why the spit turns most effectively at the limit edge and the 109 doesnt
 

i found out long ago that if you turn a 109 to the limit eventually you reach 200 kph and starts turning very slow

on the other hand to sustained turn the spit the best is fly it at the stall limit that is as slow as posible

why is this?

anybody?

maybe the slats in the 109 are actually a disadvantage?

No just the fm is very bad ATM spits can turn like a biplane!!!! :(

Generally slats cause more drag and effect also higher energy bleeding but other hand allows to get higher angle of attack - good for deflection shoting. Spit other hand has elipitical wing desing which reduced induced drag which is important at slow speed and high angle of attack and with lower wings loading it casue less energy bleeding in turns then 109.

I found that slats in CLoD 109 dont work also like should. It is open too late - at too low speed - ab. 150 km/h where it should open at 180 km/h - in level flight with idle power. I think it open also at too high angle of atack - it should open earlier.

Also slats should casue gentle stall in 109 and easy recover in stall or spin.

What we need is the Dynamic Stall in the FM, I think that those strange turns that some planes do (not only the Spit) without lose control is due to the lack of this Dynamic Stall, they reached the point where this stall should start but its not modeled in the FM.

Acctualy the 109 stall is not easy to recover in CloD. In the old IL2 when the plane started to stall was only necessary to neutralize the controls and the 109 recovers alone. In CloD the 109 stalls and enter in a flat spin very fast and it is very difficult to recover. This is not historically accurate i guess. The 109 had a gentle stall. Someone with better english have to report this in the bugtracker.

That is the standard stall system, Dynamic Stall is a different type of stall.

i think spits smallest and fastest turn are at about same speed, 109 samllest turn is at a slower speed than its fastest, thats why spits tend to be called easier as you dont have to watch geometrics as much (know when priority drifts to smaller and slower or faster and wider turn)

Dynamic stall

Lolz

A nice video, the reproduction of the vortex produced by the Dynamic Stall :grin:

http://www.youtube.com/watch?v=Om8Osyxy494

From seeing the cfm clip: That is for me the definition of stall: the breakdown of flow on top of the wing. I do not know of any other definition of stall.

So can somebody explain to me what's so special about dynamic stall?

From http://en.wikipedia.org/wiki/Stall_%28flight%29

There she blows!

Slats do not cause more drag - higher angles of attack permitted by slats do.

1, The Spitfire doesn't have elliptical wings, from the aerodynamic POV. Otherwise stall would be awful - a true elliptical wing stall as a whole. That's why most planes have a washout/twist built in the wing to 'ruin' the even lift distribution and make the outer wing area stall later than the inner.
2, Lower induced drag on the Spit doesn't have anything to do with wing shape, its simple that its a huge wing, and needs less angle of attack to provide the same lift. Less angle of attack - less drag.

The wing is elliptical. Lift distribution is modified to a certain degree that's true, but it still has lift more evenly distributed than the wing of a 109. And the elliptical shape is responsible for that. Your claim is not exactly true, because induced drag simply has something to do with the shape and lift distribution. You are right that the wing of a spit is large and that's why lower angle of attack ... ok. But the shape contributes too.
BTW if the elliptical shape didn't bring advantages, why would the Brits bother to manufacture them?

I'd love to see some lift distribution graphs to support that.

Certainly shape is a factor, but I do not think it's a major or measurable factor compared to sheer wing size. The Spitfire had a very large wing for a very small airframe, much larger than any other with the possible exception of the Zero.

If wing shape would have been such a factor, planes like the Curtiss Hawk, Zero or Hawker Hurricane wouldn't run circles around the Spitfire, but they did.

Simply because the British Air Ministry specified an 8-gun armament, and Supermarine could not find space in the wings to house them without enlarging the original trapezoid wing of the Spitfire (which was meant for a four gun armament). The design team was simply practical about it.

Spit has a negatively twisted wing that means that angle of attack will be always lower on the wingtip + wingtip probably uses different airfoil than root with different lift characteristic so that it will never stall first. That means spit can have eliptical wing without dangerous stall characteristics.

There are plenty of resources on the internet. Not sure if one can find exactly the spitfire's lift distribution, but generally there are many sources for elliptical and other shaped wings.

Size, shape, weight, airfoil .... many variables go into the equation. No need to make simplifications like this.

http://en.wikipedia.org/wiki/Supermarine_Spitfire
In 1934, Mitchell and the design staff decided to use a semi-elliptical wing shape to solve two conflicting requirements; the wing needed to be thin, to avoid creating too much drag, while still able to house a retractable undercarriage, plus armament and ammunition. Beverly Shenstone, the aerodynamicist on Mitchell's team, explained why that form was chosen:
The elliptical wing was decided upon quite early on. Aerodynamically it was the best for our purpose because the induced drag, that caused in producing lift, was lowest when this shape was used: the ellipse was ... theoretically a perfection ... To reduce drag we wanted the lowest possible thickness-to-chord, consistent with the necessary strength. But near the root the wing had to be thick enough to accommodate the retracted undercarriages and the guns ... Mitchell was an intensely practical man... The ellipse was simply the shape that allowed us the thinnest possible wing with room inside to carry the necessary structure and the things we wanted to cram in. And it looked nice.

So again, you are doing a simplification here.

My 2 cents...

Lift is related to the wing foil used and the surface area of the wing.
An elliptical wing is not needed to increase the surface area or change the wing foil. However....

One of the big culprits of drag in a wing are the wing tips. The elliptical wing is very good at not creating a vortex in the wing tips thus reducing drag.


See http://en.wikipedia.org/wiki/Wing_tip

That's simply called washout and is found on the vast majority of WW2 fighters. There's nothing magic or uncommon in it.

Elliptic planform theoretically means even lift distribution. Even lift distribution means the whole wing stalls all at once. With a twisted wing you no longer have an even lift distribution, no reduced induced drag, and no dangerous stall charateristics.

Simply to put from the aerodynamic POV, it's not an elliptic wing.

Again the problem is that the Spitfire does not have an elliptical wing from the aerodynamic POV as explained above, so the theoretical lift distribution properties of a aerodynamic wing do not apply to the Spitfire.

What I have pointed out that you have made a very specific claim about the relative lift distribution on the 109 and Spitfire, based on generalisations. I wonder if even Supermarine or Messerschmitt were aware of how it looked like back in the 1940s...

It's a simplification but its ultimately giving the right results as can be cross-checked by practical examples. I am quite certain that the airfoil shape has next to non-measurable effect on the Spitfire turning characteristics and it shows no special qualities - fighters with low wingloading tend to turn well, nothing new in that.

Whatever increased efficiency they may or may not have gained by using the shape they lost it as they sacrificed the aspect ratio in return. Elliptical wings seemed to be a nice idea in 1930s, and the theory was that they would offer some advantage, but as it turned out it simply did not, and everybody dropped them quickly, including Supermarine when it first got a chance (Mark 2x series Spitfires).

I have to agree with Kur this time.

The elliptical form in itself had aerodynamically only most minimal to vanishing advantages above a trapezoid wing with rounded wingtips but had some advantageous side effects such as increased wing aera and reduced relative chord thickness due to the long chord lengths. That is why supermarine chose elliptical wings above trapezoid wings because these side effects provided advantages with respect to the specifications issued by the ministry.

It came at the cost of a wing very difficult to produce and it was commonly abandoned by all air forces.

If the elliptical form would have been so advantageous why did so few other air forces not adopt them? Supermarine was neither the inventor nor the patent holder of the elliptical wing.

I think you answered your own question when you noted

War espically WWII was more about logistics and economics.. Along those same lines is one of the reason they went with the P51 over the P38.. economics

Just found this article, really nice to read.
http://thoughtality.com/the-spitfire-wing
It looks like the decision was really influenced by the need to accommodate 8 guns.

A trapezoid wing with rounded wingtips comes close to the "ideal" elliptical wing.

And as Kurfurst mentioned, the advantages of truly elliptical wing are more theoretical than practical. Just in 1934 when the wing was designed it all looked a bit different than during WWII. Average performance of fighter planes was much lower and they probably saw the need for good low speed handling and efficiency. As performance and speed increased these aspects were less important. Also the 8 guns in wings design became obsolete with introduction of more powerful canons.

Back to the original question. I believe the 109 performs worse than the spit at very low speeds, because when it has to deploy slats, the wing is already working far behind its optimum. The spit can achieve similar lift without slats and with lower angle of attack. So yes, the induced drag would be lower. (I don't want to dig into boundary layer separation and stall questions)

At the same time Kurfurst is right, that this aspect became obsolete during WWII.

Agreed, and the He 70 sure had a wing that Mitchell and the guys had peeked at...



/mazex

I read somewhere Spit's turning capabilities were also related to the way the wing root was designed and implemented, hence forcing the stall to start at the wing tip and moving inward to the root, so avoiding the 'stall as a whole' mentioned by kurfurst at first.

Actually some supermarine engineer said that they looked at the He70 rather in terms of smoothing things up. The He70 wing is albeit elliptically also thicker than that of the spit and a gull wing.

But when you look at the wing root fuselage transition at the trailing edge the similarities are there with the long stretched curve and the soft transition on the upper side:

http://www.luftarchiv.de/flugzeuge/heinkel/he170v1.jpg

http://www.luftarchiv.de/flugzeuge/heinkel/he270_3.jpg

(courtesy: http://www.luftarchiv.de/index.htm?/...inkel/he70.htm)

http://www.aeroflight.co.uk/wp-conte...itprop-vic.jpg

Well most designers tend to design wings that stall near the fuselage first. That allows the pilot to realize he is about to stall while the plane is still controllable by ailerons. And that's why the elliptical wing has to be twisted so the angle of attack is lower where ailerons are. Actually all wings are twisted to prevent sudden loss of lift and control. So no, the idea of stalling at wingtips first is a bad one. The wing is designed to stall near fuselage first.

Partly it was a Mitchell design signature, because Mitchell believed the ellipse presented the best aerodynamic compromise available. He also designed a heavy bomber (the B.12/36) and a flying boat with thin, elliptical wings; on some later projects, such as a two-seat, carrier borne version of the Spitfire, he compromised and used wings with straight leading and trailing edges.
A really interesting book to get a hold of is British Secret Projects 3 Fighters and Bombers 1935-1950

Quite similar to Heinkel whose chief designers the brothers Günther had some strange fancy for elliptical wings.

But as I said the elliptical planform in itself brought minor to none primary aerodynamical advantages over trapezoid wings with rounded wing tipps. Only secondary advantages because of higher wing surface allowing to reduce AoA for same lift and a small relative chord thickness. He may as well have achieved the same advantage with a large trapezoid wing with rounded wing tipps like in his seaplanes that he used for winning the snyder trophy.

You're right, I knew it one way or the other. Thanks!.

Had Mitchell lived longer he may well have decided the same thing; as I mentioned some of his late design projects used different wing shapes. The carrier borne and two seat Spitfire derivatives are described more fully in Morgan and Shacklady's book and I'll dig out my copy of Secret Projects.