Spitfire XIV vs Bf-109 K-4 vs La-7 vs Yak-3

[Hunter368]

Originally Posted by drgondog

He is self taught on the subject and his teacher failed him miserably. I KNOW there is a lot I don't know maybe in spite of my education.. but he doesn't know what he doesn't know and makes some truly 'interesting' statements - and NEVER produces facts, in complete context of the issue, or simply moves on.

Bill,

While watching you two (Soren and you) argue everyday does get old.............
I had to LMFAO while reading this little barb. That is a good one though.

[drgondog]

Originally Posted by Soren

Ok Bill, lets solve this;

I know the purpose of downward wing twist (washout), I've explained it on here various times before; it is for preventing tip stall, or to put it more thuroughly keeping the outboard wing section from stalling before the inboard section, making sure the a/c doesn't suddenly enter an uncontrollable spin without warning as-well as keeping the ailerons effective up until the stall. The 109's slats were positioned the way they were for the very same reason.

Actually not quite right. The purpose of twist was in fact to wash out the stall angle of attack to keep aileron control - but the pupose is to maintain control in the roll axis - not to prevent 'entering an uncontrollable spin'. It certainly was nice if the aircraft gave an indication of stall, but a.) not all aircraft entered a violent and uncontrollable spin, and b.) that characteristic was not pre-determined by analytical methods - otherwise Tank would have foreseen this in the design of the 190 wing

However in the case of the 190 you will note that the wing twist was applied to such a degree as to provide elliptical lift distribution under G's (which btw is the reason for the violent departure), it was purposely done so to achieve the maximum 'e' factor and therefore L/D ratio in turns. Now ofcourse you wont see that on Lednicer's comparison as his simulation was done under 1 G, something you seem unable to grasp.

Something you have repeatedly 'missed' Soren is that Lednicer plots the twist as a function of semispan for the Spit, the 190, the 51B and D and quite clearly states that the 190 went from +2 at root to 0 at 81% then NO twist from 81.5% to tip... are we in a 'grasping' contest? Minus one for you.

You can recover if you prove Lednicer wrong in his grasp of Fw 190 twist vs semi span plot on page 86.


.

Let's take these one at a time

From pages 550-551 - chapter Elements of Finite wing theory, "Principles of Ideal-Fluid Aerodynamics", Krishnamurty Karamcheti, Professor of Aeronautics and Astronautics- Stanford Univesity.. Published by John Wiley and Sons -1966

"To obtain an elliptic lift distribution on a (geometrically and aerodynamically) untwisted wing, the spanwise distribution of the chord should be elliptic"

Point 1. Elliptical Wing is the optimal planform for minimum Induced Drag
Point 2. Varying the tip ratio to approximately .4 will closely approach an Elliptical Wing as far as reducing the induced drag at the sacrifice of adding more weght (for same aspect ratio)
Point 3. The downwash corresponding to an elliptic lift distribution is a constant all along the span, further the rolling and yawing moments on such a wing are zero no matter how the chord, the angle of attack and the wing section are arranged.

Further, from 12:8-9 Spanwise Lift Distribution under Load "Supersonic and Subsonic Airplane Design" by Gerald Corning Professor Aeronautical Engineering Department - University of Maryland 1960

Point 4. The downwash corresponding to a trapezoidal wing planform varies along the span
Point 5. The spanwise lift coefficient for a trapezoidal wing planform changes with the downwash along the span.
Point 6. The G forces have bearing only on the elastic properties of the wing - and have nothing to do with lift distribution Unless and Until the wing twists or bends to change the relative angle of attack from 'no load' angle.
Point 7. The changes which tend to throw lift load Outboard are a function of bending rigidity, while the changes which tend to throw lift load Inboard are a function of torsional rigidity.

Therefore - pulling high G's seemed to affect the Fw 190 for two reasons (not known when designed) a.) aeroelastic bending of the Fw190 wing, moving the lift distribution outboard, and b.) not having twist in the outboard 20% of the span. As Lednicer quotes the LW report dated January 1944 you may presume he knows more about the German explanation than you do.

Page 89 of Lednicer's Report.

Now - it is your turn to present facts and references to support all of your points... but you 'skip' your turn usually so I'm holding my breath.

Education - Experience - and now References.

[drgondog]

Originally Posted by Hunter368

Bill,

While watching you two (Soren and you) argue everyday does get old.............
I had to LMFAO while reading this little barb. That is a good one though.

Hunter - if it is 'old' for you, think about me! Lol.

I just will not let him skate on this subject of aero/structres when he makes so damn many mistakes - then insults the guy that disagrees with him - 'for not grasping the obvious'.

have a great day and put this battle on 'ignore'

[Soren]

Oh no you don't Bill, answer my questions first!

The below just proves what I've been saying all along:

From pages 550-551 - chapter Elements of Finite wing theory, "Principles of Ideal-Fluid Aerodynamics", Krishnamurty Karamcheti, Professor of Aeronautics and Astronautics- Stanford Univesity.. Published by John Wiley and Sons -1966

"To obtain an elliptic lift distribution on a (geometrically and aerodynamically) untwisted wing, the spanwise distribution of the chord should be elliptic"

Point 1. Elliptical Wing is the optimal planform for minimum Induced Drag
Point 2. Varying the tip ratio to approximately .4 will closely approach an Elliptical Wing as far as reducing the induced drag at the sacrifice of adding more weght (for same aspect ratio)
Point 3. The downwash corresponding to an elliptic lift distribution is a constant all along the span, further the rolling and yawing moments on such a wing are zero no matter how the chord, the angle of attack and the wing section are arranged.

Further, from 12:8-9 Spanwise Lift Distribution under Load "Supersonic and Subsonic Airplane Design" by Gerald Corning Professor Aeronautical Engineering Department - University of Maryland 1960

Point 4. The downwash corresponding to a trapezoidal wing planform varies along the span
Point 5. The spanwise lift coefficient for a trapezoidal wing planform changes with the downwash along the span.
Point 6. The G forces have bearing only on the elastic properties of the wing - and have nothing to do with lift distribution Unless and Until the wing twists or bends to change the relative angle of attack from 'no load' angle.
Point 7. The changes which tend to throw lift load Outboard are a function of bending rigidity, while the changes which tend to throw lift load Inboard are a function of torsional rigidity.

[Soren]

Oh and next time read all of what Lednicer says in his article:

Lednicer:
"A wartime Focke Wulf report (Ref. 14) indicates that at higher loading conditions (i.e. when pulling more gs) elastic deformation of the Fw 190 out wing shifts the load distribution outboard [elliptical effect = entire wing generates lift at the same angle of attack]. This would cause even more of the wing to reach its stalling lift coefficient simultaneous. Combined with the sharp stalling features of NACA 23000 airfoils, this would produce the harsh stall found in by Capt. Brown. A gentle stall would be evidenced by a more gradual progression of the 2D stall spanwise. "

Hmmm.. you turn Bill!

[Soren]

I just will not let him skate on this subject of aero/structres when he makes so damn many mistakes - then insults the guy that disagrees with him - 'for not grasping the obvious'.

No mistakes made by me, you on other hand Bill, well lets just say you look lightly upon the facts.

[DerAdlerIstGelandet]

Originally Posted by starling

my name is not bill.anyway,did the 109 not have a tendancy to crash on take off or landing.perhaps only aces could handle this problem.there is no need to get narky if one believes or not whether the said a/c had these inherent design faults.yours,preacher.

No one is getting cranky here. I just asked you to explain yourself, because you said the 109 is going to crash on take off and landing. That implies that is going to do so all the time, which is not true.

If that were the case then the top aces would not have flown the aircraft. If that were the case it would not have been the most numerous fighter built.

If not properly handled, yes it could happen. Is it going to happen all the time? No. Did it happen an ungodly amount of times? No.

My advice to you, so that this problem does not arise again is to actually explain your posts instead of using one liners.

Originally Posted by Glider

You could always look at it the other way. What was the Mk21 most likely to encounter? the 109K

Interesting little side note. A lot of people say that the problem with the 109 was because of its narrow track. pbfoot who has a 109E and a Spitfire readily available to him actualley went and measured them and the Spitfire's track was actually a bit narrower.

Originally Posted by Soren

I tried being nice towards you Bill but that went right out the window when YOU starting throwing mud into my face because I misunderstood a computer generated pressure distribution illustration. You were the one who insisted on being rude and calling names, which in my book is childish & prick like behavior - I thought you were smarter than that.

You do the same thing Soren. You are just blind to you own faults.

Originally Posted by drgondog

Now - it is your turn to present facts and references to support all of your points... but you 'skip' your turn usually so I'm holding my breath.

Education - Experience - and now References.

We are all waiting...

[Soren]

And from Gene (Crumpp):

"Aeroelasticity is simply a byproduct of flying and all aircraft experience it. The NACA 23000 series of airfoils have a harsh stall with no washout due to the fact they produce elliptical lift along the entire airfoil. That means with no washout the entire wing stalls at once. This is why the FW-190's wing is twisted to prevent it.

When aeroelasticity removes this twist then the FW-190 exhibits a harsh stall."

[Soren]

You do the same thing Soren. You are just blind to you own faults.

So you claim atleast..

We are all waiting...

No need to wait, it has already been presented, read my new posts above..

[DerAdlerIstGelandet]

Originally Posted by Soren

So you claim atleast..

And a majority of this forum as well.

Originally Posted by Soren

No need to wait, it has already been presented, read my new posts above..

I do not see any actual proof with sources.

[drgondog]

Originally Posted by Soren

Oh and next time read all of what Lednicer says in his article:

Lednicer:
"A wartime Focke Wulf report (Ref. 14) indicates that at higher loading conditions (i.e. when pulling more gs) elastic deformation of the Fw 190 out wing shifts the load distribution outboard

So, the above is what Lednicer said. Above is what I said and referenced in other sources

Below is your mangled context inserted in the above quote

[elliptical effect = entire wing generates lift at the same angle of attack]. This would cause even more of the wing to reach its stalling lift coefficient simultaneous.

For an untwisted wing, below critical Angle of Attack, your statement while true in THAT context, is irrelevant to the Fw 190 and irrelevant to this discussion.

"Combined with the sharp stalling features of NACA 23000 airfoils, this would produce the harsh stall found in by Capt. Brown. A gentle stall would be evidenced by a more gradual progression of the 2D stall spanwise. "

Do you really know what you just wrote? The CONTEXT of the 'sharp stalling features of the 230xx airfoils' combined with 'this would produce the harsh stall found 'in by' (what??) Capt Brown - is missing the important point referenced by Lednicer - namely that the Fw 190 spanwise lift distribution shifted outward due to elastic deformation of the wing.

Here is the entire quote that you selectively parsed as you always do.

"A wartime Focke Wulf report (Ref 14) indicates that at higher wing loading conditions (i.e. when pulling more gs) elastic deformation of the Fw 190 outer wing shifts the load distribution outward. This would cause more of the wing to reach its stalling lift coefficient simultaneously. Combined with the sharp stalling features of the NACA 230xx airfoils, this would produce the sharp stall found by Capt. Brown.

Hmmm.. you turn Bill!

I noted in my prior posts that you selectively quote stuff that you think supports your thesis, then reach deep (somewhere) and pull out wierd stuff and place it somewhere in the quote. You could Not have proved my point any better.

You really have no idea what you said about the elliptic wing, nor how it possibly could have helped make your point by inserting it (elliptic wing lift distribution statement) into the entire quote from Lednicer, while removing the key point I made about aeroelastic deformation as a root cause, combined with zero angle twist the last 20% of the Fw 190 span..

You don't understand what you are reading, and you don't know the context of airframe design considerations - which largely are "it depends" rather than "absolutes"

Soren, you make up stuff as you go.. I have this vision of Opus and Bill the Cat (or Lucy and Charlie Brown) talking about the Theory of Relativity every time you go theoretical on us.

[Soren]

And a majority of this forum as well.

That's a bold claim seeing how many members there are.

I do not see any actual proof with sources.

LoL! The first is directly from Lednicer's article!

[DerAdlerIstGelandet]

Originally Posted by drgondog

Soren, you make up stuff as you go.. I have this vision of Opus and Bill the Cat (or Lucy and Charlie Brown) talking about the Theory of Relativity every time you go theoretical on us.

Originally Posted by Soren

That's a bold claim seeing how many members there are.

Seriously...

Originally Posted by Soren

LoL! The first is directly from Lednicer's article!

For once...

[Soren]

Sorry but you can't wiggle yourself out of this one Bill!

Here it is DIRECTLY from the article:


So Bill what is a matter ? Are unable to read suddenly ?

[Soren]

And what Crumpp wrote (Going to dispute him as-well Bill ?):

"Aeroelasticity is simply a byproduct of flying and all aircraft experience it. The NACA 23000 series of airfoils have a harsh stall with no washout due to the fact they produce elliptical lift along the entire airfoil. That means with no washout the entire wing stalls at once. This is why the FW-190's wing is twisted to prevent it.

When aeroelasticity removes this twist then the FW-190 exhibits a harsh stall."