Bf 109E rate of roll

[Kurfürst]

Here's a more complete version from niklas's site,showing stick forces as well, it's not quite even playing field.. I wonder if anyone



There are some comments of 109E roll rate in the August 1940 Luftwaffe tactical comparison on my site : http://www.kurfurst.bravehost.com/


I've seen an article on a recently restored 109E test flight, the pilot said the ailerons were very impressive, and he compared them to the spit w metal ailerons, but 50% higher roll rate, but nothing more specific. I suppose because of the square wingtips of the 109E..?

Speaking of clipping, I always wondered about that clipped/Unclipped Spit roll rate graph. It seems to originate to RAE, but the trouble with it is that half a dozon reports I have on the same things is just showing it's something alien.

I have ww2 pilot queries, in which they were asked wheter they could compete the 190 in roll - the vast majority said not a chance, ask back for normal wings. I have pilots on restored warbirds, they say the metal ailrons were pretty much the same as the 109s (ie. 80-90 degrees peak), and the clipped at 3 secs for a 360 degree roll. The NACA tests specifically says they can't obtain full deflection over 140 mph ias with 40 lbs, and RAE in comparison with the Mustang notes 45 deg/sec roll rate at 400 mph ias would require 72 lbs stick force on the Spit.

Then there's the British tests on wheter clipping worths it or not, and they say...


Finally here's some timed roll rate tests on two spit 12s, one was considered having 'poor' ailerons, the other good ones, decribed in the rest of the report. Linked via M williams site : http://www.spitfireperformance.com/mk12roll.gif It agrees well with the findings of RAE posted above.

Compare with the trend on NACA roll chart posted. It just don't agree at all, and I wonder why is this, I tend to b inclined that this is probably showing some MkV experimental aileron type testing, there were quite a few such tests in 1943. Does anyone have a detailed report that the NACA roll chart is originated from?

[Juha]

Hello Kurfürst
I expected that You can deliver some facts. Quill also flew a captured Bf 109E in Oct. 40. According to him (Op cit. p. 183) "to my surprise and relief I found the aileron control of the German fighter every bit as bad, if not worse than, at high speed as the Spitfire I and II with fabric-coverred ailerons. It was good at low and medium speed but at 400 mph and above it was almost immovable."

CJE
Best I came across is the following info on Bf 109F-4. Source: Jukka Rautio's Mäntämoottorihävittäjän suorituskyky Osa 6 in Suomen Ilmailuhistoriallinen Lehti pp. 10 - 13. According to it DVL's test results in spring 44 were (flown at 3000m because it was not possible to do the tests at the planned 6000m due "the enemy's air activity")
The fastest roll was made at 500kmh (TAS), time for full roll (360deg)was 4,5 sec. at 600kmh time was 7 sec and at 700kmh 13,5 sec.

Juha

[CJE]

Thanks to all for this most interesting discussion.
French also test-flew a captured E-4 but strangely enough they did not bother recording its rate of roll.

[Kurfürst]

Hi Juha,

I have that DVL flight test, and it's indeed by far the most detailed roll rate test I have ever seen, probably because it's was done for theoretical research work! I was very impressed with it, though the stick forces appear to be much higher than reported in Finnland tests I am aware of, and Southwood's oral account. These datasets may be incompatible, or maybe it's effected because the testbed aircraft in DVL's tests was Bf 109F, by late 1944, it was quite possibly a bit worn out.

As for J. Quills comments, they seem to be very nicely aligned with British findings, the roll rate at high speed seems equally bad, though the stickforces on the 109 are much lower. I wonder if the full British report on that has more.

[Graham Boak]

It's a long time since I read the US report, but on the graph it states "increased wing". As the US received an HF Mk.VII (now in the NASM) this will refer to the high altitude extended tips - not the standard wing. Comments?

I must admit being surprised that the RAE were unable to detect a difference between the standard and clipped roll rate. If it hadn't produced any difference, it would not have passed initial trials and disappointing comments from the service would have prevented it being widely adopted. Perhaps there was some psychological effect? Alternatively, could this have anything to do with differences between the maximum roll rate achievable and the time taken to reach this?

[Juha]

Firstly micron468
Thanks for the graph, much appreciated!

Kurfürst
Yes, the test subject was wing twist. On the results, IMHO the roll rate was rather good at 500kmh and at 600kmh. Do You know at what altitude the other tests were made? According to Raunio the problem in the test was that the pilot could not turn the stick greater than 20 kp force at 600kmh because of the narrowness of the cockpit and so was able to use only 6 deg. aileron at that speed. At higher altitude the ailerons should have been lighter. Also in 109G the skin of the wings was thicker so there should have been less aerodynamic twist and a little better rollrate at high speeds.

BTW the Raunio's article was in number 3/2005, I left that out in my earlier message.

On British test on 109E, I cannot remember seeing any graphs of it but in Quill's book pp. 183 - 184 "The A & AEE reported on the Me 109E in Oct. 1941:"The flying controls have excellent response and feel at low speeds but are far too heavy for manoeuvring at high speeds. The extreme heaviness of the ailerons makes rolling almost impossible at speeds obove 400mph."

But if Spit Mk V with metal covered ailerons could achieve only 40 deg/sec at 400mph(640kmh) (at what heigh?) and 109F-4 could made a full roll in 7 sec at 600kmh, was 109 so bad, at least from F onwards?

Juha

[Graham Boak]

It'll be IAS, so the height is irrelevant. The Mk.V could only achieve 400mph in a dive, anyway.

[Juha]

Thanks Graham, I suspected that, so Smith's graph is identical to that of NACA. Do You Know what was appr. IAS equivalents for 109F 's 500kmh (TAS) and 600 kmh (TAS) at 3000m? Or other way around what were appr. TAS equivalents for Spit V's 310mph (IAS) and 375mph (IAS) at 10000ft?

Also 109E could achieve 400mph only in dive and I think same was true for F-4 at 3000m.

Juha

I should have first look my archives, so for 109F-1 and -2 at 3000m 469kmh (IAS) = 553kmh (TAS) and 486kmh(IAS) = 573kmh (TAS). Source Kennblatt for Bf 109F-1 and F-2. Berlin 1941.

To be honest I was thinking that the difference between IAS and TAS in this case was appr. 50 kmh but it seems to have been appr. 85kmh.

[Juha]

And 35mph (56kmh) seems to be rather good appr. for the difference between IAS and TAS for Spit Mk V at around 310mph at 10000ft. This according to some tests shown at www.spitfireperformance.com.

Juha

[Graham Boak]

True Air Speed is Equivalent air speed divided by the square root of the relative density (sigma). I think you can assume that for this flight region Equivalent airspeed equals indicated airspeed. This may introduce a few knots difference because of the pressure error on the Spitfire's instruments.

for sealevel root sigma = 1 (by definition)
for 10000ft root sigma is 0.8594
for 20000ft 0.7299
for 30000ft 0.6117

You can interpolate for other heights from that. Values come from the International Standard Atmosphere as tabulated by the Kingston (Hawker) Project Office 1964.

So 310 kts IAS at 10000ft is 361 mph
375 mph at 10000ft is 436 mph