Problems with trimmer

Wait... so you're saying that when the AP channel adjusts for something like a headwind that the FFB doesn't move the stick to follow where the AP moves the control surfaces to? I don't understand how that's possible.

I'll have to go fly the thing and watch the stick to see if it moves in this case. I won't need to buy a FFB stick :).

Also yeah... what you said in the second part of your last post where you corrected yourself is correct :). But that's not what your other post seemed to say :).

That's why I said "No." to the other post :).

Ranma, that is a cool way to show us this topic. The rubberband demonstration is really nice. Thx

All the FFB does for the helicopters in DCS is change the location of the centering force. When you press the trimmer, it will set the centering position to the location of the joystick at the time it's pressed:

Most of the FFB effects in DCS are very simplistic, only adding a force trim effect but nothing else. Some aircraft like the Su-25T will go a step further and do things like make the FFB force stronger as airspeed increases and shake the stick if you're going too fast or entering a stall:

And the TF-51D will occasionally jerk the stick to simulate wind, but as far as I know none of the modules do anything FFB-related to wind or auto-pilot.

Good explanation with the rubber band Ranma13. I do understand what you are getting at and you are correct.

Another way to see this in game is when sometimes you are in a auto hover, you think you have everything trimmed perfectly, but your heading/yaw AP channel is actually pushing 15% left rudder. (for example) You have a target locked on the shkval to the left side of the HUD, you activate Turn to TGT but the shark struggles to turn because the AP doesn't have enough authority to command the full amount of rudder needed.

I've been flying the shark for a long time so i have no issues flying it or understanding this, i just question if the real deal has the issue i described earlier.

" My only issue with the trim is when for example. You are in a hover , pitch down 20deg, tap trim & center stick, then the shark will dip the nose double that to 40deg."

Yeah I like the rubber band explanation :)... It clearly demonstrates why we should hold trim ;).

Flight Director does the same thing as holding down the trim button, except it doesn't disengage force trim effect.

Ahh, so pressing FD turns off all the AP channels, but still keeps the FFB joystick where you last trimmed it. And I can see hitting FD would cause a jump, as the AP channels would no longer fight to keep the helicopter in the AP's designated positioning.

The way it is modeled at the moment is simply wrong. The trim is to make the helicopter stable and not to owereakting. Holding the trim button is simply wrong , because it takes all the dampening force away from the stick. And this is dangerous.

No, it's modeled correctly. You're trying to fit your idea of how an auto-pilot should work into the Ka-50 and calling it wrong because it doesn't match your expectations.

If by dampening force you mean what the West would call SAS, then holding the trim button doesn't remove it. The autopilot channels have two functions when they're enabled: the hold channel that tries to hold the attitude of the aircraft, and the SAS system. As long as the channels are on and not flashing, the SAS system is always enabled. Pressing trim only disables the attitude hold of the aircraft, but not the SAS. The only way to turn off the SAS is to turn off the channels. This isn't dangerous per se, it just makes the helicopter a bit harder to control.

Ok, this is what I thought. When you turn off all the 4 AP channels, you COMPLETELY turn off the autopilot, and thus the SAS. The only thing left is the FFB trim. Right? This explains why there is an FD button, which doesn't shut off the SAS.

Unless there's some master AP on / off switch I don't know about.

Yes, correct. With the AP channels off, the attitude hold and SAS are disabled, leaving only the force trim. The Flight Director button disables the attitude hold, but keeps the SAS and force trim enabled. Holding down the trim button keeps the SAS, but disables the attitude hold and force trim. If you have a non-FFB joystick, holding down the trim and enabling Flight Director will do the same thing. The difference is only apparent when you're using a FFB joystick.

Edit: Added this table for clarity:

---------------------------------------------------------
| Type               | Force Trim | SAS | Attitude Hold |
---------------------------------------------------------
| Trim button        |            |  x  |               |
| AP channels off    |     x      |     |               |
| Flight Director on |     x      |  x  |               |
---------------------------------------------------------

Yes, correct. With the AP channels off, the attitude hold and SAS are disabled, leaving only the force trim. The Flight Director button disables the attitude hold, but keeps the SAS and force trim enabled. Holding down the trim button keeps the SAS, but disables the attitude hold and force trim. If you have a non-FFB joystick, holding down the trim and enabling Flight Director will do the same thing. The difference is only apparent when you're using a FFB joystick.

Interesting. That's probably the clearest answer we've had yet on how the AP works. Thanks!

Using the X65F with my GlovePIE autotrimming script and now the option of "Joystick Without Springs and FFB" Trimmer Mode in Options->Special->Ka-50, I seem to be able to simply leave Flight Director off, now. It's less squirrely and more like Enemy Engaged... but better physics, obviously. I mean better behaved. The SAS axis channel damping in combination with the attitude hold (but no manual trim within the sim, only in GlovePIE's virtual PPJoystick) seem to do their thing better now and there's no need to cycle through the GlovePIE script modes from Manual, to Standard Dynamic Trim, to Flight Director Dynamic Trim by double-clicking the pinkie button a couple times since there's no actual in-sim manual trim to clear... I believe, correct me if I'm wrong. I just do it once to get to Standard or Flight Director versions depending on how much bank I want to be able to hold.

I probably need to tweak my script a little so there's less wobble upon input and to change the quickness of the script response, but doing the auto-trimming loop thing in the script while it's also seeing the raw input seems to currently work well enough right now after finally updating to the beta last night. And when I stop sort of commanding a rate input on the X65F, it seems to do attitude hold pretty acceptably... similar to doing manual trimming with my pinky finger clicking frequently whenever I would find an attitude I wanted to keep. I rarely used Manual Trim mode on the GlovePIE script because I always found it clunky with a normal spring-loaded (X52) or fixed-position pressure (X65F) stick, but the Dynamic Trims were always much more seat-of-your-pants and required constant adjustment than this... you had to constantly fly the helo every second, which I enjoyed but could be a handful... not so much now with option of no-spring & FFB.

Then there are various things I can do to utilize heading hold for the rudder channel, like steer towards target, which seems to have quite a bit more channel authority than the damping, though still not as much as I'd like. It's not true "automatic dynamic trim update" rate-command/attitude-hold like ADOCS and Comanche had and later block Apaches are apparently supposed to eventually get if they ever move to side sticks (think Janes Longbow series), but it's definitely usable.