Slats deploying at high speed ?

[GrapeJam]

I'd put my faith in what Skip Holm & Mark Hanna have said, that the 109 & Spit are very close when it comes to turning and that both are excellent dogfighters.

 

Btw, I remember watching Bf-109 Red 7, a G-4, complete several sustained turns during an airshow, and none took over 18 seconds to complete. The pilot again is ofcourse highly trained, and knows the limits of the aircraft better than the pilots back then as his understanding of the various subsystems and the aerodynamics is vastly better (he knows what the slats are there for, how & why they operate in every detail), which explains why he is able to do that despite the low power settings used.

 

 

 

And you got war time pilots who said the Spitfire easily outturned the 109, so which one are you gonna take as more credible, modern pilots who fly unarmed planes loaded with low fuel for air show or war time pilots who actually flew pristine planes in combat condition?

 

Soviet tests put a Spitfire LF MK IX running at low boost (because of the lack of high octane fuel) turning 3-4 seconds faster than the G2. And the G2 was in good condition as it achieved it's speed correctly.

 

Or are you just gonna cherry pick what support your argument again?

 

And stop with the "The Brits didn't know what the slats were for" because of one test that wasn't even actually carried out, just a post war guess comparison for the press. Tons of other tests by the British showed they clearly understood how the slats worked, after all the slats were invented by them. Stop repeating debulked myth.

Edited May 7, 2015 by GrapeJam

[Ala13_ManOWar]

The Slats are actually Pressure deployed......

 

But yes not airspeed.

Of course, we have to bear in mind AoA changes makes the lowest dynamic pressure point (where virtually dynamyc pressure is 0, so all static pressure) move along the trailing edge in vertical axis. Those changes in "pressure" are the ones responsible for slats deploying and stall horns. So yes, pressure, because AoA :smilewink:.

 

 

Talking anecdotes, I have also seen 8 Spitfires at Duxford airshow (16 Spits year, yes :thumbup:) keeping a tight turn in front of public while P-51 and 109 had to make a quite bigger one clearly not able to turn as tight. Means that something? Mr Hanna aircraft were modern ones with no extra loadout and low show fuel. We all forget that things when we claim something. Here in DCS that also counts, for instance clearly Dora isn't the Dora we usually read about in stories with full fuel, but half or low fuel she's a killer and matches quite well!! When you say this or that plane turned as much or more than I you aren't considering what your and his config was (and more, we should count energy state, speed, altitude...). May be you were in a full fuel 109 and he was in a low fuel P-51 so YES, by a bit he actually was more manoeuvrable... in that condition. But absolute flight test condition says 109 turns more than P-51 and here it's also true if you use that conditions.

 

 

And more on topic, the problem I think is we are so badly used to old sims we cannot forget them yet. Some sims out there, a reference in another times, are out of scale mates... out of speed scale, out of altitude scale, out of RL scale. So may be we're used to "see" a tight turn at high speed looks like something close to Hollywood movies, but RL is not like that and DCS matches RL not movies. May be that one reason we "see" a not so tight turn at high speed (not looking so high speed to us) so we think slats shouldn't deploy or something, but in RL you're getting A LOT of G's doing that, and a high AoA, so of course slats deploys, they have to!

 

S!

Edited May 7, 2015 by Ala13_ManOWar

[Hummingbird]

And you got war time pilots who said the Spitfire easily outturned the 109, so which one are you gonna take as more credible, modern pilots who fly unarmed planes loaded with low fuel for air show or war time pilots who actually flew pristine planes in combat condition?

 

Soviet tests put a Spitfire LF MK IX running at low boost (because of the lack of high octane fuel) turning 3-4 seconds faster than the G2. And the G2 was in good condition as it achieved it's speed correctly.

 

Or are you just gonna cherry pick what support your argument again?

 

And stop with the "The Brits didn't know what the slats were for" because of one test that wasn't even actually carried out, just a post war guess comparison for the press. Tons of other tests by the British showed they clearly understood how the slats worked, after all the slats were invented by them. Stop repeating debulked myth.

 

*sigh*

 

Believe in what'ever you want to believe GrapeJam, I'm done argueing with you. I deal with facts, not feelings.

 

As for cherry picking, you've got wartime 109 pilots saying they could easily outturn Spitfires as well. So how about you follow your own advice and stop cherry picking :megalol:

[NineLine]

I deal with facts, not feelings.

 

I'm confused, aren't you both discussing the findings of pilots, just happens to be different time periods that these pilots flew these aircraft?

[Hummingbird]

I'm confused, aren't you both discussing the findings of pilots, just happens to be different time periods that these pilots flew these aircraft?

 

No, thing is you've got wartime pilots saying both things where'as the opinion of modern pilots is the same across the board. Combine this with our aerodynamic understanding and we get a more objective picture than relying solely on wartime recollections, esp. if you only choose to hear it from one side.

 

I'm still of the opinion that the Spitfire is the better dogfighter, but also that these two aircraft are very close in this respect and that the difference is nowhere near as great as what some will have you believe.

[NineLine]

No, thing is you've got wartime pilots saying both things where'as the opinion of modern pilots is the same across the board. Combine this with our aerodynamic understanding and we get a more objective picture than relying solely on wartime recollections.

 

I'm still of the opinion that the Spitfire is the better dogfighter, but also that these two aircraft are very close in this respect and that the difference is nowhere near as great as what some will have you believe.

 

How many modern pilots were asked compared to wartime, bigger your sample size, more chance you might have for discrepancies right? And how do modern pilots really know how these planes do in combat? I mean, honestly, they can get a 'feeling' better than most, but its nothing like having a bad guy breathing down your neck and your life hangs in the balance... I would imagine that would cause you to push your aircraft a little further, IMHO....

[GrapeJam]

*sigh*

 

Believe in what'ever you want to believe GrapeJam, I'm done argueing with you. I deal with facts, not feelings.

 

You talk about facts, eh?

 

This is fact:

This is fact:

 

As for cherry picking, you've got wartime 109 pilots saying they could easily outturn Spitfires as well. So how about you follow your own advice and stop cherry picking :megalol:

 

Oh you want me to bring the real quote?

http://www.virtualpilots.fi/feature/articles/109myths/

"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.

 

This bolded part is often omitted(or as I like to call it, "cherry picked out") when this quite is brought up when talked about 109 outturning spitfire. Early spitfires were fitted with 2 blades 2 pitches propeller and had poor acceleration.

 

And the fact that the Germans tested a captured Spitfire and it handily outturned the 109.

Edited May 7, 2015 by GrapeJam

[[DBS]TH0R]

Back to the topic, here is a video showing what happens with the airflow around the wings with the slats (circa 1938 ):

 

Edited May 7, 2015 by T}{OR

[GrapeJam]

The question is though, were the slats on the 109 large enough to provide significant amount of lift during turning? Or were they mainly there to retain ailerons control and the amount of additional lift provided was insignificant? As German test'd showed.

Edited May 7, 2015 by GrapeJam

[Hummingbird]

The question is though, were the slats on the 109 large enough to provide significant amount of lift during turning? Or were they mainly there to retain ailerons control and the amount of additional lift provided was insignificant? As German test'd showed.

 

The slats provided extra lift over the area that wasn't effected by the prop wash, significantly increasing the overall lift of the wing, just as German testing showed. Why else do you think ME choose to keep them on :rolleyes:

 

ME tested everything from washout, to wing fences to fixed and automatic slats, and the final result was a clear advantage with the outboard mounted slats, as they greatly reduced the stall speed and improved the turning capability and landing characteristics of the aircraft. The very same reason that the Soviets started putting slats on their fighters after having tested captured 109's.

 

You don't put full span slats on a prop job with the wing straight in the prop stream.

Edited May 7, 2015 by Hummingbird

[Ala13_ManOWar]

... significantly increasing the overall lift of the wing, just as German testing showed. ...

Didn't we saw a German test previously that only showed a small amount of lift and telling slats were for aileron control purpose? :huh:

 

Anyway, I think I don't get the whole point at this moment. Exactly what are you looking for now? You just want to outturn everything out there with a B&Z fighter? Want the aircraft not to stall when you tight turn/overpush controls? Or what? 109K4 was the heaviest 109, also powerful but keeping same wing (not same, with two huge bumps in the middle...) so worst wing loading of the model. What exactly do you want to demonstrate? I'm serious, just curious and would like to know.

 

S!

[GrapeJam]

The slats provided extra lift over the area that wasn't effected by the prop wash, significantly increasing the overall lift of the wing, just as German testing showed. Why else do you think ME choose to keep them on :rolleyes:

 

ME tested everything from washout, to wing fences to fixed and automatic slats, and the final result was a clear advantage with the outboard mounted slats, as they greatly reduced the stall speed and improved the turning capability and landing characteristics of the aircraft. The very same reason that the Soviets started putting slats on their fighters after having tested captured 109's.

 

You don't put full span slats on a prop job with the wing straight in the prop stream.

 

Oh so what are these?:

 

 

http://forums.eagle.ru/showpost.php?p=2371074&postcount=59

http://aviadejavu.ru/Site/Crafts/Craft31461.htm

 

You really need to drop the habit of ignoring things that don't support your argument and keep repeating debulked myths.

Edited May 7, 2015 by GrapeJam

[[DBS]TH0R]

You don't put full span slats on a prop job with the wing straight in the prop stream.

 

Naturally, for that the slats need to be mechanically driven. Automatic, air pressure driven slats would then never deploy on a 109 if they were in the propeller stream. The other solution are fixed slots.

 

 

In the context of the above, do please explain to me the conclusion of the test you yourself shared some time ago:

 

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940025432.pdf

 

In this test the high lift devices (including leading edge) are directly in the propeller stream.

 

 

Didn't we saw a German test previously that only showed a small amount of lift and telling slats were for aileron control purpose? :huh:

 

We saw it mentioned and certain pieces from it extracted, not the full document. Unless he provides documents or mentions where he got this information from - there is a word for it: baloney.

Edited May 7, 2015 by T}{OR
added ManOWar's quote

[Hummingbird]

Oh so what are these?:

 

 

http://forums.eagle.ru/showpost.php?p=2371074&postcount=59

http://aviadejavu.ru/Site/Crafts/Craft31461.htm

 

You really need to drop the habit of ignoring things that don't support your argument and keep repeating debulked myths.

 

Those are fixed slots!! :doh:

 

*sigh*

Edited May 7, 2015 by Hummingbird

[Hummingbird]

Naturally, for that the slats need to be mechanically driven. Automatic, air pressure driven slats would then never deploy on a 109 if they were in the propeller stream. The other solution are fixed slots.

 

 

In the context of the above, do please explain to me the conclusion of the test you yourself shared some time ago:

 

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940025432.pdf

 

In this test the high lift devices (including leading edge) are directly in the propeller stream.

 

 

Yes, and as you correctly pointed out this only works if they are mechanically operated, which is the case in said document as well which actually features a leading edge slat/flap design (because of the droop).

 

One of the conclusions of said test is that lift is significantly increased over the areas energized by the prop stream, although this was already known long before, and the test was really more about testing the characteristics of that particular configuration.

Edited May 7, 2015 by Hummingbird

[IIIJG52_Otto_]

Oh so what are these?:

 

 

http://forums.eagle.ru/showpost.php?p=2371074&postcount=59

http://aviadejavu.ru/Site/Crafts/Craft31461.htm

 

You really need to drop the habit of ignoring things that don't support your argument and keep repeating debulked myths.

 

The leading edge slats was invented by Gustav Victor Lachmann in 1918.

 

Gustav Victor Lachmann was a German aeronautical engineer who spent most of his professional life working for Handley Page.

http://aircraftdesigners.blogspot.com/2011/09/gustav-victor-lachmann-1896-1966.html

 

There are a lot of evidences that the Soviets added the Slats to La-5, and LAGG-3 series 35, after production started, to match the performances with some captured Bf-109´s

[IIIJG52_Otto_]

re-quote myself :music_whistling:

 

I think this book explains clearly what was the behavior of automatic slotted slats, and how they were used.

"For more experienced pilots,

real maneuvering only started when the slots were out

. For this reason, it is possible to find pilots from 1940 who will tell you that the spitfire turned better than Bf-109...

I myself had many dogfights with Spitfires and could always out-turn them."

 

Oberleuteutnant Erwin LeyKauf (German ace of 7/JG54, who survived the war with 33 kills to his credits)

"SPITFIRE Vs Bf109, Battle of Britain" by Tony Holmes, (ed. Osprey publising 2007), page num. 60

.

[IIIJG52_Otto_]

Didn't we saw a German test previously that only showed a small amount of lift and telling slats were for aileron control purpose? :huh:

 

S!

 

 

I have already explained in another post http://forums.eagle.ru/showpost.php?p=2373035&postcount=75

 

In the book " DESIGN FOR AIR COMBAT" by Ray Whitford -1987- The benefits of automatic slats in combat, are well explained:.

""" Slat with a slot (slotted stat)

Though complex, requiring rails and rollers in addition to actuators, this is probably the most widely used leading-edge device for combat aircraft. However, when account is taken of the resulting increase in maximum lift and its favourable effect on lateral/directional flying qualities, the extra complication is amply justified.

....

The slotted leading edge was originally proposed by Handley Page and Lachmann around 1920 and proved extremely beneficial in extending the lift curve, as shown in Fig 64. Designed to operate automatically, it consists of a slat quite free to move on tracks. At low AOA the slat is held flush against the leading edge. At high AOA the high local suctions on the slat create a forward chord-wise force, pulling out the slat. The slot so formed allows the wing to continue lifting to a higher AOA. significantly increasing the maximum lift coefficient. A slight chord extension also occurs. """""

[NineLine]

re-quote myself :music_whistling:

 

So according to that quote, you could get a different answer which turned better, depending on the pilot.

Edited May 8, 2015 by NineLine

[Hummingbird]

So according to that quote, you could get a different answer which turned better, depending on the pilot.

 

Obviously.

[NineLine]

Obviously.

 

I am trying to determine the point of this thread..... obviously.

[Hummingbird]

I am trying to determine the point of this thread..... obviously.

 

You took it the wrong way, what I'm saying is that one can't take wartime anecdotes from one side only and then claim it to be the truth, esp. since you can easily find another one which contradicts it.

[GrapeJam]

Those are fixed slots!! :doh:

 

*sigh*

Did you even read the last links?

 

 

There are a lot of evidences that the Soviets added the Slats to La-5, and LAGG-3 series 35, after production started, to match the performances with some captured Bf-109´s

Nope, it was added even before the German invasion.

[GrapeJam]

I have already explained in another post http://forums.eagle.ru/showpost.php?p=2373035&postcount=75

 

Yeah, but was that even about the 1/3 wing span slat style of the 109?

[[DBS]TH0R]

I am trying to determine the point of this thread..... obviously.

 

Another locking I suppose. :D

 

OP question was answered several times now.

 

 

One of the conclusions of said test is that lift is significantly increased over the areas energized by the prop stream, although this was already known long before, and the test was really more about testing the characteristics of that particular configuration.

 

Hence the difference between power on and power off stalling behavior. With that being said, 109 root section of the wing that gets "energized" doesn't have any high lift devices except normal flaps that are used during landing / TO and perhaps heavy maneuvering. My in-game tests show level power off matching IAS values Dave Southwood wrote after flying the G-2:

 

Stall speeds are 155kph clean and 140kph with gear and flap down.

 

 

Yeah, but was that even about the 1/3 wing span slat style of the 109?

 

When we stop beating around the bush, this is the premise of certain people around here. That the slats provide higher AOA and increase lift is not a question - when they cover full span of the wing. Whether they also do all of that when they are placed on the outboard 1/3 of the wing (in power on condition), or simply "complete the stall" still needs to be proven to / by some.

 

So far I haven't seen anyone posting anything proving that having slats on the outboard 1/3 of the wing yields in any CLmax increase or results similar to those of full span slats. Merely theory.

 

(Mind you in engineering terms, or in my language at least, everything is a theory. Be it proven in practice or not.)

 

While on the other hand we have seen full-scale wind tunnel measurements on Bf 109 V24 mentioned before saying they only complete the stall, and a quick Wikipedia search showed the same answer pointing to a source from this book: "Clancy, L.J., Aerodynamics, Section 6.9"

 

Partial-span slots are usually found only on the outboard portion of the wing where they ensure airflow over that portion of the wing will remain unstalled at higher angles of attack than the inboard portions of the wing. This ensures the wing root stalls first and contributes to docile stall behaviour and maintaining aileron control throughout the stall. Using slots in this manner produces a similar result to employing washout on a wing, but through a different means.

 

Saying that I trust Wikipedia is a long shot, at best, however the article about slots (general purpose as slats being the same) with a source is there.

Edited May 8, 2015 by T}{OR
spelling