Flaps of the 109

[niklas]

I want to start another discussion about the flaps of the 109. Imo there´s a misunderstanding by HTC that leads to an unacceptable low maximum airspeed of the 109 flaps.

I haven´t found ANY proof in all manuals i have for the 280km/h speed limit in a flight with flaps just 20-30° down. It doesn´t exist afaik, if you have a proof pls show me.

First of all to the maximum Speeds with full flaps down:

The F1/F2 description says:


Maximum Speed was 300km/h or 186mph with full flaps down, the F4 in AH m raises full flaps at ~165mph or so. I don´t know whether they changed the wing of the F4 compared to the F2, afaik they did not.

Then there´s a interesting note about the G2:



So maximum speed for full flaps down is ~155mph what seems to be modelled correctly.

But there´s absolutly no hint about the maximum flying speeds with flaps just 20° or 30° down.

What IS mentioned in the G2 manual is the flying limit to OPERATE the flaps SIMULTANOUSLY with undercarriage, also just 250km/h. But this is absolutly no hint about the maximum speed allowed for 20-30° flaps.

Why did germans care about operating limit? Well, flaps produce a pitch down moment (not modelled in AH), undercarriage (drag below COG) too logically. THAT was really dangerous and THIS was obviously the reason for the rather low OPERATING limit but not the FLIGHT limit once 20 or 30° were set and the aircraft trimmed!!!! (The limit for operating flaps ALONE isn´t given btw.)

The germans seem to be punished for something only because they were more precise in forseeing problems during flight that have definitly also blessed any other fighter at this time (though the fw190 was well known for small trim changes with undercarriage and flap usage). Just because allied manuals don´t mention speed limits for operating flaps doesn´t mean that their fighter did not react violently when pilots suddenly turned down flaps at 400mph!!!

So what was the absolute flight limit for the 109 with flaps just 20 or 30° down? I can´t say it exactly, but this little part is from a work dealing with turn fighting of the 109E:



It says:
"... . In relation to the gain of cL with flaps up to a deployment to bKL = 30°,  regarding R(adius) the further deployment to 40° or 50° gives no advantage. The optimum for turning time is generally for flap angles between 25 and 30°.
For the tactical usage in dogfights, for the 109 E a flap down angle of 25° can be allowed immediatly at 400km/h and Alt. 0 with using a RAM limiter and RAM relais (Note: probably for automatic switching back to lower angles when the speed was exeeced). For the Me110C with same circumstances an angle of 28° can be allowed. The fixing flaps and operating of the horizontal stabilizer(trim) has to be released (Note: obviously operating flaps trimmed the 110 up)"

So the dangerous point was about 400km/h or 250mph for the 109E with 25° flaps.

Compare it to allied speed limits. For the P51 III 275mph was allowed at 20° flap angle,  less angles at slighty higher speed. And the 109 pilot could set ANY low angle, 5, 10, 15°, whatever.

Because a special relais should start working 400km/h ( this relais enjoy  all fighters in AH btw...) you can assume that the real critical  speed was even a bit higher.

Because all fighters in AH enjoy the automatic realease though i doubt that they had it in real life i don´t see any reasons why not to clear the 109 for higher speeds with flaps at low angles.

Btw i think the same misunderstanding flap operating speed and flap maximum speed limit applies to the 190. Again, pls. don´t punish german fighters because they were more detailled and careful to their pilots mentioning operating speed limits in their manuals.

Thx
niklas

[storch]

This really needs to be done again.  There is no basis for the any of the LWs flaps being limited as they are.  Perhaps Pyro will be able to correct the modelling in the next version.

[Angus]

Ok, my 5 cents.
The flaps were manually deployed right, with a wheel on the left side. I've read that deploy time from nil to full was about 30 secs.
So, model that in AH, it's a liability.

But what about the upper limit then?
This is a completely stageless flap deployment. I bet you could squeeze down some flaps at quite high speeds, while easily deploying at low speeds.

Or am I wrong?
Quite curious really.

[HoHun]

Hi Niklas,

Here's the deflection limit over speed curve for the Me 109E.

I'd assume it was similar for the Friedrich and following models.

Regards,

Henning (HoHun)

http://hometown.aol.de/WBHoHun/1-109-2.jpg

[Angus]

So, you could squeeze down flaps some at very high speeds.
Would the upper limit be a force factor then?

[Crumpp]

Great post, Niklas!
Thanks for posting that document as well Henning.

Crumpp

[niklas]

Nice chart Hohun. The numbers in my doc goes along with it, confirming it, being a bit more conservative (typical...) with "only" 400km/h @ 25°.

I also assume that the Friedrich and Gustavs were comparable in this aspect. Weren´t the wing strenghtened from time to time with later models?

It´s interesting that the flap usage isn´t mentioned in any flight manual i have. Probably it was considered as a kind of tactical secret at the outbreak of the war. The british testing the Emil did  not spend a single trial on using flaps in turn fights afair. Well, they knew only all or nothing from their own fighter. Huh, being not accustomed to slats they were already frightened enough by these devices in turns....

niklas

[VO101_Isegrim]

Originally posted by niklas
I also assume that the Friedrich and Gustavs were comparable in this aspect. Weren´t the wing strenghtened from time to time with later models?
niklas

The wing was definietely strenghtened while going from F to G. A description sheet of the 109 G-1 notes the the entire wing structure was beefed up (main spar, ribs and plating). I suppose this was due to the heavier underwings loads the 109Gs were supposed to carry (gondolas, drop tanks etc.).

[Angus]

The wing got strengthened throughout the series, so did the tail section, and perhaps the fuselage.

But to this:
"It´s interesting that the flap usage isn´t mentioned in any flight manual i have. Probably it was considered as a kind of tactical secret at the outbreak of the war. The british testing the Emil did not spend a single trial on using flaps in turn fights afair. Well, they knew only all or nothing from their own fighter. Huh, being not accustomed to slats they were already frightened enough by these devices in turns"

Duhh.
The British were well accustomed to slats, after all they had a history with Handley-Page, - exactly the same design as the 109 slats.
Slats are however no magic, although a very clever move IMHO.
Cleverly designed flaps do create more lift than slats, and if a whole arm is not required for wheeling them down in the middle of combat, the better vote goes to being able to deploy them with say, a finger.....

It's like claiming that a Bicycle is more advanced than a motorcycle

[Crumpp]

The British were well accustomed to slats, after all they had a history with Handley-Page, - exactly the same design as the 109 slats.

I don't know Angus.  When you see things Like "embarrassed by it's slats opening up"  you have to wonder just how accustom that test pilot was to the slats.

IMO he had no clue how they were used.

Crumpp

[Wotan]

Angus has no clue either. A week ago he didn't know how 109 flaps worked, now 'he's read it takes 30 secs' to crank the wheel.

Wasn't he the one claiming the 109 slats 'routinely broke' or some such nonsense?

Anyone can go back and read what 'Brits' thought of the 109s slats and you get picture that they either had no real understanding of them or that as Niklas states they were unfamiliar.

Even Angus's reply here:

'a whole arm to drop flaps' is ridiculous. As if the 109 needed both hands on the stick or something.

Ask him the Spitfires flaps 'up or down'
 thats it...

How advanced was that?

[Crumpp]

Angus has no clue either.

I wholeheartily disagree.  Angus is a very intelligent and fair individual whom I think very highly of.

I have not seen him be anything but fair.    I will say too that folks in this forum take any slight to their "favourite plane" with way too much emotion.  The dynamics of the 109, P38, AND some of Spit crowd is a complete turn off.  

I am not innocent either and have thrown my share of stones.

On the whole I value Angus's input.....

In spite of his obvious Spitfire bias.


Crumpp

[Angus]

Ok, Wotan, I hear an ecco inside yer skull, so lets fill in the void a bit, shall we. Straight from the Horses's mouth
A week ago approximately, I did indeed ask how they worked, from memory as I went, I asked about whether they were manually deployed, and how long it took, my memory saying something like 30 secs from none to full.
Nobody has quoted any precise times at given speeds may I add, so I just take the liberty of suggesting that nobody knows better.
I guess you suggest that cranking was perhaps quicker than using pneumatics? Well, bring up some info, please.

Now to the slats.
I was involved in the infamous slat thread, and immediately managed to insult some merry band of 109 fans by merely suggesting that if the slats myth of undesirable "snap" effect were true, they could originate in lack of maintenance/damage problems rather than the aerodynamic design itself.
Well, this was not accpepted in any form.
"109 SLATS ARE PERFECT AND CANNOT FAIL" was the word.

So, I did what probably nobody else did. I read up and made several calls.
Results are displayed in the slats thread.
A quick summary:
1. From IAR aerodynamic textbook:
The slats have to be well balanced and glide easily to have the desired effect, otherwise they really don't
2. From an old 109 Document, I can write it up if you like:
The aircraft needs to be "flown in" very carefully for the slats to be well balanced.
3. I called an old LW Wingco, who flew from the early 60's onwards. His tutors were the old-core LW aces, Rall, Steinhoff, Hartmann. Ok, he loved the slats, especially for landing. The rough side was the sudden amount of lift when they deployed. This actually caused wing failiures of some Phantom Jets.
4. Some persons on the thread still insisting that I had nothing in my hands, no sources, etc, etc, finally pissed me off enough, so I just phoned Gunther Rall.
He solved the myth in one go.
"In a rough turn, the outboard slat would deploy, and snap the aircraft.
"I did not like them in combat"
"They were however very good when landing. Without them the landing speed would have been very high"

So, please tell me I have no clue about what I am typing.
When I ask, I am looking for some information, - sometimes I don't bother telling that I may know much more than nothing.
And I do make an effort to gather information and learn some, - I do not pretend to know everything.
But in that slat matter, and now it comes to the flaps, it seems that there are some who's mouth is bigger than brain.

Regards

Angus

[Wotan]

Angus you just make it as you go...

[Angus]

Can you be more specific?

Or are you just saving yer sore arse?

Your 6, that is