K4 Accelerated Wing Stall

[Page.Down]

Modern Day Jet's use slats as well. The difference from a 109 and an F-18 Super Hornet however, is that the slat technology was re-engineered and it looks like it's hydraulically controlled via yoke inputs from the pilot.

 

Here's a video showing exactly that on the F-18. Watch the leading edge of the wing under a high G maneuver; You will notice it angles down, and then back up when the pilot lets off the G's.

 

Start Watching at the 3:40 mark.

 

Edited April 26, 2015 by Page.Down

[Yo-Yo]

I'd have to do some research, but rarely is the information available to that extent with precise testing parameters. And that holds true for pretty much any plane of the time. There just wasn't a testing standard for stalls under precise controlled conditions. Let alone specified of Accelerated Wing Stalls. Most of what is said is pilot accounts from people who have flown the 109, both in the war and in air shows. There are also reports of 109's nose diving into the ground without any attempt at recovery; This was due to high speed dives and surface locks which made it impossible to pull out of, the Plane/Trimming was the only means to pull a 109 out of a high speed dive in such cases.

 

But one thing all planes have in common are accelerated wing stalls. How severe, they were varied from plane to plane.

 

For example a 190 pilots were taught NOT to use snap rolls because it would induce the stall and eventually a flat spin. Given the roll rate of 190's a snap roll wasn't necessary as a defensive maneuver.

 

Erich Brunotte told that in 190A he often performed a pair of 180 degrees snap rolls (accelerated stalls) at high speed to force his opponent to overshoot. So, the snap roll was not so fatal...

[[DBS]TH0R]

Start Watching at the 3:40 mark.

 

Fixed the link for you:

 

 

It's quite obvious that the Bf-109 atm suffers from stalling way too early and violently, it certainly in no way behaves like the real thing.

 

---

 

The real thing features a very gentle stall, which does not happen before plenty of warning in the form of buffeting, and the stall itself is characterized by a very mild wing drop (the slatted area being able to retain smooth airflow at higher AoAs) It most certainly isn't as sensitive to pitch changes as it is right now ingame, nor will it flick over on its back as if it were a Fw190 upon stalling. Such characteristics go against everything known about the 109's flight characteristics.

 

Unless we have been flying two different planes I see no such thing in DCS Bf-109K4?? Just to be clear I've tested all three planes again and I can ride that 109 on the verge of stall all day long. It is so easy to anticipate it and counteract it. The same can't be said for the P-51 and Fw-190. The stalls with those planes are violent and one needs to be very careful. Especially P-51. When you run out of energy in the turn the thing becomes a brick.

 

I get both the buffeting and mild wing drop. Can you show us how you fly the thing?

 

Zalty 3:00 mark is a better example of it, albeit cut short due to altitude as I was forced to correct or crash if I kept on it.

 

If I was to do that I a P-51 I'd end up in those trees below. The buffeting effect is visible just before you stall. Perhaps the effect could be increased?

[Page.Down]

Erich Brunotte told that in 190A he often performed a pair of 180 degrees snap rolls (accelerated stalls) at high speed to force his opponent to overshoot. So, the snap roll was not so fatal...

 

True but by the end of the war there weren't pilots like him lol.

 

Newer pilots were taught not to do it. And there is documentation to support that as well.

 

 

 

Question 180 degree snap roll would leave a 190 inverted... or ready to enter a Split S maneuver.

 

I don't see exactly how that is similar since a true snap roll is 360 degrees.

 

Given the roll rate of 190's a snap roll is over kill.

Edited April 26, 2015 by Page.Down

[Page.Down]

Fixed the link for you:

 

 

 

 

Unless we have been flying two different planes I see no such thing in DCS Bf-109K4?? Just to be clear I've tested all three planes again and I can ride that 109 on the verge of stall all day long. It is so easy to anticipate it and counteract it. The same can't be said for the P-51 and Fw-190. The stalls with those planes are violent and one needs to be very careful. Especially P-51. When you run out of energy in the turn the thing becomes a brick.

 

I get both the buffeting and mild wing drop. Can you show us how you fly the thing?

 

 

 

If I was to do that I a P-51 I'd end up in those trees below. The buffeting effect is visible just before you stall. Perhaps the effect could be increased?

 

Well I don't have a problem with the stall being there, what I have a problem with is the stall occurring at 380-420km/h IAS with slats out, and less than 50% deflection.

 

Again, that is not low speed for a 109 and the stall is more pronounced at lower speeds, but the purpose of slats was to alleviate that stall and allow for greater AOA.

 

Based on the videos, such doesn't seem to be the case.

 

And I do believe if that's true, then the Dora and P51's may be too pronounced as well. Even considering they didn't have slats. I haven't flown the P51, so I don't know how bad it is, but it's VERY bad in the Dora.

 

A Snap roll is damn near suicidal to perform. Which was conveyed to new pilots in 190's.

Edited April 26, 2015 by Page.Down

[Page.Down]

Yo-Yo since we are talking about 190's as well;

 

I have an issue with the Dora that I have been wondering about.

 

190's were notorious for vertical reversals; It was one of their trademark maneuvers.

 

Yet, I struggle to follow a P51 in a vertical loop with equal energy states.

 

In short I see "AI" P51's out maneuvering the dora in the vertical, but not in the horizontal.

 

Is that supposed to be like that? Granted I know a human player is completely different, but I'm struggling to grasp how a mid to low energy P51 can do a loop at low altitude, when the Dora cannot follow them?

[[DBS]TH0R]

Well I don't have a problem with the stall being there, what I have a problem with is the stall occurring at 380-420km/h IAS with slats out, and less than 50% deflection.

 

Again, that is not low speed for a 109 and the stall is more pronounced at lower speeds, but the purpose of slats was to alleviate that stall and allow for greater AOA.

 

Thanks for clearing this up. Yeah, I can see you pulling no more than 1/3 through out the travel distance in one direction. Would be interesting to read comments on how much stick movement was required in a real 109.

 

Have you tried powering back a bit in your turns? I can see your throttle remains the same throughout most of the maneuvers. Based on that report linked earlier here and in DCS this plane is reluctant to lose speed.

 

 

In short I see "AI" P51's out maneuvering the dora in the vertical, but not in the horizontal.

 

Is that supposed to be like that? Granted I know a human player is completely different, but I'm struggling to grasp how a mid to low energy P51 can do a loop at low altitude, when the Dora cannot follow them?

 

AI FM is "wishful", at best. They fly on rails and can sustain much more hits that human pilots can in MP. :)

[ZaltysZ]

Fair enough, at what point did I say this was at high speed exactly?

 

I clearly stated 380-420km/h and this can be seen in the video.

 

So I guess I don't understand your point regarding high speed which isn't in question?

 

This K4 begins to stiffen from 300km/h. The faster you go, the more elevator deflection you loose, that is why I am giving you examples with high speed, because at high speed you can overpull the physical stick without danger that virtual one will be overpulled too, and then see how virtual one is being gradually overpulled while you loose the speed.

 

Due to large difference between positions of virtual and physical sticks at high speed it should be easier to see how stiffness modeling works and how it causes overpull with decreasing speed. Exactly the same principles apply when you go from 500km/h to 380-420km/h, but due to smaller speed change and larger max deflection angle, it is easier to dismiss the modelling of stiffness as culprit and put blame on other things.

 

I have attached a picture from your 2nd video. Left one looks like a settled condition, and right one is taken at start of shudder. Right one has virtual stick pulled more. The difference is small, but important if you already were near critical aoa in the left picture. Was it due to overpull caused by stiffness modelling? Maybe. Was it pilot error? Maybe. That is why such lower speed case isn't suitable for explanatory examples.

Edited April 26, 2015 by ZaltysZ

[Page.Down]

Thanks for clearing this up. Yeah, I can see you pulling no more than 1/3 through out the travel distance in one direction. Would be interesting to read comments on how much stick movement was required in a real 109.

 

Have you tried powering back a bit in your turns? I can see your throttle remains the same throughout most of the maneuvers. Based on that report linked earlier here and in DCS this plane is reluctant to lose speed.

 

 

 

 

AI FM is "wishful", at best. They fly on rails and can sustain much more hits that human pilots can in MP. :)

 

Well in theory, and I've seen and tested it in game... throttling back would be unnecessary... If I lessen up on my pull the 109 will maintain speed indefinitely unless I pull a harder AOA and as such speed drops and the stall issue becomes more relevant.

 

I dunno honestly.... What I wouldn't give to get a feel for the real stick forces of the 109.

[Page.Down]

This K4 begins to stiffen from 300km/h. The faster you go, the more elevator deflection you loose, that is why I am giving you examples with high speed, because at high speed you can overpull the physical stick without danger that virtual one will be overpulled too, and then see how virtual one is being gradually overpulled while you loose the speed.

 

Due to large difference between positions of virtual and physical sticks at high speed it should be easier to see how stiffness modeling works and how it causes overpull with decreasing speed. Exactly the same principles apply when you go from 500km/h to 380-420km/h, but due to smaller speed change and larger max deflection angle, it is easier to dismiss the modelling of stiffness as culprit and put blame on other things.

 

I have attached a picture from your 2nd video. Left one looks like a settled condition, and right one is taken at start of shudder. Right one has virtual stick pulled more. The difference is small, but important if you already were near critical aoa in the left picture. Was it due to overpull caused by stiffness modelling? Maybe. Was it pilot error? Maybe. That is why such lower speed cases isn't suitable for explanatory examples.

 

Yes, I understand.

 

But you are contradicting yourself with how it really works in game.

 

 

IF that was true. Let's say 400km/h IAS let's say 50% deflection is best case real world scenario.

 

The Virtual joystick limits movement beyond that point.

 

So what happens based on what your saying is; I can wrench 100% physical stick deflection and it means NOTHING at all since the Virtual Joystick stops at 50%.

 

You care to test that scenario in game?

 

Don't say I didn't warn you about the Accelerated Wing Stall, because that's exactly what happens when you physically push beyond the thresh hold. The Virtual Joystick mimics that maneuver 1:1 at nearly ALL SPEEDS up to 500km/h

 

Even pilot accounts attest to that fact. It's not the Virtual Joystick catching up.

 

You can test this yourself, and when you wing stall, that is me saying I'm right, and the the virtual joystick does NOT limit your physical travel on your joystick.

[ZaltysZ]

But you are contradicting yourself with how it really works in game.

 

How?

 

IF that was true. Let's say 400km/h IAS let's say 50% deflection is best case real world scenario.

 

The Virtual joystick limits movement beyond that point.

 

So what happens based on what your saying is; I can wrench 100% physical stick deflection and it means NOTHING at all since the Virtual Joystick stops at 50%.

 

Yes, but if you can't keep 400km/h or higher, virtual joystick won't stop at 50% anymore. Lower speed = higher limit. If your speed drops to 350km/h, virtual joystick will stop at, let's say, 60%, and if 60% is too much for aircraft, it will stall.

[Page.Down]

How?

 

 

 

Yes, but if you can't keep 400km/h or higher, virtual joystick won't stop at 50% anymore. Lower speed = higher limit. If your speed drops to 350km/h, virtual joystick will stop at, let's say, 60%, and if 60% is too much for aircraft, it will stall.

 

You are missing my point.

 

An accelerated wing stall would be impossible if the virtual joystick worked that way.

 

You said it yourself.

 

IF I'm limited to 50% or 60% virtual, but I can wrench 100% on my physical joystick, the extra 40% is meaningless and non existent, which means the stall is impossible at any speed.

 

In short you are saying the Virtual Joystick limits AOA to a maximum without stalling. And as such how far I physically move my joystick is meaningless since I am unable to push beyond that limit to stall the aircraft.

 

 

Best example of what you are saying, vs what I am saying is the difference between Mousaim in War Thunder vs full realistic controls.

 

Mouseaim has a feature called instructor (think of it as a virtual joystick that flies the plane for you) Not only does this virtual joystick fly the plane for you... It prohibits ANY maneuver that can stall the aircraft. Making Snap rolls impossible, flying inverted, to name a few maneuvers.

 

It simply doesn't work that way in DCS.

 

In WT with mouseaim you can't even do a 0 power glide, without disabling the engine aspect of instructor. It will not allow you to stall out due to lack of speed and will automatically throttle up to maintain speed.

Edited April 26, 2015 by Page.Down

[ZaltysZ]

IF I'm limited to 50% or 60% virtual, but I can wrench 100% on my physical joystick, the extra 40% is meaningless and non existent, which means the stall is impossible at any speed.

 

Why? Are implying that stall is impossible unless stick if pulled fully back?

[ZaltysZ]

In short you are saying the Virtual Joystick limits AOA to a maximum without stalling.

 

Virtual joystick limits deflection angles of control surfaces. You don't need fully deflected elevator to reach critical aoa.

[ZaltysZ]

Mouseaim has a feature called instructor (think of it as a virtual joystick that flies the plane for you) Not only does this virtual joystick fly the plane for you... It prohibits ANY maneuver that can stall the aircraft. Making Snap rolls impossible, flying inverted, to name a few maneuvers.

 

It is getting weird. :) Virtual stick is the stick inside the cockpit. It is directly linked to aircraft control surfaces and its position is shown in red square (ctrl+enter). When you move your real physical stick (the one on the table), your input is transformed to movement of virtual stick by application of response curves and stiffening model. There is no autopilot, instructor, mouse aim, fly by wire or similar assistance.

Edited April 26, 2015 by ZaltysZ

[Page.Down]

Why? Are implying that stall is impossible unless stick if pulled fully back?

 

Correction:

 

No I didn't say that:

 

You made it impossible when you said the Virtual Joystick stops at a certain deflection with no regard to the speed at which it occurs. It basically means that stalling is impossible regardless of deflection of the virtual joystick or the physical.

 

 

What you are not understanding is, what the virtual joystick shows as my location of control is EXACTLY where my physical control on my joystick is.

 

So there's a 1:1 relationship there, and you are implicating that is false, while at the same time saying the stall is impossible.

 

I never said it was impossible, I said it's characteristic doesn't match the speed and purpose of slats relative to the AOA.

 

It is clearly shown in the videos as such.

Edited April 26, 2015 by Page.Down

[ZaltysZ]

You said that not me.

 

Where?

[Page.Down]

Where?

 

Edited my post read again.

[Solty]

I don't understand the problem. It was always like that in any other sim ever. There is no way around it, unless your stick can realy stop your movment IRL by giving you the resistance that real pilot had.

 

In game if you go over a certain speed the pilot is unable to pull more as he doesn't have the physical strenght to do so. (even though u can on your digital stick that cannot represent that force). But when you slow down, the forces become lighter and if you were deflected 100% and your pilot was only able to pull 50%, now at the lower speed he is able to pull 60% and with every second in a turn you become slower and forces on the stick become lighter that means that your pilot is able to pull miore (which he does).

 

I don't see anything illogical here.

[Echo38]

I suggest you read abit about the real 109's flight behavior before claiming my words are assumptions

Skip Holm

Pitch control is also delightful and very positive at 250 mph and below. As pitch and accompanying G is increased, the leading edge slats start to deploy. I have not found either aircraft to have any problems with asymmetrical slat deployment, as we see in other aircraft such as an A-4 for instance. The aircraft reacts very well to heavy maneuvering, and there is never any discomfort in pulling Gs, as wing separation and accompanying wing drop is mild, is easily noticed and dealt with by lightening up on the G.

 

In other words the complete opposite of the 109 we have ingame atm which does NOT react well to heavy maneuvering at all, being on the verge of a violent flick stall in pretty much any meaningful turn you make.

 

And here you present nothing I've not already seen, but only more assumptions. Specifically, in this post, you are assuming that what Holm meant by "delightful" and "very well" and "mild" and "easily noticed," are the same as what you mean by those terms.

 

Has it never occurred to you that one man's "mild" is another man's "severe"? That one man's "delightful" is another man's "difficult"? For this reason, such subjective terms are virtually useless when comparing aircraft, real or virtual. Test data--numerical data--matters, provided that the tests are thorough; pilot opinions, on the other hand, only go so far.

 

Although not a 109 expert (and, I'd wager, neither are you, judging by how much you overlook, regarding the subject--here as well as in other threads), I've done a fair share of reading on the subject. I've not only examined several articles by Hanna, Holm, et al., long before you ever joined this forum, but by many other such experts as well. That I haven't "read a bit" about the 109 is another of your (false) assumptions.

 

Regardless: you are making a wholly baseless assumption that the 109 pilot's idea of "mild" is the same as your idea of mild (and so on), every time you pull out a quote rife with such subjective words, and try to use it to support your opinion (no hard numbers, just feelings) about the same subjective aspects. Too many assumptions! A simulator cannot be built upon them.

 

Must I tell the story about the P-40 vs. A6M wartime acceleration test again? I grow tired of bringing it up every time people use solely-subjective words to try to prove something about a virtual aircraft's accuracy, but I suspect that I do need to, if my point in my previous post about assumptions was entirely missed (which it was).

Edited April 26, 2015 by Echo38

[Page.Down]

I don't understand the problem. It was always like that in any other sim ever. There is no way around it, unless your stick can realy stop your movment IRL by giving you the resistance that real pilot had.

 

In game if you go over a certain speed the pilot is unable to pull more as he doesn't have the physical strenght to do so. (even though u can on your digital stick that cannot represent that force). But when you slow down, the forces become lighter and if you were deflected 100% and your pilot was only able to pull 50%, now at the lower speed he is able to pull 60% and with every second in a turn you become slower and forces on the stick become lighter that means that your pilot is able to pull miore (which he does).

 

I don't see anything illogical here.

 

Solty,

 

Think about it.

 

If it is impossible to deflect the elevator past a certain point as "supposedly" simulated by the virtual joystick. Then how far I pull on my physical joystick is irrelevant since the stall would be impossible to induce. What that actually means is there is no control stiffening at lower speeds and a pilot can use full deflections as needed, any other scenario makes it impossible to induce the stall otherwise.

 

 

The point is he's describing it wrong to a point that doesn't make logical sense.

 

 

That is NOT what happens in game virtually or physically. IF I pull to hard physically on my joystick, I WILL INDUCE that stall; And the Virtual joystick confirms it at every point in those videos.

 

He is wrong in his description of how it works.

 

 

In either case that isn't the basis of the discussion.

 

The issue is the stall is too pronounced relative to the speed at which it occurs relative to the slats being extended, and relative to the virtual and physical inputs of the joystick.

 

In short the stall characteristic is overly sensitive/exaggerated. And it's even worse on the Dora and P51 based on what others have said simply because Doras and P51's didn't have slats.

 

The purpose of slats specifically is to reduce the stall characteristic while increasing the available AOA. And the stall is induced by increasing AOA at relative speeds, which means control stiffening or "simulated artificial" limitations of deflections in the virtual control is an incorrect observation.

Edited April 26, 2015 by Page.Down

[Hummingbird]

And here you present nothing I've not already seen, but only more assumptions. Specifically, in this post, you are assuming that what Holm meant by "delightful" and "very well" and "mild" and "easily noticed," are the same as what you mean by those terms.

 

Has it never occurred to you that one man's "mild" is another man's "severe"? That one man's "delightful" is another man's "difficult"? For this reason, such subjective terms are virtually useless when comparing aircraft, real or virtual. Test data--numerical data--matters, provided that the tests are thorough; pilot opinions, on the other hand, only go so far.

 

Although not a 109 expert (and, I'd wager, neither are you, judging by how much you overlook, regarding the subject--here as well as in other threads), I've done a fair share of reading on the subject. I've not only examined several articles by Hanna, Holm, et al., long before you ever joined this forum, but by many other such experts as well. That I haven't "read a bit" about the 109 is another of your (false) assumptions.

 

Regardless: you are making a wholly baseless assumption that the 109 pilot's idea of "mild" is the same as your idea of mild (and so on), every time you pull out a quote rife with such subjective words, and try to use it to support your opinion (no hard numbers, just feelings) about the same subjective aspects. Too many assumptions! A simulator cannot be built upon them.

 

Must I tell the story about the P-40 vs. A6M wartime acceleration test again? I grow tired of bringing it up every time people use solely-subjective words to try to prove something about a virtual aircraft's accuracy, but I suspect that I do need to, if my point in my previous post about assumptions was entirely missed (which it was).

 

Sure, what'ever floats your boat mate :thumbup:

[otto]

Has it never occurred to you that one man's "mild" is another man's "severe"?

 

Unless you have evidence or numbers this is just an assumption.

Do you even fly the 109 in game ? No. So you're just making assumptions that the FM is 100 righ .

 

One of the D9's cannons has a bug for months. Nobody fixed it.The mustang firing bug that totally ruing fps is there for years but thank god the accelerated stall for the 109 in accurate.

[Echo38]

Do you even fly the 109 in game ? No. So you're just making assumptions that the FM is 100 righ .

 

I make no such assumption. I never said, nor implied, that the FM is 100% right. You are (falsely) assuming that I believe that. Do not put words in my mouth.

 

Unless you have evidence or numbers this is just an assumption.

 

I have seen a veritable plethora of evidence to support my claim that various people use the same word to mean different things. I am not going to bother throwing it before you, however, because I cannot believe that you are unaware of the truth of this; rather, you look to be trolling me. Enjoy.

Edited April 26, 2015 by Echo38

[Flagrum]

The implementation of the controls stiffening behaviour was just one attempt to explain an "unexpected" behaviour of the plane - which was entering a stall.

 

If we agree upon the fact that only the deflection of the virtual stick is relevant for the aircraft - regardless of how the relation of physical and virtual stick actually is implemented - the main question seems to be: should the aircraft able to enter a stall?

 

Page.Down, why should it not? If you pull too much on the (virtual) stick for a given airspeed, the aircraft will depart.

 

So what is your evidence that the aircraft should not depart into a stall in the situations that you have recorded?