109s and Flaps

[gyrene81]

oh yeah i know what site you're talking about, i was just on it today, but i don't remember anything about a slip mechanism.

and 350kph is 217.5mph...not 189, i'll take the 217.

[morfiend]

oh yeah i know what site you're talking about, i was just on it today, but i don't remember anything about a slip mechanism.

and 350kph is 217.5mph...not 189, i'll take the 217.

 I said between those speeds,depending on source,remember these are pilot comments and gauges being what they are,we can take it as anecdotal and not factual.

  One pilot stated he buried the needle,thats over 900Km in a 109 and he pulled out with 50 meters to spare,do you think this is fact?

 It would make sense that some type of friction slip device was installed in the flaps wheel,there's several videos that show what you actually have to do to deploy the flaps in the 109. The only reference I could find about using them in combat was from Marseille,it's said he would offer turning combat and throttle down to reduce speed to deploy flaps. There's no mention of the airspeed,alt or how much flaps.

 Another thing to consider,IAS and TAS,which one is the pilot referring to?  you could be at 300mph TAS yet be at a low enough IAS to drop flaps,depends on alt.

       Of course most fights in AH are at such low alts that the difference between IAS and TAS is negligible.

[gyrene81]

i know, i've read the interviews repeatedly and the diving speeds they claimed to have survived are a bit outrageous...the one comment that struck me was about the flap speeds they supposedly used at 20,000ft in spite of being told not to, the interviewer didn't question if it was ias or tas. oddly no other pilots interviewed over the years disputed it.


so, let me ask you this, do you agree that 217mph is a good maximum safe speed for landing gear but not for 8 degrees of flap?

[morfiend]

Gyrene,

 this 217 does it come from POH? is so I would think you would drop gear then start to drop flaps as you had to turn the wheel many times to get to full deployment.

  Dont get me wrong,I'd love to see the 109's be able to drop flaps at higher speed,provided there's proof that they could in RL.

 We only have to press a button,a 109 pilot had to rotate the wheel something like 15 times to get full deployment.


   

  PS: It might have been in 1 of the videos that they state about the slip mechanism to prevent lowering at too high a speed,the ailerons also dropped with the flaps!

[FLS]

forgot to answer this. higher cofl is created from angle of attack and speed, leading edge slats change the (i believe) camber of the wing to increase the cofl at slower speeds and thus allow the plane to fly at slower speeds than it could without them, not 400mph. the 109 used automatic slats (unlike some modern aircraft) that deployed when aerodynamic forces on the leading edge of the wings decreased to the point where they could deploy, still not 400mph. is that a sufficient answer?

It's sufficiently wrong about the speed. Do you know what caused the aerodynamic forces to deploy the slats? As I mention a few times already in this thread, it's angle of attack. Any time you have the required AOA the slats deploy, regardless of speed. That's why they can deploy at 400mph. You can take 2 minutes and test this in AH. The K4 will be around 360 but the F will deploy over 400.  Flaps and slats both increase Cl. This increases lift for a given speed and AOA. It doesn't just happen at low speeds. The physics don't change when the speed increases. Slats and flaps still increase the Cl at high speeds. This means that slats can deploy at speeds where you might want to use 8 degrees of flaps. You just need to pull to the required AOA. If you're blacking out before you reach that AOA then you don't need flaps or slats until you get slower.

[Krusty]

Morf, there's also a good chance those WW2 tachs had major errors in high end speed. That's why they used ground speed confirmation with radar, not relying on instruments in the plane doing tests, for most official tests.

Edit: Also the ailerons both dipped either 10 or 15 degrees only on the maximum flap deployment. I thought that was rather clever of Messerschmitt.

[JOACH1M]

Can we all agree that flaps in a 109 are necessary in a dogfight

[gyrene81]

It's sufficiently wrong about the speed. Do you know what caused the aerodynamic forces to deploy the slats? As I mention a few times already in this thread, it's angle of attack. Any time you have the required AOA the slats deploy, regardless of speed. That's why they can deploy at 400mph. You can take 2 minutes and test this in AH. The K4 will be around 360 but the F will deploy over 400.  Flaps and slats both increase Cl. This increases lift for a given speed and AOA. It doesn't just happen at low speeds. The physics don't change when the speed increases. Slats and flaps still increase the Cl at high speeds. This means that slats can deploy at speeds where you might want to use 8 degrees of flaps. You just need to pull to the required AOA. If you're blacking out before you reach that AOA then you don't need flaps or slats until you get slower.

see that's where i think there is a small problem. on the g models the slats were installed on roller rails which made them more reliable and decreased the incidence of asymmetric deployment. but it also decreased the amount of aerodynamic pressure needed to make them retract because they weren't spring loaded. i did try it with the g6, g2, f4 and g14, below 5000ft high g turn at 335 up to 400+ mph and they do deploy as soon as you enter the turn, which doesn't make sense because they won't deploy when going into a nearly 90 degree climb at 350mph. close to the same aoa, should be the same aerodynamic pressure at the start as going into a turn.

i'm probably wrong and guilty of misinterpreting the technical information, been wrong before, but nothing i've studied says they should react the way they do in ah. you should peruse that site morfiend talked about...interesting first hand information about the slats
http://www.virtualpilots.fi/feature/articles/109myths/

Gyrene,

 this 217 does it come from POH? is so I would think you would drop gear then start to drop flaps as you had to turn the wheel many times to get to full deployment.

  Dont get me wrong,I'd love to see the 109's be able to drop flaps at higher speed,provided there's proof that they could in RL.

 We only have to press a button,a 109 pilot had to rotate the wheel something like 15 times to get full deployment.


    

  PS: It might have been in 1 of the videos that they state about the slip mechanism to prevent lowering at too high a speed,the ailerons also dropped with the flaps!

the 217mph for max safe speed of landing gear deployment does come from the poh. do you have a link to the video talking about the slip mechanism? that myths site is a very interesting read, especially about high speed (400mph+) handling capabilities.

[morfiend]

 Gyrene,

 I wish I had a link for you but I went through about 17 or 18 google pages on flap speed deployment,or as Bf109 flap speed deployment in the search and waded through alot of junk on models and such,I may have even linked to the video from one of the sites.

 I assumed this was common knowledge and would actually like to see a drawing/blueprint on how it worked.


  If you can supply definitive information on the speeds that both gear and flaps could be lowered or even anything about using then in combat I'd be the first to support you in having HTC look at the operation of them.


   

 PS: yes Krusty I understand as much,thats why I asked if you,well not you specific, believed it was true.I'm sure that the pilot had more on his mind than the actual speeds involved and also above a certain speed I would imagine the rate of error would increase exponentially

[FLS]

see that's where i think there is a small problem. on the g models the slats were installed on roller rails which made them more reliable and decreased the incidence of asymmetric deployment. but it also decreased the amount of aerodynamic pressure needed to make them retract because they weren't spring loaded. i did try it with the g6, g2, f4 and g14, below 5000ft high g turn at 335 up to 400+ mph and they do deploy as soon as you enter the turn, which doesn't make sense because they won't deploy when going into a nearly 90 degree climb at 350mph. close to the same aoa, should be the same aerodynamic pressure at the start as going into a turn.

i'm probably wrong and guilty of misinterpreting the technical information, been wrong before, but nothing i've studied says they should react the way they do in ah. you should peruse that site morfiend talked about...interesting first hand information about the slats
http://www.virtualpilots.fi/feature/articles/109myths/


the 217mph for max safe speed of landing gear deployment does come from the poh. do you have a link to the video talking about the slip mechanism? that myths site is a very interesting read, especially about high speed (400mph+) handling capabilities.

I think you're confused about what AOA is. Angle of attack is the angle that the air meets the wing. It has nothing to do with your aircraft angle in relation to gravity or the horizon.  Remember lift is AOA plus speed. You can have a high angle of attack flying straight and level when you fly slow enough to require a high coefficient of lift. This is why there is a tendancy to think slats are for slow speed flight. When not turning, if speed is high AOA is low. With low AOA the slats aren't active.  Even Gunthar Rall stated that slats were for landing and taking off and ignored the fact that they help turning too. That's anecdotal evidence that pilots aren't the best source for aerodynamic information. But it depends on the pilot. I've seen the site you linked and it explains everything I've been trying to tell you. There is also a pilot explaining that if you didn't have slats out in your turn you weren't turning your best. Note that even he mixes up low speed with the AOA at low speed as the reason for slat deployment. It's clear from his descriptions that he's taking about maneuvers at high AOA.

"The Bf 109s also had leading edge slats. When the 109 was flown, advertently or inadvertently, too slow, the slats shot forward out of the wing, sometimes with a loud bang which could be heard above the noise of the engine. Many times the slats coming out frightenened young pilots when they flew the Bf 109 for the first time in combat. One often flew near the stalling speed in combat, not only when flying straight and level but especially when turning and climbing. Sometimes the slats would suddenly fly out with a bang as if one had been hit, especially when one had throttled back to bank steeply. Indeed many fresh young pilots thought they were pulling very tight turns even when the slats were still closed against the wing. For us, the more experienced pilots, real manoeuvring only started when the slats were out. For this reason it is possible to find pilots from that period (1940) who will tell you that the Spitfire turned better than the Bf 109. That is not true. I myself had many dogfights with Spitfires and I could always out-turn them.
One had to enter the turn correctly, then open up the engine. It was a matter of feel. When one noticed the speed becoming critical - the aircraft vibrated - one had to ease up a bit, then pull back again, so that in plan the best turn would have looked like an egg or a horizontal ellipse rather than a circle. In this way one could out-turn the Spitfire - and I shot down six of them doing it. This advantage to the Bf 109 soon changed when improved Spitfires were delivered."
- Erwin Leykauf, German fighter pilot, 33 victories. Source: Messerschmitt Bf109 ja Saksan Sotatalous by Hannu Valtonen; Hurricane & Messerschmitt, Chaz Bowyer and Armand Van Ishoven.

The improved slats worked the same way as the older slat design according to the site you linked. Lift is mostly low air pressure above the wing. The high air pressure under the wing is a smaller portion of the total force. The pressure on the leading edge changes with AOA. A simplified picture of airflow over a wing doesn't show you the aerodynamic forces acting on the wing and may mislead your understanding of how air pressure moves the slats. 

[mtnman]

I think you're confused about what AOA is. Angle of attack is the angle that the air meets the wing. It has nothing to do with your aircraft angle in relation to gravity or the horizon.  Remember lift is AOA plus speed. You can have a high angle of attack flying straight and level when you fly slow enough to require a high coefficient of lift. This is why there is a tendancy to think slats are for slow speed flight. When not turning, if speed is high AOA is low. With low AOA the slats aren't active.  Even Gunthar Rall stated that slats were for landing and taking off and ignored the fact that they help turning too. That's anecdotal evidence that pilots aren't the best source for aerodynamic information. But it depends on the pilot. I've seen the site you linked and it explains everything I've been trying to tell you. There is also a pilot explaining that if you didn't have slats out in your turn you weren't turning your best. Note that even he mixes up low speed with the AOA at low speed as the reason for slat deployment. It's clear from his descriptions that he's taking about maneuvers at high AOA.

"The Bf 109s also had leading edge slats. When the 109 was flown, advertently or inadvertently, too slow, the slats shot forward out of the wing, sometimes with a loud bang which could be heard above the noise of the engine. Many times the slats coming out frightenened young pilots when they flew the Bf 109 for the first time in combat. One often flew near the stalling speed in combat, not only when flying straight and level but especially when turning and climbing. Sometimes the slats would suddenly fly out with a bang as if one had been hit, especially when one had throttled back to bank steeply. Indeed many fresh young pilots thought they were pulling very tight turns even when the slats were still closed against the wing. For us, the more experienced pilots, real manoeuvring only started when the slats were out. For this reason it is possible to find pilots from that period (1940) who will tell you that the Spitfire turned better than the Bf 109. That is not true. I myself had many dogfights with Spitfires and I could always out-turn them.
One had to enter the turn correctly, then open up the engine. It was a matter of feel. When one noticed the speed becoming critical - the aircraft vibrated - one had to ease up a bit, then pull back again, so that in plan the best turn would have looked like an egg or a horizontal ellipse rather than a circle. In this way one could out-turn the Spitfire - and I shot down six of them doing it. This advantage to the Bf 109 soon changed when improved Spitfires were delivered."
- Erwin Leykauf, German fighter pilot, 33 victories. Source: Messerschmitt Bf109 ja Saksan Sotatalous by Hannu Valtonen; Hurricane & Messerschmitt, Chaz Bowyer and Armand Van Ishoven.

The improved slats worked the same way as the older slat design according to the site you linked. Lift is mostly low air pressure above the wing. The high air pressure under the wing is a smaller portion of the total force. The pressure on the leading edge changes with AOA. A simplified picture of airflow over a wing doesn't show you the aerodynamic forces acting on the wing and may mislead your understanding of how air pressure moves the slats. 

I'm not saying the 109's didn't use combat flaps (I can't since I haven't bothered to research it at all), but it's interesting that with a clear description of combat turning like this, there's no mention of flaps? 

The sounds, vibrations, throttle use, control of speed, shape of turn, but no flap use?  Especially when considering it was in reference to how technique may have differed between inexperienced and experienced pilots.

In AH, flap use would have been an early part of a description like that!

[gyrene81]

thank you fls, i think i understand aoa fairly well, obviously i'm no expert in aerodynamics. i do have trouble understanding aoa in relation to banked angles in downward spiral turns and upward spiral turns at the same speeds. or why the slats will deploy in an upward spiral turn but not in a downward spiral turn under the same speeds and g load. now i need some tylenol...


just my opinion but, one pilot is anectdotal, big fish that got away story, but multiple pilots from multiple countries with the same experiences in the same aircraft is a resource. when you look at their statements, aside from some obvious exaggerations trying to recall heat of the moment incidents and basic pilot bravado, the same things are said in slightly different ways. the ones who survived multiple combat engagements weren't college educated aeronautics experts but they neither were they low iq idiots.

the pilot you quoted was quite obviously talking about the stall buffet encountered when he pulled too hard in a low speed turn, several other pilots gave similar descriptions. every pilot on there said almost the same thing, pull hard (increase aoa) in a low speed turn to the point of near stall (decrease aerodynamic pressure on the leading edge) and the slats would pop. not one said anything about high speed slat deployment, but then what is considered high speed? 100mph on the ground is fast but at 3000 feet a 109 is near stall speed.

Me 109 G:
"- How often did the slats in the leading edge of the wing slam open without warning?
They were exteneded always suddenly but not unexpectedly. They did not operate in high speed but in low speed. One could make them go out and in by moving the stick back and forth. When turning one slat functioned ahead of the other one, but that did not affect the steering. In a battle situation one could pull a little more if the slats had come out. They had a positive effect of the slow speed handling characteristics of the Messerschmitt.
- Could the pilot control the leading edge slats?
No. The slats were extended when the speed decreased enough, you could feel when they were extended. "
- Kyösti Karhila, Finnish fighter ace. 32 victories

and every other source of information i can actually comprehend says the same thing, high aoa and low speed.

and thanks for indulging me in this sir...  

[gyrene81]

I'm not saying the 109's didn't use combat flaps (I can't since I haven't bothered to research it at all), but it's interesting that with a clear description of combat turning like this, there's no mention of flaps?  

The sounds, vibrations, throttle use, control of speed, shape of turn, but no flap use?  Especially when considering it was in reference to how technique may have differed between inexperienced and experienced pilots.

In AH, flap use would have been an early part of a description like that!

i'm glad you brought that up...

Me 109 F/G:
"- Did pilots like the slats on the wings of the 109?
Yes, pilots did like them, since it allowed them better positions in dogfights along with using the flaps. These slats would also deploy slightly when the a/c was reaching stall at higher altitudes showing the pilot how close they were to stalling.....this was also useful when you were drunk "
- Franz Stigler, German fighter ace. 28 victories

Me 109 G-6:
"The story of Valte Estama's 109 G-6 getting shot down by a Yak-6 was also an interesting one. Their flight of nine planes was doing high-altitude CAP at 7,000 meters (23,000').
(snip) So it happened that the devil fired at him. One cannon round hit his engine, spilling out oil that caught fire. Estama noticed that it wasn't fuel that leaked or burned, just oil.
He pushed the nose of the plane and throttled up. His feet felt hot, but the fire was extinguished and there was no more smoke. The speedometer went over the top as the speed exceeded 950 km/h. The wings began to shake and Estama feared the fighter would come apart. He pulled the throttle back, but the stick was stiff and couldn't pull the plane out of the dive. Letting the flaps out little by little gradually lifted the nose. The plane leveled at 1,000 meters (3,300').
Clarification of the escape dive: "It didn't stay (vertical) otherwise, it had to be kept with the stabilizer. I trimmed it so the plane was certainly nose down. Once I felt it didn't burn anymore and there was no black smoke in the mirror, then I began to straighten it up, and it wouldn't obey. The stick was so stiff it was useless. So a nudge at a time, (then straightening off with trims).
Then the wings came alive with the flutter effect, I was afraid it's coming apart and shut the throttle. Only then I began to level out. To a thousand meters. It was a long time - and the hard pull blacked me out."
- Edvald Estama, Finnish fighter pilot

to morfiend, after 18 months of searching believe me, if i had just one solid document that showed 109 flaps being deployed above 190mph i would have posted it already...

[FLS]

The reason high AOA is associated with low speed is simply because it's more common than high speed high AOA. The pilot you quoted had the same experience that you did. At high speed he never pulled enough AOA to pop the slats. Once you were told it was possible and tried it you did it right away. The pilot I quoted said that his fellow experienced 109 pilots did not fully appreciate their slats. Slats improve high AOA handling because it improves lift. More lift is a benefit at any speed. That's just physics. Because more lift at high speed is likely to black you out it's normal to slow down to the point where the increased lift helps you without making you black out. For example the speeds where you would otherwise wish for combat flaps if you didn't have slats.

I think you'll find that every reference to slats only working at low speed actually describes entering a high AOA condition.

In a spiral climb you slow down and need more AOA for the same lift. In a spiral dive you speed up and need less AOA for the same lift.

Look on the bright side. At least there was no math.  

Re: Edvald Estama  If he's in compression then it's hard to understand how flaps helped compared to trimming the stabilizer. I'm not saying he was misquoted it's just puzzling. Typically in compression the higher air density at lower altitude is what helps you regain control.

Just to clarify my comment on Gunther Rall. I'm sure he was a gifted pilot that knew everything about flying the 109. He probably just preferred a lower G dogfight and didn't use slats at high speeds. If the pilots and POH writers knew they were going to be quoted in flight sim debates I'm sure they would have expressed themselves differently.

[gyrene81]

ok thank you, now i'm getting a clearer picture.

finally found a video that shows the slats performing exactly the way you described...start at 2:54 and watch the leading edge of the starboard wing very carefully.

http://www.youtube.com/watch?v=_a_TETqe1Cg&feature=player_embedded

Re: Edvald Estama  If he's in compression then it's hard to understand how flaps helped compared to trimming the stabilizer. I'm not saying he was misquoted it's just puzzling. Typically in compression the higher air density at lower altitude is what helps you regain control.

Just to clarify my comment on Gunther Rall. I'm sure he was a gifted pilot that knew everything about flying the 109. He probably just preferred a lower G dogfight and didn't use slats at high speeds. If the pilots and POH writers knew they were going to be quoted in flight sim debates I'm sure they would have expressed themselves differently.

ya i'm not sure about what estama said. the other pilots who described high speed dive recovery said they used the "flettner" (trim tab?) to regain level flight. and i can only imagine what rall would have said with some of us asking him questions...but i would have been in hog heaven talking to the man.