Interceptor vs Escort.

[FLYBOYJ]

Originally Posted by ricardo

I'm agree with you Soren.... but that's not all... that captured Bf109G, that the British tested against their Spitfire Mk XIV, was not a pure fighter...it was actually a Bf109G-6/U2 (which carries underwing 20mm cannons). We all know that it is not a 100% objective test as those underwing OVERWEIGHT reduces performance. I saw an image of that captured fighter and what I can tell you is that it looks like a Bf109G-14 with 20mm gondolas under each wing.

Check this out:
http://1000aircraftphotos.com/Contri...Simms/3600.htm

"OVERWEIGHT reduces performance" To a point...

The effect of weight on stall speed is usually small, but in the most inopportune circumstances that small effect can have inordinately great consequences. Stall speed changes as the square root of the weight ratio. In more concrete terms, reducing aircraft weight by 10% below the maximum certificated gross weight will cause the stall speed to be reduced by 5%. Conversely, an airplane loaded 10% over the maximum weight will have the stall speed increased by 5% relative to the stall speed at maximum weight. That increase may equate to a difference of only two or three knots in stalling speed. If, however, the pilot is counting on operating the airplane within two or three knots of the published stalling speed, a 10% overloaded condition can reduce that expected stall speed margin to zero.

[Soren]

The underwing gondolas made the wing heavy, "Not a good thing !", and disturbed the airflow over the wings aswell. All this significantly reducing the aircrafts maneuverability.

[Soren]

Originally Posted by FLYBOYJ

On paper it doesn't seem much - I'm willing to bet dollars to donuts that 0.05 will make a differance at the end of the stick!

Not when the stick needs greater force in general

Originally Posted by FLYBOYJ

And I agree

Which means you agree that the 109 is MUCH more forgiving in the stall.

Not during stall warning!

Are we only talking stall "warning" here ?

Anyway Wing aspect ratio reduces induced drag by MUCH larger margin than the elliptic planform.

If it looks like a duck, acts like a duck.....

Hahaha !

As I said before: 3/4 of good stall characteristics is knowing when the stall is going to happen. The other 1/4 is knowing what the aircraft is going to do when it does stall.

But remember the Bf-109 is going to stall later and much more forgivingly than the Spitfire, which is my point.

[wmaxt]

First, the 109 was captured WITH the underwing gondolas installed, Obviously they flew like that so how does that invalidate the test?
Second, Slats may delay the stall but that doesn't have anything to do with the ferocity of the stall.
Third, I've read the stall of the Bf-109 is much closer to the P-51 than the Spit, blaming it on the gondolas alone isn't correct though they might make it worse.

wmaxt

[Soren]

Auto-Slats makes stall recovery very easy, and thats a fact wmaxt.

As to the ferocity of the stall, German and Finnish pilots describe it as VERY gentle in the 109.

[wmaxt]

Originally Posted by Soren

Auto-Slats makes stall recovery very easy, and thats a fact wmaxt.

As to the ferocity of the stall, German and Finnish pilots describe it as VERY gentle in the 109.

Very easy in relation to what, permanent loss of control?

I'm not an an expert on the subject, do you have something more tangable I could look at?

I've never heard of a high speed, hi AoA stall being gentle especialy in a single engine fighter with P-torque to contend with, this includes accounts i've read relating to the Bf-109.

Anybody else?

wmaxt

[FLYBOYJ]

Soren - this got nothing to do with stick forces and little to do with the aspect ratios between a Spit and a -109

Basic Flight 101 - when a wing stalls (except a swept back wing) it stalls at the wing tip first. When this happens the stick vibrates - That is your basic stall warning. That .05 percent cited earlier about the elliptical wing probably equates to a nice little buzz at the stick - no forces, just a "buzz."
An elliptical wing does this the best because of the shape of the wingtip. Many early training aircraft had an elliptical wing or something similar because of this.

A wing with LE slats is going to stall later (a slower airspeed) the stall warning will not be apparent until the burble starts on the wingtip. The warning is not pronounced as early as an elliptical wing.

Now perform a power-on stall, the Spit will give warning first, "break" first and require less and slower opposite rudder than the -109, BECAUSE....

While the 109 is hanging there, with its slats out, that big ole prop is building up more and more p factor, to keep level you're already adding opposite rudder. What do you think is going to happen at the break? A nice jerky snap that will require immediate opposite rudder or else the 109 will go spinning.

This characteristc goes back to the Spit out turning the 109 arguement and those who say seasoned 109 pilots could hold the turn with a Spit. You know why? They mastered the feel of stall burble and when the aircraft will break in the stall.

And although I never flown a Spit or -109, I could tell you that any high speed, hi AOA stall IS NOT going to be gentle as wmaxt pointed out and If I have my guess, the 109 will be a lot more violent than the Spit although the Spit won't be a parachute ride either. (I've done these in a T-34 felt like I spent 3 hours in a gym afterwards))

[Maestro]

FBJ is right. Listen to the pro, Soren.

[DerAdlerIstGelandet]

Originally Posted by wmaxt

First, the 109 was captured WITH the underwing gondolas installed, Obviously they flew like that so how does that invalidate the test?
Second, Slats may delay the stall but that doesn't have anything to do with the ferocity of the stall.
Third, I've read the stall of the Bf-109 is much closer to the P-51 than the Spit, blaming it on the gondolas alone isn't correct though they might make it worse.

wmaxt

I agree and disagree with you. At the same time I would want to test the aircaft as found but also I would want to compare it to an aircraft in a similar configuration. So I agree and disagree with you.

[FLYBOYJ]

Found some actual pilot reports with regards to ME-109 and Spitfire Stall characteristics:

This was taken from the RAF pilot report on the first captured -109 May 4, 1940

Stalling Test
“The airplane was put through the full official tests. The results may be summarized by saying that the stalling behaviour, flaps up and down, is excellent. Both rudder and ailerons are effective right down to the stall, which is very gentle, the wing only falling about 10 degrees and the nose falling with it. There is no tendency to spin. With flaps up the ailerons snatch while the slots are opening, and there is a buffeting on the ailerons as the stall is approached.. With flaps down there is no aileron snatch as the slots open, and no pre-stall aileron buffeting. There is no warning of the stall, flaps down. From the safety viewpoint this is the sole adverse stalling feature; it is largely off-set by the innocuous behaviour at the stall and by the very high degree of fore and aft stability on the approach glide.”

From James Robert Feuilherade, flies a IX Spit in South Africa

“The aircraft has very gentle stall characteristics, and there is nothing "nasty" about it. You get a nice buzz on the stick as you approach the stall giving you plenty of warning.”
And below is a section of an Air Ministry report on the Spitfire Vc Stalling characteristics........

According to this information it turned out that both aircraft possessed good stall characteristics, however the -109 gave no stall warning "dirty" the most critical time you need stall warning. This may have attributed to the many landing accidents that the -109 encountered. It seems the Spitfire gives ample stall warning both dirty and clean, and I believe this is due to the Elliptical wing. With this, I would feel a lot more comfortable flying a Spit than a -109.

[Soren]

First off I wasnt specificly talking a high speed stall FJ, so I don't know why wmaxt mentioned this.

Now about the 109 and its stall characteristics...

Messerschmitt put automatic slats on the 'outer' part of the wings. At sufficient AoA, these open, effectively extending the lift vs AoA curve. Basically this means that on the Bf-109, the outer wing sections stall at a considerably higher AoA than the inboard parts of the wing. What does this do? It virtually eliminates the wing-drop of the wing when the wing starts to stall. Plus, it allows full aileron usage up to the point at which the outer part of the wing starts to stall. This leads to a very gentle stall until the wing slats themselves stall.

So the Bf-109 will stall later and much more gently than the Spitfire, but(Assuming the Spitfire atcually had an elliptic wing "Which it didnt") I would agree that its final stall warning 'might' not be as pronounced as in the Spitfire, however it is reached much later in the 109. So nontheless the Spitfire doesnt have better stall characteristics than the 109. This is what my point was all about...

Now about the Spitfire's wing, well as I've already said it has a 2 degree twist to it, so the lift distribution IS NOT elliptical.

[FLYBOYJ]

Originally Posted by Soren

First off I wasnt specificly talking a high speed stall FJ, so I don't know why wmaxt mentioned this.

Now about the 109 and its stall characteristics...

Messerschmitt put automatic wing-slats on the 'outer' part of the wings. At sufficient AoA, these open, effectively extending the lift vs AoA curve. Basically this means that on the Bf-109, the outer wing sections stall at a considerably higher AoA than the inboard parts of the wing. What does this do? It virtually eliminates the wing-drop of the wing when the wing starts to stall. Plus, it allows full aileron usage up to the point at which the outer part of the wing starts to stall. This leads to a very gentle stall until the wing slats themselves stall.

So the 109 will stall later and much more gently than the Spitfire, but(Assuming the Spitfire atcually had an elliptic wing "Which it didnt") I agree that its final stall warning 'might' not be as pronounced as in the Spitfire, however it is reached much later in the 109. So nontheless the Spitfire doesnt have better stall characteristics than the 109. This is what my point was all about...

Now about the Spitfire's wing, well as I've already said it has a 2 degree twist to it, so the lift distrobution IS NOT elliptical.

Soren, I know that the LE slats do, I've flown aircraft with them, and the slats don't stall, the whole wing does. The Slats change the shape of the wing, increasing the wing area, they're a great device. Just because you stall later (or slower), it doesn't mean anything if you don't know its coming. As shown, the Spit talks to you - its telling you its going to stall - the 109 doesn't do this at the most critical time the aircraft is in the air, at landing! A 2nd Lt. Eliminator! Besides even with the slats both aircraft carry very similar stall speeds!

The tests posted show the data, sure the LE slats help, but they also hurt as well. I'll rephrase my comment from yesterday - good aircraft stall characteristics? 1. - 25% stall warning, 2 - 25% knowing what the aircraft is going to do when it stalls and 3 - 50% winding up in a desired attitude after the stall.

Now as far as aerodynamics on the Spit's wing - we could discuss this all day if its really elliptical aerodynamically, but the bottom line, it carries the shape, the tips stall earlier than a rectangular wing and that's my point. As seen by the posted pilot reports, both aircraft stall well, but with the -109 giving no stall indication when its dirty, well that's an accident waiting to happen and apparently it did on many occasions!

[wmaxt]

As we were talking about max performance capabilities and related issues I was talking about the stall charecteristics in the same performance regime ie. high speed/high AoA.

Slow speed power off stalls were good in all the major aircraft in WWII. In that situation the slats would be very nice. Power on stalls were more interesting and rapid application of power in any of them could prove fatal (some were better than others) without the proper attention to procedures.

Flyboy is correct.

Back to the subject.
We still don't have enough infrmation to quantify the relative performance of the P-51/Bf-109 other than they were close and the Bf-109K should have had an edge.

wmaxt

[Glider]

Soren. I am with FJ on this point. Adaquate warning of a stall is of vital importance in particular when under pressure and heads up, not looking at the instruments, which is most likely in a combat situation.
We often talk about this stalling speed compared to that. In reality it varies quite a lot depending on the position of the plane, a little bank or a slight angle on the climb makes all the difference.
If an aircraft doesn't give you warning of a stall then its almost certain that the average pilot is going to play it safe as to stall in combat is going to result in: -
a) Losing position compared to the oppinent
b) a stall which loses speed and momentum
c) which makes you an easy target if anyone is close to the right position

The fact that a plane has good stalling characteristics doesn't help you avoid the stall in the first place.

[Soren]

Originally Posted by FLYBOYJ

Soren, I know that the LE slats do, I've flown aircraft with them, and the slats don't stall, the whole wing does. The Slats change the shape of the wing, increasing the wing area, they're a great device. Just because you stall later (or slower), it doesn't mean anything if you don't know its coming. As shown, the Spit talks to you - its telling you its going to stall - the 109 doesn't do this at the most critical time the aircraft is in the air, at landing! A 2nd Lt. Eliminator! Besides even with the slats both aircraft carry very similar stall speeds!

The tests posted show the data, sure the LE slats help, but they also hurt as well. I'll rephrase my comment from yesterday - good aircraft stall characteristics? 1. - 25% stall warning, 2 - 25% knowing what the aircraft is going to do when it stalls and 3 - 50% winding up in a desired attitude after the stall.

Well then we agree.... the Spitfire didnt have better overall stall characteristics than the 109.

Upon landing the Spit's stall characteristics were better, but in a dogfight the 109's were better. (Not that the Spit's werent good)

Now as far as aerodynamics on the Spit's wing - we could discuss this all day if its really elliptical aerodynamically, but the bottom line, it carries the shape, the tips stall earlier than a rectangular wing and that's my point.

FJ there's nothing to discuss about the Spit's wing being Elliptical or not, cause it simply wasnt. The "Wash-out" was there to help the wing the same way the 109's slats did(although not as effectively), but at the same time it ruined the microscopic advantage of the elliptical shape.

As seen by the posted pilot reports, both aircraft stall well, but with the -109 giving no stall indication when its dirty, well that's an accident waiting to happen and apparently it did on many occasions!

Yes because of the landing gear. Other than that pilots quote the 109 as very predictable, and stalls were very gentle.