Messerschmitt 109 - myths and facts - article now out

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Uncle Joe
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Post by Uncle Joe » 27 Mar 2005 10:37

Topspeed wrote:I confess that when stating 10-12 G:s with a Me 109 and 15-20 G:s with a Mustang I had no factual basis on my claim. Thanks for the accurate data you brought along Huck.
Possibly the Mustang wings bent at 10 G:s and a violent stall which causes to loose conciousnesss with a Me 109 occurred at 7-8 G:s.


Either way; what I mean is that Mustang wings bent before the stall occurred at high speed ( 470-550 mph ) and Me 109 when pulling too hard caused the plane to flip on its longitudal axis very rapidly to the left ( torque related )...plane remained intact.

I did practise this phenomena with a flying scalemodel of both Me 109 and P-51D ( same scale and same engine ). Results indicated the same I stated here earlier. 109 model snapped rapidly if one applies stick back from a high speed...when doing the same with a Mustang and it initiated a loop without a problem.

I restate what I said in the beginning of this debate; Me 109 high speed stall is vicious and takes place without a warning. It may be also called accelerated stall as Uncle Joe here mentioned.
To get an idea of 109 stall, please take a good look at Jukka Raunio´s "Lentäjän Näkökulma II". It has excellent info on 109 handling taken from test reports etc. 109 g-stall stall was one of the mildest in WW Two fighters while that of the P-51 was one of the harshest. Did your scale model have properly working slats?

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Topspeed
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Post by Topspeed » 27 Mar 2005 10:53

Raunio has no mentioning about this phenomena in his book.

He is talking about normal stall. Slats were only operative at low speeds. In accelerated stall at under 350 km/h.

But he says that the stickforces were exceptionally heavy; possibly to avoid stalls in a battle ! So he hints that there was an intentional "locking" to avoid such a situation.

I base my finding of this phenomena on the description of a pilot who did experience it on a dogfight against La-5s. He barely regained conciousness before hitting the waves at the Bay of Baltic Sea and actually managed to save the plane and scored a La-5.
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Grendel-B
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Post by Grendel-B » 27 Mar 2005 18:25

Topspeed wrote: I did practise this phenomena with a flying scalemodel of both Me 109 and P-51D ( same scale and same engine ). Results indicated the same I stated here earlier. 109 model snapped rapidly if one applies stick back from a high speed...when doing the same with a Mustang and it initiated a loop without a problem.
You don't really mean experiences with SCALE MODEL planes equal real plane's behaviour? Oh mercy. Those are two completely different things. Aerodynamics, speeds and equipment is different. They're no way comparable to the real thing.

So far I haven't seen any evidence in any literature or in any interview with 109 pilots that Me 109's high speed stall was any different from normal stall - which was very well behaving, almost elegant. Even more important, who the hell a 109 pilot even could make a high speed stall - since in higher speeds the stick was stiffer than in low/medium speeds and it was very hard if not impossible to pull the stick so much fast enough to make such elevator deflection.

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Post by Topspeed » 27 Mar 2005 19:59

Well then you haven't read all the aviation books available yet.

I dunno how many times one has to repeat this but this regular stall at low speeds in an aircraft is a different phenomena than so called high speed g-stall.

Mustang has very nasty stall and Me 109 had slats to compensate the reduced wingarea caused otherwise early stall caracter. However slats did not compensate the stall at high speeds. To prevent the 109 from stalling the stickforces were made extra heavy to prevent this pilot induced error from happening. This can be read from the " Pilot's Viewpoint II " by Jukka Raunio that was earlier mentioned by Uncle Joe.

I agree with Grendel-B that scalemodels are not quite like the real thing. OTOH I am certain that they are much more reliable source in WW II fighter behaviour than some aviation enthusiasts " I think it behaves like this mode " of some dedicated computer simulator " ACES "-games. Especially good are the 1/12 scale models hence they are in power to weight ratio wise close to originals and bigger Reynolds number compensates to some extent with lesser wingloading of the small models.
I especially enjoyed to fly a 109 model...after I got to know all its nasty habits I easily learned to avoid them...high speed or accelerated stall was one of them..large turning radius is one aspect good to remember too.
Mustangs are fun too, but the laminar airfoil of a P-51D does not work in a model, but still it is a pleasure to fly...I think next thing would be to study a scale model laminar foil for a Mustang. : )

IMHO please Grendel-B don't tell me how close these models are to real thing or aren't . After you have succeeded 150 flights without a mishap then tell tell me if they fly like the real or not, since you obviously ave no glue what ya talking about when you refer to present day aircombat models.

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Post by gabriel pagliarani » 28 Mar 2005 08:27

1:5 is the limit under which aerodynamical effects are not reproducible by models. If the model is reduced to less than 1/5 of the original span, even if all the shapes are identical even if reduced, aerodynamics change. This phoenomenon is linked to the dimensions of air moleculas. About the fine P51 document send by Uncle Joe, it contains a lotta of useful informations. The max dive speed limit 500 mph might be related or not to max stall speed: this is a structural limit and trespassing it the wings could be folded as a scissor stall occurring or not. Logically P51 was not a supersonic and its structure was limited under Mach limit ( over 500 mph) I have copied the downsided curve giving the stall imit when pushing the cloche at certain low speeds and I reproduced with a green stripe it in the positive region. Within the green limit the plane has a fully simmetrical behaviour or the cloche could be pulled or pushed in the same manner. The blue zone is the extra region showing the difference in attitude between PULLING THE CLOCHE (+G) and PUSHING THE CLOCHE (-G) Note that G limits provided by North American are +8G and -4G only: even if it was possible to trespass those for a while during a dogfight surely +20 G were out of the real possibility of the P51.

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Post by Topspeed » 28 Mar 2005 09:16

There is a AMA made research about the models behaviour in accordance to the original. It goes only for speeds and meneuvring.

All big models certainly look like they would fly like real ones, but according to study they are indeed the furthest from the real thing unless they'd fly 2x what they generally do. In this respect smaller models are closer to the real ones maneuvring.

Problem is that model flyers depend on what is available for engines and a 1/4 scale Merlin would cost too much.

Certainly for a windtunnel the 1/12 scale models are useles.

Get your hands into the stydy and you'd be amazed.
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Post by Topspeed » 28 Mar 2005 09:37

gabriel pagliarani wrote: surely +20 G were out of the real possibility of the P51.
Surely I corrected it into 10 ! :lol:

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Post by Uncle Joe » 28 Mar 2005 10:44

Topspeed wrote:Well then you haven't read all the aviation books available yet.

I dunno how many times one has to repeat this but this regular stall at low speeds in an aircraft is a different phenomena than so called high speed g-stall.

Mustang has very nasty stall and Me 109 had slats to compensate the reduced wingarea caused otherwise early stall caracter. However slats did not compensate the stall at high speeds. To prevent the 109 from stalling the stickforces were made extra heavy to prevent this pilot induced error from happening. This can be read from the " Pilot's Viewpoint II " by Jukka Raunio that was earlier mentioned by Uncle Joe.
Well, let´s see the horse´s mouth and read what Pekka Kokko writes in his report on which Raunio´s description is based on:"Koneen kaarto-ominaisuudet ovat sikäli hyvät muihin suuren siipikuormituksen omaaviin koneisiin nähden, ettei konetta jaksa vetää liian tiukkaan kaartoon ennenkuin nopeuden vähetessä alle 350 km/t ja vajaata moottoritehoa käytettäessä. TÄLLÖIN SAA ERITTÄIN TIUKASTI VETÄEN KONEEN SAKKAAMAAN LÄPI (capitals added, UJ), josta on seurauksena solasiivekkeiden aukeneminen ja korkeusperäsimen keventyminen. Vetoa vielä kiristettäessä ja nopeuden vähetessä pysähtyy kaarto ja kone alkaa vavahdella: vetoa jatkettaessa kone kiepsahtaa vasemmalle ja nokka painuu (kone muljahtaa), vetoa hellitettäessä sensijaan voidaan jatkaa kaartoa." So, what Kokko means is that when the 109´s slats deploy, the Mustang has already flicked out of the turn. So, you basically did not understand s single word of Raunio´s text.

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Post by Topspeed » 28 Mar 2005 18:24

I have had the book for 15 years and it is right beside me. Read all of it and you'll see the "light".

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Post by Topspeed » 28 Mar 2005 18:30

Grendel-B wrote: Even more important, who the hell a 109 pilot even could make a high speed stall - since in higher speeds the stick was stiffer than in low/medium speeds and it was very hard if not impossible to pull the stick so much fast enough to make such elevator deflection.
Well you'd be amazed how much force the pilots generate when the mr.Grim Reaper is knocking on your shoulder. I am not saying it happened often...as you say yourself and Raunio in the book the stickforces were made intentionally heavy to avoid it.

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Post by Topspeed » 28 Mar 2005 18:34

If you need to get informed about stall in general here is more info:
http://www.grc.nasa.gov/WWW/K-12/airplane/short.html

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Post by Uncle Joe » 28 Mar 2005 23:45

Topspeed wrote:I have had the book for 15 years and it is right beside me. Read all of it and you'll see the "light".
Why should I for it is obvious to anyone with brains that it is you who need to read the book again. Raunio´s thesis for the high control forces is avoiding of overstressing the structure in dive recoveries and manoeuvres (nothing to do with accelerated stall). He never mentions accelerated stall in this context. Never!

If your only reply to a quote from the official test report is a reference to a NASA site most suitable for juveniles, get ready for the men in white coats. Your delusions may lead to Lapinlahti or Harjamäki.

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Post by Topspeed » 29 Mar 2005 08:19

Maybe we are talking about different edition of the book.

I thought you were writing from a loonie house. Totally useless to start getting fresh with me.


Insert from the book ( translated in english page 247 ):

Longitudal control was possibly intentionally heavy. Means to lighten it were common knowledge. Great stickforces per each G were possibly made to prevent structures from braking or to prevent unintentional stalls during a dogfight from happening.

So Uncle Joe...tell me what is your problem ? :P

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Post by Topspeed » 29 Mar 2005 08:34

Uncle Joe wrote:
Topspeed wrote:I have had the book for 15 years and it is right beside me. Read all of it and you'll see the "light".
Why should I for it is obvious to anyone with brains that it is you who need to read the book again. Raunio´s thesis for the high control forces is avoiding of overstressing the structure in dive recoveries and manoeuvres (nothing to do with accelerated stall). He never mentions accelerated stall in this context. Never!

If your only reply to a quote from the official test report is a reference to a NASA site most suitable for juveniles, get ready for the men in white coats. Your delusions may lead to Lapinlahti or Harjamäki.
I think this text without any reference to reality will get you banned from here. I am sorry to say that.

I am also not talking about accelerated stall....just stalls during combat and in high speed turns.
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Post by Topspeed » 29 Mar 2005 08:36

Uncle Joe wrote: So, what Kokko means is that when the 109´s slats deploy, the Mustang has already flicked out of the turn.
Kokko does not mention Mustang.

I know perfectly the difference of a low speed stall between a Mustang and a Me 109. We are not talking about it here at all.

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