K4 Accelerated Wing Stall

[Derbysieger]

I see the slats coming out all the time when I fly hard maneuvers in the DCS K4 and there is a bit of room for harder maneuvering once they are deployed before I get buffeting but I'm not in a position to judge how much room for harder maneuvers they should give us before the aircraft stalls.

 

What we need are tests with real data from the sim, not just videos, to compare it to RL data if available. Anecdotal evidence is not good enough to judge if it stalls at the right time or not. IMO the videos show not enough to really judge what is happening.

 

I can ride the K4 right on the edge of a stall with minimal corrections after I find the sweet spot but I can not pull and instantly have the stick at that sweet spot. I need to find it first.

[Bounder]

The slats were not a warning point for a stall; Inexperienced German pilots used it as such, and were under the presumption that they were pulling to many G's.

 

An experienced Ace pilot has always contradicted this pilot account, and even stated newer inexperienced pilots were afraid to push a 109 that hard.

 

ME-109E's were known to turn with early model spitfires in sustained turns; But an inexperienced pilot would not have been able to.

 

 

I'll quote the manual from another thread on same subject (p33)

The wing of the 109 is made with no washout, i.e. with the same angle from wing root to wingtip. Most Allied fighters of the time were designed with the angle of incidence greater at the wing root and decreasing across the span, becoming lowest at the wing tip. This gives the 109's wing increased lift compared to similar Allied fighters, while the tip stalling problem normally solved by washout on other designs is solved on the 109 with the use of automatic leading-edge slats that normally extend before the wingtip can stall. The overall result is an excellent high-lift wing that is also difficult to stall.

 

Since the 109s slats deploy before the wing stalls as AoA increases, deployment can be used by inexperienced pilots as an indication to stop increasing AoA if they are not used to the 109 yet. As such any indication, including speculated audio cue, that slats are deployed may help inexperienced 109 pilots avoid unexpected stalls. Experienced pilots will of course know how much further they can increase AoA following slat deployment and may pull harder.

 

On the 'bang' noise, it was something I read/heard somewhere, may not happen every time and may be an old wives tail for all I know, just thought I'd mention it in case there is any truth to it.

[Page.Down]

I'll quote the manual from another thread on same subject (p33)

 

 

Since the 109s slats deploy before the wing stalls as AoA increases, deployment can be used by inexperienced pilots as an indication to stop increasing AoA if they are not used to the 109 yet. As such any indication, including speculated audio cue, that slats are deployed may help inexperienced 109 pilots avoid unexpected stalls. Experienced pilots will of course know how much further they can increase AoA following slat deployment and may pull harder.

 

On the 'bang' noise, it was something I read/heard somewhere, may not happen every time and may be an old wives tail for all I know, just thought I'd mention it in case there is any truth to it.

 

And then I'll quote Eric Brown:

 

Since I did not attempt to increase AOA, since my AOA was established at a higher speed, it means the stall should be impossible at the lower speed of 380-420km/h (assuming of course I could maintain the same AOA when I started the maneuver at 500km/h) The fact that slats deploy doesn't negate the fact I can increase my AOA and not stall the plane at the same speed 380-420km/h. The problem is I do not see that increase in AOA and the stall in fact occurs at a lower AOA which was established at 500km/h initially.

 

[Page.Down]

I think what I'm trying to say is; Buffeting is occurring too soon without an increase in AOA. And the Virtual joystick position confirms this in my videos;

 

Note the Second Video at the 1:00 mark which Zalty pointed out, was clearly a crass pilot error on my part, pulling almost 70% deflection according to the Virtual Joystick. But at no point outside of that did I duplicate that same error. And to be blunt, I can easily avoid the buffeting just by letting up on the stick, but if I did that, I wouldn't be maintaining my established AOA from the start of 500km/h.

 

I think the testing standard people can do would be to start at 500km/h. Pull into a bank turn at that speed and quickly increase AOA to the point of buffeting, then maintain that AOA. As speed decreases buffeting should cease unless you increase your AOA as speed decreases.

 

The fact I'm bleeding off speed doesn't matter pertaining to normal stall aerodynamics.

Edited April 27, 2015 by Page.Down

[Derbysieger]

This description is pretty much what I see in DCS though. Especially if I compare it to both the other fighters. You CAN throw the Bf 109 pretty hard around at low speeds. If I fly very slow (~270-300km/h, 168-186mph) in the P-51 or Fw 190 the aircraft is much, much harder to maneuver compared to the K4.

 

Maybe it needs to be fine tuned but overall I would say that is a good description of what I see when I fly the Bf 109. Stick length (extensions) also play a role in what you can achieve.

 

And btw you constantly pull more on the virtual stick than I can sustain.

[[DBS]TH0R]

^^ Seconded.

 

 

Thor:

 

I never said this. I think you might be quoting someone else.

 

Oh, thats right. I messed up my reply when removing non essential quotes. That was Otto's post. Apologies.

 

 

And then I'll quote Eric Brown:

 

Since I did not attempt to increase AOA, since my AOA was established at a higher speed, it means the stall should be impossible at the lower speed of 380-420km/h (assuming of course I could maintain the same AOA when I started the maneuver at 500km/h) The fact that slats deploy doesn't negate the fact I can increase my AOA and not stall the plane at the same speed 380-420km/h. The problem is I do not see that increase in AOA and the stall in fact occurs at a lower AOA which was established at 500km/h initially.

 

 

 

Please define "slower speeds" for me. Also, the report says no more than 40" were used which unless I completely misunderstood the conversion means no more than 1.4 ATA. In your tests you are well above that value constantly throughout the video.

Edited April 28, 2015 by T}{OR

[Echo38]

+1. Further, I've heard stories of an audible 'bang' as slats were deployed in 109s (which allegedly 'scared' inexperienced pilots) and wonder if this sound effect was added in DCS it might give us an extra vital cue of slat deployment before full stall

 

When I saw this discussion on another forum, a long time ago, I think the consensus concluded that the 109E had a different slat mechanism than later 109's, and it was these early-type slats that tended to "stick" and thus "go bang," with the later ones presenting fewer or no such problems. I do not have a reliable source for this; it's just a memory I have of hearsay. Still, it might serve as a pointer for someone with access to good sources, to go digging. : )

Edited April 27, 2015 by Echo38

[9.JG27 DavidRed]

thats my impression as well...the bang was typical for early 109 versions, i.e. Emil...also, if you pull carefull enough, you can make the slats in the K4 go out very slowly, and if you have silk hands, you also can keep them in a half-out position if you want to....though, if you just start an agressive turn, the slats will bang out...wonder whether this would make any noise audible...

[OnlyforDCS]

 

I think the testing standard people can do would be to start at 500km/h. Pull into a bank turn at that speed and quickly increase AOA to the point of buffeting, then maintain that AOA. As speed decreases buffeting should cease unless you increase your AOA as speed decreases.

 

The fact I'm bleeding off speed doesn't matter pertaining to normal stall aerodynamics.

 

Yes it does. As you are bleeding off speed the stiffening forces will drop off and your virtual pilot will pull back automatically increasing your AOA. To achieve your described manouver you have to maintain AOA, and to do that you have to slowly push your physical stick forward to maintain the virtual stick in the same position it was when you started the manouver.

Edited April 28, 2015 by OnlyforDCS

[Solty]

Guys this is from Hanna's Buchon experience. It had the G model wings.

"Another peculiarity is that when you have been in a hard turn with the slats deployed, and then you roll rapidly one way and stop, there is a strange sensation for a second of so of a kind of dead area over the ailerons - almost as if they are not connected ! Just when you are starting to get worried they work again !"

The main problem some in this thread had, was that the wing droped very rapidly... So this seems to be very similar to what the 109 does according to Hanna. Of course how much, and how quickly... that is debatable, but I would imagine that it is not left to simple "feeling" but rather some math and physics simulation in game.

 

And another quote

"As the slats pop out you feel a slight "notching" on the stick and you can pull more until the whole airframe is buffeting quite hard."

and this is what I was refering to with my last post.

 

The problem is not with the wing stalling but the way that we "feel" it in game. Buffeting should be more pronouced, and I think that that "pop" sound for the rapid slat deployment should be there. It happens whenever any metal thing moves, there is always a sound that is audiable, especially as we don't have the ability to feel the "notching" on our stick, so that would make us aware that slats are coming out and simulate the feeling through sound.

[Hummingbird]

"Another peculiarity is that when you have been in a hard turn with the slats deployed, and then you roll rapidly one way and stop, there is a strange sensation for a second of so of a kind of dead area over the ailerons - almost as if they are not connected ! Just when you are starting to get worried they work again !"

The main problem some in this thread had, was that the wing droped very rapidly... So this seems to be very similar to what the 109 does according to Hanna. Of course how much, and how quickly... that is debatable, but I would imagine that it is not left to simple "feeling" but rather some math and physics simulation in game.

 

You've misunderstood what Hanna wrote, what he's talking about is rapidly rolling the aircraft level or to the other side after having been in a hard turn and the effect it has on the feel of the ailerons. He isn't talking about stalling the aircraft.

 

The whole section:

 

"The roll rate is very good and very positive below about 250 mph. This is particularly true of the Charles Church's Collection clipped wing aircraft. Our round tipped aeroplane is slightly less nice to feel. With the speed further back the roll rate remains good, particularly with a bit of help from the rudder. Above 250 mph however the roll starts to heavy up and up to 300 or so is very similar to a P-51. After that it's all getting pretty solid and you need two hands on the stick for any meaningfull roll rates. Another peculiarity is that when you have been in a hard turn with the slats deployed, and then you roll rapidly one way and stop, there is a strange sensation for a second of so of a kind of dead area over the ailerons - almost as if they are not connected ! Just when you are starting to get worried they work again !

 

Pitch is also delighful at 250 mph and below. It feels very positve and the amount of effort on the control column needed to produce the relevant nose movement seems exactly right to me. As CL max is reached the leading edge slats deploy - together if the ball is in the middle, slightly asymmetrically if you have any slip on. The aircraft delights in being pulled into hard manuevering turns at these slower speeds. As the slats pop out you feel a slight "notching" on the stick and you can pull more until the whole airframe is buffeting quite hard. A little more and you will drop a wing, but you have to be crass to do it unintentionally. Pitch tends to heavy up above 250 mph but it is still easily manageable up to 300 mph and the aircraft is perfectly happy carrying out low-level looping maneuvers from 300 mph and below. Above 300 mph one peculiarity is a slight nose down trim change as you accelerate. This means that running in for an airshow above 300 mph the aeroplane has a slight tucking in sensation - a sort of desire to get down to ground level ! This is easily held on the stick or can be trimmed out but is slightly surprising initially. Maneuvering above 300, two hands can be required for more aggressive performance. EIther that or get on the trimmer to help you. Despite this heavying up it is still quite easy to get at 5G's at these speeds. "

 

And 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. Pitch force tends to get heavy at speeds above 300 mph, but is still easily managed with a little 2-hand pull or left hand re-trimming."

 

In short the stall of the ingame aircraft is too violent, with the ingame aircraft going into a flick roll, where'as the real thing only experiences a mild wing drop, and this is according to both Hanna, Holm & Southwood who are all in complete agreement regarding the 109's flying characteristics.

 

Furthermore pilots describe being able to pull the stick back quite some way before the stall actually happens, which again nothing like what we have ingame.

Edited April 28, 2015 by Hummingbird

[Solty]

You've misunderstood what Hanna wrote, what he's talking about is rapidly rolling the aircraft level or to the other side after having been in a hard turn and the effect it has on the feel of the ailerons. He isn't talking about stalling the aircraft.

 

The whole section:

 

"The roll rate is very good and very positive below about 250 mph. This is particularly true of the Charles Church's Collection clipped wing aircraft. Our round tipped aeroplane is slightly less nice to feel. With the speed further back the roll rate remains good, particularly with a bit of help from the rudder. Above 250 mph however the roll starts to heavy up and up to 300 or so is very similar to a P-51. After that it's all getting pretty solid and you need two hands on the stick for any meaningfull roll rates. Another peculiarity is that when you have been in a hard turn with the slats deployed, and then you roll rapidly one way and stop, there is a strange sensation for a second of so of a kind of dead area over the ailerons - almost as if they are not connected ! Just when you are starting to get worried they work again !

 

Pitch is also delighful at 250 mph and below. It feels very positve and the amount of effort on the control column needed to produce the relevant nose movement seems exactly right to me. As CL max is reached the leading edge slats deploy - together if the ball is in the middle, slightly asymmetrically if you have any slip on. The aircraft delights in being pulled into hard manuevering turns at these slower speeds. As the slats pop out you feel a slight "notching" on the stick and you can pull more until the whole airframe is buffeting quite hard. A little more and you will drop a wing, but you have to be crass to do it unintentionally. Pitch tends to heavy up above 250 mph but it is still easily manageable up to 300 mph and the aircraft is perfectly happy carrying out low-level looping maneuvers from 300 mph and below. Above 300 mph one peculiarity is a slight nose down trim change as you accelerate. This means that running in for an airshow above 300 mph the aeroplane has a slight tucking in sensation - a sort of desire to get down to ground level ! This is easily held on the stick or can be trimmed out but is slightly surprising initially. Maneuvering above 300, two hands can be required for more aggressive performance. EIther that or get on the trimmer to help you. Despite this heavying up it is still quite easy to get at 5G's at these speeds. "

 

And 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. Pitch force tends to get heavy at speeds above 300 mph, but is still easily managed with a little 2-hand pull or left hand re-trimming."

 

In short the stall of the ingame aircraft is too violent, with the ingame aircraft going into a flick roll, where'as the real thing only experiences a mild wing drop, and this is according to both Hanna, Holm & Southwood who are all in complete agreement regarding the 109's flying characteristics.

 

Furthermore pilots describe being able to pull the stick back quite some way before the stall actually happens, which again nothing like what we have ingame.

So... that means that if slats are deployed there should be a feeling of not working ailerions after a quick roll...? Interesting, now I understand why it is seen as peculiar. You are right I might have missread that.

 

Hmmm... but Holm states that at the 300mph he needs both hands... and this is why also, we may be getting the idea that the plane is easy to stall. With 2 hands on the stick you can feel your own strenght put into the plane. In DCS (or any other game) we cannot as we have digital imputs. 300mph is 482kph, which means that the pilot has a problem with pulling but the player can't feel it. Again, this leads to people stalling 109 easier even though it gives quite a bit of warning.

 

K4 is also a plane that is heavier than the Bf109G6 or Buchon... that means the plane will stall easier, maybe it could have more rapid wing drop (however unlikely). Although, we cannot say that 109=109 as we know, E3 version was seen as possible to turn with Spitfire by the pilots and F was seen as the best balanced one while G and K as fast and good for B&Z with K4 beeing an amazing climber (24m/s).

 

Again I sustain my previous statement. The K4 need a little bit more pronounced buffeting when slats are deployed.

Edited April 28, 2015 by Solty

[Hummingbird]

What Hanna is talking about is the feel on the stick, according to him became so light that it feels as if the ailerons aren't connected, he isn't saying that they aren't working which they obviously are, otherwise he wouldn't be able to make said roll at all ^^

 

As for stick travel, again when'ever mentioned a long travel is mentioned to make the aircraft stall.

[DB 605]

Again I sustain my previous statement. The K4 need a little bit more pronounced buffeting when slats are deployed.

 

I assume you don't have FFB stick? because with MS FFB2 there is plenty on buffeting before stall, exactly like it should be according to pilot notes/memoirs.

[GrapeJam]

I assume you don't have FFB stick? because with MS FFB2 there is plenty on buffeting before stall, exactly like it should be according to pilot notes/memoirs.

 

Well I think we've got the answer to our problem.

[Solty]

I assume you don't have FFB stick? because with MS FFB2 there is plenty on buffeting before stall, exactly like it should be according to pilot notes/memoirs.

No I don't :/

 

 

But I have just checked the 109 again... and well... yeah it does move around wierd. I mean... it is/is not stalling. I can't tell. The plane snaps but then doesn't follow into a spin... just stops the motion and stops again, and again and again.

 

It seems to be entering a stall and then quickly stops, jerks around. It is hard to describe even. The wing doesn't go down too much, but it does sink very quickly but very shallowly.:joystick:

 

I was trying to make abrupt movments to get to stall, but it just goes out of it right after it goes into it...:huh:

 

And it is not connected to slats, as they are already deployed but the plane just snaps on the left wing and even though I keep my pull... it just stops and reenters with another snap to the left.:mad:

[NineLine]

Well I think we've got the answer to our problem.

 

I must be weird, I don't have a FFB stick, but the 109 speaks to me quite clearly when its not happy...

[[DBS]TH0R]

I must be weird, I don't have a FFB stick, but the 109 speaks to me quite clearly when its not happy...

 

Same here. I'll dust off my MSFF2 just to see the difference.

[Page.Down]

I must be weird, I don't have a FFB stick, but the 109 speaks to me quite clearly when its not happy...

 

True enough, but the problem is the 109 speaks to you after buffeting, not during. And if you watch the virtual joystick during buffeting, while maintaining AOA, you see it all over the place;

 

To me, I see that as a stall, not a buffet. That is the plane changing vectors without stick inputs.

 

I'm not sure if buffeting causes a change in vectors which can instigate the stall making it worse?

[NineLine]

True enough, but the problem is the 109 speaks to you after buffeting, not during. And if you watch the virtual joystick during buffeting, while maintaining AOA, you see it all over the place;

 

To me, I see that as a stall, not a buffet. That is the plane changing vectors without stick inputs.

 

I'm not sure if buffeting causes a change in vectors which can instigate the stall making it worse?

 

Are you saying there shouldn't be any movement in the virtual stick during buffeting? I would imagine depending on the situation and how extreme the buffeting is, the stick would move accordingly...

[Page.Down]

Are you saying there shouldn't be any movement in the virtual stick during buffeting? I would imagine depending on the situation and how extreme the buffeting is, the stick would move accordingly...

 

I think it happens to soon, as I said before. I don't think buffeting should be occurring at the lower AOA's than what I started with.

 

And that's what I'm seeing.

 

 

As I said many times in this thread; IF you establish and maintain a given AOA from high speed, regardless of how low your speed gets buffeting should stop; Especially when slats are out, because slats specifically increase AOA. And if I have not increased that AOA that I established at 500km/h (Assuming I can maintain the AOA with little to no variance) then buffeting occurs to soon at the speeds in question, which means the stall is premature as well.

 

And Force Feedback discussion is irrelevant to that assessment. FF allows you to feel the buffeting, but it doesn't tell you if that buffeting and stall is occurring prematurely.

 

 

The devs can easily simulate these conditions without the use of a real pilot; In a make-shift sandbox test environment. And as such determine when AOA is constant from a high start speed, that as speed decreases should buffeting persist and/or stall at the speeds in question.

 

Most people can agree with this assessment based on physics principals; The issue isn't the physics it's the FM specifically of the K4 I'm questioning... under those precise testing conditions. Which a human player cannot simulate consistently, but a sandbox simulation without a human pilot can.

Edited April 28, 2015 by Page.Down

[NineLine]

I think it happens to soon, as I said before. I don't think buffeting should be occurring at the lower AOA's than what I started with.

 

And that's what I'm seeing.

 

 

As I said many times in this thread; IF you establish and maintain a given AOA from high speed, regardless of how low your speed gets buffeting should stop; Especially when slats are out, because slats specifically increase AOA. And if I have not increased that AOA that I established at 500km/h (Assuming I can maintain the AOA with little to no variance) then buffeting occurs to soon at the speeds in question, which means the stall is premature as well.

 

And Force Feedback discussion is irrelevant to that assessment. FF allows you to feel the buffeting, but it doesn't tell you if that buffeting and stall is occurring prematurely.

 

What is telling you that it is occurring prematurely?

[Hummingbird]

The problem is that the ingame aircraft snaps into the stall too early and too quickly, that's it.

 

Pilots talk about having to pull back the stick further to stall the Bf-109 than in other aircraft, which is most certainly not the case ingame atm.

 

The reason for this is that the real aircraft stalls at a higher AoA than similar type aircraft without slats, due to the fact that the slats delay the onset of the stall over the outer wing section (which is the section that normally stalls first), which in turn increases the CLmax of the entire wing seeing as the outer wing section can now keep flying for as long as the root section (which as I've explained before is already further energized by the prop thrust) - and even further infact, providing full aileron even some ways into the stall.

Edited April 28, 2015 by Hummingbird

[Hummingbird]

What is telling you that it is occurring prematurely?

 

Stick travel.

[NineLine]

Stick travel.

 

Based on what? What evidence do you have to show this is occurring too early?