Leading Edge Slats on the Me-109

[Crumpp]

RAE evaluation that the aircraft was 'too stable'

It is a fact the RAE pilot felt that way. It is also a fact the RAE had no defined stability and control standards outside of pilot opinion. They did not have the measurements and definitions of the NACA or the RLM.

It is also a fact if you apply those definitions and standards, the Bf-109 was designed to be thrown around the sky at maximum performance the physics and physiological limits of the real world allowed.

Gust factor is a very real limit to airplanes. Flying around the other day, I had to stay below Vno just cruising because the sky was so bumpy.

If you pull a 6G maneuver and hit a gust acceleration, you have damaged the airplane. Not only that, 6G's sucks!! It is very uncomfortable and exhausting! IIRC, the USAF did a study and a fighter pilots ability to accurately track a target for a gun solution is degraded ~85% of normal after a few seconds exposure to just 4.5G's.

What Mtt did was apply a stability and control standard to ensure the pilot could quickly and precisely maneuver the guns onto target in order to make the most accurate shot possible. They tried to ensure the airplane achieved maximum performance to get where it needed to be in a condition to destroy other airplanes.

The designed a stable shooting platform and built an airplane around it.

[Crumpp]

Crumpp to cut-n-paste quotes from a website with the title 109 myths as PROOF that uneven slat activation could NOT cause spins..

Why don't you get some experience in an automatic slat equipped aircraft and come back to tell us how it works.

You don't seem to count my experience so share yours!!

[Crumpp]

Bf 109 into a stall and spin when the slats deployed on one wing and not the other

Airframes break apart in flight, Flaps break, engines breakdown, spark plugs foul, fabric balloons, and slats malfunction...




All things mechanical can fail especially if not properly maintained or abused.

What does that have to do with me or the physics of how slats operate?

[ACE-OF-ACES]

Originally Posted by Crumpp

Why don't you get some experience in an automatic slat equipped aircraft and come back to tell us how it works.

Why? When I have something better, as in an actual WWII Bf109 quote, i.e.

Originally Posted by Oberleutnant Erwin Leykauf

Less experienced pilots could put a Bf 109 into a stall and spin when the slats deployed on one wing and not the other in a tight turn. When slats deployed unevenly in tight turns, they would disrupt the airflow, causing the ailerons to ‘snatch’ enough to shake a Bf 109, spoiling the pilot’s aim

Originally Posted by Crumpp

You don't seem to count my experience so share yours!!

Don't take it personally!

I just think the experience of an actual WWII Bf109 pilot trumps Crumpp's modern civilian aircraft pilot experience when talking about how a Bf109 acts..

Guess I am just silly like that!

[ACE-OF-ACES]

Originally Posted by Crumpp

Flaps break, engines breakdown, spark plugs foul, fabric balloons, and slats malfunction...

All things mechanical can fail especially if not properly maintained or abused.

What does that have to do with me or the physics of how slats operate?

Not sure Crumpp..

But it sounds like your saying you know better than Oberleutnant Erwin Leykauf wrt how slats worked on a Bf109 in flight..

If so,

well..

I guess you can 'feel' that way..

Just know that I an others are probally going to stick with Oberleutnant Erwin Leykauf experance on this mater over yours

[II/JG53 Rolf]

AOA - Sir, you have just done the same thing. While he posted numerous pilot records about slats, you choose one from a single book as a proof... Is the book reliable in all aspects? Does the author really understand aerodynamics? Now I don't have the book in my place, so I can't check it, but it seems to me that this is one I've actually read and there were several mistakes caused by authors misunderstanding of how things work and were designed.

It sort of reminds me a book by Stephen Bungay who was trying to mathematically prove that the 8 machine guns of a spit/hurry were more effective than 2 cannons of Bf-109 E...

Now to your quote - "...Less experienced pilots could put a Bf 109 into a stall and spin when the slats deployed on one wing and not the other in a tight turn..." Sir, Less experienced pilots is the key here. It means they ignored the warning the slats had given them and continued pulling on the stick ... It was mistake of a pilot not a plane... and less experienced pilots avoided near stall conditions at all... and it and it has been reported many times...

World would be a better place if we listened to each other instead of shouting...

And THE QUESTION about slats has both answers actually - they do both in logical sequence...

[taildraggernut]

purely in the interest of balance.

Stalling the 109
Me 109 E:
"The airplane was equipped with a 60 foot trailing static head and a swiveling pitot head. Although, as may be imagined, operation of a trailing static from a single-seater with a rather cramped cockpit is a difficult job, the pilot brought back the following results:
Lowering the ailerons and flaps thus increases CL max of 0.5. This is roughly the value which would be expected from the installation. Behaviour at the stall. The airplane was put through the full official tests. The results may be summarized by saying that the stalling behaviour, flaps up and down, is excellent. Both rudder and ailerons are effective right down to the stall, which is very gentle, the wing only falling about 10 degrees and the nose falling with it. There is no tendency to spin. With flaps up the ailerons snatch while the slats are opening, and there is a buffeting on the ailerons as the stall is approached.. Withs flaps down there is no aileron snatch as the slats open, and no pre-stall aileron buffeting. There is no warning of the stall, flaps down. From the safety viewpoint this is the sold adverse stalling feature; it is largely off-set by the innocuous behaviour at the stall and by the very high degree of fore and aft stability on the approach glide.
It is important to bear in mind that minimum radii of turn are obtained by going as near to the stall as possible. In this respect the Bf.109E scores by its excellent control near the stall and innocuous behaviour at the stall, giving the pilot confidence to get the last ounce out of his airplanes turning performance."- RAF Royal Aircraft Establishment (RAE) Farnborough handling trials,Bf.109E Wn: 1304. M.B. Morgan and R. Smelt of the RAE, 1944.

Nice report, but apparently the RAE knew nothing and didn't have nice spangly testing equipment.....see quote below.

Originally Posted by Crumpp

The behaviors of the Bf-109 are fairly well documented and we have some measured data. There is enough there to construct a reasonable facimile. Unfortunately the RAE did not have a standard or the measuring equipment developed by the NACA until later.

Me 109 E-4:
"I was amazed at how docile the aircraft was and how difficult it was to depart, particularly from manoeuvre - in a level turn there was lots of warning from a wide buffet margin and the aircraft would not depart unless it was out of balance. Once departted the aircraft was recovered easily by centralizing the controls."
- Charlie Brown, RAF Flying Instructor, test flight of restored Me 109 E-4 WN 3579. Source: Warbirds Journal issue 50.

Here is where someone has basically confirmed the aircraft will spin, of course this is a contemporary report on a restored aircraft which is not loaded the same as a wartime machine.

Me 109 G:
"- How the Messerschmitt reacted to hard pull? Did she stall?
There is the general opinion that you could not make her stall by pulling but she could 'slip'."
- Kyösti Karhila, Finnish fighter ace. 32 victories. Source: Interview by Finnish Virtual Pilots Association.

Note the oppinion was 'general' and not explicit.

Quote:
Me 109 E:
"I was particularly interested in the operation of the slats, the action of which gave rise to aileron snatching in any high-G manoeuvres such as loops or tigh turns so I did a series of stalls to check their functioning more accurately. The stall with the aircraft clean, with half fuel load and the engine throttled right back occurred at 105 MPH (168 km/h). This was preceded by elevator buffet and opening the slats about 20 mph (30 km/h) above the stall, these being accompanied by the unpleasant aileron snatching as the slats opened unevenly. The stall itself was fairly gentle with the nose dropping and the port wing simultaneously dropping about 10 degrees."
- Eric Brown
- The author writes about an "unpleasant" event. Nothing catastrophic! Surely all of the planes of that time had features, that were unpleasant, just as well as many planes today have. Curtiss Hawk 75 was surely unpleasant to fly with the rear fuselage fuel tank filled, as flying acrobatics could get you killed. P-51 was at least unpleasant with fuselage tanks filled.

I'm sure all Mr Brown meant was 'unpleasant' and there is nothing more to be read into it.

Me 109 E:
"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.

Another pilot report, subject to all the ego and fading memory issues, there is no clear evidence that the 6 Spitfires shot down were not being flown by fresh young pilots of the RAF.

Me 109 E:
"And there I discovered the first thing you have to consider in a 109. The 109 had slots. The slot had a purpose to increase the lift during takeoff and landing. In the air automatically it's pressed to the main wing. And if you turn very roughly you got a chance, it's just by power, the wing, the forewing, comes out a little bit, and you snap. This happened to me. I released the stick immediately and it was ok then. "
- Major Gunther Rall in April 1943. German fighter ace, NATO general, Commander of the German Air Force. 275 victories. Source: Lecture by general Rall.

Heres a point showing the true function of the slats.

Me 109 E/F/G: - The plane had these wing slats and you mentioned they pop open uneven?
"Two meter slots on fore wings. The reason was to increase the lift during low speed take off and landing. To reduce the length of runway you need. In the air, if you make rough turns, just by gravity, the outer slot might get out. You can correct it immediately by release of stick, you know? Only little bit, psssssssht, its in, then its gone. You have to know that. And if you know it, you prevent it."
- Major Gunther Rall. German fighter ace, NATO general, Commander of the German Air Force. 275 victories. Source: Lecture by general Rall.

Same guy same reasoning, slats were for low speed handling.

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. Source: Interview by Finnish Virtual Pilots Association.

Slightly confusing, the slats didn't open at high speed?, but another confirmation of the true function of slats.

Me 109 G:
"- In a battle, which was the case: did the pilot endure more than the Messerschmitt could do or vice versa?
The fact is that when you pulled hard enough the wing leading edge slats slammed open. After that the pilot could not tighten the turn. The plane would have stalled. I don't know, I never tried to find out what the plane would do after that. I never heard anybody else saying that he would have banked so hard that the slats came out. I did that a few times, for example once over the Isthmus I tried to turn after an enemy, banking so hard that both slats came out, but I had to give up.
- How did the slats behave in such a situation, did they go in and out ?
It depended on speed, if you pulled more,they came out, then back in
The slats came out completely, never half-way?
I never came to watch them so intensely. You just knew they had come out, you could see them and feel that the lift increased pretty much.
- So the plane warned that now you are on the edge.
Yes, you knew the plane is about to spin."- Antti Tani, Finnish fighter ace. 21,5 victories. Source: Interview by Finnish Virtual Pilots Association.

Interesting, after the slats were open you didn't wan't to pull more or the aircraft would stall, a pilot showing a healthy reluctance to go beyond the envelope, and finishing by saying the aircraft would spin.

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. Interview of Franz Stigler.

I just liked the drunk part.

Me 109 G:
"As CL max is reached the leading edge slats deploy - together if the ball is in the middle, slightly asymmetrically if you have any slip on. The aircraft delights in being pulled into hard manuevering turns at these slower speeds. As the slats pop out you feel a slight "notching" on the stick and you can pull more until the whole airframe is buffeting quite hard. A little more and you will drop a wing, but you have to be crass to do it unintentionally."
- Mark Hanna of the Old Flying Machine Company flying the OFMC Messerschmitt Bf 109 G (Spanish version).

Mark Hanna was killed in a Buchon in a low speed low altitude departure...

Me 109 G:
"There was nothing special in landing the plane. It was heavy but the wing slats opened up when speed slowed down and helped flying in slow speed."
-Kullervo Joutseno, Finnish fighter pilot. Source: Hannu Valtonen, "Me 109 ja Saksan sotatalous" (Messerschmitt Bf 109 and the German war economy), ISBN 951-95688-7-5.

Again the true purpose of slats

Me 109 G:
"It was beneficial to keep the throttle a little open when landing. This made the landings softer and almost all three-point landings were successful with this technique. During landings the leading edge slats were fully open. But there was no troubles in landing even with throttle at idle."
-Mikko Lallukka, Finnish fighter pilot. Source: Hannu Valtonen, "Me 109 ja Saksan sotatalous" (Messerschmitt Bf 109 and the German war economy), ISBN 951-95688-7-5.Source: Hannu Valtonen, "Messerschmitt Bf 109 and the German war economy"

it's all about the low speed handling qualities for approach and landing.

Me 109 G:
"We didn't have time for acrobatics but we weren't forbidden from doing them, though. Snap roll was fast and easy, and the engine didn't cough as in older planes. Immelman turn was splendid when you tightened the stick a bit on the top. The automatic wing slats did their trick and you didn't need ailerons at all for straightening the plane."
-Otso Leskinen, Finnish fighter pilot. Source: Hannu Valtonen, "Me 109 ja Saksan sotatalous" (Messerschmitt Bf 109 and the German war economy), ISBN 951-95688-7-5.

Snap roll is a spin entered at high speed.

"Unexperienced pilots hesitated to turn tight, bacause the plane shook violently when the slats deployed. I realised, though, that because of the slats the plane's stalling characteristics were much better than in comparable Allied planes that I got to fly. Even though you may doubt it, I knew it [Bf109] could manouver better in turnfight than LaGG, Yak or even Spitfire."
- Walter Wolfrum, German fighter ace. 137 victories.

Depends on who is flying them I guess.

[raaaid]

stall is not equal to spin

you know what stall is?

think youre flying level but actually going so slow you are aactually falling as a rock

at some point the game modelled this

[taildraggernut]

Originally Posted by Crumpp

If you have never flown a slat equipped aircraft, it is a different experience despite the slats being totally unnoticeable for the vast majority of their operation.

Once you have, the idiosyncrasies of the slats becomes part of the airplane and the tactile clues are comforting acknowledgements that everything is working as it should.

Once you explore the low speed performance of a slat equipped aircraft you will miss them on airplanes that lack such a device.

I don't miss aircraft with slats at all, I am quite capable of handling aircraft without them, of course if you feel your own competence is questionable then there is nothing wrong with 'training wheels'

[ACE-OF-ACES]

Originally Posted by II/JG53 Rolf

AOA - Sir, you have just done the same thing. While he posted numerous pilot records about slats, you choose one from a single book as a proof...

Ah.. I see where you are confused

Note what I posted was a quote of an actual WWII Bf109 pilot.. Not my 'take' or 'interpretation' of what the actual WWII Bf109 pilot said.

Which is very different from the website Crumpp provided where the webiste provides you their 'take' and/or 'interpretation' of what the WWII pilots actually were trying to say or meant to say.. I guess some folks need others to do their thinking for them?

Hope that helps!

Now allow me to point out to those reading this post how Rolf and Crump totally ignored the actually WWII Bf109 pilot's quote I provided that said uneven slat activation can cause spins and tried to make this about me!

Nice try guys!

Gold star for effort!

But no sale!