Some opinion about maneuverability of Bf109K-4

[Hummingbird]

Considering that the Yak 3 had a wingloading of 183kg/m2, which is 5 kg lower than the G2. Airfoil: Clark YH, which has similar clmax to the 109's airfoil, about the same powerloading, has no slats, yet totally own the 109G2 in turning I seriously think he's overestimating the effect of the slats.

 

According to the Soviets perhaps, but according to them the La-5Fn did the same, whilst in German tests the Bf-109G6 turned tighter.

[Hummingbird]

Any documentation to back this theory up?

 

Theory?! Haha, why do you think the slats are placed where they are? And how else do you suppose the 109 was able to keep from stalling until 130 km/h with power on? :D

 

To give you another example you can see the same effect on the P-38, which due to its tandem engine design was able to energize a lot of its wing area and as such greatly increase the overall CLmax of the wing, enabling it to turn a lot tighter than its high wing loading would otherwise suggest. This aircraft is often badmouthed due to its high wing loading, but aerodynamics actually made it an excellent fighter, proving yet again how misleading wing loading is.

 

It's the exact same reason that the 109 didn't stall until 80 mph with power on, because it could keep the root section from stalling before the outboard slat equipped section until a very high Clmax was reached.

 

But since you want specific documentation:

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

Edited April 16, 2015 by Hummingbird

[GrapeJam]

According to the Soviets perhaps, but according to them the La-5Fn did the same, whilst in German tests the Bf-109G6 turned tighter.

 

Yeah, the La-5FN which made only 510km/h at SL instead of 583km/h, seeped CO2 into cockpit(a flaw that was presented only in the first La5, and was later fixed on the La5F onward) and the engine ran so rough that the test pilot temporarily lost his hearing.

 

Anyway, funnily enough, Soviet's test of the G2 has roughly the same turn time as Finnish test, speed was also correct so that test actually hold credibility.

Edited April 16, 2015 by GrapeJam

[[DBS]TH0R]

I am well aware of why and how leading edge slats work and what their purpose is. Besides, it has been explained how effective they are earlier in this thread. Perhaps you ought to re-read it again to better understand my question.

 

EDIT: Thank you for the document non the less.

Edited April 16, 2015 by T}{OR

[Hummingbird]

Yeah, the La-5FN which made only 510km/h at SL instead of 583km/h, seeped CO2 into cockpit(a flaw that was presented only in the first La5, and was later fixed on the La5F onward) and the engine ran so rough that the test pilot temporarily lost his hearing.

 

The high cockpit noise was due to the placement of the exhausts, it has nothing to do with the engine, which was said to run fine btw. The aircraft was also described as being in fine condition.

 

Top speed reached at SL was 520 km/h (TAS), measured with an external trail end measuring device.

 

Anyway, funnily enough, Soviet's test of the G2 has roughly the same turn time as Finnish test, speed was also correct so that test actually hold credibility.

 

Actually not, the Russian turn time similar to the Finnish one is with gunpods on.

[Hummingbird]

I am well aware of why and how leading edge slats work and what their purpose is. Besides, it has been explained how effective they are earlier in this thread. Perhaps you ought to re-read it again to better understand my question.

 

EDIT: Thank you for the document non the less.

 

If you are well aware then why ask? What part is theory according to you?

 

Are you denying the fact that prop thrust increases the lift over the wing section covered by the accelerated funnel of air? Or the benefits gained by increasing the lift over the outboard section to match that of the energized root section?

 

I find it rather funny that you would question it considering that you have these very good examples of said "theory" in action with the Bf-109 & P-38 aircraft.

 

I'll repeat myself from earlier:

 

The reason that Messerschmitt didn't go with full span slats is simple: It wouldn't do much good on a prop fighter. (A jet is a different matter, explanation below)

 

The span of the slats was carefully established around the knowledge that the wing root always stalls at a later AoA than the outboard section, and that the higher CLmax of the wing root is increased even further as air is accelerated over the wing by the prop when power is turned on.

 

As a result the slats were designed & placed so as to cover the areas which are out of the accelerated airstream and don't benefit from the extra lift generated in this area, the slats increasing the lift of the outboard section to match that of the root section. End result is that the overall lift of the wing with power on is increased by as much as 20%.

 

Full span slats would've been just as easy to produce and were infact manufactured and used on several other aircraft designs where the wing was raised above the prop wash. Putting full span flaps on a prop job with the wings situated directly in the middle of the prop wash would however have been an extremely bad move as the deployment of the slats would have then been counteracted during a large part of the AoA range, which in the end would only result in an actual loss of lift when it was most needed. Hence Messerschmitt's decision to only add slats to the outboard section of the 109's wings, as this would greatly benefit the aircrafts maneuverability and stalling speed with power on, whilst aircraft with the wings out of the accelerated airstream (or jets) often featured full span slats or slots.

Edited April 16, 2015 by Hummingbird

[[DBS]TH0R]

I am referring to posts #20 and #59. Unless there isn't a discrepancy between said posts and yours then my question is indeed unfounded.

[GrapeJam]

The high cockpit noise was due to the placement of the exhausts, it has nothing to do with the engine, which was said to run fine btw. The aircraft was also described as being in fine condition.

 

Fine compared to what? The Germans captured a pristine Ash 82FN engine before?

 

Top speed reached at SL was 520 km/h (TAS), measured with an external trail end measuring device.

 

* is forszah, War Emergency Power.

Are you going to tell me that Soviet instruments were so bad that it had a 60km/h disparancy at SL?

 

Actually not, the Russian turn time similar to the Finnish one is with gunpods on.

The G2 had 2 rows: 1 with gun pods and one without, the one without gunpod had a turn time of 20,5-21,5s.

[Hummingbird]

The G2 had 2 rows: 1 with gun pods and one without, the one without gunpod had a turn time of 20,5-21,5s.

 

20-21.5 sec, it took 1.5 secs longer to the left.

 

The Finnish test specifies a 22 sec time for a 360 deg turn, same as the Soviet test with gunpods.

[GrapeJam]

20-21.5 sec, it took 1.5 secs longer to the left.

 

The Finnish test specifies a 22 sec time for a 360 deg turn, same as the Soviet test with gunpods.

And you're sure Finnish test wasn't turning to the right?

 

Really 21.5s, 22s, it makes very little difference, 0.5s is a perfectly acceptable margine of error.

 

And the G2 in Finnish test had no gun pods, it was also limited to 1.3 ata.

[NineLine]

Oh man... when did we get a Yak 3 and G2 in game?? I have to go home tonight and pick those up!

 

That's right... Thread topic: 'Some opinion about maneuverability of Bf109K-4'

 

Keep it on the DCS Modules, specifically the Kurfurst please. This is my last written warning.

[Hummingbird]

I am referring to posts #20 and #59. Unless there isn't a discrepancy between said posts and yours then my question is indeed unfounded.

 

Post #20 is down right wrong, and for the reasons explained in my recent posts.

 

Ofcourse the slats will increase the overall CLmax of the wing, they prevent the outboard section from stalling altogether for pete's sake! ^^

 

It's exact same reason that other designers relied on downward wing twist (washout) = to prevent the tips from stalling too early before the root section. Only problem with that method is that you don't actually increase the lift of the outboard section to match that of the root section, you just decrease its AoA so that it stalls at roughly the same time as the root.

The slats on the other hand actually increase lift, A LOT, on the outboard section to match that of the root section, resulting in a significant increase in overall lift.

 

As for post #59, what about it?

Edited April 16, 2015 by Hummingbird
small typo corrected "AoA" to "time"

[GrapeJam]

Oh man... when did we get a Yak 3 and G2 in game?? I have to go home tonight and pick those up!

 

That's right... Thread topic: 'Some opinion about maneuverability of Bf109K-4'

 

Keep it on the DCS Modules, specifically the Kurfurst please. This is my last written warning.

No, I'm just using the Yak 3 as an example that the slats don't increase lift as much as some here think.

[Hummingbird]

And the G2 in Finnish test had no gun pods, it was also limited to 1.3 ata.

 

I know, that's the point I've been making, showing you the discrepancy, one that is there because of differences in testing methods, invironments & equipment etc...

 

Now let's stick to the topic.

[GrapeJam]

I know, that's the point I've been making, showing you the discrepancy, one that is there because of differences in testing methods, invironments & equipment etc...

 

Now let's stick to the topic.

Yeah, except the G2 in Soviet test wasn't limited to 1.3 ata.

[Hummingbird]

No, I'm just using the Yak 3 as an example that the slats don't increase lift as much as some here think.

 

You can't use as an example at all though, seeing as it's a completely different design.

 

Only way for you to use it as an example would be if one ever featured slats so you could actually make a direct comparison of one with & without slats. But there was/is none.

[NineLine]

No, I'm just using the Yak 3 as an example that the slats don't increase lift as much as some here think.

 

Just stay focused guys, thats all I ask, these stray way to close to ego arguments more than good helpful discussions. I often wonder how you guys have any time to fly in the sim when you are all too busy waging forum war ;)

 

And this isnt singling you out Grape, its the entire thread and threads like this....

[GrapeJam]

Anyway, why is the K4's weight still at 3182kg? Even if this figure is without MW50(which weighted 77kg), adding it up, the K4 would still weight only 3259 kg, 97kg lighter than it should be.

[Hummingbird]

The Bf-109 K-4 featured an all up weight of 3,362 kg fully loaded with all the extra equipment available, safe for drop tank & gun pods.

 

But hey the Mustang is rather light ingame as well, so..

 

PS: Interesting note whilst looking at the stalling speeds of other aircraft, the Me262 stalls at 175 km/h (108 mph) flaps up, clean, no benefit with engines on or off either - prepare for all the propjob pilots to scream once this baby becomes available :megalol: (The Me262 & Spit XIV are going to dominate the WW2 servers ^^)

Edited April 16, 2015 by Hummingbird

[GrapeJam]

The Bf-109 K-4 featured an all up weight of 3,362 kg fully loaded with all the extra equipment available, safe for drop tank & gun pods.

 

Yeah, but what's the K4's weight in DCS?

 

But hey the Mustang is rather light ingame as well, so..

 

Light?

 

The P51D in DCS at full weight is 4566kg, 10066lbs, the weight's perfectly accurate.

 

PS: Interesting note whilst looking at the stalling speeds of other aircraft, the Me262 stalls at 175 km/h (108 mph) flaps up, clean, no benefit with engines on or off either - prepare for all the propjob pilots to scream once this baby becomes available (The Me262 & Spit XIV are going to dominate the WW2 servers ^^)

Yeah, what's the Me262 thrust to weight ratio again?

Edited April 16, 2015 by GrapeJam

[Hummingbird]

Yeah, but what's the K4's weight in DCS?

 

Light?

 

The P51D in DCS at full weight is 4566kg, 10066lbs, the weight's perfectly accurate.

 

I was more refering to the fact that it feels a little too light ;) Seriously those ingame manu figures probably don't mean anything.

 

Yeah, what's the Me262 thrust to weight ratio again?

 

A much better one than any prop job at high speed. It's not supposed to hang around in a sustained slow speed turn fight if that's what you think, but rather stay at high speed and only turn with opponents for the first 180 deg, and if it hasn't dispatched them by then, simply break off, extend up out of reach, turn around and give it a go again.

 

With a good pilot it will be near untouchable, just as it was/is in IL2.

 

But now we're straying, so if we wanna continue that debate I suggest a new thread in the WW2 subforum.

Edited April 16, 2015 by Hummingbird

[NineLine]

Seriously those in game menu figures probably don't mean anything.

 

What? They change with your load, so I would imagine they do mean something....

[Hummingbird]

What? They change with your load, so I would imagine they do mean something....

 

Yes, but I don't think they necessarily reflect the actual weights used in the "behind the scenes" calculations.

 

But if they do, well then it's a bit worrying that they got these wrong as well.

[gomwolf]

Oh c'mon, do you think stall speed in TAS gets lower with higher altitude or something? Plus air war on the Eastern front was all low altitude, usually tree top level so there's a good change it's at SL.

 

British test of captured G2/trop had stall speed of 112mph IAS clean, seems pretty agreeable to me.

 

Regarding the climbrate, Finland's pretty cold so it should increase engine's power at low altitude because of denser air.

 

 

That is exceptionally bad result between captured aircraft test and captured aircraft was shotdowned once. I couldn't believe it could be perfect performance.

[NineLine]

Yes, but I don't think they necessarily reflect the actual weights used in the "behind the scenes" calculations.

 

But if they do, well then it's a bit worrying that they got these wrong as well.

 

Pretty sure they do effect the behind the scenes calculations, otherwise how else would they be effected when adding and removing ordnance?