drgondog
Major
This is precisely what you said in post 64 page 5
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.
Summary of your first post which I took exception to
A. "wing twist was applied to such a degree as to provide elliptical lift distribution under G's (which btw was the reason for violent departure..
In the case of A I pointed out two things repeatedly - The departure was caused by aeroelastic effects to the wing under G loading and that the Fw 190 had an unusual twist concept - namely 2 degrees from root to zero at 81.5 percent of span - then stayed zero to the tip.
But, I pointed out, twist is applied to (ALL) trapezoidal wings to attempt to approach an elliptical wing efficiencies for lift distribution and induced drag
Here is what I said on Post 77 to support my thesis
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.
Summary-
I state unequivovally that "G forces have nothing to do with lift distribution, per se", that G forces DO affect the elastic properties of the wing which in turn DO affect the lift Distribution.
I conclude that the Fw 190 experienced the violent stall in high G turns because Aeroelastic effects combined with the lack of twist in the outer 20 percent of its span
You did not understand the reason for the violent stall until I quoted the German Report dated January, 1944 and Lednicers observations on page 89 of his report. You subsequently copied the paragraph from his report and posed it as 'your find' explaning what you had said all along on Page 6, Post 89
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!
Summary -
Here you quote from page 89 of Lednicers Report (my reference to you in my post 77 above and present it as your idea!!
Then you quote from Gene in your Post 87
"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."
I restate what Lednicers page 89 says
"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.
Summary-
I say the issue is more related to the elastic deformation (aeroelastic effect) in the outer wing than just simply the fact that it had zero twist..
Then in your Post 89 you quote Lednicer's report paragraph word for word as I just stated it and tell me "You can't wiggle out of this one"
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
Summary - so Far you appear to have moved to Lednicer from your Original Thesis below..
A. 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. to
How did you get there?
You checked with Gene first, and quoted him directly.. but even a very good as Gene is he didn't remember the part of the Lednicer report about aeroelastic efffects - and you 'parroted' his observation about no twist was the cause for CL max being reached simultaneously (BTW I believe he is right but he forgot the part about elastic deformation in the tip region accelerating the issue)
Finally you write to Gene
Hello Crumpp,
I (Or we) need your knowledge on something, you see recently I got into an argument with a member at another forum for saying this:
The Fw-190's wing achieved elliptical lift distribution during G's because of aeroelasticity negating the original 2 degree twist applied to the 190's wing. This is what caused the violent departure in turns when pulling G's as compared to when stalling at 1 G.
This is your final 'modification' after my repeated bashings of your earlier statements and BTW is is Still Wrong in one respect.
The aeroelastic effect was Not to Negate the 2 degree twist, it was to affect the outer zero twist tip area..
I suspect that the torsional load created by the aileron, combined with the lack of twist in the outer 20% is what did it - and was TOTALLY unanticipated by any Focke Wulf structural engineers who did not have the analytical methods today to model the airframe under complex loads.
So, look at your original statements, look at my rebuttals including specifically the content from aero texts at the beginning and Lednicer's report, Look at my corrections to your statements, look at Gene's contributions and see your 'position statement above evolve -
from 'eliptical lift under high G's' to 'aeroelastic effect negating the original 2 degree twist' ... that is a long reach Soren and you still didn'tget it right.
I rest my case.