Experimental flight model following FD at “high” speeds

[Mark Amber]

Hello,

I have been happily flying TBM900 without the “experimental flight model” button checked in XP. Everything seems to work as I would expect. 
 

Somewhere here on the forum I was reading that the experimental flight model was either recommended or optional. So I turned it on and started a new flight. I even made a new airframe (I wasn’t sure if this was needed). 
 

I did have a well documented “bumping” issue. I was bouncing up and down like a bus on a street with potholes on the runway. 
 

in addition to that issue and more problematic, I started having more issues around 15k feet. It felt like the flaps were in T/O with the autopilot off. Like there was a lot of drag and a LOT of lift. The autopilot would not hold the attitude of the flight director. It was trying to trim, and it was commanding the control surfaces. The autopilot was unable to maintain FL270 with Torque power in the “cruise” band, even with the FD showing nose down it continued to climb at 100-150 ft/min any additional throttle just added to the pitch up with the autopilot unable to correct further. I imagine based on this there is some limit which the autopilot runs the trim out to, because I was able to trim nose down manually, disengaging the autopilot, and fly level by hand but I was almost out of trim. In the old flight model this is not a problem. In “non experimental” I am flying right now at FL270 with power in the cruise band at Mach 0.54 and the autopilot works fine  

So I expect this is a regression in the experimental model or my user error. Do you developers have any idea? I am happy to go through the paces, but also maybe you could talk a little about if the experimental model is needed. 
 

-mark

[Mark Amber]

I am going try some other configurations of the cabin and payloads tomorrow. After going back and forth I can say with the experimental flight model ON it seems to all work better overall. The runway “bumpiness” is obviously just nonsense but everything else about it feels better. 
 

tonight I did go through the joystick settings and check for phantom axis. 
 

I imagine that “experimental mode off” was a crutch and with experimental mode “on” I am just seeing either a weird sim-specific problem (joystick button mapping problem... again, the axis are all fine) or some sort of user error on my part. I will try to recreate my flight tomorrow where I had this issue. 

[Mark Amber]

I now cannot re-create this today. 
 

is there a setting which could be bound to a joystick button (besides AP trims switch in the 3D cockpit) which could cause the altitude hold/AP to lose effectiveness and explain what was happening yesterday?

[Goran_M]

There could always be some kind of rogue key or button assignment that could override what we're doing in the TBM, but there is no way for us to find it.  An easy way would be to delete the contents of your preferences folder and restarting the sim.  However, this will delete all your key, button and axis assignments.  But it is definitely the most effective way to determine the cause.

[moespeeds]

I had a similar problem, running out of down trim in cruise. I initially thought it was a cg issue related to an economy addon that was loading the aircraft. 

The fix for me was to map my joystick pitch axis to something else, like mixture, then change it back to pitch. It's like something in the mapping got corrupted.