reported Long lasting yaw oscillation caused by the rudder

[DummyCatz]

Currently in 2.9.2, whenever a sideslip is recreated by just rolling the aircraft at a speed around 400 knots, the rudder slaps hard to reduce the sideslip and results in a long-lasting yaw oscillation, as if yaw damping doesn't exist, which I found unacceptable from a handling quality point of view. 

According to section 9.1.3 Directional Auto Flap Up CAS from the NASA technical memorandum 'Simulation Model of a Twin-Tail, High Performance Airplane' (https://ntrs.nasa.gov/api/citations/19920024293/downloads/19920024293.pdf), the yaw rate (multiplied by cosine of angle of attack) feedback component is used to augment the Dutch roll damping.

In the case of DCS, the oscillation is caused by the rudder itself, indicating either it is over-gained (system unstable/phase margin too low), or a wrong type of feedback (sideslip) is used according to another report https://forum.dcs.world/topic/338130-the-rudder-should-not-be-using-sideslip-feedback-for-yaw-dampening-causing-a-very-slow-yaw-response

 

F18 yaw oscillation.trk

[DummyCatz]

A new track for 2.9.4 showing an extremely long duration of rudder oscillation.

F18 very long lasting rudder oscillation.trk

[Teleblaster]

This appears to be the only bug report on this topic, which is shocking as it’s such a huge problem and happens to me (and several people I fly with) all the time. 

[Teleblaster]

Still nothing on this? This is a huge problem with the flight model. It’s not an isolated thing, anyone who flies the Hornet regularly in the DCS Dogfighters server can tell you all about it, including a guy who flies the F-22 IRL. I’m disappointed that this isn’t getting any attention from ED. I was hoping to see a fix in this update. 

[BJ55]

You're doing something wrong, maybe during startup, if I take control of the last .trk and press FCS Reset the yaw oscillation quits.

[DummyCatz]

12 hours ago, BJ55 said:

You're doing something wrong, maybe during startup, if I take control of the last .trk and press FCS Reset the yaw oscillation quits.

How does it has anything to do with startup when the mission is starting in the air?

There was no failure indication of any kind. If FCS reset works then it only means the yaw-rate or sideslip feedbacks are momentarily reset to zero that stopped the FCS from overreacting.

Edited June 6, 2024 by DummyCatz

[BJ55]

2 hours ago, DummyCatz said:

the mission is starting in the air

This is a new information! You noticed the same behaviour even in other missions and starting from c&d?

I've never ever had those weird yaw oscillations in hundreds of flight hours (for the most I use TTI missions).

[DummyCatz]

34 minutes ago, BJ55 said:

This is a new information! You noticed the same behaviour even in other missions and starting from c&d?

I've never ever had those weird yaw oscillations in hundreds of flight hours (for the most I use TTI missions).

This was to keep the track concise and on point as requested by BIGNEWY. There's already some tracks of a full mission posted by others in another thread.

 

[Lord Vader]

Hi @DummyCatz

We've been investigating this potential issue you described for some time, while we fine tune the FCS, including the rudder performance.

Your track is fine for that purpose and we thank you for that.