Bf109 K-4 pre-stall buffeting...

I like your elementary arithmetic wingspan circulation calculations... Prandtl, Glauert, Treftz and Fr. Lotz worked in vain. :)

 

It was never any secret that it was a very simplistic example, and that for the very reason that it was just there to explain a point in a simplistic manner.

 

You're always welcome to demonstrate how in your mind outboard mounted slats didn't increase the overall CLmax of the wing, esp. in a power on situation :thumbup:

Please demonstrate YOUR and SCIENTIFICALLY correct vision of the matter OR give the CORRECT test results for 109F/G/K wind tunnel or flight test results FOR 109F/G/K maximal lift coefficient that prove your point of view.

 

Please never refer to 2D or rectangular wing wind tunnel results for isolated wing. Please do not refer to the reports referred to the different types of the planes with different taper ratio, etc, etc.

 

We did that with the Fw190 & P-51... didn't get us very far...

I must have missed that ;)

 

Link? Or are you talking about those few circles you flew?

 

Yeah you must, esp. the physics and the original documentation from both FW AG & NA, but let's just ignore that right? :thumbup:

 

I don't need to give you these links, you already saw them, but here goes:

http://forums.eagle.ru/showpost.php?p=2599422&postcount=140

http://forums.eagle.ru/showpost.php?p=2600000&postcount=146

http://forums.eagle.ru/showpost.php?p=2600086&postcount=150

 

There's lots more, but what does it matter? doesn't change anything anyway, your minds are set.

Edited January 13, 2016 by Hummingbird

We never refuse to correct something that was found outside ED if it is really proven. There are always many reasons to make a mistake: insufficient info or contradicting docs, bugs in the code, project build problems, etc.

Sometimes changes in one place can cause unexpected effect in the place we can not even think about.

 

We always check the issues reported. But we never will follow some "experts" who think that only they are the greatests aerodynamic guru with a secret knowledge.

 

Our experts are a lot of documents that always are cross-checked, cross-compared, cross-recalculated.

Our experts are pilots currently flying the planes or pilots who flew the original planes.

We made L-39, for example, as a plane that is very popular in many countries, with no fear of criticism after it was tested in Russia by a lot of L-39 pilots and instructors.

 

And nobody says that we must satisfy some persons who demand to prove, prove and prove. If we publish something it's only our good will and extra time spent to produce it.

 

You were provided with orginal documentation from both FW AG & NA, it doesn't get anymore scientific or real than that. Still didn't change a thing..

***sniped***

 

But again, you are still basing that off a video, we have no real reference for this video, you couldn't even be bothered to show your control input through the video. So its like you want to do half the work and everyone else to just assume the other half is there.

.

 

Is that all I needed to do to get you to see the issue? Well damn, let me fire up my machine and record a new video with control inputs shown.

 

Won't make any difference but ok I'll do it.

And will not.

 

Trust me, I know.

Yes, I ignore these calculation because (please read it twice or thrice if you do not understand)

 

the square-law L/D polar is not valid for the high AoA and CL

 

The second point is that this "rabbit from a hat" results never shows the whole set of input data and used math - it's a great secret, of course... I understand... but it's not a way the evidences for a discussion is presented.

 

In that case you probably shouldn't have mentioned propeller efficiency as the reason the charts didn't match the ingame results ;)

 

According to the ingame results the Fw190 is missing some 400 hp in sustained turns at 350-400 km/h.

I only point one of reasons that is not so obvious (prop efficiency figures) but there is the second and it must be obvious for any person who deals with flight dynamics... very significant differnece in wing loading and non-quadratic polar...

 

1. The prop efficiency is virtually the same for both aircraft, within 1%.

2. CLmax (which can be derived from stall speed) is used to calculate the actual lift to weight ratio, your claim that "the square-law L/D polar is not valid for the high AoA and CL" is nothing but a red herring, sorry.

 

And, by the way, I have a puzzle for anybody who wants to try to put a beam of light for the power figures for P-51 and Jumo-213: do these figures take in account the jet thrust - both, only one or neither?

 

What generates more exhaust thrust, a 2100 hp engine or a 1680 hp one?

Edited January 14, 2016 by Hummingbird

What i noticed is that i can catch the stall of the p51 ,it falls on one wing gradually, easyer to catch the stall at a lower speed .

 

On the other hand the 109's stall is more violent it's either 1(wing stalls) or o(wing doesn't stall) and there is very little between the wing falling hard and not falling at all.

 

It doesn't make sense. For an almost equal wing loading(whel loaded with fuel like below) the 109 has s thicker wing ,slats, and a better power to weight ratio.It should be the p51 that stalls harder and the 109's stall should be easyer to ride.

 

 

p51 wing loading 185.02 28% fuel

109 wing loading 187.9 10% fuel

 

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Edited January 15, 2016 by otto

I think that you are comparing apples and oranges. And the stall is more violent in a wing with slats... you know, the whole wing stall at nearly the same time in the 109 config. Will be better if you can do the same test with a 109 with slats and a 109 without slats.

What generates more thrust at idle - AL-31 with closed nozzle and with the open nozzle?

 

So you're saying that the P-51 gained more exhaust thrust because of a narrower exhaust nozzle now?

 

Both the 109 & 190 were equipped with proper ejector exhausts that directed the flow straight back, the P-51's curved less acutely.

 

I'm just gonna stick to the jets from now on....

Edited January 15, 2016 by Hummingbird

Hummingbird, I'd like to see MATH from you. Something more doubtless and solid than bare fragmental statements you are claiming. Here and now. And otherwise you are free to claim anything you want. I am sick and tired spending the time I could use more fruitfully.

 

Hi Yo-Yo on behalf of the people that read your comments but don't actually get involved with the topics I want to say thank you for your comments.

 

It really is insightful to read your post and understand how you work, I can entirely understand your frustration however we really do appreciate you spending time answering (some times fruitlessly) peoples questions! :thumbup:

Edited January 15, 2016 by Krupi

I think that you are comparing apples and oranges. And the stall is more violent in a wing with slats... you know, the whole wing stall at nearly the same time in the 109 config. Will be better if you can do the same test with a 109 with slats and a 109 without slats.

 

 

A stall is more violent in a wing with slats ?

 

Concurrent testing was concluded by the Scientific Research Institute of VVS and LEE NKAP in testing the effectiveness of elongated automatic slats on the MiG-3. With slats, the engineers and test pilots noted that the fighter ceased to stall without warning, the fighter also proved easier to control while executing aerobatic maneuvers. The MiG-3 was easily leveled prior landing; in other words, it gave more control and did not have a tendency to roll over to the side when the pilot pulled on the control stick.

- The results noted: Automatic slats, length 2004 mm, on the serial MiG-3 considerably eliminated stalls and increased controllability when speed was lost. Before a stall, the aircraft would warn the pilot by rocking, and when a stall was imminent, the aircraft dipped its nose and banked to the right. The installation of the slats considerably simplified piloting and made it possible to control the aircraft with a loss of speed.

- From empirical tests it was seen that fighters with “smooth” wings, critical speed leveled off at 190 km/h but when the slats were added the speed dropped to 155-160 km/h. In certain conditions, for example when turning, the MiG-3 completely stopped stalling. Its behaviour tended to give more warnings than with 1573 mm slats.

- The majority of test flights were done by test pilots A.I. Zhukov, V.N. Savkin, V.T. Sahranov, noting that thanks to the slats, piloting the plane was a lot easier."

 

 

I can post about 1000 pieces of text that show that aircraft stall characteristics improve when having slats.

Edited January 15, 2016 by otto

Speaking of jet thrust, what kind of thrust is modelled in DCS WW2?

 

Propeller thrust obiviously, but besides

 

exhaust thrust?

coolant/oil radiator thrust?

A stall is more violent in a wing with slats ?

 

Concurrent testing was concluded by the Scientific Research Institute of VVS and LEE NKAP in testing the effectiveness of elongated automatic slats on the MiG-3. With slats, the engineers and test pilots noted that the fighter ceased to stall without warning, the fighter also proved easier to control while executing aerobatic maneuvers. The MiG-3 was easily leveled prior landing; in other words, it gave more control and did not have a tendency to roll over to the side when the pilot pulled on the control stick.

- The results noted: Automatic slats, length 2004 mm, on the serial MiG-3 considerably eliminated stalls and increased controllability when speed was lost. Before a stall, the aircraft would warn the pilot by rocking, and when a stall was imminent, the aircraft dipped its nose and banked to the right. The installation of the slats considerably simplified piloting and made it possible to control the aircraft with a loss of speed.

- From empirical tests it was seen that fighters with “smooth” wings, critical speed leveled off at 190 km/h but when the slats were added the speed dropped to 155-160 km/h. In certain conditions, for example when turning, the MiG-3 completely stopped stalling. Its behaviour tended to give more warnings than with 1573 mm slats.

- The majority of test flights were done by test pilots A.I. Zhukov, V.N. Savkin, V.T. Sahranov, noting that thanks to the slats, piloting the plane was a lot easier."

 

 

I can post about 1000 pieces of text that show that aircraft stall characteristics improve when having slats.

 

I´m not saying the contrary. I know that slats reduce the Vs. Maybe I put the sentence up side down

And the stall is more violent in a wing with slats... you know, the whole wing stall at nearly the same time in the 109 config

I try again: "The slats like how they are configured in the 109, placed near the wingtip avoid that premature stall that start in the wingtip of the wing, and yes you got all the benefit of a wing with slats but then if you reach the new Vs that wing is going to stall from the wingtip to the root near at the same time thus entering in a more "violent" stall"

 

Also again don´t compare apples to oranges, the wing of a Mig-3 seems very different from a Bf-109 wing