Possessed autopilot, needs a ton more down trim?

[moespeeds]

So I got a few flights in tonight, and had many issues with trim at cruise and the autopilot.

 

It seems to need way more down trim, many times I found myself holding the stick forward to keep it from climbing with the autopilot in ALT because it had reached max down trim. Now I'm using Onair Company and they load the aircraft, and don't allow me to adjust the load so who knows if they are loading it tail heavy, but I did do an empty flight and had the same issue.

 

Additionally, the autopilot seems to be possessed, randomly jumping into a steep climb out of nowhere when in HDG and ALT mode.

[Graeme_77]

As you mentioned it’s worth checking both the payload and maintenance screens. If the flight control surfaces are damaged then you will have issues. Also, what was your indicated airspeed when you experienced the steep climb out of nowhere?

 

[moespeeds]

Maintenance was fine, I check it every takeoff. 

Payload I'm not sure,  because onair loads the plane and you can't change that or it invalidates the flight. 

I did test it with just a 190lb passenger and 25% fuel and same issue. 

IAS around 180.

Edited June 3, 2020 by moespeeds

[Graeme_77]

I can’t say I’ve ever seen either issue, although I’ve heard of pitch issues with aircraft damage. I’m sure the developers will be along soon, but in the meantime can you post a screenshot of the PFD and MFD when you have the pitch up problem?

[moespeeds]

I'm in vr, the screen shot will look like a blob. 

What specifically would you be looking for in the pfd or mfd? 

[Graeme_77]

Really just to see if anything at all is out of place or unusual. I’d be looking at power settings, pitch attitude, trim positions. 

[moespeeds2]

Trim is full forward, NG 80-90%, pitch level, until it suddenly pitches to the moon out of nowhere, about 30 degrees up. No warning, no turbulence, just a sudden, uncommanded pitch up. Checked joystick center (Virpil T50) and all is good, works fine with other aircraft. Trim tab is not broken, and 

Like I said, I continually run out of forward trim as well, to the point where I need to hold constant forward pressure on the stick just so the autopilot can hold the nose level. Otherwise, it just continually climbs. 

I'm very familiar with the G1000, have several other aircraft with it. Where should the CG be with this thing? When I check it, it always seems to be around -2. I've tested this at 0, and +2 with similar results.

[Graeme_77]

No idea about the X-Plane C.G. as I only use the built in payload manager. However on my version it’s set to -7.1 centimetres and a payload weight of 95 kg on the initial w&b screen, before loading the flight. If I use the load manager to push the C.G. forward X-Plane reports -11 cm, and fully aft +11cm.

could you have some other plugin affecting it?

the only time I get a pitch up is if I deliberately fly beyond Vmo and even then it’s a gentle pitch up.

[moespeeds]

Def not above Vmo, speed doesn't seem to change the situation either way. It feels like a CG issue to me. I think I'm just gonna reinstall the thing tonight and see if that solves it.

[moespeeds]

Ok so I did a bunch of testing. 

To begin with, I re-installed the aircraft.

Climb to 16k, set NG to 93% and engage ALT and HDG hold. Aircraft holds, and accelerates normally to about 180 IAS. AP has trim about 80% down, everything seems fine. 

Then I very very slightly bump the stick, I mean barely move it, and the aircraft violently pitches up into about a 30 degree climb, and continues to pitch up. Full forward stick to recover, and when I check, ALT and HDG hold are still engaged, but the aircraft continues to want to pitch up, no matter what speed I fly. Trim is now full down, and the AP will recover if I manually guide the aircraft back to the set altitude, but I have to hold about 20% forward stick to keep it from pitching back up. AP still has full down trim set. 

Now if I disengage the AP, it's as if my stick has come out of sync with the in game yoke. The aircraft now wants to keep pitching up, and I need to keep constant forward pressure at any speed, and full down trim to fly level. I only attain neutral pitch again at around 100 kts IAS, 10k ft. Upon landing, full flaps, I still had about 80% down trim in at touchdown.

So basically, everything goes just fine, until I bump the stick slightly with AP engaged, and then the stick comes out of sync with the in-game yoke.

Tried this with the option for "simulate heavy controls" or whatever it's called, on and off.

[Graeme_77]

I’ve never heard of anything like that before - Is it possible you have multiple controls bound to the same pitch axis?

Actually, I have an idea. Let me do some testing.

Edited June 3, 2020 by Graeme_77

[Graeme_77]

OK, so I’ve seen something similar with another model, only once or twice on 11.50b9. It seemed to have the trim snap to the full aft position and stay there. However, I was never able to replicate it and haven’t seen it with the TBM. What plugins are you running? May be worth hopping onto the Hotstart discord as there’s a lot of TBM experience there.

[moespeeds]

Trim isn't snapping to full, the trim doesn't move unless myself or the AP move it. The in game yoke is coming out of sync with the physical yoke, if you touch it while the AP in engaged. 

Trim is otherwise working fine.

 

Just tested the G1000 on the Pocket Rocket, and it's fine, does not do the same thing. If you bump the stick, the AC bobbles, but the AP corrects and resumes like it should.

[Goran_M]

This is definitely not normal behaviour.  

Did you check the maintenance manager for any damage?  Do you have some kind of hardware that could be overriding the trims?

As a last resort, you could try deleting the contents of preferences folder and re-calibrating, but this a rather drastic step.

Also, we ask that you don't compare the TBM to other aircraft.  Reason being, for example, the pocket rocket has a completely different autopilot to the TBM.  The TBM requires the AP Trims switch to be turned on before the Autopilot will work.  Regardless of the AP button being pressed on the Autopilot panel.  

There is a lot of code behind each system on the TBM, and much of it works outside of the X-Pane envelope.  

You're more than welcome to join the Hot Start discord.  There may be someone who has experienced the same thing as you have, who may be able to help you.

https://discord.gg/nW4pkw

Edited June 3, 2020 by Goran_M

[moespeeds]

No damage. Checked that. 

Nothing physical that would affect trim. 

[Graeme_77]

So your experience is apparently unique with the TBM. Therefore we need to understand what is different on your system compared to everybody else. 

Any Plugins? What Axis bindings do you have? 

[mbaclawski]

Are you Using a Saitek Trim wheel along with the Pitch trim in the Autopilot ???   I get Jumps like that coming off Autopilot because the Trim wheel 

stays in the position it was in when you Activated the Autopilot. There was a Setting in FSUIPC to disable that but so far I haven't found one for X Plane . 

[moespeeds]

I got it!

So I remapped my pitch axis. I also had an issue where if I pressed the front right hat on my warthog up or down, I got a CTD. I stumbled on that by accident, since I had nothing mapped to them. When I went into controls, I had them mapped as custom, but with no bindings. I'm not sure which one fixed the autopilot problem, but the wacky behavior and CTDs are gone once I rebound pitch and cleared those hat bindings.

[Graeme_77]

Excellent, glad you got it fixed, and thanks for letting everybody know too! Hope you enjoy the TBM now.

[moespeeds]

I enjoy it very much, it's really grown on me. 

 

Thank you for the help!