FW190 vs. BF109: Turn Radius (2011)

[ink]

Sure. The 190 is an energy fighter....

not to hack your reply but I just want to point out something....all fighting is "Energy fighting" whether its BnZ or TnB or "knife fighting" which is a combination of BnZ and TnB

I see a lot of people say BnZ is "energy" fighting...its kind of a misnomer, for it is ALL Energy fighting.

[Stoney]

A stall is part of the flight envelope. It's not a very efficient part but you're still flying. The wings don't stall completely all at once, The inner wing with the flaps stalls first, the ends generally stall last. Since this is where the ailerons are they retain roll authority.

Actually, for most of the planes in the game, the wingtips stall first, then the root.  Its why everything wants to roll over on its back when you stall the plane.  Now, these days, most commercially produced planes are designed to stall at the root and not the tip, so you maintain aileron authority.  Just another important Cliff Clavin piece of info... 

[Stoney]

I suspect the huge difference & I'm sure the areo guys will pan me for this, is that in AH, many planes can be held in the buffet and turn quite well while in this situation. Realistically, I'd Imagen that with the air separating at the wings and all the turbulence above the wing (causing the buffet) would cause the plane to just drop and loose even more e, preventing one from maintaining a turn in the buffet for longer than a split second.

Well, in-game, and HTC can correct me if I'm wrong, the buffet tells you that the plane is close to stall speed--not that it has already stalled.  So, in reality, you haven't stalled yet, you're basically on the edge of a stall, close to the maximum lift coefficient, so the best turn radius is effectively in, but not beyond, the buffet.  Its the same in real life, its just that no one in real life wants to have their plane depart controlled flight like we coax them to do in-game...

[Angus]

Stoney, my point with the 190's nimbleness was exactly the rollrate, not the turn. It would be able to enter a turn quite fast.
When it comes to sustainability the 109 will normally have the edge, with the only exception of the altitude where the 190 has more engine power, and then a light 190.
For the rough turn, the 109 had the tendency of dipping the outboard wing, - but there you are talking of a turn entry at high speed.
Actually, you could make a Spitfire do that as well.

[bozon]

I suspect the huge difference & I'm sure the areo guys will pan me for this, is that in AH, many planes can be held in the buffet and turn quite well while in this situation. Realistically, I'd Imagen that with the air separating at the wings and all the turbulence above the wing (causing the buffet) would cause the plane to just drop and loose even more e, preventing one from maintaining a turn in the buffet for longer than a split second. For example, in a 109 or a spit, I can hold the plane in the buffet for as long as necessary, even climb while its buffeting....

First, this picture is horribly wrong because it deleted the single most important part of the airflow - the big circular airflow on the trailing edge of the wing. Instead, (many) textbooks show this nice flow going past the trailing edge, leaving it undisturbed  as if the wing never passed through the air. It is the circular flow that is responsible for the generation of lift. What happens in a stall is that the one semi-ordered rotational flow breaks into small vortices as in the 3rd sketch. This destroys the "suction" of air from over the wing and stops the large-scale circular flow pattern around the whole wing (the air above flow faster than the air below bla bla Bernuli).

Here, see what happens behind the wing (cuts part of the circular flow behind):
http://youtu.be/Vjk9Ux2COx0
The advantage of this movie is that it uses drifting particles to visualize the flow instead of smoke. Smoke trails tend to stick to the laminar flow and do not highlight the rotational flow behind the wing. Some of the smoke is sheared and enter the vortex, but then it is well mixed and look like uniform faint haze, so it is hard to see - this is why it is named "separation" of the air flow. The air does not really leave the wing (no vacuum over it which would actually increase lift..) it is the smoke lines used in wind tunnels that give this impression.

The transition in many cases is not as sudden as you might think. The large circular patters on the trailing edge starts to wobble and small vortices break off of it before it is completely destroyed. This instability is part of the buffeting. You can see it in this movie (this time with smoke, notice the difference in what you see vs. the other movie):
http://youtu.be/6UlsArvbTeo
The wobbles of the flow lines behind the wing is the onset of stall, but the wing still produces lift at this stage.

Another effect is that parts of the plane reach this stall before others. A twist along the length of the wing will cause the root to stall before the tips. In a real plane there may be turbulence created around parts that are not supposed to create lift at all, like fuselage/canopy sections that are not ideally aligned with the airflow at high AOA.

[moot]

Very nice demos..

[mthrockmor]

Forgive my ignorance of aeronautical engineering but...

Don't they have CAD programs that you enter the plane design and it can basically tell you exactly what the plane can do at what altitudes? I've "heard" that these programs are now small enough to fit onto laptops. Is this true? If so, would this not help answer these types of questions?

On a related note years ago I read a story from Naval Aviation where the test flight unit in Maryland compared the F6F, F4U and Fw-190. I don't recall which versions of the birds though the general outcome was the Navy planes were pretty close to each other and both out turned the 190, though only modestly so. This is from memory so I could be way off, but it seems the 190 was a pretty good turner. Maybe better then how it is modeled in AH.

But I could be all wet on both accounts.

Boo

[PJ_Godzilla]

Forgive my ignorance of aeronautical engineering but...

Don't they have CAD programs that you enter the plane design and it can basically tell you exactly what the plane can do at what altitudes? I've "heard" that these programs are now small enough to fit onto laptops. Is this true? If so, would this not help answer these types of questions?

On a related note years ago I read a story from Naval Aviation where the test flight unit in Maryland compared the F6F, F4U and Fw-190. I don't recall which versions of the birds though the general outcome was the Navy planes were pretty close to each other and both out turned the 190, though only modestly so. This is from memory so I could be way off, but it seems the 190 was a pretty good turner. Maybe better then how it is modeled in AH.

But I could be all wet on both accounts.

Boo

There are CFD methods that can provide very good correlation with test/real-world. My background (before crossing to the dark side) otoh, was with rigid-body and elastodynamic CAE using ADAMS and I'd say your results THERE are only as good as the model you postulate.

[PJ_Godzilla]

not to hack your reply but I just want to point out something....all fighting is "Energy fighting" whether its BnZ or TnB or "knife fighting" which is a combination of BnZ and TnB

I see a lot of people say BnZ is "energy" fighting...its kind of a misnomer, for it is ALL Energy fighting.

Sure, I'll buy that. However, I'm referring to BadBoy's local definition with respect to the E-M diagrams. Recall, if you've seen this - and IIRC, Shaw uses the same local defn - that the "energy fighter" and "angles fighter" can be defined readily by a comparison of their E-M diagrams. In some cases, the differentiation is almost impossible or is subject to configuration (consider Ki-84 vs. Spitty 9). Also note that what is an energy fighter in one compasrison will be an angles fighter in another (consider FW190d vs. Spitty 9, then FW190d vs. Me262).

So, I'll buy your generality but was being pretty specific here.

BTW, if you haven't seen Badboy's development of the E-M, you can find it here: http://www.simhq.com/_air/air_011a.html

[FLS]

Actually, for most of the planes in the game, the wingtips stall first, then the root.  Its why everything wants to roll over on its back when you stall the plane.  Now, these days, most commercially produced planes are designed to stall at the root and not the tip, so you maintain aileron authority.  Just another important Cliff Clavin piece of info...  

I thought it was torque that rolled them over when they departed. Why would the wingtips stalling first instead of last cause that? If the wingtips stall first why do you still have roll authority right up to departure?

If the wingtips stall first wouldn't you also see a difference in behavior between stalling with flaps out and flaps in since the inner wing would still stall first with flaps out?

[PJ_Godzilla]

I thought it was torque that rolled them over when they departed. Why would the wingtips stalling first instead of last cause that? If the wingtips stall first why do you still have roll authority right up to departure?

If the wingtips stall first wouldn't you also see a difference in behavior between stalling with flaps out and flaps in since the inner wing would still stall first with flaps out?

Imagine you're in a turn. The velocity of the tip relative to freestream is lower - and usually hits stall speed first. Stoney points out obliquely that, back in the day, they didn't use aero or geometric washout to get either a higher max alpha or a lower alpha, respectively, to prevent tip stall.

As for the inner wing stalling first flaps out, no... first, the relative airpseed is higher there, second, popping flaps reduces the stall speed.

Interesting side note: Stoney actually got the NACA sections i/b, o/b for the 190. It looked to me from that as though the 190 actually has aero "wash-in" - the tip section has a lower max alpha than the i/b section. No wonder the 190 had vicious tip stall.

[FLS]

Performance in a turn is really a separate issue. Flaps increase the effective incidence so even with wash-in enough flaps would create washout.

[Stoney]

I thought it was torque that rolled them over when they departed. Why would the wingtips stalling first instead of last cause that? If the wingtips stall first why do you still have roll authority right up to departure?

If the wingtips stall first wouldn't you also see a difference in behavior between stalling with flaps out and flaps in since the inner wing would still stall first with flaps out?

Here's a response I posted in another thread that explains why most WWII fighters are susceptible to tip stall:

http://bbs.hitechcreations.com/smf/index.php/topic,307351.msg3974910.html#msg3974910

The torque is the primary force that encourages them to flip over on their backs, because there's not enough aileron authority when stalled to counteract the other destabilizing forces (primarily torque).  In a hard turn, you may even create a situation where one tip is stalled and the other isn't.

[PJ_Godzilla]

Performance in a turn is really a separate issue. Flaps increase the effective incidence so even with wash-in enough flaps would create washout.

Ah, okay, you're talking about stall without turn. In this case, I agree - popped flap should decrease max alpha inboard. However, real world, I'd expect one side to stall first. I also agree that sufficient flap inboard in the absence of wash-in (or with sufficiently small wash-in) would create wash-out.

I just don't see why, given that freestream for all sections would be slightly different and given confounding torques like the engine, and given stall (where aero forces don't straighten much of anything) you'd expect anything without strong washout to NOT tip stall. Even with good washout, if the velocity drops enough or if alpha is high enough, I'd still expect no predictable roll answer if there is an engine torque present.

[PJ_Godzilla]

The torque is the primary force that encourages them to flip over on their backs, because there's not enough aileron authority when stalled to counteract the other destabilizing forces (primarily torque).  In a hard turn, you may even create a situation where one tip is stalled and the other isn't.

This is more like the scenario I was talking about. In the 109, I'd expect, if I'm able to induce a left tip stall (harder, given the slats on the 109), a fairly wicked roll about the negative longitudinal but a much milder one turning the other direction - since turning right, engine torque and the lift asymmetry will tend to counter.