Yaw Damper/Trims

[Acarter87]

Firstly, I absolutely love this plane. everytime I get into, I'm amazed at just how good it is! I am generally an airline guy but I can't get enough of this beauty.

I'm after some advice from the more knowledgable GA pilots out there. I'm trying to handfly as much as possible rather than just chucking on the AP once I'm off the ground.

I take off and switch the yaw damper on, assuming I should do this, however when I do it trims left rudder so the plane tends to roll left rather than fly straight.

Should I be trimming right aileron to level out or am I doing something wrong? obviously if I turn the yaw damper off and trim rudder myself like I'm driving a Cessna it's fine.

Cheers,

Ant

Edited June 8, 2019 by Acarter87

[Eseem]

Piling on, should we expect roll stability with YD on, given there's no fuel imbalance or uneven drag? If we need to trim for roll with YD on, do we trim aileron or rudder?

My experience right now is the same as above, on climb with YD on the aircraft trims for left roll.

Edited June 14, 2019 by Eseem

[Eseem]

Apparently, YD includes an auto trim system that should ensure coordinated flight as long as YD is engaged, i.e. no rolling tendencies, according to Daher

Is this not yet implemented correctly, or is something wrong with the installations / how the aircraft are managed / third party addons in the case of the two of us experiencing these rolling tendencies?

[Acarter87]

I think this forum is dead

[RobW05]

Yaw damper won't trim out roll tendencies, so you have to counteract with aileron trim. Fuel imbalance and torque will make you roll all the time, there's rarely a situation where you can have aileron trim centered with wings level. 

I think totoritko mentioned once that the TBM is pre-trimmed for zero roll at about 50% torque. This means it tends to roll left at higher setting and right at lower setting, not taking into account other factors like fuel imbalance. 

[Eseem]

I think you are only partially correct. Fuel imbalance and other things affecting CG displacement or unequal L/D would require aileron trim, however as far as I'm able to find out the YD should autotrim for coordinated flight, and should be able to do so without aileron trim even with changing power levels. In the Dash 8 you really only trim rudder to accound for power changes, though manually (check the q400 copypasta for more info on this, lol). The PC12, a very similar airframe, certainly has this function included in their very similar avionics suite, however imperfect:

Quote

The PC-12's yaw damper incorporates an auto-trim feature that automatically centres the ball as power levels change. The system did a good job of keeping the aircraft in trim, but was unable to keep up with rapid power changes.

https://www.flightglobal.com/news/articles/flight-test-pilatus-pc-12-power-of-one-187732/

 

[RobW05]

4 hours ago, Eseem said:

however as far as I'm able to find out the YD should autotrim for coordinated flight, and should be able to do so without aileron trim even with changing power levels

Sure it will do, it will keep the ball centered for you, keep your nose straight. But it's no "wing leveller". 

[Eseem]

On 6/18/2019 at 5:21 AM, RobW05 said:

But it's no "wing leveller". 

If it's set up for it, it definitely could be. Yaw absolutely impacts roll through dihedral effect, and even becomes a stronger rolling force than ailerons at and beyond crossover alpha. I found a few written claims through this thread, and the consensus seems to mostly be that aileron is a one-off, or needed on old and bent airframes, but of course different types and styles gives different experiences and some use it more than others. What I read concurs largely with what I've seen and been told jumpseating turboprop twin commuters, and in any case it's all exactly opposite of how I'm experiencing roll trim requirements when simming with the TBM.

In addition, simming is mostly done with spring-centered controls which is much more sensitive to aircraft being in trim than real controls which you operate like you do a steering wheel in a car to keep it on a mostly straight road; without thinking about it much and little effort. Fighting this rolling with trim back and forth all the time is taking the fun out of handflying it IMO, some "dumbing down" should at least be optional if the real thing would be anything close to this sensitive about the longitudinal axis. 

Lastly, as a glider pilot, the rudder is my most important banking control surface, so why wouldn't it be on the TBM?? (<- joke, also answer provided above)

[RobW05]

I think all what you mentioned above is absolutely valid, especially regarding our flight controls which are noisy and of course give no force feedback, thus don't allow for all the tiny corrections you would do without thinking about it IRL. But still I think torque is a factor, even more so because we're flying a 850shp beast, tremendous power given its relatively light weight. Roll tendencies would definitely be present imho. One could argue if it's a little exaggerated of course, but that would be a question for the lucky guys flying those birds IRL . Given the fact that Hotstart really pushed the limits with this model in so many ways i would think that it's correct.

But if you think it isn't i would suggest to just ask Toto or Goran what they think about it. They are very responsive on questions in their discord channel. 

[Eseem]

I would love to! Who are they? Pilots? Devs? What Discord?

[RobW05]

They are the devs behind this fabulous TBM 900

Look for the discord channel "Hot Start".

[Eseem]

Some insight from our friendly real life TBM flyer: