reported earlier Negative static lateral stability in PA mode

[Ahmed]

Recorded in a laptop with keyboard, but I think it still illustrates the issue.

The flight model/FCS exhibits negative static stability when in PA mode. After rolling to a 30º bank, going hands off results on the aircraft overbanking progressively. This is highly unusual for a fixed wing aircraft and would definitely be documented in the NFM if it were a known handling characteristic.

 

latstab.trk

[BIGNEWY]

Hi, 

first question why using a keyboard? is that part of what you think the problem is? 

second please PM me any public evidence you have to support the claim. 

thanks

[Hiob]

IIRC when using the Keyboard for stick movement, the stick won't self center but stay put until you actively steer it back in the opposite direction. May that be the issue here?

[BIGNEWY]

The team do already have this reported it seems. 

thank you

[Dragon1-1]

I noticed that the Hornet, when rolled to any other angle than zero, will not hold that roll attitude. Track attached, please watch with CTRL+ENT controls indicator to verify what is commanded and what is not. Also pay close attention to the roll indicator on the HUD. The first few turns are in cruise configuration. The Hornet will slowly attempt to right itself, creeping back to zero roll when rolled to 60 or 45 degrees, as shown on the HUD. Worse is the issue shown during the landing configuration part, where the Hornet will increase the bank angle once rolled to similar angles, and will do so quite rapidly. Neither is correct behavior for an FBW aircraft, and the latter is not good behavior for any aircraft. 

BugBadRoll.trk

[Swift.]

https://forum.dcs.world/topic/296648-negative-static-lateral-stability-in-pa-mode/#comment-4927263

[Dragon1-1]

Yeah, that's the second part of the problem. However, lack of neutral stability in cruise configuration is possibly a separate issue. The point is, it doesn't hold high bank angles in any flight regime.

[Razor18]

I had now uncommanded roll 3 times in 2 days. Yesterday after an hour of flying, plane started to roll right, first just gentle, then gradually to the point when no full left stick could counter it. Today after a takeoff and climbout, about 3 minutes after takeoff, and then when trying it again , already during startup. Both stabs and the aileron deflected full right, unfortunately FCS screen unreadable but it was like left aileron down 40, right aileron up 8, and the stab numbers were also totally assimetric to the right (Guess LEFT 2 down, right 18 up or something)... Just as the outside picture shows it.

Tried to Reset and FCS BIT TEST 2 more time, nothing. No axis assignment mix up, checked. If it were, would have occure right after liftoff anyway on all 3 occasions I guess. Any clue?

 

Edited July 31, 2022 by Razor18

[rob10]

1 hour ago, Razor18 said:

I had now uncommanded roll 3 times in 2 days. Yesterday after an hour of flying, plane started to roll right, first just gentle, then gradually to the point when no full left stick could counter it. Today after a takeoff and climbout, about 3 minutes after takeoff, and then when trying it again , already during startup. Both stabs and the aileron deflected full right, unfortunately FCS screen unreadable but it was like left aileron down 40, right aileron up 8, and the stab numbers were also totally assimetric to the right (Guess LEFT 2 down, right 18 up or something)... Just as the outside picture shows it.

Tried to Reset and FCS BIT TEST 2 more time, nothing. No axis assignment mix up, checked. If it were, would have occure right after liftoff anyway on all 3 occasions I guess. Any clue?

Did you check and see what the controls indicator was showing (RCTRL-ENTER is default IIRC)?  This really sounds like you're getting some kind of undesired control inputs.  Any ordinance/tanks/pods on the plane that could make it asymmetric?

[Razor18]

Looked up some tracks. If I call up Control screen, it looks like after a random time the little line on the X axis begins to wander slowly from centre towards right. (Guess it must be the trim tab?) So I try to counter it, first a little deflection is enough, then it goes out of control. What I do not understand, from outside view, I hold the control surfaces with the stick totally symmetric reg. right - left, they are level with the wing even during the most violent uncontrollable spin the aircraft goes into. So it doesn't look like the would be induced "aerodynamically".  I do not see the trim button moving on the stick on screen, but for good measures, now I deleted keyboard trim inputs. Will unplug replug stick USB too, who knows, what helps. Thanks for the tip anyway...
Is there any app that can log/record my controller outputs to see if the creeping trim input are coming from the stick?

Edited July 31, 2022 by Razor18

[Minsky]

2 hours ago, Razor18 said:

Is there any app that can log/record my controller outputs to see if the creeping trim input are coming from the stick?

Try VKB Joy Tester, the download link is near the bottom of this page.

[Razor18]

Thanks, MInsky,

does it also log/record whatever command comes from the joy? If it only monitors real time, there will be no trace of trimm creep, if I try to look it up later.

Edited August 1, 2022 by Razor18

[Minsky]

49 minutes ago, Razor18 said:

does it also log/record whatever command comes from the joy? If it only monitors real time, there will be no trace of trimm creep, if I try to look it up later.

It has endless log for button presses, but axes are real time only, I'm afraid. It records the last 15-60 seconds (depending on how wide you expand the window), and then overwrites it ECG-style.

[Razor18]

Didn't know about logging function ! Coool, thanks !

[BIGNEWY]

posts merged