resolved Apache turns right violently in hover

[Rongor]

This appears suddenly and in these moments the green SCAS line in the indicator display instantly jumps to the left limit. It's triggered by wind coming from the left.

It's easily reproducable so at this point I didn't attach a trackfile (yet).

 

You need wind in the mission. Take off into a stable hover, nose into the wind (10 kts will do). Then slowly give a little right pedal to gradually turn the nose right.

The moment you have the wind at 270° relative to your nose, yaw control is running wild for a moment, violent yaw to the right sets in, SCAS yaw will be at its left limit.

Apparently it does not happen while yawing left around a complete circle.

[placsea]

Hi Rongor, here's the video I posted in the discord where we were discussing this. Thought it might be helpful for folks if they've been experiencing this. 

 

 

[Swift.]

So I think I can see what's happening here. It would appear that as you slow down the wind being experienced by the aircraft is suddenly removed. 

You start with wind from the left, blowing the nose to the left. If you suddenly removed that wind, the nose would consequently veer to the right (for the same pedal position).

Now look at the video, at 0:29 the TSD wind goes from 5 knots from the left to CALM. And in that instant, the nose snaps to the right.

[Scaley]

This looks like it's tail rotor VRS. Some new lines of code relating to tail rotor VRS have been added to the flight model config.lua. If you set the tail rotor VRS effect to zero in this file the observed behaviour goes away. 

Edited September 23, 2022 by Scaley

[DOG]

3 hours ago, Scaley said:

This looks like it's tail rotor VRS. Some new lines of code relating to tail rotor VRS have been added to the flight model config.lua. If you set the tail rotor VRS effect to zero in this file the observer behaviour goes away. 

That would make a lot of sense.

[Fakum]

@ScaleyCan you post the file location and highlight the line of interest please? Thanks,

[Scaley]

2 minutes ago, Fakum said:

@ScaleyCan you post the file location and highlight the line of interest please? Thanks,

See this thread:

If you search that Lua file for anything with "scaley" you'll find all the edits I've made tagged.

[ZQuickSilverZ]

Mine is doing the same thing.

It's worth noting I hold a manual hover for several seconds (say 30 or so) but once I hit that attitude hold I veer to the right every single time.

I will say I am using a VKB Gladiator NXT EVO with dry clutch meaning I have no return to center.

I am starting to wonder if using a springless stick is messing with the logic of the Trim/AP overrides (or dampening whatever you want to call it).

Are any of you flying dry clutch?

Another guy I fly with is using a Warthog and has had no issues like this. This has to be some sort of bug.... the behavior experienced is just too repeatable. Exactly like in the video posted above.

 

EDIT: I just noticed he did not activate attitude hold but when I try to use it attitude hold consistently puts me into a clockwise spin.

Edited September 24, 2022 by ZQuickSilverZ

[Swift.]

34 minutes ago, ZQuickSilverZ said:

Mine is doing the same thing.

It's worth noting I hold a manual hover for several seconds (say 30 or so) but once I hit that attitude hold I veer to the right every single time.

I will say I am using a VKB Gladiator NXT EVO with dry clutch meaning I have no return to center.

I am starting to wonder if using a springless stick is messing with the logic of the Trim/AP overrides (or dampening whatever you want to call it).

Are any of you flying dry clutch?

Another guy I fly with is using a Warthog and has had no issues like this. This has to be some sort of bug.... the behavior experienced is just too repeatable. Exactly like in the video posted above.

 

EDIT: I just noticed he did not activate attitude hold but when I try to use it attitude hold consistently puts me into a clockwise spin.

 

Its a bug based around EDs initial implementation of tail rotor VRS......

Luckily you can fix it using Scaleys FM edit as posted above (make sure you have the most recent version)

[Raptor9]

Feedback has been submitted by the SME team regarding the tail rotor VRS and has been reported.

Not going into the details, but in reality the weathervane effects of the AH-64 vertical tail should force the nose into the direction of the relative wind (whether it be high-speed sideways flight or a strong crosswind) long before any VRS effects can manifest in the tail rotor.

But as of now, I don't have any other news I can share on this matter.

[Picure]

Had this happened to me too twice on rotorheads, thought it was lag or something

[Apache 64]

Am 24.9.2022 um 17:43 schrieb Raptor9:

... the AH-64 vertical tail should force the nose into the direction of the relative wind (whether it be high-speed sideways flight or a strong crosswind) long before any VRS effects can manifest in the tail rotor.

But as of now, I don't have any other news I can share on this matter.

But I would have another way to reproduce this effect.
Mission WITHOUT wind, environment completely neutral.
Take off, stabilize hover, and try to hover slowly to the left.
You need a little rudder left to keep the nose 90 degrees to flight axis.
After a really short time, the helicopter turns abruptly around its axis to the right. You see at this moment a SCAS deflection to the left but without the expected effect. Manual left rudder does not help either.
Hovering to the right works much better.
What I also noticed is that simple straight flights, almost always point with much more nose to the left than before the last patch. Even at very high speeds. All without wind.

[Raptor9]

49 minutes ago, Apache 64 said:

But I would have another way to reproduce this effect.
Mission WITHOUT wind, environment completely neutral.

Even at very high speeds. All without wind.

You misunderstand, the term "relative wind" means relative airflow direction, regardless of environmental winds or aircraft movement. Any aircraft moves through an airmass, therefore it makes no difference if the airflow is caused by aircraft movement or air movement, because the resultant airflow across a surface is the same.

[Apache 64]

vor 14 Stunden schrieb Raptor9:

You misunderstand, the term "relative wind" means relative airflow direction, regardless of environmental winds or aircraft movement. Any aircraft moves through an airmass, therefore it makes no difference if the airflow is caused by aircraft movement or air movement, because the resultant airflow across a surface is the same.

No.. Have understood completely right. And therefore the helicopter should never turn nose right if i crab flight sideways to the left. 

And also with a hundred plus knots forward flight without other wind than my flight speed the nose don't should point 15 degrees left and i have to put half right rudder to compensate. 

I wrote "without wind" only to exclude an additional source of error from outside. 

Edited September 26, 2022 by Apache 64
Addition

[FalcoGer]

It would be nice if this was patched in a somewhat timely manner as a hotfix, even rolling back to the old version until the flight model has been fixed is better than the current state, or maybe just officially edit that fmconfig and remove the vrs effect for the apache for now and put it back in after testing for any game breaking effects such as this one. Any workarounds by editing the FM by hand of course results in a failed integrity check. Since I only play online, this is not an option.

This bug makes flying rather impossible. I'm no real pilot or particularly skilled, but before I was able to be relatively stable and allow engagements, now the aircraft breaks away, I loose control and even full left rudder doesn't do anything except driving my power requirements to 120%, at which point I must decrease collective, causing me to sink. Then suddenly the aircraft seems to think: "Oh you want full left rudder? sure, here you go." and it yaws hard left, literally trying to kill me. What little control I had left at the time now goes out the window and I loose another 200ft to recover, because of course I need to build airspeed and drop my collective to avoid the rotor to stall out. Any missiles being on the way at the time are of course trashed.

This is completely breaking this aircraft and make it unusable in a hover, only allowing running engagements. And it's not like this only happens every now and then, it happened every single flight for me since the update, both with and without wind and everyone I talked to also experienced this issue in short order after the update. It's literally impossible to hover stable for more than 15 seconds or so. Disabling the yaw SAS channel also does nothing to help this.

Edited September 27, 2022 by FalcoGer

[Apache 64]

Now the bird flies again. The open beta patch from today has solved this. Good job! Thanks ED.