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Whats your opinion on the new FW FM?

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Many of these home flight sims use lifting line theory.

 

If that was the case with the digital nature engine, then it would produce values like for lift coeficient vs. angle of attack and for drag versus lift under the condition of "normal" airflow around the foil accordingly.

 

As flaped wing areas would be straight forward to include, I would guess that those sections are equally affected for starting to deviate from real world values at high AoA. IF all of the above would be the case, could this be an explanation for the "flap issue" we are seeing in aircraft as the Yak? After all, the "flap effect" is used at slow speeds and at max. AoA.

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hen it would produce values like for lift coeficient vs. angle of attack and for drag versus lift under the condition of "normal" airflow around the foil accordingly.

 

Yes...linear polars with values to infinity..... 

 

The end points are determined empirically.

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Aircraft performance math uses newtonian physics based on F=ma to determine the edges of the envelope.  A given amount of force will produce a given maximum performance point.

 

Lifting line theory determines the same thing in a different frame of reference.  It is useful for looking at torques and moments about the CG to define aircraft behavior.

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BTW, for all the community gripes...

 

I just gave the community the "Keys to the Kingdom" to determine what is going on with your FM's.

 

http://forum.il2sturmovik.com/topic/21732-whats-your-opinion-new-fw-fm/?p=373839

 

Don't sit there and do nothing but continue to gripe.  Get some data and it can be proven or disproven beyond a shadow of a doubt.

 

 

 

I would guess that those sections are equally affected for starting to deviate from real world values at high AoA.

 

Yes, that is limitation of lifting line theory and a home computer limits the power.  A more accurate FM could be created but like the simulators at work, you could not afford it as it would require a multi-million dollar investment, mechanics, IT staff, Hanger to house it, and an entire room for the computing power required.

 

It seems like these games do a very good job for what they have to work with so do not be too hard on the developers.  A knowledgeable community can help them out and make things even better under the right circumstances. 

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You can do a full roll in the 190 using rudder only, with no aileron input at all.

 

Combine rudder input with aileron input and the result is almost always an accelerated stall with an inverted flat spin knocking on the door. In testing, I've been trying to hold the stick forward to offset this.

 

I've ended up decreasing rudder input in settings to the lowest sensitivity as I think their may be a global FM issue here.

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Yaw roll coupling appears to be one of the more difficult things these home computer sims "simulate".  

 

So we are all on the same page about the mechanics of what a rudder is supposed to be able to do in order to be called a rudder!

 

1. Keep the aircraft in coordinated flight.   In a real aircraft it does not take much rudder to keep a bank coordinated.  If the ailerons are correctly balanced then there is very little adverse yaw some some aircraft require more input than others based on the specifics of that design.  The developers might be going for that effect or they might simply have overdone it.

 

Do not look at the ball (inclinometer).

 

 http://www.aircraftspruce.com/menus/in/inclinometer.html

 

Look over the nose and add just enough rudder so that the aircraft rotates about the longitudinal (lengthwise) axis just like there was a solid rod extending thru the propeller spinner to the tail.  If the nose yaws off that axis, the roll is uncoordinated.  Uncoordinated rolls can lead to stalls if excessive rudder input is used.  Usually they lead to a reduction in airspeed and a sloppy boat turn entry. 

 

2.  The rudder can always lift the wing at the stall point.  In a tractor propeller aircraft, the thrustline pretty much keeps some degree of effectiveness over the rudder all the way to zero airspeed.  A good pilot can walk the wing down on a high powered piston aircraft with rudder use.  Torque effects are always present but a wing has a tremendous amount of roll wise dampening that effectively covers up the effects.  Once the wing is no longer flying, that torque moment drops the wing until the angular velocity returns the dampening force.  Rudder can counteract this quite effectively.

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Control harmony seems way overbalanced to me - ailerons seem to behave normally but rudder is hyper- sensitive, so it is very difficult to coordinate rudder and aileron input without snapping into an accelerated stall.

 

This is why I adjusted the rudder effectiveness to the lowest possible setting and this seems to improve things so far.

 

The pitch axis during maneuvers feels like the COG is shifted to back of the aircraft, like pilots describe the P-51 with the full back fuel tank. It feels like being in a rocking chair.

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The Yak video is typical online experience. Even that is damaged yak-1 no less.

 

I can't imagine what yak-3 or yak-9U will be capable of if this is what yak-1 is doing.

 

+1

 

This is a good point to think about for the developers, even if the Yak-1 we have in game is not probably too much different from the first Yak-9 series.

 

Yak-1b is coming, and the FW diving "iusse" with the Yak-1 is somenthing that does really feel strange at least.

 

May be would be time to check some more time the Yak-1 FM/DM, and this before the situation could became embarrassing with the new (improved) Yak-1 versions, if not Yak-9 as said above.

Edited by 150GCT_Veltro

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So everybody who have brain know this  Fw 190 fighter version is not realistic. We have materials and documections to prove it. So ?

Edited by Art

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So everybody who have brain know this  Fw 190 fighter version is not realistic. We have materials and documections to prove it. So ?

 

So put together a coherent report about what you think is wrong and send it to the developers (i.e., Han) instead of continually making snide little remarks about how you don't like it. 

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That is actually been done LuKeFF, complete with math, documents (both Allied and Focke Wulf) that all support the same conclusion. 

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Hello.

Interpreter. Excuse me.))

In "Foka" corrected the critical angle of attack. In "Foka" fixed lift of the wing. Now it's right. Now it is impossible to make high-speed turns. Stall = tailspin. As in life.))

The aircraft for speed. Excellent roll rate. Excellent weapon. Handle in the stomach = no.))

 

The problem of the rudder in the overall game. He correctly modeled. Developers know about it. Maybe someday it will correct.

Good luck.)) 

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Not sure if it's placebo effect but the 190 seems to turn better and the stall characteristic is much less harsh now, it's much less likely to enter a spin now.

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In "Foka" corrected the critical angle of attack. In "Foka" fixed lift of the wing. Now it's right. Now it is impossible to make high-speed turns. Stall = tailspin. As in life.))

 

 

 Yes they did this:

 

 

 

Fw 190 A-3 aerodynamic characteristics corrected to meet the now available data (in short, its fineness ratio was reduced a little while its climb rate at high altitudes increased somewhat);

 

 

Fineness ratio is a function of the physic shape and dimensions of the design.  It does not change.  It is the thickness divided by the chord ratio for the wing and length divided by diameter for the fuselage.  IN other words, instead of adding more available power without increasing absolute power and recalculating their basic aerodynamic data, they changed the physical shape of the design mathematically and continued to use the same flawed aerodynamic starting point.  It is simply a shortcut to achieve specific performance in ONE area at the expense of other performance.

 

The original error in the FW-190 flight model is quite obvious if you understand the physics.  They got their power input confused by using performance at a lower power setting used by TASGi against the BMW 801 power output curves.  That point was proven and the reason why the FW-190 FM got the "fineness ratio" adjustment.  The absolute power relationship to the L/D ratio was not correct in the orignal FM.

 

Problem with that technique is we have not changed the basic error in absolute power and are still working within the erroneous relationships of the forces of flight established in the original error.   In the system that is the aircraft, we have not reset any of the relationships and the aircraft is still not representative of it power production.

 

Lift and drag have a direct relationship.  When one increases, the other increases in proportion to the L/D ratio of the design.  We have L/D curves for the aircraft that are not representative.

 

Why?  Changing the fineness ratio adjusted the drag of the design.  That did free up more power to increase the climb of the aircraft model.  In reducing the drag, they shifted they simply shifted the error in the L/D curve.  If you reduce the drag, you will reduce the lift according to that L/D ratio.

 

This change is drag would introduce a new error in the stall.

 

That is also why we see what very much appears to be an error in the stall angle of attack as listed by the developers.  If one knows the science, one can simply look at the airfoil selection and stall angle of attack to see that something is very wrong.

 

You can easily compare the Yak 1 stall angle of attack of ~18 degrees at RE of 5.8 x 10-6.   

 

 

 

Stall angle of attack in flight configuration: 18 °

 

1gqbnl.jpg

 

Notice where the zero lift is achieved.  That is the effect of camber of the airfoil and about where the designer will set the angle of incidence.  In the case of the Clark Y, is -4 degrees.

 

That means our stall body angle is going to be adjusted by that angle of incidence.

 

Some Aerodynamic data:

 

Clmax root airfoil= 1.5

Aspect Ratio of the Yak 1 = wingspan^2/Wing Area = 5.8

 

Our Induced Angle of Attack is going to be ai = 18.24(1.5/5.8) = 4.71 degrees

 

Our body angle at the stall point would then be 18 degrees root airfoil + 4.71 degrees due to induced drag - 4 degrees to achieve zero lift at body angle zero for take off purposes = 18.71 degrees.

 

In other words it gives very good agreement with the Developers assessment of the Yak 1.  Anybody with some aeronautical knowledge would say IL2 BOS model is correct as far as stall angle in the clean configuration.

 

We can prove the hypothesis that the orignal error still remains in the FW-190 by doing the same process.

 

 

 

Stall angle of attack in flight configuration: 15.5°

 

NACA 230015 root airfoil at 3.8 x 10-6 at sea level:  That roughly about the Reynold number of the NACA 23015 airfoil at stall speed for an FW190 at sea level.  That puts the stall angle of attack at 16 degrees.  

 

The math is simple.

 

RN = (Velocity in Feet per Second * Chord in FT)/ kinematic viscosity of air at sea level.

 

Kinematic viscosity = Dynamic viscosity / density

 

110 mph = 161fps

 

RN = (161fps*5.95ft)/ .000156927 = 6.1 x 10-6 RE

 

That is a little higher than our 5.8 x 10-6 RE for the Clark Y so we can reduce our CLmax accordingly to put the airfoils on the same RE for angle of attack comparison purposes.  The reality is that Reynolds number is based upon Velocity and the FW-190 will always be at a higher velocity in a 1G level stall.  The wing of the FW190 will always have a higher Reynolds number.

 

 

So looking at our aerodynamic data for the NACA 23015 airfoil, since CLmax is highly dependant upon Reynolds number, we can say our airfoil is going to produce a CLmax of 1.8 at 6.0 x 10-6 RE and a CLmax of 1.5 at 2.6 X 10.6.  Now the polar allows to extrapolate the value but I am lazy and wish to error on the side of caution.  Let's use 1.6 which is a value somewhat less than extrapolation would give us.  

 

Some Aerodynamic data:

 

Clmax root airfoil= 1.5

Aspect Ratio of the FW190A3 = wingspan^2/Wing Area = 6.1

 

Our Induced Angle of Attack is going to be ai = 18.24(1.6/6.1) = 4.78 degrees

 

Well we know the FW-190 had a -2.5 degree angle of incidence and not very surprisingly, the NACA 23015 airfoil achieves zero lift at -2.5 degrees.

 

33dbaeo.jpg

 

Clmax 1.6 = 15 degrees 2D AoA

 

Stall Angle = 15 degrees + 4.78 degrees induced angle of attack -2.5 degrees angle of incidence = 17.28 degrees angle of attack

 

 

The developers have the stall angle of attack at 15.5 degrees.  The slope of the airfoil lift polar suggests that is a large drop of about 7% to 9% in CLmax.

 

You can factually say that your FM has had both a reduction in Drag and a reduction in Lift.  It should have had a straight increase in power according to the testing data I saw from ZeHairy.  The aerodynamic data should have then been recalculated at the new performance point with the correct power.

 

 

Hope this helps the community and the Devs!

Not sure if it's placebo effect but the 190 seems to turn better and the stall characteristic is much less harsh now, it's much less likely to enter a spin now.

 

 

Maybe they just quietly fixed it! 

 

Edited for clarity " The aerodynamic data should have...."

Edited by Crump
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Just flew it. Nothing is fixed. still falls out of the sky and behaves like a brick. At least that is what it felt like in the half hour i flew it.

An official word would be nice but  as usual  there wont be any i guess.

Edited by Irgendjemand

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Just flew it. Nothing is fixed. still falls out of the sky and behaves like a brick. At least that is what it felt like in the half hour i flew it.

An official word would be nice but  as usual  there wont be any i guess.

 

There was nothing in the change logs.

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yes. the 190 got fixed - the external view of the pilot's head is now fixed. now sit down and shut up. :huh:

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An official word would be nice but  as usual  there wont be any i guess.

And official list of all the things that were not changed might not be that useful.

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yes. the 190 got fixed - the external view of the pilot's head is now fixed. now sit down and shut up. :huh:

 

My, how appreciative you are..  :rolleyes:

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yes. the 190 got fixed - the external view of the pilot's head is now fixed. 

 

 

It's honestly like they are making a joke about it. When I read it I wanted to break something  :angry: Not literally. Just figuratively.  :cool:

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We have heard some claims that full size aircraft should not agree with the infinite wing (2 Dimension airfoil data).  That is simply not true and would make designing any aircraft problematic at best. There is some minor variation due to weapons and antenna for a full size aircraft to be within 4 to 7% of the 2D airfoil data.  That is not much at all.

 

s2dwg9.png

 

 

That is why aeronautical engineering is a science and not guesswork, a religion, or black magic.  We can predict with some degree of accuracy what the heck the thing will do in the air from drawing on a piece of paper and working a calculator.  As long as we don't screw up the math!!

The root airfoil determines the CLmax of the design and is the basis the engineers use for performance predictions.  Models give good agreement with that 2D data.  Full size aircraft give good agreement with the models.  That is the foundation of aeronautical engineering.

 

As long as the scaling factor (Reynolds number), surface finish, and construction of the airframe are done correctly, full size aircraft will agree with the 2D airfoil data.  If they do not then something is wrong and it cause for the design team to investigate the problem until it does agree.

 

In other words, if the 2D data says the CLmax of an airfoil is 1.6 at a Reynolds number of 6.0 x 10-6, then the full sized aircraft will achieve a CLmax of 1.6 also at a Reynolds number of 6.0 x 10-6.   That is how the physics works.

 

Now, the standards are surprisingly low for surface finish and construction of the airframe.

 

Surface finish standards to achieve good agreement is defined as nothing rougher along the leading edge of the wing than what you get if the surface was finished with 320 grit sandpaper.  I challenge you to take a piece of 320 grit sandpaper out to your local airport and ask any airplane owner if you can rub down a spot on his plane in order to compare which is smoother, the paint or the sanded portion.  You can go to your local museum and ask to do the same on any World War II military aircraft paintjob.

 

I am sure they will not let you do it so take the sandpaper to your car and see which is smoother....the paint or the sanded portion.  ;)

 

The standard for construction of the airframe are no major leaks...in other words no gaps in important areas like where the wing root joins the fuselage and on the cambered portion of the wing you must be able to place the edge of a straightedge (ruler) and rock it back and forth without it clicking.  If it did, that would mean a loose fitting skin or a skin that is not a smooth curve.

 

It is not some super high unachieveable standards.  It pretty simple stuff that generally would caught and fixed long before the aircraft was mounted in the wind tunnel.

 

dop55w.jpg

 

The portion of the NACA 23XXX airfoils is underlined because that airfoils family tends to deliver a higher CLmax which is exactly why both Grumman and Focke Wulf picked the NACA 230015 airfoil as the root airfoil.

 

Now let's see the how that data aligns between a model and flight testing.

 

We have good data on the F6F Hellcat.  That is fortunate because Grumman used the same airfoil selection of the NACA23015/NACA23009 on the Hellcat as Focke Wulf used on the FW-190.  

 

Let's see how Grumman's test align with the 2D data for the airfoil.

 

First the root airfoil NACA 23015:

 

33dbaeo.jpg

 

At an RE of 6.0 x 10-6 the NACA 23015 2D airfoil give us a CLmax of 1.7.

 

Our F6F Hellcat though will be  just under that Reynolds number at sea level.

 

Stall speed = 78 mph = 114 FPS

 

F6F Chord = 8.1 ft

 

RN = (114 FPS * 8.1 Ft)/ .000156927 = 5.8 x 10-6 RE

 

The 2D data will be just under the Clmax of 1.7 or about 1.65.

 

Now lets look at what Grumman Measured in the Langley tunnels and their results:

 

b67wr4.jpg

 

Lets look closer at the clean wing CLmax range of the NACA 23015/NACA 23009 wing design used by Grumman and found to be between 1.5 to 1.6 found in the measurements!!

 

ejheuf.jpg

 

Not surprisingly, a CLmax of 1.58 for the NACA 23015/NACA 23009 wing is the middle of road selection.

 

Now lets look at some flight testing done at 10,000 feet on a Grumman F6F Hellcat in which the CLmax was measured!!

 

This flight testing of the actual aircraft specifically to determine the CLmax of the wing.

 

2zgx8hc.jpg

 

Here is the condition that the test aircraft was flown in:

 

28ckh8i.jpg

 

Power Off stall CLmax when the pilot attempted to control the aircraft.  This is very important and speaks to the NACA conclusions of the effect of angular velocity on CLmax.  Here the aircraft achieves a Clmax of 1.5.

 

SEE POST 753 Power OFF Graph

 

 

 

Let's calculate the Reynolds Number that the aircraft at flying at 10,000ft.

 

RN = (114FPS*81.)/.0002004 = 4.6 x 10-6 RE for the flight test.

 

That is pretty close to the CLmax of 1.58 predicted by Grumman at 4.7 x 10-6 RE.  The flight test is within 5% of their middle of the road model measurement off the model and 10% below the 2D data so it is outside the normal variation.  Pretty Good agreement and probably could have gotten better had the pilot not jerked the stick up when the longitudinal buffet kicked in.  

Edited by Crump
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Here Grumman gets a CLmax of 2.0 for the clean wing power on CLmax.  Propeller effects really give the airfoil selection a boost and we end up with that very high CLmax the designer's were looking for in the wing root selection.  The measurement is 21% over what the 2D data predicts.  

 

SEE POST 753 Power ON Graph

 

Once more, had the pilot controlled the stall and reduced the angular velocity, that value would have been higher.  If you read the report, the pilot got a CLmax of 2.2 out of the clean wing in a power on stall.

 

Speaks for itself.

 

Now let's look at the landing condition and see how the prediction aligns with measurements!

 

r1zfab.jpg

 

vxggu1.jpg

 

Again, we are looking at the RE of 4.7 so the data is just about as close to an exact match as you can get.   

 

In other words, Grumman's assessment  as a middle of the road clean wing CLmax of 1.58 for the NACA 23015/NACA23009 airfoil wing design is pretty good at 4.7 x 10-6 RE.

 

Now Reynolds number and Clmax have a direct relationship.  The higher the Reynolds Number, the higher the CLmax of the airfoil.

 

Let's see what Focke Wulf said is the CLmax of their clean wing design using the NACA 23015/NACA 23009 airfoil selection at 6.1 x 10-6 Reynolds number...

 

This from Focke Wulf:

 

oqf2tt.jpg

 

zn7x2d.jpg

 

Which is the same as Grumman's clean wing CLmax for the same airfoil selection at 4.8 x10-6 RE...in other words we should be seeing a CLmax of over 1.6 at the FW-190's Reynolds Number!

 

ejheuf.jpg

 

So in conclusion we can believe that Kurt Tanks clean wing Clmax of 1.58 is in good agreement with other tested data on the NACA 23015/23009 airfoil selection at a Reynolds number of 6.1 x 10-6 stall speed vicinity of the design.  It represents the power off stall CLmax of the design straight from the design teams own data.  That airfoil series was selected for its high CLmax like every other engineer who picked it.

 

Or we can believe that physics was altered on the European side of the world and Focke Wulf was just an extremely incompetent designer who could not even get in the ballpark of the clean wing Clmax even with 60 degrees of 35% wing coverage Split Flaps deployed....

 

It is up to the reader to decide! 

Edited by Crump
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for some reason the Power Off and Power On stall graphs from the NACA report did not get into the post. 

 

Here they are:

 

Power OFF

 

oizwn5.jpg

 

Power ON

 

15hel3a.jpg


That is a lot of information.  Take your time and read it.

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And official list of all the things that were not changed might not be that useful.

 

Actually, it'd probably be super helpful - it'd do away with the supposition that follows every patch.

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It can be a word?))

Here is how it was.

Developers reconfigured Fw-190 on the document:

post-2090-0-02341300-1470820990_thumb.jpg

This purging of the aircraft in a wind tunnel at Chalais Meudon. The critical angle of attack is 15.5 degrees. But the Germans made a mistake. They are not correctly defined correction factor. In repeated trials, they found that the angle of the amendment should not be 1.5 degrees. The amendment should be 0.25 degrees. This report was created by them "Messungen an einer Fw 190 im grossen Windkanal von Chalais Meudon bei Paris", Focke-Wulf Bericht Nr.06006, 1943". Developers obviously this is not taken into account. The critical angle to be 16.75 degrees, rather than 15.5. That is, the plane should be a little more stable in extreme turns.

We have sent a report on this issue. I hope someday they will consider it.

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It can be a word?))

Here is how it was.

Developers reconfigured Fw-190 on the document:

attachicon.gifПоляры Фокке-Вульф.jpg

This purging of the aircraft in a wind tunnel at Chalais Meudon. The critical angle of attack is 15.5 degrees. But the Germans made a mistake. They are not correctly defined correction factor. In repeated trials, they found that the angle of the amendment should not be 1.5 degrees. The amendment should be 0.25 degrees. This report was created by them "Messungen an einer Fw 190 im grossen Windkanal von Chalais Meudon bei Paris", Focke-Wulf Bericht Nr.06006, 1943". Developers obviously this is not taken into account. The critical angle to be 16.75 degrees, rather than 15.5. That is, the plane should be a little more stable in extreme turns.

We have sent a report on this issue. I hope someday they will consider it.

Its an airplane so many people are passinate about. If they want to please their customers they better should consder correcting this quickly if they want to have the money of those people for future products.

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Its an airplane so many people are passinate about. If they want to please their customers they better should consder correcting this quickly if they want to have the money of those people for future products.

 

I hope as well that they will do that. As for German planes, there's 2 plane series  that you have to do absolutely right, the 109 and the 190. As for the rest, it matters quiet a bit less given that the 109 and the 190 were the types that represented most of the airforce.

 

We can not know what made the devs think the lift parameters used in the game so far are in fact correct. Vachik gave a plausibe explenation how things might have happened that is also simple enough to be reasonable.

 

I hope they discard all this info not because of some sort of professional pride. Or of (justified) fear that another 21 page (that's where we have come so far here) thread will open about the 19 being "so uber now!".

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Not sure if it's placebo effect but the 190 seems to turn better and the stall characteristic is much less harsh now, it's much less likely to enter a spin now.

 

I had the same feeling as well. But i'm not that sure because there is nothing in the changelog.

 

Grt M

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It can be a word?))

Here is how it was.

Developers reconfigured Fw-190 on the document:

attachicon.gifПоляры Фокке-Вульф.jpg

This purging of the aircraft in a wind tunnel at Chalais Meudon. The critical angle of attack is 15.5 degrees. But the Germans made a mistake. They are not correctly defined correction factor. In repeated trials, they found that the angle of the amendment should not be 1.5 degrees. The amendment should be 0.25 degrees. This report was created by them "Messungen an einer Fw 190 im grossen Windkanal von Chalais Meudon bei Paris", Focke-Wulf Bericht Nr.06006, 1943". Developers obviously this is not taken into account. The critical angle to be 16.75 degrees, rather than 15.5. That is, the plane should be a little more stable in extreme turns.

We have sent a report on this issue. I hope someday they will consider it.

That's an excellent analysis and if true confirms my impression of the current FM (actually during ingame tests I couldn't even reach 15.5° before stalling but I blame human error + tiny lag for that).

 

Hope your report will be considered.

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Critical angle of attack is one thing, but if i understand Crump right, the problem is actually more deeply rooted.

 

 

 

The original error in the FW-190 flight model is quite obvious if you understand the physics. They got their power input confused by using performance at a lower power setting used by TASGi against the BMW 801 power output curves. That point was proven and the reason why the FW-190 FM got the "fineness ratio" adjustment. The absolute power relationship to the L/D ratio was not correct in the orignal FM. Problem with that technique is we have not changed the basic error in absolute power and are still working within the erroneous relationships of the forces of flight established in the original error. In the system that is the aircraft, we have not reset any of the relationships and the aircraft is still not representative of it power production. Lift and drag have a direct relationship. When one increases, the other increases in proportion to the L/D ratio of the design. We have L/D curves for the aircraft that are not representative.

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This purging of the aircraft in a wind tunnel at Chalais Meudon. The critical angle of attack is 15.5 degrees. But the Germans made a mistake. They are not correctly defined correction factor. In repeated trials, they found that the angle of the amendment should not be 1.5 degrees. The amendment should be 0.25 degrees. This report was created by them "Messungen an einer Fw 190 im grossen Windkanal von Chalais Meudon bei Paris", Focke-Wulf Bericht Nr.06006, 1943". Developers obviously this is not taken into account. The critical angle to be 16.75 degrees, rather than 15.5. That is, the plane should be a little more stable in extreme turns. We have sent a report on this issue. I hope someday they will consider it.

 

Do you have that report?  I think that information is actually from a later report and it may or may not refer to these polars.

 

Here is a snippet I was given and does imply there was an issue with Chalais Meudon windtunnel.

 

259d1zk.jpg

 

That does seem to imply they got the jet inclination wrong.  That will effect the freestream angle and change the wings measured angle of attack.

 

Here they list the change in angle is 1.85.  15.5 degrees + 1.85 degrees = 17.35 degrees which gives very good agreement with what the airfoil data.  In fact it puts ir right at the CLmax of 1.58 that Focke Wulf says represents the clean wing Clmax and Grumman data for the same airfoil combination.  So that does work out.

 

None of that is a direct measurement in the tunnel but will be mathematically corrected based on the raw data collected in the tunnels.  When they did that mathematical correction, their angle of attack calculations delivered an impaired polar

 

2rf38fk.jpg

 

This was one of the first report I came across on microfilm at the Paul Gerber Facility Archives when researching for an FW-190F8 Restoration.  Polars were not something we needed so I ripped off a copy but did not get the entire report as it was rather lengthy.

 

That report is a drag measurement.  They were investigating the drag of various weapons and mounts for the FW-190G series.  The wind tunnel speeds listed were 13 m/s and 18 m/s.

 

21kxpv7.jpg

 

6f40tz.jpg

 

The zero thrust drag point is listed on the polar and the wind tunnel speeds were slower than a Focke Wulf could actually fly.  That means low Reynolds numbers and low Clmax will be recorded.

 

You can confirm that by the math using the power settings listed on the Polar for zero thrust drag.

 

The power ratings listed on the polar measure the power output of the engine at the zero lift drag component.  It is a time honored technique.

 

In fact, the CAFE foundation holds a patent on being able to measure this in-flight instead of having to use a wind tunnel as they did in the 1940's.

 

https://engineering....A-46372-872.pdf

 

What you do is measure the point at which there is no pull or push force on the propeller shaft.  That is the point that thrust = drag.

 

In this case we have two measured points.  

 

Focke Wulf used the relationship of Power and Velocity.  Once you have a measured point, you can use the physical relationship of force development to figure out what your performance will be at any other point.

 

For example.

 

If we know from flight testing that it takes 1348Hp to achieve 305KEAS then let's run the math to see our velocity at 9hp.

 

Our parasitic component of drag has a direct relationship with velocity and changes at the cube of velocity.

 

Therefore we know:

 

Pr2/Pr1 = (V2/V1)^3

 

That formulation is right out the book for BGS system aircraft performance calculations using subsonic incompressible flow theory.  

 

9hp/1348hp = (V2/305)^3

 

9hp/1348hp = V2^3 / 305^3

 

305^3 * 9/1348 = V2^3

 

 189431 = V2^3 = 57 KEAS = 29 m/s

 

Parasitic drag is the smallest component of drag and least significant at low speeds.

 

Let's see what our induced drag will be at 9 PS.  At 305KEAS, our FW-190A3 produces 71.5hp worth of induced drag.  Let's see how much power it would take for the aircraft to fly that slowly!  If it equals what our engine produced, then the airplane can fly that slowly.  It should be considerably more power than the BMW801D2 can produce.

 

The power of Induced drag has an relationship with velocit

 

1670bhp * .85 = 1419.5thp

 

1419.5 - 9 hp = 1410.5 hp

 

1410.5

 

Pr1/Pr2 = V2/V1

 

= 1410.5hp / 71.5hp  = 305KEAS / V1

 

9* V1 = 305 * 71.5 

 

V1 = 21807.5 / 1410.5

 

V1 = 15.4 knots = 9 m/s....

 

It is very easy to prove our Focke Wulf was NOT traveling at any speed the aircraft could fly in those polars.  From the math you can easily see that the tunnel wind speed was very low and our values confirm it the 13 m/s to 18 m/s speed is the correct range.

 

Quite simply, the 13m/s and 18m/s speeds listed in the report represent Focke Wulfs measurement speeds used in the wind tunnel to establish drag data.  That information was used to construct the Drag Data for aircraft sheet posted in that thread and predict the speed changes with various configurations and combat loads.

 

The aircraft cannot fly at power settings of 9hp and 4 hp.  The only useful thing we can do is measure the parasitic drag and get an idea of the stall characteristics.

 

The Reynolds number at those airspeeds corresponds to the CLmax measured on the polar.

 

18M/S = 65.6 FPS

 

RN = (65.6fps * 5.95 ft)/.000156927 = 2.48 x 10-6.

 

That is going to give you a CLmax of 1.2 on the NACA data. 

 

It all checks out and cross checks with how the science works using both Allied and Focke Wulf data.

 

Edit'd:  Angle of Attack not Angle of Intact...stupid autocorrect!!

Edited by Crump

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That's an excellent analysis and if true confirms my impression of the current FM (actually during ingame tests I couldn't even reach 15.5° before stalling but I blame human error + tiny lag for that).

 

Hope your report will be considered.

Out of curiosity, how will you conduct such test accurately in game? 

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Critical angle of attack is one thing, but if i understand Crump right, the problem is actually more deeply rooted.

 

 

Yes, it basically looks like they started their FM math at the wrong point.

 

It looks like they used VVS data for speeds and German data for power and weight.  That is what ZeHariy's data pointed too and I had the VVS data.  Together, we were able to prove it so the Devs did the right thing and tried to fix it. 

 

The problem was the VVS speed data was for a lower power setting than the power data from Germany.  That means their mathematical system that is the Focke Wulf FM in BoS started out required more power to get lower performance than the actual aircraft.

 

They tried to fix it by reducing the power their FM requires instead of resetting the entire system to represent an increase in absolute power.

 

Now they are stuck on Polars using them to represent CLmax.  Those polars were never intended to show CLmax.  Focke Wulf already knew that information!  Notice Grumman's investigation is specifically investigating stalling.  The stall occurs at CLmax.  Grumman actually used what is called the "Normal Force" Coefficient which is not the same as a Lift Coefficient.  The differences are small and engineering-wise it shows very good agreement with their CLmax predictions.  You can say they were right and their data gives good agreement.

 

Those Focke Wulf polars were intended to improve the wing rack designs on the FW-190G series and make sure they would not kill the test pilot if he stalled.

 

The bottom line is the 2D data of the root airfoil is the basis of the design.  Your CLmax at the same Reynolds number is not going to vary too much off that.  If it does, it is big red flag to the design team and they will look to fix it.  Think of it as a bug in the programming.

 

Your FW-190 is being represented with a big aeronautical bug in the programming!!

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Here's what the Soviets apparently thought of the FW 190...interesting emphasis of the FW being relatively good at low speed in the horizontal.

 

http://www.lonesentry.com/articles/ttt/russian-combat-fw190.html

 

Vertical-maneuver fighting with the FW-190 is usually of short duration since our planes have a better rate of climb than the German planes, and because the Germans are unable to withstand tense battles of any length.

 

:lol: :lol: :lol:  of course - nice propaganda ;)

 

About the FM discussion: If the Devs have the right datas, would they use it 1:1 ? I think not. Because it was in the BoS beta as a guy proves the wrong implementation of the FW190 bars which not exists "as it is in the game". These exists until now without a reason, which says a lot.

Edited by I./ZG15_dasSofa

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Out of curiosity, how will you conduct such test accurately in game? 

It's difficult to measure it accurately because only devs have the tools nessecary to do that. What I did was keeping the plane in level flight by (sink rate = 0) as good as I can while reducing airspeed and increasing the pitch angle steadily. At the point of stall I made a screenshot, drew vektor lines along the horizon and assumed chord line of the wing and measured the angle (my measurement gave sth around 14° if I'm not mistaken).

Edited by 6./ZG26_5tuka_

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It's difficult to measure it accurately because only devs have the tools nessecary to do that. What I did was keeping the plane in level flight by (sink rate = 0) as good as I can while reducing airspeed and increasing the pitch angle steadily. At the point of stall I made a screenshot, drew vektor lines along the horizon and assumed chord line of the wing and measured the angle (my measurement gave sth around 14° if I'm not mistaken).

Very approximate but thank you for your answer :)

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:lol: :lol: :lol:  of course - nice propaganda ;)

 

About the FM discussion: If the Devs have the right datas, would they use it 1:1 ? I think not. Because it was in the BoS beta as a guy proves the wrong implementation of the FW190 bars which not exists "as it is in the game". These exists until now without a reason, which says a lot.

 

The Devs have said many times that the refraction effect needed to get rid of the bars would cause a huge performance drop.

 

I really don't get that attitude against these devs...

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The Devs have said many times that the refraction effect needed to get rid of the bars would cause a huge performance drop.

 

I really don't get that attitude against these devs...

 

The attitude stems from the fact that they will take a hardline stance of "We're always right and you're always wrong - prove we're wrong." up until the point that something quietly changes.

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If they want to please their customers they better should consder correcting this quickly if they want to have the money of those people for future products.

 

And blackmailing them with petulant little statements like that is just going to make the developers dig in even more. It's fine to criticize things, but it's the tone and manner in which it's done that's most important. 


 

 

About the FM discussion: If the Devs have the right datas, would they use it 1:1 ? I think not.

 

Utter nonsense. If they have the right data and they have time to correct something, they will fix it. This idea that they will keep flight models "incorrect" just to spite people is ludicrous.  

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