fixed high AoA roll when going less than 300kias

[777coletrain]

A high AoA roll when going less than 300kias will pull the airplane out of the slip stream. I'm able to do this rolling to the left and the right. 

F16 Spin 6 08 22.trk

[Nightwolf]

Noticed you can also induce an uncontrollable spin by just holding forward and lateral stick input below around 300 kts. The plane doesn't seem to be able to decide what rudder input it wants which wobbles the plane out of controlled flight. Once that happens even releasing all control inputs, the FLCS just holds inputs that keep it in that spin and it doesn't recover itself.

[NineLine]

I'll have the team take a look.

[Exorcet]

I'm not sure if it's too easy to enter a spin/deep stall, but once you do it being unrecoverable isn't too unexpected. You need to use manual pitch override to recover. It makes a massive difference. However, don't pitch down too much or it might make things worse.

[FullMetal_cooKie]

It's even happening above 300 knots...

[FullMetal_cooKie]

I'm just going to leave this here

 

Yeah nice work...

[Hummingbird]

44 minutes ago, FullMetal_cooKie said:

I'm just going to leave this here

 

Yeah nice work...

 

Calm down, this is a relatively small issue. Overall the FM has been MUCH improved with this latest update!

Now that being said, I can recreate the scenario you're talking about above and depart the aircraft if I apply FULL roll & pitch command at 300 knots & below in dry power only, and it seems to happen only if you do a complete rotation in roll (360 deg). Based on what I can see, it seems to be the rudder causing the issues, the FLCS seems abit conflicted as to how much rudder & in which direction in needs to be applied in a high AoA rolling maneuver below 300 knots.

 

In full wet (full AB) power however, I can do this crazy maneuver the aircraft doesn't depart (but still the rudder is abit funky):

 

 

Edited June 8, 2022 by Hummingbird

[NineLine]

56 minutes ago, FullMetal_cooKie said:

I'm just going to leave this here

 

Yeah nice work...

I moved this post back to this bug report, please do not hijack other peoples threads to promote yours. The dev responsible is on vacation right now, when he returns he will have a look, but you should supply more evidence that this isn't expected behavior. Right now, whether it is right or wrong, you are only giving opinion. 

[DummyCatz]

Large, simultaneous pitch and roll command and consecutive 360 degree maximum command rolls are prohibited according to -1. This is to avoid departures due to inertia roll coupling, which is a prominent issue with a relaxed static stability aircraft such as an F-16. Although the FLCS may have means to suppress it, such as reducing the AOA limit and roll rate limit, it may still happen when the inertia coupling caused pitch-up moment overwhelms the pitch-down moment generated by the horizontal stab.

An example of inertia coupling caused departure in an F-16B:

(This is not a spin.)

Edited June 9, 2022 by DummyCatz

[DummyCatz]

9 hours ago, Hummingbird said:

Based on what I can see, it seems to be the rudder causing the issues, the FLCS seems abit conflicted as to how much rudder & in which direction in needs to be applied in a high AoA rolling maneuver below 300 knots.

I'd like to mention that when AOA > 35 deg, a function called 'Yaw Rate Limiter' activates that commands the flaperon and rudder to negate any yaw rate built-up. (You can search for it in -1). Simply put, the flaperon will deflect into the yaw, and the rudder will deflect against the yaw. But it seems that currently in DCS, the rudder also deflects into the yaw, which seems to be another bug.

Edited June 9, 2022 by DummyCatz

[Hummingbird]

Yeah I agree @DummyCatz, it's the same conclusion I've come to. 

Edited June 9, 2022 by Hummingbird

[777coletrain]

I'm fine with this if it is accurate to the actual jet, although I have noticed the rudder is very strange when below 300kts and there is a lot of adverse yaw when rolling 

Edited June 9, 2022 by 777coletrain

[Hummingbird]

Yeah I've noticed the same @777coletrain, and I don't think this instability in yaw is correct behavior but more likely an unintended bug. But we'll see. At least the FM is basically spot on in pitch rate & stability now based on the information I have available.

Edited June 9, 2022 by Hummingbird
small typo

[777coletrain]

I agree @Hummingbird, I just wanted to make a bug report so they knew. It's a pain to throw around the pattern now so the sooner it is fixed the better

[Hummingbird]

I'm sure they will be on it quick

[Zergburger]

in any spin or departure right now the rudder will hold deflection into the spin

[DummyCatz]

Coming back from 2.9.11.4686. This was originally a bug of being overly prone to entering a deep stall. Back then, performing a high-AOA loaded roll would often result in a yaw departure, making deep stalls very frequent. That bug was subsequently fixed to significantly reduce, if not entirely eliminate, the likelihood of entering a deep stall.

While inertia coupling is a real phenomenon that can lead to departures, the FLCS do have some logic to mitigate these effects and enhance sideslip stability (like sideslip feedback that is unique to later FLCS).

What do you all feel about the likeliness of entering a deep stall in the latest update?

[TobiasA]

I haven't been able to enter one yet.

But I have seen people getting into one.

[DummyCatz]

On 12/31/2024 at 5:44 PM, TobiasA said:

I haven't been able to enter one yet.

But I have seen people getting into one.

Just try pulling and rolling the aircraft to its AOA limit at high altitudes. This would maximise the possibility of getting into one.

[TobiasA]

I need to try that.

[AlexCaboose]

It doesn't seem correct currently. Doing a tuck under jink has a high probability of entering a deep stall. 

[TobiasA]

It seems correct though.

 

 

[AlexCaboose]

@TobiasA I've spoken with a Viper driver who mentioned that one of the ways they get it out of control is by loading the buckets with concrete. A tuck under jink shouldn't result in a deep stall according to him. Evidently they go through an entire class on the FLCS and putting it out of control like this is pretty difficult.

[TobiasA]

vor 10 Stunden schrieb AlexCaboose:

@TobiasA I've spoken with a Viper driver who mentioned that one of the ways they get it out of control is by loading the buckets with concrete. A tuck under jink shouldn't result in a deep stall according to him. Evidently they go through an entire class on the FLCS and putting it out of control like this is pretty difficult.

I have never spoken to a real Viper pilot, so I can't tell. I just haven't been able to depart the F-16 yet.

[stefasaki]

On 1/2/2025 at 12:43 PM, TobiasA said:

It seems correct though.

 

 

That is an asymmetric loading test conducted at high altitude. Shouldn’t happen with a clean aircraft and low altitude, as it’s now the case in DCS. It’s a typical airshow maneuver, which never resulted in a deep stall to my knowledge