Having trouble with pitch trim

[frostycab]

I've run into a small(?) problem with the pitch trim. It doesn't work for me.

To be more precise, I've checked the CBs are all in, and I can see the pitch trim indicator moving, but it doesn't appear to affect the stabilisers at all. Trimming full up or full down shows no movement on the external view, and as soon as I attempt a takeoff the aircraft just wants to pitch up with neutral stick even with full down trim commanded and set. I have to hold the stick at half-forward deflection just to maintain pitch.

I've looked through and I can't find any control conflicts anywhere. Does anyone have any ideas?

[Raven (Elysian Angel)]

Not really, sorry. It worked flawlessly for me, but I noticed trim is very sensitive and during most flight regimes I don't need to deviate much from the -3 units pitch trim set before take-off 

Control conflicts shouldn't happen indeed since HB left all the axis-controls blank - for which I am grateful: I don't like pre-set axes...

[Art-J]

A shot in the dark, but have you checked if your game/simplified flight mode hasn't reset itself to ON after an update? It shouldn't, but it's known for making trims inop in any module.

[frostycab]

6 minutes ago, Art-J said:

A shot in the dark, but have you checked if your game/simplified flight mode hasn't reset itself to ON after an update? It shouldn't, but it's known for making trims inop in any module.

Not that I can see. SFM is still unchecked in the Gameplay options. Good suggestion though.

[frostycab]

OK, someone on the HB Discord managed to work it out. I needed to disable the "Force Feedback" in the MISC options page in DCS. Apparently it causes problems for non-FFB controls sometimes. Didn't even know it was there.

[Victory205]

Due to the way the F-4E trim system works in concert with a control feel bellows, the stabilator will show full trailing edge down while on the ground and won't move with trim inputs. When airspeed increases, the stabs will begin to show their trimmed position and trim works normally.

If you are getting uncommanded pitch up in the air after confirming that the pitch axis is mapped properly, go to the DCS Options>Misc Menu and ensure that " Use Force Feed Back is Unchecked" 

Then read this-
 

 

Edited May 22, 2024 by Victory205

[-IRRE-Rolluptito]

Exactly the same problem for me. Any solution or idea ?

[Zabuzard]

Exactly the same problem for me. Any solution or idea ?

As others said before, make sure you have disabled the Force Feedback checkbox in the Misc settings of DCS.

And it is normal and correct behavior that, on the ground, the trimming won't move a thing. Details in the link posted above :)

[-IRRE-Rolluptito]

Oh indeed ! I was disabling the wrong thing...

Misc -> Force feedback unchecked solved the problem.

I was doing constant looping (and it was kind of fun ).

[Raven (Elysian Angel)]

1 hour ago, -IRRE-Rolluptito said:

I was doing constant looping (and it was kind of fun ).

Made you feel like an AI aircraft, then?

[Ozzie]

Yep - had the same problem - had to turn off force feedback in misc settings, or I was flying with stick at 3/4 forward to counteract something going on, the odd thing is that this had not affected any other aircraft, seemed specific the the F4 - other than that very impressed with the module well worth waiting for.

Thanks again for the above info couldn't find a reference elsewhere to this, worth raising the profile for this as it may be a harder to solve issue for others with less patience.

 

 

Edited May 23, 2024 by Ozzie

[ebabil]

Well I have two sticks (Warthog for planes and MSFFB2 for helicopters) So every time I want to play with Phantom, should I keep disabling and enabling FFB?

[Elor]

Thanks guys. I've had the same issue.

[kablamoman]

12 hours ago, Zabuzard said:

As others said before, make sure you have disabled the Force Feedback checkbox in the Misc settings of DCS.

I just spent all night trying to figure out what's going on with no luck.

On the controls overlay you can see the actual stick position and the in-game trimmed center position diverging quite erratically and in opposition to every manually made pitch input with the stick. The problem is not as noticeable at speed, but once you've slowed down to approach speeds it's especially noticeable and induces oscillations that make the thing borderline unflyable. I am not sure if this is a bug (potentially with FFB, even though I've made sure it's off, and have toggled it to be certain), or perhaps a side effect of how stick forces have been modelled-- but I can say that with a fixed center spring and cam stick it does not work out well at all, and it certainly does not fly like anything I've ever experience in real life or in the sim.

Basically, small adjustments to pitch on approach, where you should be able to comfortably hold a steady deflection are impossible as the stick simulation actively works against your inputs (or seems to).

[omohat]

So I have a FFB stick and I was facing this issue that the trim setting was having no effect; the trim indicator was showing full nose down trim but the plane was pitching up violently unless I applied3/4 forward stick pressure (checking the external model showed that the stabilator was not moving with trim adjustments despite the indicator in the cockpit moving).

Disabling Force Feedback on the Mics tab solved the issue but I've lost force feedback effects natively (which I did have before). Luckily I can still use an external program to generate FFB effects (VPForce Telem) but this feels like a bug somewhere in the FFB implementation.

[Geskes]

On 5/22/2024 at 8:28 PM, frostycab said:

OK, someone on the HB Discord managed to work it out. I needed to disable the "Force Feedback" in the MISC options page in DCS. Apparently it causes problems for non-FFB controls sometimes. Didn't even know it was there.

Thank you for sharing, sir.  

[Victory205]

Good answers to common issues can be found here-
 

 

[schmiefel]

On 5/22/2024 at 11:32 PM, Zabuzard said:

As others said before, make sure you have disabled the Force Feedback checkbox in the Misc settings of DCS.

I already had this FF checkbox deselected under MISC, but I have a similar very frustrating trim behavior, like @kablamoman recognized too, with my Virpil stick (VPC Alpha on a 50mm extension) and base (MT-50CM2 center mounted at my rig between my legs). Trim button inputs seem to have no effect until I move the stick slightly but then it results in an exagerated pitch change up or down. Seems completely not possible for me to reach a somehow balanced trimmed situation because each click of the trim button results in a different amount of trim inputs. Is there some kind of cross influence with maybe micro movements of the stick while applying trim inputs or are there other dependencies? May I have to set bigger deadzones for the center (I am currently at 3 and have a curve 15 for both stick axes)? Are there other DCS systems that get in the way besides the FF-checkbox as trimming the non digital birds in DCS was always a pain in the ass...?

[Super Grover]

On 5/23/2024 at 9:14 PM, omohat said:

So I have a FFB stick and I was facing this issue that the trim setting was having no effect; the trim indicator was showing full nose down trim but the plane was pitching up violently unless I applied3/4 forward stick pressure (checking the external model showed that the stabilator was not moving with trim adjustments despite the indicator in the cockpit moving).

Disabling Force Feedback on the Mics tab solved the issue but I've lost force feedback effects natively (which I did have before). Luckily I can still use an external program to generate FFB effects (VPForce Telem) but this feels like a bug somewhere in the FFB implementation.

If you use FFB, the stick forces should centre the stick at around that 1/2 forward position for cruise conditions. I mean, you shouldn't need to move the stick, but the neutral position won't be in the geometrical centre of the axis range. Please note that the trim moves the neutral position of the stick and does nothing else - as in real aircraft.

 

9 minutes ago, schmiefel said:

I already had this FF checkbox deselected under MISC, but I have a similar very frustrating trim behavior, like @kablamoman recognized too, with my Virpil stick (VPC Alpha on a 50mm extension) and base (MT-50CM2 center mounted at my rig between my legs). Trim button inputs seem to have no effect until I move the stick slightly but then it results in an exagerated pitch change up or down. Seems completely not possible for me to reach a somehow balanced trimmed situation because each click of the trim button results in a different amount of trim inputs. Is there some kind of cross influence with maybe micro movements of the stick while applying trim inputs or are there other dependencies? May I have to set bigger deadzones for the center (I am currently at 3 and have a curve 15 for both stick axes)? Are there other DCS systems that get in the way besides the FF-checkbox as trimming the non digital birds in DCS was always a pain in the ass...?

From your description, I can see that your observation is not how it should work. You shouldn't need to touch a non-FFB stick when applying trim to get an instant effect on the stabilator. Could you please do a short test flight where you exhibit the problem and send us the track so we can investigate the underlying calculations and conditions?

[schmiefel]

1 hour ago, Super Grover said:

From your description, I can see that your observation is not how it should work. You shouldn't need to touch a non-FFB stick when applying trim to get an instant effect on the stabilator. Could you please do a short test flight where you exhibit the problem and send us the track so we can investigate the underlying calculations and conditions?

Attached you'll find the track files. I put some screenshots from my settings in the VPC software and in DCS. too.

For those test I left the settings like described above.

As I did some further testing, I recognized that changing the input delays to much shorter times in the VPC device configuration software and applying larger deadzones to the X and Y axes helps a bit, but I am still not possible to reach some kind of 'stable' trim.

I am pretty sure that those kind of jets with no digital flight control will never settle at a zero trim state, but with my kind of input devices (that seem to be pretty solid on axis calibration etc.) there is always the trim going slightly up or down and even the roll trim can't get  stabilized and both seem to be off from the start. I didn't check the loadouts in the freeflight scenarios, maybe there is some imbalance from different loadouts.

But the most issue to me is that I couldn't input a certain amount of trim with each click of the trim hat and even if I set much broader deadzones the virtual stick in the cockpit always moves in the direction of trim for a short moment. Is that like the real stick behaves?

Or does this somehow have to do with this old - and still not solved - issue, that different aircraft respond in different ways to keyboard or button inputs for changing certain dial amounts. I kind of could solve this for e.g. the usage of rotary encoders on my VPC throttle device for changing pressure and course settings by reducing the delay times to 20ms to not get value changes from 2...5 increments with every rotary 'click':

The VPC default settings for button delay:

DCS axis settings for the stick:

DCS MISC settings:

I have recorded the two testflights with OBS but upload and processing still takes some time (approx. more than 30 min. after posting this just for SD resolution) as its recorded in 4k resolution:

 

24-05-24 trim testtrack02 nev.trk 24-05-24 trim testtrack01 cau.trk

[Super Grover]

Thank you, @schmiefel. I watched the videos, and they look as if no trim input has been applied. I'll investigate the tracks and let you know about my findings. Unfortunately, I don't own any Virpil joystick, but we have other team members who do, so we should be able to verify everything. The only thing missing is probably the screenshot of what you assigned to your trim commands in DCS - could you please upload it?

[schmiefel]

24 minutes ago, Super Grover said:

I watched the videos, and they look as if no trim input has been applied.

Well, that's kind of funny, because when you check the video recordings you even could see that the trim button of the virtual stick in the cockpit is activated and moving when I apply a trim input through the assigned joystick hat.

And here are my assignments for trim:

and that's the stick I use:

Edited May 24, 2024 by schmiefel

[Super Grover]

You're correct. I was looking at the controls display and ignored the HAT on the stick. What happens when you keep the trim button pressed for longer, like a second or so? The time required to move the pitch trim between the most extreme positions is around 10 seconds.

[schmiefel]

1 minute ago, Super Grover said:

What happens when you keep the trim button pressed for longer, like a second or so? The time required to move the pitch trim between the most extreme positions is around 10 seconds.

I didn't measure and test it to that extreme, but not applying very short presses results instantly in heavy pitch up or down and crazy climb or decent rates. I can do a track and video with that, too, tomorrow if needed.

[schmiefel]

did some more tests, this time with already applied very short delay times for the Virpil button events and a doubled deadzone in the DCS controls settings: This helps a little to better  control the trim inputs but doesn't cure that the trim works kind of strange for me as it reacts not very reliable on a certain amount of input and seems to change itself over the time without a change of the power settings and / or stick deflection. Plus it looks like as if the trim is connected to the stick in some way that doesn't work right as long as one has no FF-controlled stick.

The tracks and videos show first continuous applied and second approx. 1sec long trim inputs in both directions while doing no stick inputs until I needed to recover the dive or prevent a power on stall. But as you can see hopefully in both the tracks and the videos the virtual stick in the cockpit moves with each trim input, but as I had deactivated FFB in the settings already and I don't have a FFB-stick my real stick of course does nothing.

 

24-05-25 trim full deflect testtrack02 cau.trk 24-05-25 trim approx 1sec testtrack02 cau.trk