DVL data on Bf 109 roll rates

[Kurfürst]

Originally posted by Angus
Hehe, - this:
"The spit was a light plane for it´s size, one would assume a rather flexible wing"
FYI, the wing was flexible, as were other WW2 fighter wings. However the Spitfire wing was VERY strong and much stronger than many other. So, while I know it was made stiffer in later models, I rather doubt it flexed any more than most.

Read NACA 868.

[gripen]

Originally posted by Kurfürst

Yep. Even though if the instrumentation would be just as good everywhere, the power would strongly effect the rate of roll (the 109F-2 was only flown at continous power), and the RAE typically did it`s trials without guns and ammo, half fuel load.

Actually not, the measured value is peak roll rate so weight has no effect. Read hitech's post above.

Originally posted by Kurfürst
The most serious issue in comparing with the NACA chart is IAS/TAS conversion.

Well, rough and good enough IAS to TAS conversion in standard atmosprehe is very easy to do. Infact only you have had serious problems with it in this thread.

Originally posted by Kurfürst
NACA 868 notes some 65% reduction of roll rate for the Spitfire due to wing twist, but curiously, there is no sign of that on the RAE curves they copied. I guess there`s more in the original report on that, it`s just a bit 'filtered'.

Actually that 65% value comes from RAE tests as noted above and RAE curves for the Spitfire V contain this. Notable thing is that NACA choosed to use RAE data on NACA 868 report instead their own measurements and the reason is quite obivious; RAE measurements are better made.

Regarding wing twist it should be noted that there is not much difference in aileron reversal speeds of the Spitfire V and the Bf 109F.

gripen

[Kurfürst]

Originally posted by gripen
Well, rough and good enough IAS to TAS conversion in standard atmosprehe is very easy to do. Infact only you have had serious problems with it in this thread.

[/B]

Don`t make me laugh gripen. You 'very easy' IAS/TAS conversion is an utterly primitive and error prone method of simply assuming "IAS is roughly 20% smaller than TAS at 3000m" as you have already told us.

To me it seems there is only one person with problems here, it`s you and your ego. But as I said, I couldn`t care less about what some egomaniac posts who was already judged to be unworthy of reading by posters who otoh earned the respest of everyone for their honesty.

Notable thing is that NACA choosed to use RAE data on NACA 868 report instead their own measurements and the reason is quite obivious; RAE measurements are better made..

[/B]

Only you think things are that simple. You are telling the same mantra for yourself, and you are also the only one believing it.
In the, you are mumbling and nodding to yourself. To outsiders, it looks quite weird.

Regarding wing twist it should be noted that there is not much difference in aileron reversal speeds of the Spitfire V and the Bf 109F.

[/B]

Yes of course Gripen, of course.
But let`s see the facts, when the USAAF tested a Bf 109F, to their surprise they found the 109 wing being just as rigid as their own two-spar designs. I guess the rather massive main spar coupled with a box spar worked rather well.

The aileron reversal speed for the Me109 can be derived in FB 1951 and is around 611 mph while the Spitfire had only 510 mph (source avia report 6/10126 from the RAE).The supposedly rugged P47 has a reversal speed of only 545 mph (source NACA report 868). The NACA report notes 35% reduction of roll rate at high speed for the two spar P-47C, but as high as 65% for the Spitfire.

[Charge]

Originally posted by Angus
"FYI, the wing was flexible, as were other WW2 fighter wings. However the Spitfire wing was VERY strong and much stronger than many other. So, while I know it was made stiffer in later models, I rather doubt it flexed any more than most. "

The flexing happens because the wing had big area and it was thin. The 109 has a smaller and thicker wing so it was more rigid.

Spitfire's tubular wing spar was very strong but is has not much to do with torsional rigidity of a wing. The wing's planform shaping structure defines more of this quality.

This is why I think that new and used Spits may have had quite different rolling charactreristics, whereas 109s and 190s had prolly more uniform performace despite their service age.

-C+

[gripen]

Originally posted by Kurfürst

Don`t make me laugh gripen. You 'very easy' IAS/TAS conversion is an utterly primitive and error prone method of simply assuming "IAS is roughly 20% smaller than TAS at 3000m" as you have already told us.

Feel free to laugh but quick and dirty 20% conversion is better than yours, see Knegel's comment on your calculations.

Originally posted by Kurfürst
To me it seems there is only one person with problems here, it`s you and your ego. But as I said, I couldn`t care less about what some egomaniac posts who was already judged to be unworthy of reading by posters who otoh earned the respest of everyone for their honesty.

Only you think things are that simple. You are telling the same mantra for yourself, and you are also the only one believing it.
In the, you are mumbling and nodding to yourself. To outsiders, it looks quite weird.

So why don't you just ignore my postings then?

Originally posted by Kurfürst
The aileron reversal speed for the Me109 can be derived in FB 1951 and is around 611 mph while the Spitfire had only 510 mph (source avia report 6/10126 from the RAE).

Actually FB 1951 gives the reversal speed in TAS and RAE data gives it IAS (or EAS). Feel free to convert values comparable. The RAE 1231  (DSIR 23/12865) gives reversal speed 580 mph EAS for the Spitfire V with standard wings and that value is calculated from flight test results.

gripen

[Kurfürst]

Originally posted by gripen
Feel free to laugh but quick and dirty 20% conversion is better than yours, see Knegel's comment on your calculations.

[/B]

Yep the mantra again. And frankly, if I have to choose between the IAS/TAS conversions of E-Stelle Rechlin (which is the one I use), you, or Kneagel, I choose E-Stelle Rechlin.

E-Stelle Rechlin`s engineers vs. 'quick and dirty 20% conversion'.
Yes I laugh at you.

Originally posted by gripen
So why don't you just ignore my postings then?

I enjoy having another lapdog next to Milo, who keeps barking at me, toothless.

The aileron reversal speed for the Me109 can be derived in FB 1951 and is around 611 mph while the Spitfire had only 510 mph (source avia report 6/10126 from the RAE).The supposedly rugged P47 has a reversal speed of only 545 mph (source NACA report 868).

[gripen]

Originally posted by Kurfürst

Yep the mantra again. And frankly, if I have to choose between the IAS/TAS conversions of E-Stelle Rechlin (which is the one I use), you, or Kneagel, I choose E-Stelle Rechlin.

What mantra? IAS is simply the pressure difference between pitot tube and static port. Conversions in standard atmosphere are very easy make and no need to dug something from Rechlin papers.

Originally posted by Kurfürst
I enjoy having another lapdog next to Milo, who keeps barking at me, toothless.

Well, if you want make yourself laughable, it's not my problem.

Originally posted by Kurfürst
The aileron reversal speed for the Me109 can be derived in FB 1951 and is around 611 mph while the Spitfire had only 510 mph (source avia report 6/10126 from the RAE).The supposedly rugged P47 has a reversal speed of only 545 mph (source NACA report 868).

Let's have look to RAE 1231:



Now just use your favorite method to convert EAS (IAS with type specific corrections) to TAS.

gripen

[Knegel]

Kurfi,

slowly you drive me Nuts!

Your personel attacks to gripen miss any base!!

He present arguments  while you offer polemics after you think your arguments fail!

The calculation from TAS to IAS is pretty easy, if factor 0,849 or 0,861 dont make that a big different at all, althought i have to agree that 0,8 is far off!

If you have a Rechlin Be109F rolltest, which show IAS, please offer it! I would for sure like to see a faster rolling Bf109!!

After recomparing your data curve, the DVL data curve in the 1st post and my data curve, i got aware of a other mistakes on my side!

1. I took 610km/h TAS as last "30kg max stickvariation value", instead of 620km/h (wrong estimation, probably at that moment i thought the vertical lines are in 50km/h steps).

2. While estimating the 30lb and 50lb values i took the kg lines as linear increasement, but its not! The middle between 10kg and 20kg is NOT 15kg, its rather 13,6kg!!  Therfor the 30lb(13,6kg) peak is now at 223mph, instead of 210mph, and the 50lb peak is now at 287mph, instead of  274mph!!

Nevertheless your 30lb line show the flat angle of the 30lb line, therefor i still think its the wrong calculated 30lb line. Mistakes are fast made and can show significant differents!

Anyway, the Bf109F is bad in rolling at highspeed, if we compare it to most other fighters in this graphic!

btw, the SpitVa test i have, show a max stickdeflection with 50lb only up to 145mph, therfor we dont find a 'max deflection' line in this graph, which start at 160mph.
The Hurri II test show a max stickdeflection with 50lb up to 165mph, so we dont will see the typical sharp edge too.
Looks like the linkage of this both planes was setup for better highspeed movements! This explain the relative low slowspeed rollratios and the relative good highspeed results.

Another btw: I would like to know to which direction the 109F did roll in the DLV test and to what direction the other planes did roll?

I just took notice that the SpitVa and Hurri II show the slower roll to the right side! The 50lb peak value of the SpitVa(rolling left) would be around 75°/sec at around 220mph, the Hurri II have a peak value of around 69° at around 280mph(the 50lb rollratios to the left are  comparable with the 60lb rollratio to the right side).

And another btw: Iam not sure if the loadout of the planes (weapons/fuel) dont influence the rollratio! More weight = more yaw moments and more weight outside of the rollcenter. For a  middle or shoulder wing plane this wouldnt count that much, but in a low wing plane, with wingmounted guns, the weight of this guns is far outside of the rolling center, therfor they probably will cause some problems. Specialy if realy the guns, not only the amunition was left  and the tank was half full. This would bring around 400kg weight, this would decrease the needed AOA and would result in total different behaviour!

If the high result of the Spitfire in the NACA comparision realy was made without guns and half fuelload, if would explain much!

The HurricaneII in my test had 7014lb, thats 200lb more weight than normal gross weight, but the SpitVa had only 6237lb and was flown with 6184lb, thats almost Spit1a level!!

And another btw: Although the Spitwing was big, it had only a aspectratio of 5,6, while the Bf109F had 6,1. Therfor the Spit wing in general could be more thin without to lose stability in relation to the Bf109 wing!! Next to this the 109 had a higher wingload by default, therefor the wing was under higher stress in general!
How it realy was only tests can show, i only want to negate the agrument of a big + thin wing = less stable. The aspectratio much to often get forgotten, not only regarding the lift and drag!

 
Greetings, Knegel

[gripen]

Originally posted by Knegel

The calculation from TAS to IAS is pretty easy, if factor 0,849 or 0,861 dont make that a big different at all, althought i have to agree that 0,8 is far off!

Well I actually said that:

"TAS value is roughly 20% higher than IAS value depending on conditions. As an example 400 mph IAS is about 770 km/h TAS."

It means IAS to TAS and inverting results (rough) TAS to IAS correction factor 0,844 (650/770).

Originally posted by Knegel

Looks like the linkage of this both planes was setup for better highspeed movements! This explain the relative low slowspeed rollratios and the relative good highspeed results.

I don't think so; the roll rate curve should have a sharp corner when the stick force limit is reached. More likely reason is loose linkage because it explains the unlogical curve. In addition movements mentioned in the report are normal.

Originally posted by Knegel

If the high result of the Spitfire in the NACA comparision realy was made without guns and half fuelload, if would explain much!

The report does not specify the weight or condition but I don't see a reason why should RAE made a large fighter aileron comparison with non standard planes (even gun camera films from real combat were studied). Besides, the Bf 109F report only claims full tankage.

BTW if you are interested to see "the stuff" just give the address (send a privat message).

gripen

[Knegel]

Hi ,

770km/h TAS with the (still low factor) of 0,844 is 404mph, not 400. With factor 0,849 its 406mph, with Kurfis 0,86 its 411,5mph.

11,5mph = 18,5km/h, thats not a bit in such a comparison!
If the IAS/TAS factor realy was 8,6 when the test got recalculated to TAS, we should use it! I took 0,849!

Anyway,

"I don't think so; the roll rate curve should have a sharp corner when the stick force limit is reached. More likely reason is loose linkage because it explains the unlogical curve. In addition movements mentioned in the report are normal."

What stick force limit?? As i wrote, the original test show that they couldnt reach the max stickvariation from 145mph onward, so the sharp corner isnt visible on the NACA comparison, cause it start with 160mph.
But i mixed it up, its a slowspeed setup, with a smal leverage, that explain why the max stickvariation only can get reached up to 145mph with 50lb.  A longer leverage would increase the rollratio at highspeed.
They wrote: "It may be comcluded, therefor, that there was very little reduction in aleron effectiveness eighter by seperation or flow near minimum speed or by wingtwist at highspeed."

Private message is send!

Greetings, Knegel

[gripen]

Originally posted by Knegel

770km/h TAS with the (still low factor) of 0,844 is 404mph, not 400. With factor 0,849 its 406mph, with Kurfis 0,86 its 411,5mph.

I don't see much point to argue about 10 mph differences. 2% per 1000 ft is pretty much universally used quick and dirty IAS to TAS conversion factor. We are not talking about exact values here because the exact conditions are not known and I have not made any exact claims about the values during this thread.

Originally posted by Knegel
What stick force limit?? As i wrote, the original test show that they couldnt reach the max stickvariation from 145mph onward, so the sharp corner isnt visible on the NACA comparison, cause it start with 160mph.

Actually you are continously mixing NACA and RAE comparisons.

The NACA comparison was done with 30 lbs stick force limit. The Fig. 2 shows roll rates with 30 lbs stick force and the notable thing is that curves of the Spitfire and Hurricane does not typical sharp corners as can be seen in the P-40 and P-36 (RAE and RAAF  comparisons also show this):



Most probable reason for this is that the tested Spitfire and Hurricane had plenty of loosenes in aileron linkage. The curves can be compared also to RAAF comparison with same 30lbs limit:



It can be seen that the NACA data misses the peak (probably due to loosenes) but otherwise the curves are quite similar showing about 50-60 deg/s at about 100 mph IAS and bit over 20 deg/s at 400 mph IAS (aproximated).

Basicly, if the NACA tested Spitfire have had no loosenes in the aileron linlage, it would have reached about same peak rolling performance (about 80 deg/s) as RAAF tested with 30 lbs stick force.

The 50 lbs curves in the NACA 868 come from the RAE fighter aileron comparison (RAE 1231 is one of the report produced). Notable thing is that if you aproximate the 30 lbs curve from the RAE 50 lbs curve, it will be quite close RAAF curve.

Originally posted by Knegel
But i mixed it up, its a slowspeed setup, with a smal leverage, that explain why the max stickvariation only can get reached up to 145mph with 50lb.

The leverage is irrelevant in all these tests because these all give the roll rate with given stick force. And all these tests had a standard Spitfire V, the differences are caused by different stick forces and probably the loosenes in the aileron linkage of the NACA tested Spitfire as can be seen from the curve.

Originally posted by Knegel
They wrote: "It may be comcluded, therefor, that there was very little reduction in aleron effectiveness eighter by seperation or flow near minimum speed or by wingtwist at highspeed."

That has nothing to with leverage and it is a wrong conclusion as pointed by RAE in their comments on NACA tests on the Spitfire:

"Stability and control in a high speed dive. This was not touched, since the highest speed attained during the tests was 295 m.p.h. Vi. Neglect of the vital speed region round 400 m.p.h. Vi resulted in erroneous conclusions being drawn from the measurements at lower speeds. For example it is stated that "there was very little reduction in aileron effectiveness either by separation of flow near minimum speed or by wing twist at high speed." Actually, of course, loss of aileron power due to wing twist at high speeds is one of our biggest problems on the Spitfire - at 400 m.p.h. Vi about 65% of the aileron power is lost thereby."

gripen

[Knegel]

Hi,

"I don't see much point to argue about 10 mph differences. 2% per 1000 ft is pretty much universally used quick and dirty IAS to TAS conversion factor. We are not talking about exact values here because the exact conditions are not known and I have not made any exact claims about the values during this thread."


11mph make a huge different if shown in the NACA comparison graphic!


"Actually you are continously mixing NACA and RAE comparisons."

I talk about the NACA SpitVa test, the rollratios i did include in the NACA comparisons.


Page to D/L the Spit test is here: http://mitglied.lycos.de/luftwaffe1/

"......the notable thing is that curves of the Spitfire and Hurricane does not typical sharp corners.................. .
Most probable reason for this is that the tested Spitfire and Hurricane had plenty of loosenes in aileron linkage. The curves can be compared also to RAAF comparison with same 30lbs limit:"

There is the typical sharp corner! Look to 100mph for the Spitfire, this is what the SpitVa test say: " With a stickforce of 30 pounds, full deflection of the alerons could be obtained only at speeds lower than 110 miles per hour."  and " The excessive forces required to reach high rolling velocitics and the impossibility to obtain maximum aileron deflection much above 140mph miles per hour are also illustraited."

"The leverage is irrelevant in all these tests because these all give the roll rate with given stick force. And all these tests had a standard Spitfire V, the differences are caused by different stick forces and probably the loosenes in the aileron linkage of the NACA tested Spitfire as can be seen from the curve."

The leverage is not irrelevant, if we try to explain why a plane have a special behaviour and why the different Spitfires have different behaviour. Thats what i did try. SpitVa test and the P36,P40, Spit,Hurri comparison show similar results, while the 30 lb and 50 lb comparison show that a other leverage must got used!

"That has nothing to with leverage and it is a wrong conclusion as pointed by RAE in their comments on NACA tests on the Spitfire:"

Thats right, it was only another point to show.  


Greetings, Knegel

[gripen]

Originally posted by Knegel

11mph make a huge different if shown in the NACA comparison graphic!

Well, we don't know the exact conditions so we can't claim any exact IAS value. What we do know is that in the RAE comparison the values are corrected to EAS, which, at least in some degree, gives comparable values. Infact values used Kurfürst might contain type specific corrections making them less comparable.

Originally posted by Knegel
I talk about the NACA SpitVa test, the rollratios i did include in the NACA comparisons.

Yep, thats exactly the same plane as used for the NACA comparison between  Spitfire, Hurricane, P-36 and P-40 and it shows same unlogical roll rate curve.
 

Originally posted by Knegel
There is the typical sharp corner! Look to 100mph for the Spitfire, this is what the SpitVa test say: " With a stickforce of 30 pounds, full deflection of the alerons could be obtained only at speeds lower than 110 miles per hour."  and " The excessive forces required to reach high rolling velocitics and the impossibility to obtain maximum aileron deflection much above 140mph miles per hour are also illustraited."

Yes, there is a corner but unlike RAE and RAAF test, the roll rate increase still after corner. No other plane in the charts with frise type ailerons show similar curve (except Hurricane in the NACA test, which probably got similar mainteance). The most likely explanation for this is loosenes in the linkage.

Besides it should be noted that NACA choosed to use RAE values for the Spitfire instead their own test values in their after war summary of lateral control research (NACA 868). IMHO for a good reason.

Originally posted by Knegel
The leverage is not irrelevant, if we try to explain why a plane have a special behaviour and why the different Spitfires have different behaviour. Thats what i did try. SpitVa test and the P36,P40, Spit,Hurri comparison show similar results, while the 30 lb and 50 lb comparison show that a other leverage must got used!

No, the charts give directly the stick force. Regarding the leverage, only meaningfull measurement is amount of the stick movement, longer movement giving the better leverage. All these tested Spitfire Vs (NACA, RAE and RAAF tested) had exactly same leverage (even the clipped winged Spitfire V), the differences are caused by different stick forces used for the test, normal variation between planes and also probably the condition of the plane (specially in the case of the NACA test).

gripen

[Knegel]

Hi,

if the leverage was the same, how do you explain that one Spitifre can keep full stickvariation with 30lb up to 160mph, while in the other Spit the max stickvariation stop with ALSO 30 lb below 110mph?? Highspeedproblems are not relevant here!

Loosens in the lincage that make a different of 40mph i would count as bad damage and would  be pretty good visible in the 'initial roll curve', but its not!

The increasing rollratio up to 220mph, in the rollratio curve of the SpitVa, is caused by the fact that the stickforces dont increase linear with the alerondeflection.

The test say: "The alerons were relatively light for smal deflections, but the slope of the curve of the stick  force against deflection increased progressively with deflection, so that about five times as much force was required to fully deflect the alerons as was needed to reach one-half of the maximum travel. The effectiveness of the alerons increased almost linearly with deflection all the way to the maximum position."
(of course at the measured speed of max 300mph, as you stated, the other test show that at higherspeeds this was different).

As result we get a increased rollratio up to 220mph!
Before 220mph the still big deflection of the alerons caused a greater stickforce in relation to its influence to the roll speed. At 220mph with same stickforce the aleron deflection was only a bit smaler than with 200mph, but the effectivity did increase linear, so the rollratio increased. Above 220mph the 'crossline' is reached, so the same static stickforce wasnt enough to let the plane roll faster.    


Imho the two tests show that the leverage relation in the SpitV was absolutly messed up, therfor iam sure they changed it in later Spitfires, which gave a much better result, cause they was able to obtain greater alerondeflections at higher speeds.

btw, the stick itself dont need to get changed to change the leverage, this can get changed by a part in the wings or below the stick.

Greetings, Knegel

Edit: The Hurri had same behaviour, here is what the test say:
"It is interesting to to note that the force requiered to attach the rolling velocity of 0,6 or 0,8 radian per sec decreased as the speed was increased from 100 to 200miles per hour. This unusual condition results from the rapid increase of stickforce near maximum deflection"

[gripen]

Originally posted by Knegel

if the leverage was the same, how do you explain that one Spitifre can keep full stickvariation with 30lb up to 160mph, while in the other Spit the max stickvariation stop with ALSO 30 lb below 110mph??

Where do you see a Spitfire keeping full stick movement up to 160 mph IAS with 30 lbs stick force?

If I use (rough) linear estimates, the RAE tested Spitfire V (normal and clipped wing) would have reached full stick movement up to about 140-150 mph IAS with 30 lbs stick force. These values are about same as tested by RAAF.

Originally posted by Knegel
The increasing rollratio up to 220mph, in the rollratio curve of the SpitVa, is caused by the fact that the stickforces dont increase linear with the alerondeflection.

Actually that is further evidence that there was something wrong in the aileron linkage of the NACA tested Spitfire; RAE and RAAF data shows quite linear increase in stick force.

Generally feel to believe what ever test data you want to believe but to me it's quite obivious that the NACA tested Spitfire had problems in the linkage and probably in airframe over all due to extensive flying in the states. And that seem to be also the opinion of the NACA because they choosed to use RAE data for their later works.

gripen