K4 Accelerated Wing Stall

[Page.Down]

Forgive me,

 

As I am still new to DCS don't fly to often, and I do know what an accelerated wing stall is;

 

But is it normal for a K4 to wing stall at 380-420km/h IAS?

 

Is that not the purpose of Leading Edge Slats?

 

Note I don't believe I went past 50% stick deflection in fact probably less than that.

 

https://www.youtube.com/watch?v=14KMUihNl4I

 

Edited April 26, 2015 by Page.Down

[9.JG27 DavidRed]

^^very likely the stick forces and the curvature setting that comes with them...as you flew with more than 500kph, and started to deflect the stick, the virtual stick was deflected by x%.through the turn, the plane decreases airspeed.now even though you probably held your stick in one position, the virtual stick begins to move more and more back, as the forces needed to deflect the stick by x% earlier are the same as now to move the stick x+y%.

[Page.Down]

^^very likely the stick forces and the curvature setting that comes with them...as you flew with more than 500kph, and started to deflect the stick, the virtual stick was deflected by x%.through the turn, the plane decreases airspeed.now even though you probably held your stick in one position, the virtual stick begins to move more and more back, as the forces needed to deflect the stick by x% earlier are the same as now to move the stick x+y%.

 

So you are saying there is an artificial deflection of sorts in order to maintain the deflection input I was giving the joystick?

[javelina1]

subscribing... I've been interested in this as well. :thumbup:

[Flagrum]

Control stiffening depending on air speed was introduced to the module not too long ago. See the discussion here: http://forums.eagle.ru/showthread.php?t=140315

[Page.Down]

Control stiffening depending on air speed was introduced to the module not too long ago. See the discussion here: http://forums.eagle.ru/showthread.php?t=140315

 

Sadly,

 

I know what control stiffening is as well; And it mostly occurs above 500km/h IAS and surface lock occurs at around 600km/h IAS.

 

At 380-420km/h IAS there is no control stiffening at all. It's entirely dependent on Leading Edge Slats, and AOA in that situation. The issue I have is my AOA was unchanged, but the plane still stalled. And the purpose of Leading Edge Slats is to reduce the stall and allow for greater AOA.

 

In the case of ALL 109's the greatest AOA they have is at much lower speeds than what I showed in my video.

 

 

 

What I am experiencing is called an Accelerated Wing Stall.

 

It's when the speed of wind over the top and bottom of the left wing are different. Which forces the wing to lose lift, and hence the 109 rolls left.

 

It does not matter if you are banking right or left as shown in my video.

 

 

The wing stall mechanic is accurately modeled, but what I'm questioning is the speed at which it occurs. At higher speeds for example it's easier to read if you have to induce it, at lower speeds harder to read; But if your AOA remains unchanged from high speed of 500km/h and you drop to 380-420km/h that wing stall should not be present at all unless I increased my AOA, which I do not believe I had done.

 

Edit: Clarified my last statement

Edited April 26, 2015 by Page.Down

[Page.Down]

David's response does make sense, because if he's right, then it's possible I increased my AOA without knowing it.

[9.JG27 DavidRed]

if you held your stick in one and the same position, then you definitely increased your AoA, because the virtual pilot began to move the stick more and more back as airspeed decreased.

[Anatoli-Kagari9]

David has a point here, and as much as I was initially a supporter of the introduction of control force feedback for non-ff controllers, I don't find the way it is modelled the most plausible...

 

As David points out, the fact that when a given input is used it can vary in time, adapting to the loads on the controls, is probably the main reason for these accelerated stalls.

 

The virtual pilot can even have eased a bit on the stick, but with time and dynamic pressure reduction, the stick can continue to travel towards a situation that creates high AoAs and stalls the wings.

[Ala13_ManOWar]

Nice this time (many previous threads with same subject) you posted a video. Mate... you are pulling G's like mad, really think it shouldn't get stalled? Just pull gently and when you are seeing (don't tell me you don't see...) the clues of stall meaning you're being too hard on stick just relax pulling. Don't look for weird explains, you are stalling the aircraft and nobody but you.

 

http://www.planeandpilotmag.com/pilot-talk/ntsb-debriefer/the-accelerated-stall.html#.VTyrHpO1dHo

 

I have to say I don't like that term, "accelerated stall", seems like a different thing involving "speed" and that's not true, you're pulling too much AoA so you can stall at any speed going out of AoA.

 

S!

Edited April 26, 2015 by Ala13_ManOWar

[Anatoli-Kagari9]

Nice this time (many previous threads with same subject) you posted a video. Mate... you are pulling G's like mad, really think it shouldn't get stalled? Just pull gently and when you are seeing (and if you don't see you're blind) the clues of stall meaning you're being too hard on stick just relax pulling. Don't look for weird explains, you are stalling the aircraft and nobody but you.

 

S!

 

 

True that he's stalling it, but problem is why in fact that is happening...

 

The introduction of "stick forces" in the Bf109 K4 model is still work in progress, and at least for now it is weirdly asymmetric, with "forces" being added to pitch and roll axis but not at all to yaw, which makes flying the aircraft rather unrealistic IMO.... You can for instance run totally out of authority in roll and still use your rudder at will to get a nice yaw-induced roll, because there are no forces imposed on your rudder axis :-/

 

Then, the algorithm used for the implementation of these forces, needs attention IMO. As David pointed out, and I do remember how he initially fought the idea, and now somehow am with him in his critics, is causing a slowly moving stick rate past what your brain tells you was your last deflection limit. It can even happen that in between you ease a bit on the stick, but as dynamic pressure is reduced, it travels a bit further, and eventually brings the aircraft into a limit AoA, and hence stall happens....

 

Sorry but I do not have other valid comparison to explain how I think it should be modelled, but, IMO, the way it is being modelled in BoS is a lot more plausible :-/ All axis get affected, and these effects of the stick moving further and causing entry into stall AoAs does not take place.

Edited April 26, 2015 by jcomm

[Ala13_ManOWar]

True that he's stalling it, but problem is why in fact that is happening...

Because he's pulling too hard, he's stalling the aircraft, shaking and trembling, and still he not only doesn't ease the pull but increases... Really it shouldn't stall? You are all the way stalling yourself doing that!! The problem IMHO is arcade games mind and this isn't arcade any more.

 

Even though stick forces being WIP (and I have to say I liked it before them being myself who controlled the aircraft) you cannot blame them if you want to outturn everything in the sky at any given speed. That would be fine in WT but not here so I don't see the point in complaining about you got a real simulator and it stalls... Not to mention looking for weird explains.

 

 

Look again first post, he asked,

But is it normal for a K4 to wing stall at 380-420km/h IAS?

And answer is, YES mate, as long as you don't stop pulling like that it's normal. Wing slats are "a little help", not magic. The good thing we hadn't in previous threads like this is we can see in a video now.

 

S!

[Kelevra]

Because he's pulling too hard, he's stalling the aircraft, shaking and trembling, and still he not only doesn't ease the pull but increases... Really it shouldn't stall? You are all the way stalling yourself doing that!! The problem IMHO is arcade games mind and this isn't arcade any more.

 

Even though stick forces being WIP (and I have to say I liked it before them being myself who controlled the aircraft) you cannot blame them if you want to outturn everything in the sky at any given speed. That would be fine in WT but not here so I don't see the point in complaining about you got a real simulator and it stalls... Not to mention looking for weird explains.

 

 

Look again first post, he asked, And answer is, YES mate, as long as you don't stop pulling like that it's normal. Wing slats are "a little help", not magic. The good thing we hadn't in previous threads like this is we can see in a video now.

 

S!

 

I think what he means is the fact that the virtual pilot compensate during the turn, but in the video we don't see neither the stick nor the player inputs so it's hard to tell.

 

[...] you probably held your stick in one position, the virtual stick begins to move more and more back, as the forces needed to deflect the stick [...] ( increase quoter's note)

[ZaltysZ]

still he not only doesn't ease the pull but increases...

 

It is very likely he did not increase the pull and kept the physical stick at same angle which settled at mid of turn. If it was static ratio between input and output, he would not have stalled, however this ratio is dynamic (game is trying to substitute a "force required" with "deflection required" depending on speed), so if you settled on the edge of high speed pull and keep that deflection angle as speed drops, virtual pilot will be the one which increases the pull despite you not pulling the physical stick more. You need a gamer mind to overcome this mind f*ck. :pilotfly:

[Anatoli-Kagari9]

It is very likely he did not increase the pull and kept the physical stick at same angle which settled at mid of turn. If it was static ratio between input and output, he would not have stalled, however this ratio is dynamic (game is trying to substitute a "force required" with "deflection required" depending on speed), so if you settled on the edge of high speed pull and keep that deflection angle as speed drops, virtual pilot will be the one which increases the pull despite you not pulling the physical stick more. You need a gamer mind to overcome this mind f*ck. :pilotfly:

 

 

Exactly!

[9.JG27 DavidRed]

It is very likely he did not increase the pull and kept the physical stick at same angle which settled at mid of turn. If it was static ratio between input and output, he would not have stalled, however this ratio is dynamic (game is trying to substitute a "force required" with "deflection required" depending on speed), so if you settled on the edge of high speed pull and keep that deflection angle as speed drops, virtual pilot will be the one which increases the pull despite you not pulling the physical stick more. You need a gamer mind to overcome this mind f*ck. :pilotfly:

 

yet the devs are of the opinion that its the most intuitive and only realistic implementation :doh:

 

waiting for VEAO's Emil, convinced that they will not implement such a joke

Edited April 26, 2015 by 9./JG27 DavidRed

[9.JG27 DavidRed]

Because he's pulling too hard, he's stalling the aircraft, shaking and trembling, and still he not only doesn't ease the pull but increases... Really it shouldn't stall?

 

 

careful what youre stating here...as it is now, in the 109, it can happen that infact you actually ease the pressure on your stick, meaning you are pushing it slightly forward, and yet in game the virtual stick does the exact opposite.

 

should he stall at such an aoa?,...very likely...should the aoa increase while you are actually pulling the stick to ease the turn? certainly not. yet in certain situations exactly thats happening with the current implementation of stick forces.

Edited April 26, 2015 by 9./JG27 DavidRed

[gavagai]

Basically, the 109 is the only aircraft where you need to move the physical joystick in order to maintain a constant virtual joystick position if your airspeed is changing.

 

It is kind of a pita, but I can't think of a better way for it to be done. If the decreased throw didn't begin so early (seems like >400km/h) it would be less disorienting.

[Derbysieger]

I think the problem is how do you simulate realistic stick forces for everyone? I can totally understand why people don't like the current implementation but no stick force simulation at all is not the way to go.

 

I personally am mostly okay with how ED decided to implement it. It's not perfect but I don't know how you could simulate this properly without compromises.

I'm sure that rudder stiffening will be added as well in future patches, this is still a beta after all.

 

Before this change I had no problems taking the Bf 109 to places a real pilot would never be able to take it, now we're limited to a much more realistic flight envelope but it comes at the cost of odd and counter intuitive behaviour.

I think no stick force simulation at all is not a good idea. It would make the Bf 109 a much better fighter than it really was.

[Anatoli-Kagari9]

I think the problem is how do you simulate realistic stick forces for everyone? I can totally understand why people don't like the current implementation but no stick force simulation at all is not the way to go.

 

I personally am mostly okay with how ED decided to implement it. It's not perfect but I don't know how you could simulate this properly without compromises.

I'm sure that rudder stiffening will be added as well in future patches, this is still a beta after all.

 

Before this change I had no problems taking the Bf 109 to places a real pilot would never be able to take it, now we're limited to a much more realistic flight envelope but it comes at the cost of odd and counter intuitive behaviour.

I think no stick force simulation at all is not a good idea. It would make the Bf 109 a much better fighter than it really was.

 

I agree, but I would also suggest:

 

1) That the rudder becomes limited, as much as the elevator and the ailerons;

 

2) I still don't understand exactly the algorithm being used. I bleive the best way to model it would probably be by:

 

2.A) full controller and virtual stick travel always available, and match between both defined by the user set curve, or linearity ( each one will chose what better matches her/his liking...);

2.B) direct correspondency between a given cotroller position ( in pitch or roll, and yaw when this get's applied to the rudder too in the future...) and the virtual stick / rudder, although with higher dynamic pressure the speed at which the virtual stick converges to that position is reduced;

2.C) I don't know if presently, the virtual stick can move further than the position mentioned in 2.B) when dynamic pressure get's reduced. If it does, than this should not IMO be the case. For a given Delta in the controller, the same f(Delta) in the virtual stick would be available ( f being the linearity defined by the user in the OPTIONS/CONTROLS menu ). The only difference given diffrent speeds / loads on the controls surfaces would be the rate at which the virtual stick moves into that position, but it should never move further, if those loads are relaxed... - if this is already the way it is modeled then I can't really think of a better solution :-/

Edited April 26, 2015 by jcomm

[Page.Down]

Nice this time (many previous threads with same subject) you posted a video. Mate... you are pulling G's like mad, really think it shouldn't get stalled? Just pull gently and when you are seeing (don't tell me you don't see...) the clues of stall meaning you're being too hard on stick just relax pulling. Don't look for weird explains, you are stalling the aircraft and nobody but you.

 

http://www.planeandpilotmag.com/pilot-talk/ntsb-debriefer/the-accelerated-stall.html#.VTyrHpO1dHo

 

I have to say I don't like that term, "accelerated stall", seems like a different thing involving "speed" and that's not true, you're pulling too much AoA so you can stall at any speed going out of AoA.

 

S!

 

Oh I clearly saw the stall; But, I was deliberately not letting up and trying to maintain the AOA.

 

I'm trying to get the feel on the joystick where the limitation is.

 

 

At that speed and (hopeful maintaining) of the AOA, It just feels like the stall is instigated at a speed it shouldn't be as pronounced is what I'm wondering.

 

Yes I know the harder you pull on the stick the easier it is to produce that stall, but when maintaining the pull assuming I wasn't letting up or increasing the AOA, the 109 should technically not stall at that speed.

 

The 109's best turn radius is in fact at lower speeds, so maintaining that AOA should not have induced the stall, if anything at lower speeds I should be able to pull harder without inducing the stall.

 

Or at least I would think so.

Edited April 26, 2015 by Page.Down

[Derbysieger]

The problem with a test like this is how DCS currently simulates stick forces. The Bf 109 required a lot of forces to move the stick/control surfaces at high speeds.

The way DCS simulates it right now is that it limits the range of the virtual stick the faster you go. If you fly at 500km/h and then pull on the stick you will notice a moment where the virtual stick in the cockpit stops moving even though you still have a lot of range on your joystick left. It is by no means a very intuitive way of doing it but it is WIP and maybe ED can come up with a better way of doing it. Also as jcomm mentioned rudder in the Bf 109 is currently uneffected by the effect but this is known and will be added in future.

I think the Fw 190 and P-51 already have this effect for pitch, roll and yaw, it just isn't nearly as strong as it is in the Bf 109

[Page.Down]

The problem with a test like this is how DCS currently simulates stick forces. The Bf 109 required a lot of forces to move the stick/control surfaces at high speeds.

The way DCS simulates it right now is that it limits the range of the virtual stick the faster you go. If you fly at 500km/h and then pull on the stick you will notice a moment where the virtual stick in the cockpit stops moving even though you still have a lot of range on your joystick left. It is by no means a very intuitive way of doing it but it is WIP and maybe ED can come up with a better way of doing it. Also as jcomm mentioned rudder in the Bf 109 is currently uneffected by the effect but this is known and will be added in future.

I think the Fw 190 and P-51 already have this effect for pitch, roll and yaw, it just isn't nearly as strong as it is in the Bf 109

 

I fully understand that; But the fact is it wasn't at higher speeds where it was a problem, it was at lower speeds.

 

Where technically if an AOA was maintained without variation then the stall shouldn't occur unless I pull harder or I reach such a low speed that the deflection becomes more or less nullified due to lack of speed.

 

What I see and felt in the video was: At higher speed the K4 performed well with a certain deflection, but at lower speeds that same deflection became to much for the stability of the plane. And I notice the K4 banks left far easier and with a higher AOA than banking right. (I assume because of torque of course)

 

This doesn't make sense to me; Given the 109's best sustained turn radius is in fact at lower speeds and higher AOA's.

 

The only thing that makes sense to me atm, is what David said that the VR joystick is actually pulling more even though I have not done so physically on the joystick. I guess the question is why is that?

Edited April 26, 2015 by Page.Down

[Page.Down]

This particular stall is a lot more pronounced on the Dora for example; I imagine the P51 has a similar feel to that extent as the Dora.

[Derbysieger]

If you pull past a certain point at speeds higher than 300km/h (I think) this effect becomes noticeable and if you then pull past that point on your joystick the virtual stick in the cockpit moves as you lose speed. Hope that makes sense.

 

So what you really need to do is find the point where you can sustain a turn at a certain speed without moving the stick. Rudder input is also important to maintain speed and I noticed in your video that the ball was off center a lot of times even though you clearly tried to keep it centered which certainly isn't easy if you're close to a stall..