Flight Model / Engine Changes

[oldflyguy]

Hello!  I've been flying the TBM since it's release - absolutely my favorite!  I have noticed in the latest version that on take off with trims centered I must add significant forward pressure on the yoke along with "down" trim to get the aircraft to climb at the 10 degree mark.  Never noticed this in past versions.  I know in the RW I need to roll in a bit of down trim on climb out in my old C182Q (almost the same...LOL) but this seems very excessive.  I used both the standard and the experimental flight model but didn't experience any real difference.  This is with take off power set at near 100% as recommended in the POH.  This effect can be moderated to an extent simply by reducing the take off power but that's probably not a real world solution.  Has anyone else noticed this?

[Goran_M]

Nothing was changed in the controls of the aircraft in any of the updates.  I'm suspecting some kind of calibration issue.  Could you try unplugging your hardware and doing a test flight with your mouse.  If the problem goes away, it's a certainty the problem is with your hardware.  If the problem remains, then we'll diagnose further.

Edited March 25, 2020 by Goran_M

[oldflyguy]

Hi Goran!  I've tried the TBM in both of my XP installs - stable and beta.  Plug-in's removed and not.  Checked the Data outputs on control surfaces and trim settings.  With trim settings in the T/O (green) area the elevator trim tabs display significant "up" position (forcing the elevator up).  The data display shows significant elevator "up" trim in this position.  When adjusted so the data shows "0" trim the "visual" elevator trim tabs agree and are in the "neutral" position but the MFD displays significant "down" elevator trim.  I have the TBM in both installs as mentioned.  I've attached the logs from my "stable install".  At least I know it's not me...LOL!

Log.txt

TBM900_Log.txt

[Goran_M]

We have seen this behaviour in a handful of other peoples installs, but it was because of some kind of script or rogue assignment in their hardware.  

In your log file, I can see a lot of plugins, some of which could be interfering with the controls.  Can you remove all 3rd party plugins except Gizmo and try again.  I just ran a test on my end and all controls are working fine in the latest version.

 

[oldflyguy]

Hi Goran!

I removed all plug-in's and from both installs, deleted the current TBM's from both and re-installed.  I also deleted all 3rd party scenery from my beta install (I don't believe the scenery files would interfere but did this anyway).  I also re-calibrated the Gladiator joystick (again and again). The issue still exists.  Everything works except that to achieve "0" trim the elevator trim indicator on the MFD needs to be above the green neutral mark by about the width of the indicator arrow.  By the way, when booted up without the joystick connected the same condition exists.  Here's the latest log - I didn't see anything.  It would be interesting to know the conditions of those other users with the same issue...

Log.txt

TBM900_Log.txt

[oldflyguy]

So, I took the time to download a copy of XP (my 3rd) and installed the TBM.  The same issue exists on this fresh copy with the TBM as the only 3rd party product installed.  Seems to be an issue with the product, not XP, plug-in's or add-on's.  I've attached the logs - didn't fly anywhere, just fired it up...

TBM900_Log.txt

Log.txt

[Goran_M]

Did you try to completely disconnect all controller hardware?  This is how the problem was diagnosed in other people's configurations with the same issue.  When hardware was disconnected, everything worked fine using keystrokes.  Confirming the issue in the hardware.

[oldflyguy]

Hi Goran!

If you mean did I disconnect the joystick and pedals, then yes I did.  Still the same...

[Goran_M]

Looking at your last log file, I can see 2 issues. 1.  You have some kind of uncalibrated axis, which could very well be part of the cause.

 

And 2.  You have stability augmentation enabled somewhere.  Which could also be part of the problem.

 

Regarding the other people who had a similar problem, they fixed it by getting rid of some kind of trim assignment they had on a button or axis on their hardware.  Other than that, the problem seems to be isolated to your system.  

[oldflyguy]

Thanks Goran.  I will explore this.  I normally don't use any stability augmentation but now realize that on this fresh new install XP does set that.  I adjusted all my graphics settings upon booting up the new install but forgot this.  I don't think this is the issue however.  I will look into trim assignments but I think the only ones are on the joystick hat switch...

[Hangar]

I can confirm the same exact issue here. If you set elevator trim to zero using xplane's output data on screen the MFD actually indicates some down trim is being used. If you use the MFD to set the trim bar near to where the T/O indicator is you'll end up with too much up elevator. So in essence the MFD elevator trim does not seem to be synced correctly...OR we are not understanding it's use.

Also...I can tell you that you cannot center the aileron trim or the rudder trim using xplane's keyboard commands (datarefs). By default they are the "6" and "9" keys but they do not center the trim in this plane. I tried changing the key assignments to different keys with no success. Can you please fix this as well?

Ooops, almost forgot to ask...I also noticed that the plane tends to roll RIGHT and require LEFT trim in level flight (slip ball sits left of center)...seems it should be the opposite, no?

Edited April 6, 2020 by Hangar

[skiselkov]

18 minutes ago, Hangar said:

If you use the MFD to set the trim bar near to where the T/O indicator is you'll end up with too much up elevator

Please don't second-guess how built the plane by looking at the raw dataref output. T/O trim doesn't mean "center trim".

18 minutes ago, Hangar said:

I can tell you that you cannot center the aileron trim or the rudder trim using xplane's keyboard commands

That is a deliberate decision. The real aircraft doesn't have a "center trim" button, so neither does the model.

20 minutes ago, Hangar said:

I also noticed that the plane tends to roll RIGHT and require LEFT trim in level flight (slip ball sits left of center)

That is a normal tendency with high power and negative angle-of-attack, which is a common state in cruise. On a clockwise turning propeller, you will encounter a left-yawing tendency at positive AoA and a right-yawing tendency at negative AoA.

[skiselkov]

When you use the MFD mark T/O mark, you'll end up almost perfectly in trim: 

 

[Hangar]

1 hour ago, skiselkov said:

When you use the MFD mark T/O mark, you'll end up almost perfectly in trim: 

 

well that seems to work for me with alot of weight like you have there...but when i fly with my loadout (1 pilot and nobody else onboard), no baggage and half fuel the plane will insist on pointing its nose up after takeoff to nearly +20 degrees if I dont push down on the yoke or trim down right after gear-up. I'm setting elevator trim at green marker like you show in your clip. Have you tried it with low weights as I described?

I have no plugins for my testing and all trims are zeroed out before I take-off (except for elevator trim which is on green marker). 2 different and brand new controllers as well which are well calibrated (honeycomb yoke and T16000M stick) and i get same result with both.

 

Edited April 6, 2020 by Hangar

[Hangar]

2 hours ago, skiselkov said:

That is a normal tendency with high power and negative angle-of-attack, which is a common state in cruise. On a clockwise turning propeller, you will encounter a left-yawing tendency at positive AoA and a right-yawing tendency at negative AoA.

Yea, no...that's all well & good...I get it...but thats not what i see happening here at all...its not like the plane is asking for right rudder and dropping left wing on high power and AoA and then doing the opposite on low power and negative AoA..I'd love that (if it only would actually do that). Instead, it seems like it never asks for any right rudder and is only asking for left rudder...high power climbs? slip ball is left of center...high power climbing right turn? right rudder not indicated, it's just not needed here... also its not dropping right wing during low power descents...its doing it in high power situation where you just wouldnt expect it.

It's as if there's no torque effect at all...in fact if I actually edit in just a little bit of negative engine cant then all of a sudden it'll start behaving as you describe...which is good.

Edited April 6, 2020 by Hangar

[skiselkov]

22 hours ago, Hangar said:

(1 pilot and nobody else onboard), no baggage and half fuel the plane will insist on pointing its nose up after takeoff to nearly +20 degrees if I dont push down on the yoke or trim down right after gear-up

Yes, unsurprisingly, when you fly the aircraft nearly empty and at high power, it wants to climb a lot. Not really sure how you would expect it to behave. However, I think you are misunderstanding fundamentally how pitch trim works. You don't trim to a nose attitude, you trim to a speed. The aircraft is pretty well trimmed at around 115 - 120 knots with the trim in the takeoff band (notice, it's a band, a range, not a single spot - move closer to DN for only the forward seats being occupied and closer to UP for also back seats being occupied). Your nose attitude is a function of excess thrust available. At 115 knots and nearly empty, you may very well need to pitch up to 20 degrees to soak up all the excess thrust. If you want a shallower climb, you need to either:

1. reduce power, or
2. increase speed (<- this is requires a trim a change!)

Even step 1 can require a slight trim change, because the aerodynamic model also considers induced wind speed over the elevator from prop wash. In short, there is no such thing as hands-off perfect stability. The takeoff trim is simply there to make sure that on rotation, you will not experience excessive forces on the yoke. It's there to get you "into the ballpark." It doesn't mean you can let go of the controls and have the nose remain eternally nailed to a virtual point in the sky.

21 hours ago, Hangar said:

It's as if there's no torque effect at all...in fact if I actually edit in just a little bit of negative engine cant then all of a sudden it'll start behaving as you describe...which is good.

When flying at the very low weights you are (single occupant + 1/2 fuel), you will almost never get into positive AoA except right at liftoff. The reason you are seeing the aircraft have a slight tendency to roll right at high speeds almost irrespective of power is because we are simulating a fixed aileron trim tab (which is located on the right aileron, only the left aileron trim tab is controllable from the cockpit). At high speeds, the fixed aileron trim tab becomes more effective, resulting in a slight right torque on the fuselage. Again, there is no perfectly balanced point. At low airspeed, engine torque will dominate and at high speeds, fixed aileron trim will dominate. The aircraft is tuned to fly mostly roll-neutral at betwee 60-100% TRQ between approximately 170 - 210 knots. Anything outside of these two bands might require some aileron trim adjustments, or control pressures.

In this video you can see the effects that airspeed has on the aileron position. 

[Hangar]

9 hours ago, skiselkov said:

we are simulating a fixed aileron trim tab (which is located on the right aileron, only the left aileron trim tab is controllable from the cockpit). At high speeds, the fixed aileron trim tab becomes more effective, resulting in a slight right torque on the fuselage. Again, there is no perfectly balanced point. At low airspeed, engine torque will dominate and at high speeds, fixed aileron trim will dominate. The aircraft is tuned to fly mostly roll-neutral at betwee 60-100% TRQ between approximately 170 - 210 knots. Anything outside of these two bands might require some aileron trim adjustments, or control pressures.

Hi & thank you very much for explaining my findings in regards to the right roll. I had no idea about the fixed tab being aerodynamically simulated. At least now I understand what is causing all that right roll!

One quick question about this...is weight a factor in how much tab torque is created and at what speed it begins to occur? I'm asking because I notice the roll actually begins within the speed range you indicated as roll neutral (185kts). At 185kts I begin to roll right and around 190-195kts the roll is significant enough that the plane will not fly safely without correction. If I were heavier weighted would I then be able to attain neutral behavior within that 170-210 (assuming cavok and zero wind conditions of course)?

By the way...also appreciate the tip regarding the green trim marker on the MFD. While I'm aware that one typically trims for speed, my mistake was in not realizing the marker is actually a static "banded range" (since its pretty small for my tired eyes) and not knowing the speeds associated with that range (since its not documented in the manual). I was thinking it was dynamic according to weight and that we should center trim in middle of the T/O marker. By the way...I think you left your gear down for that video, otherwise you would have had to pull up alot quicker and higher :-)