get to use it but they are hard at work on it from what i can see.

So what is this guy doing?

According to the video he's in the FBW A320 dev version back in Dec. and has the plane automatically descending on a RNAV approach...

Skip to 14:40 for the final approach...

 

50 minutes ago, Virtual-Chris said:

So what is this guy doing?

According to the video he's in the FBW A320 dev version back in Dec. and has the plane automatically descending on a RNAV approach...

Skip to 14:40 for the final approach...

 

So what's happening is for some approaches the default "VNAV" might still work more or less.  The issue is with the 'flight plan manager' in the sim that doesn't not correctly see/use or parse the nav data correctly (even though the data is there).  So while some approaches work, others will not.  What FBW is doing is making a custom proper NAV (VNAV).  The default ASOBO one is a simplistic one.

Keep in mind that the entire FBW aircraft is still in development, so most things are not meant to work yet.  Basically you're getting to fly a plane as they add and fix things.

The common misconception that I see around the forums and what not; is that most simmers think the custom autopilot will correctly fly a flight plan laterally and vertically.  This is not the case.  LNAV/VNAV (NAV) are still the default ASOBO.

This video explains the difference between ILS and RNAV. Basically ILS uses a runway signal for lateral and vertical (usually 3 deg) to intercept the ILS. RNAV uses the GPS system along with the MCDU entered flight plan to track the lateral and vertical profile. As explained in the video there are still several limitations to this in both MSFS and the FBW mod. I am currently using the experimental version of the FBW mode which uses a custom autopilot. It now supports auto land which seems to work very well. Hope this helps, it can be very confusing.

https://www.youtube.com/watch?v=BeVDLt7jVwk

John

 

11 hours ago, Jeff Nielsen said:

So what's happening is for some approaches the default "VNAV" might still work more or less.  The issue is with the 'flight plan manager' in the sim that doesn't not correctly see/use or parse the nav data correctly (even though the data is there).  So while some approaches work, others will not.  What FBW is doing is making a custom proper NAV (VNAV).  The default ASOBO one is a simplistic one.

Keep in mind that the entire FBW aircraft is still in development, so most things are not meant to work yet.  Basically you're getting to fly a plane as they add and fix things.

The common misconception that I see around the forums and what not; is that most simmers think the custom autopilot will correctly fly a flight plan laterally and vertically.  This is not the case.  LNAV/VNAV (NAV) are still the default ASOBO.

Thanks. Yeah. I have tried three RNAV approaches with the dev version and it has not descended on any of my attempts. I don’t know what I’m doing wrong, but I’ve studied that video above to no avail. I give up on RNAV. 

Once FBW A320NX went as a separate aircraft, the current custom autopilot cannot handle the RNAV approached because VNAV is not modeled just yet, but it is coming in a future update. It used to work when the FBW A320NX was a Mod and used the MSFS A320neo autopilot. Try it with the default A320.

On 3/31/2021 at 2:11 AM, Virtual-Chris said:

Thanks. Yeah. I have tried three RNAV approaches with the dev version and it has not descended on any of my attempts. I don’t know what I’m doing wrong, but I’ve studied that video above to no avail. I give up on RNAV. 

We have told you in other threads also....this is NOT working yet.  It is NOT you.

Flew into LPMA RNAV23 in the FBW experimental yesterday. Vertical and horizontal guidance was displayed on the PFD. In saying that, I was visual about 5 miles out so A/P off.  

Edited April 11, 20215 yr by gb09f

Yes, I can confirm that. Had been into HTDA yesterday for the RNAV23 App. It displayed the vertical guidance.

Edited April 11, 20215 yr by 737_800