Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: agent 009 on July 28, 2005, 03:14:42 AM
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While back I posted something about the flettners being nailed shut on K-4 cause the elevators were not tabbed & this caused turbulence. From a book called flying legends or something like that. Anyway , it could well be sci-fi, read on...
K-4 fuselages, turning circle, and Flettner tabs
June 25 2004 at 7:08 AM Michael Gorman (Login mrg22)
The 109 Lair Board Members
from IP address 62.188.48.139
Response to K-4 turn circle
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Hello all,
I have been following this thread with more than casual interest! As some of you may know, I am involved in a project to restore a '109K-4 to airworthy condition. The comments here have been interesting and relevant, and prompt me to offer some thoughts of my own.
Firstly, this question of a "lightweight, redesigned" fuselage for the K-4. I am not aware of ANY original reference at all to such an exercise, and if anyone has information to the contrary, I would be very pleased to hear from them! Further, we are working with major remains of three K-4 aircraft, and I can confirm that we have found NO evidence of any alteration from the standard "G-type" fuselage in the material which we have (apart from the obvious changes in location of hatches, filler ports, etc.). I suspect we may have another "urban myth" here.
Moving on the question of turning rate (or turning circle, actually somewhat different things), this is not the place for an aerodynamics lecture. However, in quick summary, an aircraft turns because some of its lift is directed away from the vertical by banking. For a level turn, the maximum rate of turn (in degrees/second, and hence the radius of turn at a given airspeed) depends upon the balance between total lift available and aircraft weight. If the external configuration of an aircraft (wing shape/area, aerofoil section, tailplane size, fuselage, etc.) remains the same (which the '109 essentially does from G to K), then the total lift available remains the same. Bottom line, a heavier aeroplane of the same configuration has a lower maximum turning ability, and vice versa, of course.
The issue of possible trim changes is a bit of a red herring here. It's true that changing the balance of lift between mainplane/tailplane would alter the turn, because the total lift would change, as A. Lake rightly notes. The aerofoil section on the '109 has a positive pitching moment, requiring a DOWNLOAD from the tailplane to balance it. This subtracts from total lift, which reduces possible turn rate (see above).
However, it's fairly clear that the longitudinal trim WASN'T different on the K-4. Specifically, the tailplane trim range was very similar to previous (roughly +2 degrees to -6 degrees), and according to the Flugzeug Handbuch, the setup for this trim adjustment is done to the same fuselage datum as previously. Given that the tailplane did not change size, this means that there was no change in available tailplane trim forces. As Lynn rightly notes, various things were moved around internally, but this was precisely to maintain the centre of gravity in the SAME POSITION, so as to avoid flying with excessive tailplane trimming loads. The D-Motor, larger oil cooler, wider prop blades, etc., all added significant weight forward, which had to be counter-balanced.
The question of the Flettner tabs on ailerons and rudder is an interesting one, but not directly related to turning rate. First, the tabs are not trim tabs in the usual sense of the term, but are known as servo tabs, which act to reduce stick or rudder pedal forces by applying an assisting force in the direction of deflection. Now, as Brent rightly notes, there is no photo evidence of their installation on K-4s. I have looked pretty carefully, but again, any correction would be much appreciated! Your point, George, re. the manual (Flugzeug Handbuch) is absolutely correct, it shows and describes the tabs, BUT in the Ersatzteilliste for the K-4 (of July '44), plain ailerons are shown. Also, at least one of our aircraft had plain ailerons installed.
One thing I have been trying to track down, in the "Wings of Fame" (Vol. 11) article on the later '109s, it is asserted that the Flettner tabs on K-4 ailerons were "usually locked shut", having been found to "cause a major discrepancy" in required stick forces between ailerons and elevators. I have tried in vain to find an original reference for this, and if we believe that K-4s didn't have Flettner-tabbed ailerons installed anyway, then this becomes yet another "urban myth".
Sorry if this post has been rather long, but you will understand that I find the subject somewhat interesting!
Regards,
Michael Gorman
P.S. I once had an article pass by me that mentioned even G-6's being field modified with flettners, but they caused wing failure. Wish I'd saved it. Could also be sci-fi, but it is interesting nonetheless. The Flettners were not factory standard on K-4's so I've read, which might explain why some didn't have em.
Any data? I know this is one of those "tough to track down" topics.
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Hi Agent,
>Bottom line, a heavier aeroplane of the same configuration has a lower maximum turning ability, and vice versa, of course.
Let me add that if we're limiting the question to sustained turns, engine power plays a role as well, and the K-4 might not actually turn worse than a lighter, lower powered earlier version in such a sustained turn. In instantaneous turns, the lighter aircraft wins of course.
>P.S. I once had an article pass by me that mentioned even G-6's being field modified with flettners, but they caused wing failure.
I believe that's highly plausible. The same experience was made with the Spitfire, which had a very similar wing construction (though a very different wing shape, of course :-) I always suspected it would be the same for the Me 109.
What happened to the Spitfire is that at high speeds, the aileron caused a force twisting the wing opposite to the aileron input, and the twisted wing caused as much or more lift than the aileron destroyed, negating the roll or actually rolling the aircraft to the opposite side. More aileron deflection to correct the unwanted roll would not help to correct that, but it could twist the wing to the point of structural failure.
With such an aeroelastic problem, you would not want powerful ailerons (for example of the Flettner type) because it would only help the pilot to accidentally break the aircraft. High aileron forces on the other hand would prevent such accidents.
My suspicion is that this was the reason the Flettner tabs were never (or rarely?) used for the Me 109.
Regards,
Henning (HoHun)
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I suggest you look at this picture, Gentlemen... ;)
(http://www.onpoi.net/ah/pics/users/715_1121802152_715_1109860306_109_aileronflett.jpg)
I think it shows a late production - appearantly captured in half-complete stage, control surfaces are not yet connected - 109K-4.
Special interests are the rod under the wing - it`s for the actuator rod for the Flettner, and cannot be found normally on Bf 109s. One can barely see a smudged line on the aileron, that could be the flettner - I am not sure, it`s too blurry.
The 109K-4 handbuch also notes the aileron Flettner tabs, with the comment they are locked at the moment, as well as many drawings for the 109K show them.
Now the next photo also shows the aileron Flettner on a late 109 wing, next to G-10.
(http://www.onpoi.net/ah/pics/users/715_1109860349_109_aileronflett2.jpg)
The following is a 109G-6 of hungarian air force, photographed around oct-nov 1944, on the field.
(http://www.onpoi.net/ah/pics/users/715_1094981724_g-6_flettner.jpg)
Then there`s the picture of Graf`s 109G-6, photoed in 1943, it also clearly has Flettners.
So basically we have photos of aileron Flettners for G-6, G-10, and appearantly, a K-4. The servo tab was no standard by any means, but it was there and obviously intended for service from 1943 onwards.. why not put into widespread production, I guess manufacturing problems has more to do with than the boring old urban myth about the 'weak' 109 wings. After all, wheel well covers were intended for the 109G but only a handful got it, and there are 109K w/o as well. Simply, things take time to run up.
As for the wing twist problem of the Spitfire, it`s well known. The NACA 868 notes the Spits wing caused 65% reduction in roll rate at high speed, as opposed to 30% of the P-47. It`s fairly logical to me, considering the Spitwing`s rigidity was provided by the D-shaped torsion box in the leading edge... forces that applied in the back on the wing should and were very able to twist such structure - hence the complete redesign of the Spit wing structure in Mk21.
I doubt the same applied to the 109. First the wing constuction is very different, a single main spar in the centerline, supplemented by torsion box spar behind. It shouldn`t be prone to twist, and in fact butch2k noted a good while that americans were surprised of the 109F wing rigidity, which was comparable to their own two-spar designs. Moreover, butch allagedly has some photos of 109s with aileron flettners.
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Note, the aileron Flettner tabs on the G-6 was not a field mod. They were installed in the WNF factory in automn 1943, and appearantly only there - hence the few examples of pictures with them.
(http://www.onpoi.net/ah/pics/users/715_1094981724_g-6_flettner.jpg)
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Hi Kurfürst,
>I doubt the same applied to the 109. First the wing constuction is very different, a single main spar in the centerline, supplemented by torsion box spar behind.
I believe that's a misunderstanding - the torsion box should indeed be the wing nose. I haven't looked at the exact spar placement yet, though.
>It shouldn`t be prone to twist, and in fact butch2k noted a good while that americans were surprised of the 109F wing rigidity, which was comparable to their own two-spar designs.
Hm, would be interesting to see that report. I haven't read much on aeroelasticity issues so far!
Regards,
Henning (HoHun)
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Hmm, maybe I did not use the right term... 'box spar' for the 109. That`s simple to execute, basically the main spear, the surface planting and the aux. spar forms a large box, stiffening the wing structure. Because it`s simple, it`s rather widespread. Interestingly, a hungarian book for flight mechanics gives the 109 as example for a box spar, among other things, certainly it`s a good example for prop with so many innovative features. I am not sure if it had used torsion box in the leading edge, though. Probably not, my mistake.
As for US report, I don`t have it, perhaps crumpp had seen something in US archives. Here`s what butch posted :
"Author: butch2k
Rank: Over 1000 Postings
Date: 10/03/03 11:39AM
109 wing torsion is similar to what could be found in US fighter planes. No aileron reversal at high speed, which came as a surprise to US engineers in charge of evaluation the 109 aerodynamical properties."
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Hi Kurfürst,
Highly interesting, thanks!
I admit that previously, I was a bit confused by the aileron overbalance mentioned in the high-speed diving trials which, if I think about it now, would indicate the opposite effect of aileron reversal. That would indeed suggest a rather stiff wing.
Box spar - hm, that's surprising, I had always thought Messerschmitt to be the pioneer of the single-spar nose-torsion-box construction, and as far as I know, this applied to the Me 109 as well. However, I guess that doesn't mean you can't combine it with another torsion box including the auxiliary spar ...
Regards,
Henning (HoHun)
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Cool. now all we need is a pilots report on these.
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Kurfurst,
What number of Flettner tab equipped Bf109s made it into service do you think?
It is odd that the Bf109K, which was intended to unify Bf109 production into one standard instead of the mishmash of Bf109G models, was still not standardized. It is understandable though, given the pressures Germany was under at the time.
Do you know of any comparitive flight trials for Flettner tabbed Bf109s and Bf109s without? It's be interesting to see how much they improved performance.
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Butch replied to Kurfürst's thread over at AAW2 109K aileron flettner tabs.... (http://www.allaboutwarfare.com/forums/index.php?showtopic=912)
butch2k, Jul 28 2005, 10:23 PM[/i]
In fact it seems that no K-4 were fitted with them, it's the WNF/Gyor produced a/c which got them as the flettner equiped ailerons were produced by diana, a major subcontractor of WNF.
IIRC the flettner tests took place late 1942 with some operational testing done by hte JG 50 in 1943 with flettner modded G-5 and G-6.
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Originally posted by Karnak
Kurfurst,
What number of Flettner tab equipped Bf109s made it into service do you think?
[/B]
I have no idea. There are some photos of G-6s with them, and appearantly they are coming from WNF factory, near Vienna.
It is odd that the Bf109K, which was intended to unify Bf109 production into one standard instead of the mishmash of Bf109G models, was still not standardized. It is understandable though, given the pressures Germany was under at the time.[/B]
Yes, that`s what I think too. The 109K was to have retractable tailwheel and wheel well covers, but the latter are rare on early machines but can be find on later ones, ditto for the tailwheel but it`s harder to tell on the ground wheter it was just closed by the crew (mud etc.) or was fixed down.
As for the 109K, the Flugzeug Handbuch, Teil0, p13 states :
"Seitenruder mit am Boden einstellbaren Ausgleichruder (Flettner) und geschrankten Bugelkanteln versehen.
Querruderanordung links und rechts and den Tragflachen
Beide Querruder mit Ausgleichruder (Flettner) versehen). Ausgleichruder z.Zt. festgelegt."
I hope HoHun can give an accurate translation, but basically: the ailerons have Flettner, but they are at present time fixed.
Do you know of any comparitive flight trials for Flettner tabbed Bf109s and Bf109s without? It's be interesting to see how much they improved performance. [/B]
Something was posted on this by George on the LEMB message board, about a test with Williemsen on some old test-hack 109G. Unfortunately due to some hack attack most of the board`s content was lost, and I don`t have a backup on that thread (anybody has?). What I remember clearly and that the ailerons could be deflected 2/3 at some very high dive speed,and that no aileron overbalance was observed with them.. 0.7Mach it was? :confused:
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Good, I have not grown senile yet! Found on another forum the original LEMB one from George :
"The following is from a test dive on 7.10.44 in good old W.Nr. 18550 (I say that because that a/c was used in just so much of the 109 testing): the test was made by "Willemsen" (he's not known to me. Does anyone have info on him?), on an a/c equipped with ailerons with Flettners, large stabilizer and rudder, a/c weight: 333o kg, and CofG at take-off: 24.6%.
At a corrected speed of 770 kph (.75 Mach at the test altitude), Test pilot Willemsen was able to get the ailerons to travel to 2/3 of their available range (no approx. force required is mentioned), forces were the same to either side, and there was no overbalancing observed. "
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More goodies :
(http://mapage.noos.fr/olefebvre/Bf109F-K_Flugel.jpg)
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G-6s with aileron Flettners in WNF factor, automn 1943 (via radinger/otto)
(http://www.onpoi.net/ah/pics/users/715_1095071514_wnfg6_flettner.jpg)
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Originally posted by Wotan
Butch replied to Kurfürst's thread over at AAW2 109K aileron flettner tabs.... (http://www.allaboutwarfare.com/forums/index.php?showtopic=912)
Wotan,
the trouble with butch`s latest position is that before I have seen him state that he had seen some pics of 109K with flettners on ubi boards... Moreover, the scale drawing of the 109K wing which shows flettners was originally posted by him.
I am not saying anything but I had butch change his position on several issues, so I`d rather go by the 109K picture I posted that appearantly HAS a flettner, regardless of everything. ;) Otherwise, the fact that they were seriously intended is undeniable, they show up on drawings, the manual etc.
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Hi Kurfürst,
>"Seitenruder mit am Boden einstellbaren Ausgleichruder (Flettner) und geschrankten Bugelkanteln versehen.
Querruderanordung links und rechts and den Tragflachen
Beide Querruder mit Ausgleichruder (Flettner) versehen). Ausgleichruder z.Zt. festgelegt."
Ouch :-) Try to transliterate the Umlauts as follows: ä->ae, ö-> oe, ü -> ue.
>I hope HoHun can give an accurate translation, but basically: the ailerons have Flettner, but they are at present time fixed.
"Rudder features ground-adjustable balancing tab (Flettner) and trim strips with opposite bias [to avoid loss of feedback force around the rudder zero position]"
"Aileron arrangement left and right on the wings
Both ailerons feature balancing tabs (Flettner). Balancing tabs are currently fixed."
>What I remember clearly and that the ailerons could be deflected 2/3 at some very high dive speed,and that no aileron overbalance was observed with them.. 0.7Mach it was? :confused:
Radinger/Otto report overbalancing on a normal aircraft at Mach 0.79, becoming (probably) fatal at Mach 0.80. (For the latter speed, the test aircraft was rigged with 50% aileron gain to enable the pilot to keep the ailerons under control. That Me 109 was also fitted with an ejection seat! 8-O)
Regards,
Henning (HoHun)
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Did not Butch also say at one time that only ~200 of the ~1700 K-4s built had aileron Flettners fitted? Iirc correctly that was on the UBI zoo forums.
The 109K-4 handbuch also notes the aileron Flettner tabs, with the comment they are locked at the moment
So if Flettners were locked, it would seem there was some truth that Flettners made the a/c harder to control > ie precision flying like when trying to line up a target.
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The V-tailed Bf 109 test plane was also fitted with the ailerons with geared tabs and the report contains some data on ailerons. Claimed time for one roll was 4 s with tabs and 4,5 without them, no speed claimed (with the tabs the speed was probably higher because the tabs decrease roll rate at slow speeds).
gripen
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It's funny how people wouldn't be as interested in this information if it wasn't for computer flight sims!:D
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Originally posted by MiloMorai
So if Flettners were locked, it would seem there was some truth that Flettners made the a/c harder to control > ie precision flying like when trying to line up a target.
I wonder how would Flettners made an aircraft harder to control, Milo. And why would be so many aircraft fitted with Flettners then : Spitfire XIV, Tempest etc.. were these also harder to control than their non-flettnered cousins?
It`s curious because all what a Flettner does is reducing stick forces, at low speeds where the controls are light anyway it shouldn`t effect much, and at high speed I wonder how can be controls so precisly with very high control forces (ie. w/o a flettner)
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I can only imagine that having lighter aileron forces at high speed would improve the control harmony of the 109, making it more like the 190 which had close to an ideal balance of aileron/elevator forces?
Btw; exactly how does the flettner tab work - google aint giving me nothing... :confused:
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It is understandable that you would not understand Kurfy.
Now try to see, using the following example. Early power steering on cars made steering easier but precision control of the car was harder. The driver would turn the wheel and find he put in too much. Would make a correction and find he made too much of a correction. And so on, and so on,.....
This is what pilots found with Flettner ailerons.
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Uhhh, how would that be any different than a 109 pilot flying a 190 first time? They just have to get used to the difference...
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Originally posted by MiloMorai
It is understandable that you would not understand Kurfy.
Now try to see, using the following example. Early power steering on cars made steering easier but precision control of the car was harder. The driver would turn the wheel and find he put in too much. Would make a correction and find he made too much of a correction. And so on, and so on,.....
This is what pilots found with Flettner ailerons.
Erm, that doesn't jive. I've driven with and without power steering and have never had an issue with the transition or a lack of precision.
Unless Flettners do something really funky to the way an aircraft's control surfaces work I just can't see them adding any slop in. Lighter stick forces make it easier to be precise as you aren't overloading your muscles.
If what you are saying is correct, then why are the Spitfire, Bf109 and A6M, all of which suffer high stick forces in some way at higher speed, so precise at lower speed? The pilots should be mushing all over from the light stick forces at low speed, no?
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Hehe, got the wrong quote there methinks...:D
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Fixed it.
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Originally posted by Karnak
Erm, that doesn't jive. I've driven with and without power steering and have never had an issue with the transition or a lack of precision.
Unless Flettners do something really funky to the way an aircraft's control surfaces work I just can't see them adding any slop in. Lighter stick forces make it easier to be precise as you aren't overloading your muscles.
If what you are saying is correct, then why are the Spitfire, Bf109 and A6M, all of which suffer high stick forces in some way at higher speed, so precise at lower speed? The pilots should be mushing all over from the light stick forces at low speed, no?
The animosity between the two gentlemen aside, I think Milo might have a point though. I own two cars, a 1971 Opel without power steering and a 1998 Fiat with (very light) power steering. Not that I drive off the road in either one of them, but it is certainly a transition.
Is it possible that the reduced feel of the control surfaces made it more likely to enter uncontrolled flight? Or would it impose bigger stresses on the aircraft? You tell me, I'm only interested.
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I guess you never drove an early power assisted steering car Karnac. The Crysler products were the worst. Modern are much more precise.
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Originally posted by Kurfürst
And why would be so many aircraft fitted with Flettners then : Spitfire XIV, Tempest etc.. were these also harder to control than their non-flettnered cousins?
AFAIK only one Spitfire was tested with geared tab ailerons (Flettner tabs), late Spitfires and Tempests had spring tab ailerons which are quite bit different.
gripen
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Ok. cool stuff. Now is there a report on the roll difference on these later Temps & Spits? At higher speeds in particular.
These can't have been that hard to manufacture, if they were a success, one would think that Willy would have ordered em on all the G-10's & K's. A puzzle it is.
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Originally posted by gripen
AFAIK only one Spitfire was tested with geared tab ailerons (Flettner tabs), late Spitfires and Tempests had spring tab ailerons which are quite bit different.
gripen
Hmm, when I said flettner on the spits, I meant that afaik the mkxiv had a double tab on the rudder, one working as flettner and the other as trim tab. Or was it combined? Certailnly I do not remember flettner tabs on the ailerons for wartime spits. Perhaps they were concerned of the wing flex issue.
agent 009, there`s a report on spitxiv vs. tempest v roll rate, it says the latter is better above 350mph. same is said in comparison of 109G2, though the report notes they were afraid to use the ailerons fully on the 109.
I have some roll reports for the tempest v with spring tabs, it`s pretty good at high speed - 80 deg/sec iirc at 350mph.
Back on flettners, it was perhaps because they were not so essential for the 109. all 109G vets I talked about are telling me about the ailerons remaining relatively light even in dives.. perhaps some help would be nice, as it`s clearly indicated by the drawings, manual and individual examples that they meant Flettners on the ailerons, but delays were accepted.
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I don't know if this quote refers to the exact same design of tab as seen fitted in the photos above, but here is a quote from Heinrich Beauvais regarding Flettner tabs on the 109's ailerons:
Flight controls
One would have liked to have more effective ailerons, as well as lower control forces, at high speeds. I do not remember all the different methods tried to improve this, but the following two are still clear in my mind. One was designed by Blohm & Voss, adding a Flettner trim tab which resulted in a reduction of control forces: however, performance was not as smooth and effectiveness had not improved at all. A later form was the 'Keulenquerruder' (a shape of aileron tested at Memmingen in 1944) which had seemed promising, but had never been introduced. The rudder had no trim: it was 'ironed out' especially for the dive and produced fairly high aerodynamic forces during the climb. Nevertheless, it seemed the best of compomises: a spring to counteract the strong forces during the climb was considered, but never incorporated.
From "Test Pilots" by Wolfgang Späte(English language edition)
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justin,
your quote of Beauvais will be ignored.
One was designed by Blohm & Voss, adding a Flettner trim tab which resulted in a reduction of control forces: however, performance was not as smooth and effectiveness had not improved at al
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Flettner tab of course doesn`t improve aileron effectiveness.
Aileron effectiveness is an aerodynamic term and refers to the degree of roll rate achieved per degree of aileron deflection.
A Flettner tab reduces the force required to deflect the aileron, therefore it helps achiving more deflection at high speeds where stickforces could prevent deflecting the ailerons.
Therefore adding a Flettner improves roll rate at high speed by allowing higher aileron deflection angles and not by enchancing the roll rate per deflection angle (=aileron effectivness).
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Well, Kurfie has it as I thought, - at high speed the aileons are more effective. 109 trying to be 190, hehe.
Anyway, this got stuck in my head:
"At a corrected speed of 770 kph (.75 Mach at the test altitude), Test pilot Willemsen was able to get the ailerons to travel to 2/3 of their available range (no approx. force required is mentioned), forces were the same to either side, and there was no overbalancing observed. "
That aircraft was then perhaps balanced (rudder trim) to something near that speed, or to high speed anyway, since otherwise it would roll better with the engine torque than against it.
The 109 was told to be delightfully balanced in the roll plane at low speeds, - did the Flettners simply trade that off to better performance at high speeds?
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Well, theoretically adding Flettners decreases the aileron surface and thus they should decrease roll rate at the same deflection... but this change is so small that it can be safely neglected.
The drawing of the 109K wing shows 504mm x 54mm Flettner area, total area of the aileron is 1465 x 298.... what`s that 1/3 x 1/6 = 1/18 decrease in area.. ~5%.
So if it`s linear and we take the 109`s roll rate of ca 90 deg/sec at 450 kph, it`s about 85degrees w. Flettner... you won`t notice the difference withing production standards, but the stickforce is even lighter and the roll can be initiated more quickly, more important imho than the peak roll rate for a sudden evasion.
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Decreasing aileron surface is the drawback, right?
But the true effect is aerodynamic, at high speeds especially?
So, as with wing loading, large ailerons are most effective at rather low speeds, as low wing loading shines at lower speeds, right?
So, you trade off some low speed roll rate which for the 109 is :
A) A good deal, for it already has quite good roll characteristics at low speeds.
B)It badly needs better roll rate at high speeds and those can be aquired whith this method.
Basically emulating the 190 a bit, - which is the natural rollmaster of WW2.
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Originally posted by Kurfürst
The drawing of the 109K wing shows 504mm x 54mm Flettner area, total area of the aileron is 1465 x 298.... what`s that 1/3 x 1/6 = 1/18 decrease in area.. ~5%.
Hm... Flettner area is away from the most effective area of the aileron ie the trailing edge.
gripen
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Tommy Hayes followed a 109 in his Mustang over Berlin in a high speed dive. The 109 veered away ( can't remember right or left ), & Hayes mentioned he couldn't follow. Hayes ended war with 10 kills & was no beginner. This from an interview from one of the big aviation mags. haven't got it at hand, but remember well this part.
Being over berlin, the wing tank full argument is out. This would tend to support the airelon still good at high speed for 109 thinking.
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Originally posted by gripen
Hm... Flettner area is away from the most effective area of the aileron ie the trailing edge.
gripen
If a Flettner is so bad gripen, why is used on so many planes, huh? I guess the gains more than outweight the losses.
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Originally posted by Kurfürst
If a Flettner is so bad gripen, why is used on so many planes, huh? I guess the gains more than outweight the losses.
Please, don't put words to my mouth; I have not said if the geared tabs are good or bad. There were several planes with geared tabs in ailerons which worked well (say Fiat G. 50 and P-39) but apparently installation in the Bf 109 was not particularly succesfull (based on comment by Beauvais and the manual claim that the tabs were locked).
gripen
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Originally posted by Kurfürst
If a Flettner is so bad gripen, why is used on so many planes, huh? I guess the gains more than outweight the losses.
How many of each model of the 109 had operating aileron Flettners?
If they were as great, as you would like us all to believe, then why were only ~200 out of the ~1700 K-4s built have them? That is only ~12%.
gripen, comments by Beauvais will be ignored as it is in conflict with his uber German agenda.
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1. We still don't have any "official" reason for why the Flettners were locked(as per the K-4 manual). We need the document saying "Flettner tabs are to be locked because of reason X" if we want to know why they were locked, at the moment we are speculating based on anecdotes and guesswork...
Originally posted by Kurfürst
Well, theoretically adding Flettners decreases the aileron surface and thus they should decrease roll rate at the same deflection... but this change is so small that it can be safely neglected.
The drawing of the 109K wing shows 504mm x 54mm Flettner area, total area of the aileron is 1465 x 298.... what`s that 1/3 x 1/6 = 1/18 decrease in area.. ~5%.
So if it`s linear and we take the 109`s roll rate of ca 90 deg/sec at 450 kph, it`s about 85degrees w. Flettner... you won`t notice the difference withing production standards, but the stickforce is even lighter and the roll can be initiated more quickly, more important imho than the peak roll rate for a sudden evasion.
2. I can't find any exact figures for this type of tab, but I think that the reduction in roll rate at low speeds (where full aileron deflection can be reached) could be more than 5% with Flettner tabs. For example if you look at page 184 of NACA Report 868 (http://naca.larc.nasa.gov/reports/1947/naca-report-868/index.cgi?page59.gif) there is a graph(figure 70) for the F6F with spring tabs, which shows about 13% loss of rollrate at 200mph(but at 400mph, the tabbed ailerons give 70% improvement!)
Although as you can see, the massive improvement in roll-rate at high speed is certainly worth the reduction at low speed.
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Originally posted by MiloMorai
How many of each model of the 109 had operating aileron Flettners?
If they were as great, as you would like us all to believe, then why were only ~200 out of the ~1700 K-4s built have them? That is only ~12%.
gripen, comments by Beauvais will be ignored as it is in conflict with his uber German agenda.
MiloMoron, you usual hysteria aside, can you tell us how you arrived at 'only' 12% figure ie. 200 109Ks having aileron Flettners?
Unfurtunately, I fail to see what`s an, what was the word 'uber German agenda' in discussion the various improvements done to an aircraft. One would think that to you, even mentioning that there were improvements done to German aircraft, gives you a heart attack and starts a berserker rage...You should really moderate yourself. :rolleyes:
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Originally posted by justin_g
2. I can't find any exact figures for this type of tab, but I think that the reduction in roll rate at low speeds (where full aileron deflection can be reached) could be more than 5% with Flettner tabs. For example if you look at page 184 of NACA Report 868 (http://naca.larc.nasa.gov/reports/1947/naca-report-868/index.cgi?page59.gif) there is a graph(figure 70) for the F6F with spring tabs, which shows about 13% loss of rollrate at 200mph(but at 400mph, the tabbed ailerons give 70% improvement!)
Although as you can see, the massive improvement in roll-rate at high speed is certainly worth the reduction at low speed.
I can very much agree with you about speculation and guesswork.. it would be nice to work with some hard data! One guesswork I can come up with is that probably the Nov 1944 trials with Flettners were in connection with the 109K, already in service, so perhaps they did not have enough data to know the effects, and were careful.
Have Beuvuais and Spaete more to say on the subject?
On point 2, what was the execution of the spring tabs and the type of ailerons on the F6F? As iirc gripen noted, spring tabs and flettners work differently, though from what I recall they are quite similiar (it`s been long time since I read 868 and I gotto run now) - therefore the effect may vary with ailron type, tab type and area...
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LOL Kurfy, you are the only with the hysteria with another personal attack.
The number was stated awhile back by Butch in a thread (UBI Zoo maybe) where you tried to claim that Flettners were universally fitted to all 109s from the G onwards.:eek: Naturally you forget those numbers in your quest to show how uber Germany was.
When did the Germans start experimenting with aileron Flettners? You posted a pic of a G-6 in 1943.:eek: Seems your heros, the Germans, could not make them work satisfactorly.:D
Naturally you ignore, and instead put out your usual crap, so give us some numbers for 109s fitted with aileron Flettners as a percentage of the total of each model.
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Originally posted by Kurfürst
On point 2, what was the execution of the spring tabs and the type of ailerons on the F6F? As iirc gripen noted, spring tabs and flettners work differently, though from what I recall they are quite similiar (it`s been long time since I read 868 and I gotto run now) - therefore the effect may vary with ailron type, tab type and area...
Oops!:o
Actually, it says in the report that the loss of performance below 280mph was due to the ailerons max. deflection being reduced by the amount needed to deflect the tabs(spring tabs are wired to the stick, unlike the Flettner). The ailerons could be made to reach full deflection by changing the ratio of stick:aileron movement.
Hmm, The geometry of the 109's aileron/tab is available in the diagram above, but without knowing the ratio of deflection between the tab and aileron, you can't figure out the loss in aileron effectiveness, I think.
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Justin,
I think I have the deflection angles somewhere, I`ll look it up for you. Could it be that Flettners don`t show this behaviour as spring tabs at low speeds due to different setup? I am asking.
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Here you have. Sorry for bad quality :(
(http://www.jagdgeschwader52.com/orka/defanglesK4.gif)
(http://www.jagdgeschwader52.com/orka/defanglesK4_2.gif)
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Interesting stuff. Now if I could figure out how the butterfly flaps worked on the George, life would be good.
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We still got a few flying 109s around. Why can't someone just ask the guys flying them?
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Falconsix: AFAIK none of the existing 109's have Flettner tabs.
Kurfurst: One NACA report on aileron tabs states that the change in lift & drag with the tabs fitted was within their measurement error of +/- 3%. So I think the reduction in performance at low speeds would hardly be noticable with Flettner tabs.
Now we have the geometry & deflection data(thanks Orka), I think that if someone was keen enough to do the maths(and could understand the appropriate formulas:eek: ), they could figure out how much the 109 aileron Flettners reduced the control force.:D