K4 Accelerated Wing Stall

[Page.Down]

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..

 

I have tried to use the rudder to compensate for this as well, and I find the rudder induces the stall more so than not using it; The only thing I've found to avoid it, is simply to lessen my pull on the stick.

 

But that creates an unstable sustained turn such that it's more like an outward stairway of turn radius; Starting first as a sharp turn radius then stair stepping to a wider turn radius; This contradicts what reports I've read about all 109's at lower speeds; The initial turn radius should be wider, while the turn radius decreases with lower speed not the other way around.

 

Which is what I was experiencing.

 

Does that make sense?

 

And if I'm right, then I think the Dora and P51 suffer from the same issue. I certainly can attest for the Dora, but not the P51 since I haven't flown the P51 yet.

[Flagrum]

Page.Down, just enable the Controls Indicator witth RCTRL+ENTER and see what the virtual stick is exactly doing while your physical stick is kept in place.

[Page.Down]

Page.Down, just enable the Controls Indicator witth RCTRL+ENTER and see what the virtual stick is exactly doing while your physical stick is kept in place.

 

 

I can make another video with it if that would help people.

[Derbysieger]

I think you don't realize why this is happening.

 

In DCS your pilot has limited "strength" which limits his ability to pull the virtual stick past a certain point as speed increases. However, you are NOT limited by this on your physical joystick so it is very easy to pull way past that point. As the aircraft loses speed your virtual pilot will deflect the stick more and more until he is able to match the position of his virtual stick to the position of your physical joystick. If the position of your joystick is past the point where the aircraft can sustain a turn you will inevitably stall.

 

As mentioned before this is not intuitive and yes, the P-51 and the Fw 190 are effected by this as well it ijust isn't nearly as pronounced as it is in the Bf 109.

[ZaltysZ]

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.

 

Deflection of what? Your real stick or virtual stick? Even if you use linear response, relation between them is 1:1 only at lower speeds. As your speed increases, virtual stick will deflect less and less, despite you pulling your real stick fully.

 

Example. Let's say you are turning at high speed at which modeled pilot only has enough strength to deflect stick no more than 30%. If you pull 10%, virtual stick will deflect 10%; if you pull 30%, virtual stick will deflect 30%, but if you pull 40%, 70% or 100%, virtual stick will still deflect around 30% only. This is how heaviness of controls at high speed is simulated.

 

The problem begins when you pull your real stick beyond limit of virtual stick and allow the speed to bleed. As speed bleeds, heaviness of controls decreases, and virtual stick catches up with overdeflected real stick. Remember, it is ok to have real stick at 70-100% at high speed, because virtual one deflects only by 30% and that keeps aoa within allowable range, but if you keep real stick at same 70-100% at lower speeds, virtual one will be near 70-100% too, and that will cause a stall.

 

P.S don't use these % for FM reference. They are 'fake' and chosen for explanatory purpose.

[Page.Down]

Deflection of what? Your real stick or virtual stick? Even if you use linear response, relation between them is 1:1 only at lower speeds. As your speed increases, virtual stick will deflect less and less, despite you pulling your real stick fully.

 

Example. Let's say you are turning at high speed at which modeled pilot only has enough strength to deflect stick no more than 30%. If you pull 10%, virtual stick will deflect 10%; if you pull 30%, virtual stick will deflect 30%, but if you pull 40%, 70% or 100%, virtual stick will still deflect around 30% only. This is how heaviness of controls at high speed is simulated.

 

The problem begins when you pull your real stick beyond limit of virtual stick and allow the speed to bleed. As speed bleeds, heaviness of controls decreases, and virtual stick catches up with overdeflected real stick. Remember, it is ok to have real stick at 70-100% at high speed, because virtual one deflects only by 30% and that keeps aoa within allowable range, but if you keep real stick at same 70-100% at lower speeds, virtual one will be near 70-100% too, and that will cause a stall.

 

P.S don't use these % for FM reference. They are 'fake' and chosen for explanatory purpose.

 

If that was true, then the plane wouldn't stall at all.

 

What you basically just said, was my physical input on the joystick is irrelevant because the game won't allow deflection past 30%

 

IF we are to assume 30% in game deflection does not stall, then regardless of how far I pull on the joystick is irrelevant.

 

But, that isn't the case in game. Pulling to much on the joystick = stall and it is translated as such on the Virtual Joystick as well.

 

The difference is, I was presumably NOT pulling harder on the joystick and attempting to maintain a steady AOA, which in turn should mean the plane shouldn't stall if that AOA was established at higher speeds. As such at lower speeds AOA can be increased without the loss of stability; In addition to the fact Slats were designed for that purpose to increase AOA. What this means is at some point the 109 will begin to maintain speed, because I have not increased my AOA, and as such a stall is pretty well impossible under a constant speed without increasing AOA.

 

 

In short Control Stiffening is irrelevant at lower speeds.

 

And what most people don't understand is the amount of force required to move the stick in real life; It's at I believe 20lbs of force for a 109, EASY for any average person to do. At some point relative to HIGH speed. the stick force is exceeded. For example in game the K4 has surface lock at 600km/h IAS, not 380-420km/h IAS. In the case of 600km/h it does not matter how hard or far you pull on the stick you simply will not move the control surface. As such fletner tabs were used to pull out of high speed dives in such case, the rest has to do with altitude rather or not a 109 pilot survived that dive. There was even some pilot accounts that you can move the surfaces at 700km/h but it was very very difficult.

 

Unlike some Russian and British planes for example where stick forces reach as high as 50lbs of force. There are some planes whose stick forces can reach even higher yet upwards of 80lbs or more.

 

http://www.eaf51.org/newweb/Documenti/Storia/Flying_%20109_ENG.pdf

 

Read the handling section; It talks about slats allowing for higher AOA at lower speeds. And in order to induce that wing stall it was described as crass to get the wing to drop.

 

The video I showed wasn't crass, or at least I thought it wasn't. I have a new video now with the Virtual Joystick on. I'm cutting the video some because it's 15 minutes long.

 

Unfortunately, I'm used to the handling now, so instinctively I know not to pull harder in the maneuvers.

 

Bottom Line Zalty: The speeds we are talking about here has nothing to do with control stiffening, or an artificial Virtual Joystick limitation. This can be tested in game, and is clearly seen in the video I provided.

Edited April 26, 2015 by Page.Down

[Page.Down]

This new video will show that I was in fact increasing my AOA, so I believe that's more than likely what was happening in the first video.

 

But the issue remains: The increase in AOA is small, and in some cases barely noticeable. So why is the 109 wing stalling at speeds of 380-420km/h IAS with slats deployed?

 

This is not considered low speed for a 109; it's considered medium to medium high speed for a 109.

 

Low speed for a 109 is when you start dropping down to 220-280km/h IAS. Note: At low altitude. At higher altitude this changes obviously.

[iFoxRomeo]

Basicly it is similar to the ARU system in the MiG-21Bis. With increased speed, deflection decreases with constant stick position (ignoring altitude for a moment).

 

How do you expect to overcome the discrepancy between the nonexistend forces on the physical joystick vs. the forces that build up on the virtual stick?

 

How do you measure AoA in the Bf109? Are you sure the aircraft´s AoA is constant?

 

Fox

[ZaltysZ]

If that was true, then the plane wouldn't stall at all.

 

What you basically just said, was my physical input on the joystick is irrelevant because the game won't allow deflection past 30%

 

IF we are to assume 30% in game deflection does not stall, then regardless of how far I pull on the joystick is irrelevant.

 

No. I said "relation between them is 1:1 only at lower speeds. As your speed increases, virtual stick will deflect less and less, despite you pulling your real stick fully." Max deflection % is not constant, but is a function of speed, or in other words, max deflection % depends on speed. It might be 30% at high speed, 60% at medium speeds and 100% at low speeds.

 

If you pull beyond max deflection % of virtual stick, game will ignore that, but if you loose some speed virtual stick will deflect towards your physical stick until new higher max deflection % is reached. This way you can overpull by loosing speed even if you don't pull your physical stick more.

 

Check with ctrl+enter. Begin turning at high speed with constant 80% deflection of physical stick and observe how virtual stick position changes as you loose speed.

[Page.Down]

No. I said "relation between them is 1:1 only at lower speeds. As your speed increases, virtual stick will deflect less and less, despite you pulling your real stick fully." Max deflection % is not constant, but is a function of speed, or in other words, max deflection % depends on speed. It might be 30% at high speed, 60% at medium speeds and 100% at low speeds.

 

If you pull beyond max deflection % of virtual stick, game will ignore that, but if you loose some speed virtual stick will deflect towards your physical stick until new higher max deflection % is reached. This way you can overpull by loosing speed even if you don't pull your physical stick more.

 

Check with ctrl+enter. Begin turning at high speed with constant 80% deflection of physical stick and observe how virtual stick position changes as you loose speed.

 

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?

 

 

Note: This new video will show you I wasn't even remotely close to 80% physical. According to the Virtual Joystick I ranged between 25% and 50%, stalling occurred at closer to 50%. According to the Virtual Joystick.

 

Let me finish this video so you can see.

Edited April 26, 2015 by Page.Down

[Derbysieger]

Control stiffening happens fairly early in the bf 109, much earlier than in the other fighters we currently have. The effect becomes more noticeable the faster you go.

 

I think at 50% deflection you would stall eventually in any of the fighters I haven't tested this specifically but even in slow turning fights I rarely pull the stick to full deflection and at medium or high speeds you need very little input to pull a lot of G and at medium speed you can easily pull the stick far enough to stall.

[Hummingbird]

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 reason is no doubt that the effect of the slats both on the overall lift (the overall lift increase that the slats in reality constitute, esp. with power on, is seriously lacking ingame atm) and its spanwise progression along the wing with increases in AoA is incorrectly modelled.

 

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.

[Echo38]

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 reason is no doubt that the effect of the slats both on the overall lift (the overall lift increase that the slats in reality constitute, esp. with power on, is seriously lacking ingame atm) and its spanwise progression along the wing with increases in AoA is incorrectly modelled.

 

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.

 

Lots of assumptions here; I counted nine. Have you ever considered that what a given real pilot considers "gentle" may not be what you consider "gentle"? And so on, for each of the subjective--and not quantified--terms you've used here (mild, violently, plenty, sensitive, etc.) ...

[Hummingbird]

Lots of assumptions here; I counted nine. Have you ever considered that what a given real pilot considers "gentle" may not be what you consider "gentle"? And so on, for each of the subjective--and not quantified--terms you've used here (mild, violently, plenty, sensitive, etc.) ...

 

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.

Edited April 26, 2015 by Hummingbird

[Page.Down]

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 are 2 more pilot accounts of the 109 as well from Eric Brown, and Mark Hanna

 

Which confirms what Hummingbird is saying almost to the letter.

 

http://www.eaf51.org/newweb/Documenti/Storia/Flying_%20109_ENG.pdf

 

You will want to read the Handling Section specifically. As it pretty much addresses everything everyone has said thus far, but imho isn't representative either fully or correctly of how the K4 handles in game currently and at relative speeds in question.

Edited April 26, 2015 by Page.Down

[Page.Down]

Updated Video with Virtual Joystick:

 

 

Note the last few minutes of the video I was trying to induce a flat spin, which was impossible to do. That is pulling hard on the stick with full rudder into the roll and maintaining that indefinitely until a flat spin results. Basically a continuous snap roll. I was disappointed when I could not induce a flat spin.

Edited April 26, 2015 by Page.Down

[NineLine]

And here are 2 more pilot accounts of the 109 as well from Eric Brown, and Mark Hanna

 

Which confirms what Hummingbird is saying almost to the letter.

 

http://www.eaf51.org/newweb/Documenti/Storia/Flying_%20109_ENG.pdf

 

You will want to read the Handling Section specifically. As it pretty much addresses everything everyone has said thus far, but imho isn't representative either fully or correctly of how the K4 handles in game currently and at relative speeds in question.

 

So were the conditions the same as the videos in this thread? Or is that not important? Altitude, weather, weights, the use of WEP, etc?

[Page.Down]

So were the conditions the same as the videos in this thread? Or is that not important? Altitude, weather, weights, the use of WEP, etc?

 

Altitude below 1000m; Weights exactly the same, same exact weather conditions, no WEP

 

Now that is pertaining to the videos; Unless you mean specifically the document?

 

Edit: In which case the document doesn't give those conditions.

Edited April 26, 2015 by Page.Down

[NineLine]

I mean to the real world tests.

[Page.Down]

I mean to the real world tests.

 

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.

Edited April 26, 2015 by Page.Down

[ZaltysZ]

It is a long video, so description of key points of timeline would be great.

 

Does stall at around 1:00 illustrate your issue well?

Edited April 26, 2015 by ZaltysZ

[Page.Down]

It is a long video, so description of key points of timeline would be great.

 

Does stall at around 1:00 illustrate your issue well?

 

Yes and no.

 

at 1:00 that was the highest extreme in the video; Other maneuvers are less than 50% deflection on the Virtual; And I was lightening up on the joystick to maintain the shudder but not exceed it. Until my altitude was to low to continue then I corrected.

 

If I had pulled harder up to 50% deflection it would have snapped in other parts of the video.

[otto]

Slats "behaviour" of on Mig3 :

 

On the night before enemy forces invaded our country, concurrent testing was concluded by the Scientific Research Institute of VVS and LEE NKAP in testing the effectiveness of elongated automatic slats on the MiG-3. With slats, the engineers and test pilots noted that the fighter ceased to stall without warning, the fighter also proved easier to control while executing aerobatic maneuvers. The MiG-3 was easily leveled prior landing; in other words, it gave more control and did not have a tendency to roll over to the side when the pilot pulled on the control stick.

- The results noted: Automatic slats, length 2004 mm, on the serial MiG-3 considerably eliminated stalls and increased controllability when speed was lost. Before a stall, the aircraft would warn the pilot by rocking, and when a stall was imminent, the aircraft dipped its nose and banked to the right. The installation of the slats considerably simplified piloting and made it possible to control the aircraft with a loss of speed.

- From empirical tests it was seen that fighters with “smooth” wings, critical speed leveled off at 190 km/h but when the slats were added the speed dropped to 155-160 km/h. In certain conditions, for example when turning, the MiG-3 completely stopped stalling. Its behaviour tended to give more warnings than with 1573 mm slats.

-

The majority of test flights were done by test pilots A.I. Zhukov, V.N. Savkin, V.T. Sahranov, noting that thanks to the slats, piloting the plane was a lot easier."

[Page.Down]

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.

[Page.Down]

Slats "behaviour" of on Mig3 :

 

On the night before enemy forces invaded our country, concurrent testing was concluded by the Scientific Research Institute of VVS and LEE NKAP in testing the effectiveness of elongated automatic slats on the MiG-3. With slats, the engineers and test pilots noted that the fighter ceased to stall without warning, the fighter also proved easier to control while executing aerobatic maneuvers. The MiG-3 was easily leveled prior landing; in other words, it gave more control and did not have a tendency to roll over to the side when the pilot pulled on the control stick.

- The results noted: Automatic slats, length 2004 mm, on the serial MiG-3 considerably eliminated stalls and increased controllability when speed was lost. Before a stall, the aircraft would warn the pilot by rocking, and when a stall was imminent, the aircraft dipped its nose and banked to the right. The installation of the slats considerably simplified piloting and made it possible to control the aircraft with a loss of speed.

- From empirical tests it was seen that fighters with “smooth” wings, critical speed leveled off at 190 km/h but when the slats were added the speed dropped to 155-160 km/h. In certain conditions, for example when turning, the MiG-3 completely stopped stalling. Its behaviour tended to give more warnings than with 1573 mm slats.

-

The majority of test flights were done by test pilots A.I. Zhukov, V.N. Savkin, V.T. Sahranov, noting that thanks to the slats, piloting the plane was a lot easier."

 

Thanks otto.

 

And if I'm not mistaken Russian planes did use slats such as the MiG but also Yaks, and even the IL2's.... I do not know but I suspect it was an idea adopted from captured German 109's. Slats were used on the earliest of 109's as well right down to the ME-109E's. Although I think the IL2 may have had them before a german 109 was captured by Russia... Not sure.

Edited April 26, 2015 by Page.Down