Is it just my G1000/RNAV that is so inconsistent?

[TacomaSailor 191]

Still trying to make the G36T (R. Young Turbo Bonanza) fly a consistent RNAV approach every time, with only a bit of success.

Flight Plan to test KOLM RWY 17 (GPS) RNAV approach with CARRO transition

KTIW (Rwy 35) VPGIG VC018 CARRO (IAF) BOSTO (IF) OPOYU KOLM (Rwy 17)

Saved flight at 0.9 NM east of VCO18 so I can have a shorter restart for testing.   At 1-minute prior to VC018 I ACTIVATE the approach and I see the AP change the next waypoint to CARRO (approach IAF)

Everything works fine as the AP flies from BOSTO to OPOYU at 2,400' and 128 kts.  The flight plan page shows the approach is active and the magenta line connects BOSTO to OPOYU.

 

At 0.2 NM west (prior to) OPOYU (where flight path begins the 3° glide slope) the AP puts in full left aileron and begins a bank that quickly exceeds 60°.  After a few seconds the AP puts in full nose up trim, and of course the plane stalls.

The PFD and MFD both show OPOYU as the next waypoint with an increasing distance as the plane spirals downward. 

I restart the flight and try the approach several more times.  Sometimes it banks left, sometimes banks right at OPOYU but it always puts in full nose up trim and stalls.

Finally, I decide to see what happens if I recover from the stall and get the nose pointed at the airport and RWY 17.  I then switch the CDI to LOC where I have tuned the ILS.  The AP then flies a beautiful, smooth ILS approach.

So - I restart again from just east of VCO18 (Load Saved Flight) and try the RNAV approach again.  This time it works PERFECTLY and flies the plane right down to the TDZ.

????

Since I was loading a saved flight each time - I am quite sure I changed nothing between the flights that stalled and the flight that successfully completed the RNAV 17 approach. 

Just prior to this RNAV testing - I deleted all references in the Community folder to Working Title G1000 V3.0 and then downloaded a new GitHub zip, extracted it and moved it into Community.  This was done BEFORE any of the RNAV testing.  HOW do I verify the G1000 Working Title mods are actually working in my G36T?

Edited November 5, 2020 by TacomaSailor

[Bert Pieke 7,584]

If you get a Track Up view on the MFD, the mod is working. 😉

As for the sudden AP misfunction, watch the trim indicator when it happens.

In my flights, the trim will rapidly run to the top and the bottom of the range and then the plane goes into a spiral dive.  I believe there are some discontinuities in the RNAV vertical profile which turn the approach into disaster..

 

[TacomaSailor 191]

The flight plan shows NO altitude for any of the RNAV fixes so I assume the AP does not try to use VNAV - is that incorrect?

Once past OPOYU, where the Jeppesen chart shows a constant 3° glide slope the AP shows GS IF the RNAV approach is working correctly. 

When it goes into a spiral dive the PFD shows GPS AP ALT 2400 with the VS box as ... .

WHY does it work one time and not the next when I restart the flight from the same spot and never touch the controls?

I am trying to post a series of screen shots that captured the deviation but whenever I put a URL into the Insert Image box - the box turns RED.  I tested that using the URL (same website and folder - different .prn), which I have used for every other screen shot I've successfully posted here.  Now those images can't be posted but they do appear in my old threads when I go back to them. 

 

 

[MattNischan 3,778]

Vertical guidance currently is a bit of a trouble spot. It's something we're in the early to mid phases of working on but nothing yet that's been in any of our software. The sim default RNAV/VNAV will just flat out do funky funky things, like the stuff you're seeing here.

It's nothing you're doing wrong, just lots of AP, routing bugs, and lack of correct restrictions following.

-Matt

[fppilot 4,355]

29 minutes ago, MattNischan said:

It's something we're in the early to mid phases of working on but nothing yet

So why not get more urgent, release the full SDK, and get help from some developers who are highly experienced with these.....  The townspeople are in the town square chanting .....

[MattNischan 3,778]

2 minutes ago, fppilot said:

So why not get more urgent, release the full SDK, and get help from some developers who are highly experienced with these

Well, because we're human beings with day jobs and this is a free hobby.

What SDK are you referring to? I'm very confused.

[fppilot 4,355]

1 hour ago, Bert Pieke said:

If you get a Track Up view on the MFD, the mod is working. 😉

As for the sudden AP misfunction, watch the trim indicator when it happens.

In my flights, the trim will rapidly run to the top and the bottom of the range and then the plane goes into a spiral dive.  I believe there are some discontinuities in the RNAV vertical profile which turn the approach into disaster..

 

Is this just with the G36?  I continue to build hours in the DA62 and G58 and am experiencing none of this.  I did have a handful of incidents like these in the early days.  One or two was after deploying active pause for some length of time.  More than a few seconds.  The other incidents were immediately after takeoff and in those cases I had done some preflight studying with the G1000 and AP.  I now leave hands off of the AP prior to flight.  I do preset the heading bug and preselect an initial altitude to capture on the G1000, but while on the ground I stay away from anything associated with the AP functions, like FLC or VS, as well as the HDG or NAV keys, or activating the AP.  I have not experience the described issues since.

[fppilot 4,355]

5 minutes ago, MattNischan said:

What SDK are you referring to? I'm very confused.

 

40 minutes ago, MattNischan said:

Vertical guidance currently is a bit of a trouble spot. It's something we're in the early to mid phases of working on

I am confused.  Who are you ?  Sounded like you were a member of the MSFS development team.

[MattNischan 3,778]

I'm a developer on the Working Title team. I chimed in because the original poster indicated that they were using one of the WT Garmins.

I was just trying to clarify that we haven't actually touched any VNAV/RNAV code yet in our mods, so what is being seen is just the strange default behavior. We (the Working Title team, I don't speak for Asobo) are actively working on better VNAV and RNAV at the moment, though, but nothing that has been released yet.

-Matt

[fppilot 4,355]

1 hour ago, MattNischan said:

Matt

OK. I am faithfully using your G100 and G3000 mods and much appreciative..  Much appreciative!