Rudders moving on their own?

[Nealius]

Attaching a track. Happens to both A and B models. Hot ramp start. Rudder axis is not assigned to any controllers. There is zero rudder input being sent to DCS.

Some movements are smaller than others. There's at least one fairly large movement visible. Not sure what's going on here.

 

Rudderspasm.trk

[Gunslinger22]

Interesting, just finished a flight when on the ground I noticed my rudders moving, check all axis and much like your findings there were no inputs other than some DCS magic going on. 

[Nealius]

It seems to be caused by wind and/or turbulence.

Winds 6kts, turbulence 40 (average day for flying gliders): Rudder moves. From 0:56 to 1:20 you can see almost full rudder deflection during some spasms.

Winds 0kts, turbulence 0: Rudders stationary for full 2 minutes.

Rudder0Wind0Turbulence.trk RudderwithWindandTurbulence.trk

[fat creason]

Probably the Yaw SAS...

[Spartan111sqn]

2 hours ago, fat creason said:

Probably the Yaw SAS...

Yaw SAS coordinate rudder in DCS?, I thought that it was when DFCS was implemented in RL, but not in DCS, right?

[fat creason]

https://www.heatblur.se/F-14Manual/cockpit.html#afcs-control-panel

In case you're not aware, there's an AFCS panel on the left side of the cockpit. Note the labels on the AFCS panel...

Edited December 15, 2021 by fat creason

[IronMike]

Wind and high turbulence in DCS pushes rudders. I always thought this effect to be exaggerated tbh.

[Nealius]

5 hours ago, IronMike said:

Wind and high turbulence in DCS pushes rudders. I always thought this effect to be exaggerated tbh.

Just investigated with all high-fidelity non-FBW jets, plus the Mosquito for good measure (massive rudder, no hydraulics, no prop wash). 6kt crosswind from rear quarter, turbulence 40. 

A-10C II - No movement

AV-8B - No movement

AJS 37 - No movement

F-86 - No movement

L-39 - No rudder movement, but the aircraft itself yaws around on the ground

Mig-15 - No movement

Mig-19 - No movement

Mig-21 - No movement

Mosquito - No movement

The F-14A/B appears to be the only one with this involuntary rudder movement. 

[IronMike]

1 hour ago, Nealius said:

Just investigated with all high-fidelity non-FBW jets, plus the Mosquito for good measure (massive rudder, no hydraulics, no prop wash). 6kt crosswind from rear quarter, turbulence 40. 

A-10C II - No movement

AV-8B - No movement

AJS 37 - No movement

F-86 - No movement

L-39 - No rudder movement, but the aircraft itself yaws around on the ground

Mig-15 - No movement

Mig-19 - No movement

Mig-21 - No movement

Mosquito - No movement

The F-14A/B appears to be the only one with this involuntary rudder movement. 

Thank you! We will take a look as to why that is.

[Nealius]

I'll run another test with a 180-deg crosswind at ludicrous knots and thunderstorm-level turbulence to see if I can force the other modules to react. Starting to feel like a Mythbuster with less pyrotechnics. 

[draconus]

https://www.quora.com/Why-is-the-rudder-of-an-aircraft-towards-the-left-when-you-view-it-from-the-nose-when-parked-at-the-airport?share=1

https://en.wikipedia.org/wiki/Gust_lock

So wind gusts on rudders are a real thing and concern but I have no information how much the Tomcat would be affected. I guess HB will ask their SME's on the matter. That other modules do not behave the same it may as well mean just that they are not modeled to that extent.

[r4y30n]

Lack of hydraulic pressure after shut down seems plausible. With the engines running I don’t think there would be any movement, given the irreversible controls.

[Nealius]

With engines off and no hydraulic pressure, yeah I can see wind moving the rudders. On a ramp hot start with engines running and good hydraulic pressure I would think nothing less than tornado winds would move the rudders.

[IronMike]

So, @Cobra847 corrected me and pointed out that I was likely misremembering, since the animation of control surfaces is 100% driven by us, and not by the core game. Thus I likely remembered seeing it on other modules, while I likely only saw it on ours. We will investigate how plausible it would be (some good points have been mentioned above) and why it is as is where it shouldn't be like that.

Thank you all again for bringing it to our attention.

Edited December 16, 2021 by IronMike

[fat creason]

Yeah I was about to say...wind is not a factor in the rudder code anywhere. Any "involuntary" movement of the rudder is almost certainly the Yaw SAS.

Edited December 16, 2021 by fat creason