DVL data on Bf 109 roll rates

[gripen]

Originally posted by Kurfürst
Actually it shows theoretical 100% rigid wing vs. measured figures on the poorest of the 3 FWs.

That means that measured values contain wing twist.

And this has quite little to do with stick forces.

Originally posted by Kurfürst
Again you claims something that is not actually told by your sources. Showing a FW 190 curve hardly proves anything else other than for the FW, now does it?

Here is the quote again:

"This course has been adopted in Fig. 6 which shows the results obtained for the F.W.190, Mustang, Typhoon and Spitfire V (metal covered ailerons) with both standard and clipped wings. On all these aircraft instrumental records of rolling performance have been obtained at the R.A.E. similar to those under discussion for the F.W.190."

gripen

[Nashwan]

If you want to prove the Spitfire curve is similiar, why you wouldn`t post the similiar Spitfire curve?

The Spitfire curves are included in NACA 868.

What the RAE test says:

The best method of comparison of the rolling performance of different aircraft is based on the steady rate of roll a pilot can generate using a definite stick force, say 50 lb., or full aileron if this requires less than 50 lb. on the stick.  This course has been adopted in Fig.6 which shows the results obtained for the F.W.190, Mustang,  Typhoon, and Spitfire V (metal covered ailerons) with both standard and clipped wings.  On all these aircraft instrumental records of rolling performance have been obtained at the R.A.E, similar to those under discussion for the Fw 190.  In this connection it is worth noting that "instrumentation" is essential when obtaining the curves of Fig.6.  Stop-watch measurements of time to bank on fighters are rarely of sufficient accuracy, since the times to be measured are so small.

There is little.to chose between the Fw 190 and the clipped wing Spitfire over the whole speed range, although both show a considerable improvement on the standard Spitfire V. The Mustang .comes out top at 400 m.p.h. EAS but falls away appreciably below 350 m.p.h.; while the Typhoon has a comparatively poon rolling performance, at all speeds.

Now, the RAE report states clearly that these are measured results, so they have to include wing twisting. And the RAE is including them for comparison purposes, so there's little point in including a non standard Spitfire, especially without saying so. Note how they point out that the Fw 190 is the worst of the 3 samples they have.

[Knegel]

Hi again,

quote:
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Originally posted by gripen
The Spitfire V is not a late Spitfire and difference between NACA and RAE/RAAF measurements is probably caused by condition of the plane.

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Since the slowspeed and highspeed results of the SpitVa and the late SpitV( i cal it 'late', cause the SpitVa was the 1st SpitV) are pretty similar, i would like to know what conditions can make a plane only in the middle speed so much more bad??
If the SpitVa condition was more bad, we would see this specialy at highspeeds, but here it actually show better results than the late SpitV!


quote:
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Originally posted by gripen
Actually more simple and logical answer is out of spec tension of the cables.

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What "out of spec tension of the cables"?? Do you think the SpitVa cables have a to strong tension?? Only this would explain why the late SpitV can reach a higher speed with max stickvariation, if the leverage is the same.




quote:
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Originally posted by gripen
Actually that depends on geometry of the linkage.

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Now i start to think you make jokes with me! A different geometry of the linkage HAVE A DIFFERENT LEVERAGE AS RESULT!!!!
Thats what i try to explain since some posts.


quote:
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Originally posted by gripen
Believe what ever you want to believe but to make others to believe it, you should have evidence. At least Morgan's and Shacklady's bible does not claim control changes
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I have some original Spitfire wing drawings of the A and C wing, which isnt allowed to offer here, they realy dont show the same lincage, which would give a different leverage.
Actually the both testresults and a bit knowledge of the physical law are evidence. You already did agree to it without to realize it, with your statement above. A different geometry of the linkage = different leverage!

Greetings, Knegel

[Knegel]

Hi Nashwan,

donmt you think something is fishi with the ' Fig. 47, NACA Report No.868?

On the bottom they state 30lb stickforce, but the Spitfire(normal wing) show a much greater rollratio than in other sources with 30lb, while the typhoon, for exampel, show the exact 30lb curve of a other test, and also the P51B is similar to the MustangIII with 30 lb and the F6F-3 show the spring tab aleron curve at 30lb.

Your quote of a NACA comparison state a "Fig.6" where the 50lb comparison get displayed, do you have this "Fig.6" ??

Would be very interesting to see it.

Greetings, Knegel

[Nashwan]

Fig 47 Naca 868 shows 50 lbs stick force, not 30lbs.

Here's the RAE Fig 6 (Thumbnailed because it's a big pic):


NACA 868 uses these RAE figures for the 190 and Spit, and (I think) for the Mustang and Typhoon.

[gripen]

Originally posted by Knegel

Since the slowspeed and highspeed results of the SpitVa and the late SpitV( i cal it 'late', cause the SpitVa was the 1st SpitV) are pretty similar, i would like to know what conditions can make a plane only in the middle speed so much more bad??

I don't know, it seems that loosenes in the linkages affects mainly in large deflections.

Originally posted by Knegel
What "out of spec tension of the cables"?? Do you think the SpitVa cables have a to strong tension?? Only this would explain why the late SpitV can reach a higher speed with max stickvariation, if the leverage is the same.

I can't say anything about the tension of the cables without looking the manual. The curve shows only that there is no large difference at very low speed and at very high speed ie at low pressure and/or at small aileron deflection.

Originally posted by Knegel
Now i start to think you make jokes with me! A different geometry of the linkage HAVE A DIFFERENT LEVERAGE AS RESULT!!!!
Thats what i try to explain since some posts.

Well, if you would say that under pressure the leverage changes at higher aileron deflections due to loosenes in the linkage. That might explain the unlogical shape of the curve.

Originally posted by Knegel
I have some original Spitfire wing drawings of the A and C wing, which isnt allowed to offer here, they realy dont show the same lincage, which would give a different leverage.
Actually the both testresults and a bit knowledge of the physical law are evidence. You already did agree to it without to realize it, with your statement above. A different geometry of the linkage = different leverage!

If you have the evidence, I'm more than willing to believe because that would at least partially explain the difference between the curves.

gripen

[Knegel]

Hi,

if the linkage would be somehow loose, the rollratio would decrease, like the picture show, but at same the speed of max stick deflection would INCREASE, not decrease!!

A decreased speed of max stickdelfection and a decreased rollratio, at same time, only can have a different leverage as reason!

Loose linkage and bad  tension etc would let minimize the aleron variation at a given speed, therfor the pilot could keep the max stick variation at higher speeds.

According to the test torsion of the wing wasnt a problem up to 300mph!!  The other test only state that wing torsion was a problem at 400mph!


Nashwan,

do you have the Spit 50lb test somewhwere? A 25degree/sec roll increasement due to 20lb more stickforce is pretty outstanding.

Greetings, Knegel

[gripen]

Originally posted by Knegel

if the linkage would be somehow loose, the rollratio would decrease, like the picture show, but at same the speed of max stick deflection would INCREASE, not decrease!!

No, that depends on the geometry of the linkage and how the geometry changes due to loosenes. While the stick movement for the given deflection might increase, the angles of the forces in the linkage might change to less optimal direction and the increased movement (leverage) or force might be used just to bend linkage or cables instead to deflect control surface.

Originally posted by Knegel
According to the test torsion of the wing wasnt a problem up to 300mph!!  The other test only state that wing torsion was a problem at 400mph!

As RAE comments note, NACA just made erroneous conclusion due to speed range and apparently also due to condition of the plane. Below is a graph from RAE report No. B.A. 1667 "Aileron tests on Spitfire". The tested plane is a Spitfire I with canvas covered ailerons and the graph shows that at 300 mph the wing lost roughly 40% of the rollinperformance due to twist.

gripen

[niklas]

Originally posted by gripen
Here is the curves showing wing twist for the Fw 190 from the RAE test, all other planes in the test were tested same way.

gripen

Thx for bringing it up. Is this from one of the 2 later fw-190?? It says "Measured rate of roll". Difficult to say what stickforce was applied, but probably not more than 70lb. Maybe only 50lb too? Any further informations?
In any case the 50lb limit of the RAF/NACA chart is at too low speed and contradicts all pilot accounts.

niklas

[gripen]

Originally posted by niklas
Thx for bringing it up. Is this from one of the 2 later fw-190?? It says "Measured rate of roll". Difficult to say what stickforce was applied, but probably not more than 70lb. Maybe only 50lb too? Any further informations?

It's from the RAE 1231 and tested on same plane as other data (very probably PE882). The data gives rate of roll per degree aileron deflection so it's not collected from full deflection or full available force data so that graph does not tell anything about used stick forces; graph would have been pretty similar in all their Fw 190s. Note that it does not tell anything about elasticity of the linkage either.


The graph below gives an idea about the stick force used in the tests.

gripen

[Nashwan]

Nashwan,

do you have the Spit 50lb test somewhwere? A 25degree/sec roll increasement due to 20lb more stickforce is pretty outstanding.

No, the RAE test of the Spitfire is included in the report on the FW 190 for comparison purposes, but it doesn't go into details of the test, apart from the paragraphs Gripen and I have posted on this thread.

[Knegel]

Originally posted by gripen
No, that depends on the geometry of the linkage and how the geometry changes due to loosenes. While the stick movement for the given deflection might increase, the angles of the forces in the linkage might change to less optimal direction and the increased movement (leverage) or force might be used just to bend linkage or cables instead to deflect control surface.

If the linkage is loose, it mean the alerons cant get its best deflection with the used stick variation anymore. Ok??
As result of course the max roll ratio decrease! Ok??
As result the max presure onto the alerons decrease, cause smaler aleron deflection.
As result the pilot can keep the stick at higher speeds in its max position.

As long as the planes have the same linkage and leverage, the only way, how the aleron deflection get minimized and at same time the the stick force increase, is, if the alerons are mechianically blocked. But this we for sure would see on the full range of the curve, not only in the middle. And the testers would have took notice of such abig problem!

Originally posted by gripen

As RAE comments note, NACA just made erroneous conclusion due to speed range and apparently also due to condition of the plane. Below is a graph from RAE report No. B.A. 1667 "Aileron tests on Spitfire". The tested plane is a Spitfire I with canvas covered ailerons and the graph shows that at 300 mph the wing lost roughly 40% of the rollinperformance due to twist.

gripen

This should proof that the Spitfire and the FW190 curve in the test are not measured, cause the increase of roll with constant alerondeflection(max stickdeflection) is almost linear!

Originally posted by Nashwan

Thx for bringing it up. Is this from one of the 2 later fw-190?? It says "Measured rate of roll". Difficult to say what stickforce was applied, but probably not more than 70lb. Maybe only 50lb too? Any further informations?
In any case the 50lb limit of the RAF/NACA chart is at too low speed and contradicts all pilot accounts.

niklas

It must have been a constant aleron deflection, not constant stickforce in this test. The calculated max roll ratio was around 115degree/sec  at 255mph, while the NACA comparison show a bit over 160degree/sec at same speed.

So i guess with max stickdeflection the wingtwist would be even bigger, therofr the 190 curve in the Naca test, same like the Spit curve looks even more strange!

If the NACA guys wasnt able to see that the Spit wing have wingtwist, they maybe made more strange mistakes!

Greetings, Knegel

[gripen]

Originally posted by Knegel
If the linkage is loose, it mean the alerons cant get its best deflection with the used stick variation anymore. Ok??

As result of course the max roll ratio decrease! Ok??
As result the max presure onto the alerons decrease, cause smaler aleron deflection.
As result the pilot can keep the stick at higher speeds in its max position.

The last sentence might be right or wrong depending the geometry of the linkage and where the loosenes is located. The pilots input might go to bend the linkage or cables.

Originally posted by Knegel
As long as the planes have the same linkage and leverage, the only way, how the aleron deflection get minimized and at same time the the stick force increase, is, if the alerons are mechianically blocked.

No, the loosenes might cause changes in the leverages inside the linkage and even waste large amount of control force to linkage itself.

Originally posted by Knegel
This should proof that the Spitfire and the FW190 curve in the test are not measured, cause the increase of roll with constant alerondeflection(max stickdeflection) is almost linear!

No, the RAE curves show slight bending before the force limit is reached and the report states clearly that the curves are based on flight tested data. There is not much bending below 250 mph EAS even in the case of the Spitfire I.

BTW you are following Mr. Kurfürst's road now.

Originally posted by Knegel
It must have been a constant aleron deflection, not constant stickforce in this test.  

No, the steady rate of roll per degree aileron can be calculated from any measured rate of roll at any aileron deflection when the both are measured simultaneously as was done in the RAE tests.

Originally posted by Knegel
The calculated max roll ratio was around 115degree/sec  at 255mph, while the NACA comparison show a bit over 160degree/sec at same speed.

No, the calculation is rather easy; the max aileron deflection was +-17 deg and steady rate of roll per degree aileron about 9,5 deg/s at 255 mph EAS and that results about 160 deg/s (there was very little elasticity in the linkage).

gripen

[Angus]

Ehmm
"If the linkage is loose, it mean the alerons cant get its best deflection with the used stick variation anymore. Ok??
As result of course the max roll ratio decrease! Ok??
As result the max presure onto the alerons decrease, cause smaler aleron deflection.
As result the pilot can keep the stick at higher speeds in its max position.

As long as the planes have the same linkage and leverage, the only way, how the aleron deflection get minimized and at same time the the stick force increase, is, if the alerons are mechianically blocked. But this we for sure would see on the full range of the curve, not only in the middle. And the testers would have took notice of such abig problem!"

At first glance I'd figure you're right. If you have sloppy cables for instance, then eventually you will be  able to push the stick as far as it goes without so much happening.  Deflection will be less for the same movement if under stress. But a max position would also require quite some strength.
Now, the testers should however notice as you point out, and there is some person called a rigger as well. Comes with the aircraft in Squadron service.

So, I'm lost here. Where is the max position and limited by what? Were cables an issue and why? And so on.

But at the end of the day, what many seem to be missing is simply that it's the roll-rate which is in question, - the actual real life roll rate, and stick forces do not have to go linear with it because of the cockpit ergonomy.

[gripen]

Originally posted by Angus

So, I'm lost here. Where is the max position and limited by what? Were cables an issue and why? And so on.

The early NACA roll rate curve for the Spitfire V shows unlogical shape which is not supported by other measuremants. The rest here is speculation, it might be caused by loosenes or different linkage or something else (one possibility is that the aileron itself is physically different than in later measurements).

gripen