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Rudder moving without any rudder input?


Nealius

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As I understand it, the F-15C has an ARI similar to the A-10C and AV-8B, however I frequently see the F-15's rudder moving when it shouldn't. Mainly when on the ground doing control surface checks. Moving the stabs up and down moves the rudder when it shouldn't. Wiping the ailerons also moves the rudder when it shouldn't. In comparison, neither the A-10C, nor the AV-8B, nor any of the FBW aircraft with automatic rudders exhibit this behavior. From the documentation I could find, the rudder should only be moving automatically in flight and/or when pitch and roll commands are blended together. With WoW and isolated pitch-only or aileron-only inputs I'm not sure that the rudder should be moving...

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You're correct, and on the other hand, though I suspect it's also not terribly important since all it affects in-game is your control checks.

 

 

I suppose there's a possibility that it causes trouble in cross wind TO/LD.

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There also seems to be something funny with the control surfaces when taking off, if you raise gear/flaps while staying down 20-50ft to accelerate for an unrestricted climb. The stabs and rudders will jerk shortly after the gear and flaps are stowed. Sometimes it's hardly noticeable, other times it's quite strong. Maybe a separate issue unless there's a wider controls issue going on.

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The stabs and rudders will jerk shortly after the gear and flaps are stowed. Sometimes it's hardly noticeable, other times it's quite strong.

Do you notice any related pitch/yaw changes when these jerks occur, or is it just that you notice these e.g. in the external view?

 

Can't remember that I ever encountered handling anomalies with the Eagle.

i7-7700K 4.2GHz, 16GB, GTX 1070 

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Correction, it's only the rudders. I replayed the track with both internal and external views. After gear up, I had a right yaw moment followed by a left yaw moment. The controls indication showed no rudder input from me. External view, played back at half speed, showed the rudders kick right, then kick left.

 

When it first happened, I thought it was wake turbulence from the AI that took off before me, but there was plenty of separation. I flew subsequent flights before the AI took off, eliminating the wake turbulence variable, and the twerking still happened.

 

Here's a video. The controls indication also showed left toe break input when I started my takeoff roll, but I never pressed the toe breaks, so I don't know where that came from either.

 

ADDENDUM: I triple checked my control bindings and could not find any conflicting key presses or conflicting axes.

 

NtDtUAgIkiE


Edited by Nealius
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The controls indication also showed left toe break input when I started my takeoff roll, but I never pressed the toe breaks, so I don't know where that came from either
.

Whatever the reason is, a brake input by the FCS is very unlikely and it seems to be connected to the uncommanded yaw input.

i7-7700K 4.2GHz, 16GB, GTX 1070 

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The only thing I can think of is some kind of stray input from my controllers, but if that were the case I would be seeing this behavior at various times during flight instead of only after gear up and flying quite low. I also don't experience any ghost toe-brake inputs in any other modules.

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With them disconnected I wouldn't be able to fly in order to check....

? Flight controls and throttle can be controlled via the keyboard so it's no problem to do a test without any connected hardware.

i7-7700K 4.2GHz, 16GB, GTX 1070 

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Reproducing low-level flight with keyboard is not something I have the skills to do, and this phenomenon only occurs under those specific circumstances.

 

Best case scenario I could plug up my old X52 and see if it happens with that too.

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Without any wind/turbulence you don't need any rudder/elevator input during the takeoff run.

At the correct speed you only need to tap a few times on the nose up key. No special skills required.

Since the rudder deflections happen already during the takeoff run on your setup, you don't even need to get airborne.

i7-7700K 4.2GHz, 16GB, GTX 1070 

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There were no uncommanded rudder deflections on the takeoff run, only a ghost toe-brake input. The rudder bug specifically happens after gear up, at low altitude and relatively high speed.

 

So, here's some more testing:

 

1. Two flights with rudder pedals totally disconnected. Runway start, same mission, same payload. No rudder bug.

2. Two flights with rudder pedals connected. Runway start, same mission, same payload. No rudder bug.

 

But, there were three changed variables:

 

1. Rudder bug was seen in OB 2.5.5.32299; This test was done on 2.5.5.33184

2. Rudder bug was seen after ramp cold starts; This test was done with a runway start

3. Rudder bug was seen while flying in VR; This test was done in 2D

 

Unless there's something fishy going on with ramp cold starts, or VR, then updating my OB fixed it.


Edited by Nealius
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As I understand it, the F-15C has an ARI similar to the A-10C and AV-8B, however I frequently see the F-15's rudder moving when it shouldn't. Mainly when on the ground doing control surface checks. Moving the stabs up and down moves the rudder when it shouldn't. Wiping the ailerons also moves the rudder when it shouldn't. In comparison, neither the A-10C, nor the AV-8B, nor any of the FBW aircraft with automatic rudders exhibit this behavior. From the documentation I could find, the rudder should only be moving automatically in flight and/or when pitch and roll commands are blended together. With WoW and isolated pitch-only or aileron-only inputs I'm not sure that the rudder should be moving...

I could not find any mention in the -1 that WoW should disable ARI. It should disengage when:

- airspeed above Mach 1.0

- landing rollout (I understand this part one would read as WoW)

- langing gear handle down and anti-skid switch off

 

 

Also check this:

I would assume that pilots don't test the rudder and stick at the same time which would be clear that ARI is enabled on the ground too.

 

 

btw: I tried to replicate your take off but could not find rudder jitters. Try to replay my track.

F-15C rudder.trk


Edited by draconus

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