Is Spitfire really the BEST British fighter???

[Soren]

At about 358 IAS the P-51 and the FW190 roll about equally, above that speed, the P-51 has the advantage, the FW roll rate is declining sharply, the P-51 roll rate is delcining gradually.
Also, the FW requires the full 50 lbs of stick force to achieve its roll above 350 IAS, where the P-51 could still be rolled with one hand. 50 lbs of stick force is not an easy think in the cramped cockpit of the FW.

You know that is just about contradicted by every single other test carried out wit the two aircraft. The Fw-190 was known for its easy and stable controls at high speeds, on the other hand the P-51 wasnt !

P-51 pilots have actually said that flying P-51 at high speeds was like driving a truck ! Also the P-51 Redlined at 505 mph, and its controls locked up.

Originally Posted by Soren

You know that is just about contradicted by every single other test carried out wit the two aircraft. The Fw-190 was known for its easy and stable controls at high speeds, on the other hand the P-51 wasnt !

P-51 pilots have actually said that flying P-51 at high speeds was like driving a truck ! Also the P-51 Redlined at 505 mph, and its controls locked up.

P-51 elevator response starts getting heavy at about 400 ias, but not horribly so. The problem occured at somewhere over 505 IAS (the stick would start oscillating). The ailerons on the other hand, were easy to operate, smooth and responsive right up to the mach limit of the laminar flow part of the wing which was up over 0.9 M (the fuselage/canopy/tail dropped the entire planes mach down to about 0.82 M).

Also, the NACA is a pretty solid source.

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Lunatic

[Soren]

Originally Posted by RG_Lunatic

P-51 elevator response starts getting heavy at about 400 ias, but not horribly so. The problem occured at somewhere over 505 IAS (the stick would start oscillating). The ailerons on the other hand, were easy to operate, smooth and responsive right up to the mach limit of the laminar flow part of the wing which was up over 0.9 M (the fuselage/canopy/tail dropped the entire planes mach down to about 0.82 M).

Also, the NACA is a pretty solid source.

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Lunatic

Yes the main problem were the elevators, but the ailerons would also stiffen.

And your chart doesnt show 'wich' FW-190 model. Btw looking at your chart, the Fw-190 and P-51's roll rate's are first equal at 373 mph or so.

Originally Posted by Soren

Yes the main problem were the elevators, but the ailerons would also stiffen.

Not much - the P-51 (B and beyond) was the first plane to have the seal-balanced aileron, maintaining aileron effectiveness at high speeds. It also had balance tabs which helped the pilot work the aileron at higher speeds (at some cost in travel at lower speeds). The ailerons became stiffer to work at high speeds, but never so stiff they could not be worked easily by a fit pilot with just one hand.

Originally Posted by Soren

And your chart doesnt show 'wich' FW-190 model.

I am pretty sure it's the FW-190A5 - this was the plane the USAAF and NACA tested. It also happens to be one of the best rolling models of the FW190, the D's did not roll as well as the A's. Their is another chart ion the last page of the doc which shows the wing span was 34.5 feet - which FW can probably at least generally be determined by that. My capture of that page is blurry. You can download the whole document at:

http://naca.larc.nasa.gov/reports/1947/naca-report-868/

and consider the data for yourself.

Originally Posted by Soren

Btw looking at your chart, the Fw-190 and P-51's roll rate's are first equal at 373 mph or so.

Look again at the chart - the lines cross just short of 360 IAS, you've either mis-read the numbering or mis-read the graph.

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Lunatic

[KraziKanuK]

All Fw190 A and D a/c had the same wingspan, 10.5m. One can't use ws to determine the model.

The lines on the graph were calculated, with some a/c using British data.

Originally Posted by KraziKanuK

All Fw190 A and D a/c had the same wingspan, 10.5m. One can't use ws to determine the model.

The lines on the graph were calculated, with some a/c using British data.

Still, I believe it's from an FW-190A. Unless it specifically says otherwise, almost all Allied FW data has to do with one of the several FW-190A's captured earlier in the war, Dora's were only captured right at the very end of the war.

Also, the P-51B-1-NA data is from one of the first two P-51B's off the line, which was used as a test bed by the NACA. Later models had improvements to the balance tabs which are not reflected in the chart.

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Lunatic

[Soren]

I can't see how I've miss-read the chart, the last number is clearly 380 mph.

[Soren]

Oh now I see it ! Theres two P-51's on the graph.

Still doesnt agree with other tests though, and certainly not pilot accounts !

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Anyway we were talking the 109 and Spitfire.

The myth that the Spit was a better T&B fighter is bollocks, and there's alot of evidence to back this up.

One claim is that the Spitfire has eliptical wings. That means that the lift is spread elipticaly over the wings... Therefore it is "THE most effecient wing configuration possible".

However the elliptical planform has very small theoretical advantage, but only "theoretical", and only valid if the planform is truely elliptical. Spitfire's planform is only approximating elliptical, and what is left has been sold out by the aerodynamic twist it's wing has.
It has effect on just one of several factors of wing efficiency, causing only 0.05 improvement in comparison to a trapezoidal planform used on for example the Bf 109, that is, "IF" Spit's wing were truely elliptical...
You also have to take into account the fact that the profile thicknes ratio of Spit's wing is VERY thin, both in maximum and in average. This in turn leads to the small coefficient of lift. This pretty much takes away the advantage of the large wing area.

BTW, ever wondered where did all the elliptical wings go?
If they are so magically efficient, why nobody uses them anymore?
The answer is simple, later aerodynamic research has proven that most of the benefits of elliptical wing were a fallacy created by insufficient or faulty research methods. They simply were not worth the trouble.
Even the developements of Spitfire, Spiteful and Seafang gave up on the elliptic planform and went to normal trapezoid form. Wonder why?
Only thing special in it is the elliptic planform, that dropped of favour just after it, when it was found out that the theoretical benefits of elliptic planform were actually only theoretical, and practical applications did not yield benefits that would justify the almost astronomical manufacturing difficulties and costs.
In Spitfire's case the benefits of elliptic planform (even lift distribution along the span) are nullified by the 2 degree twist (washout) that was needed for at least partially taming the nasty and violent stall behaviour of such wing.

Besides, wing aspect ratio has larger effect on the lift/drag characteristics than the Oswald efficiency factor (where the theoretical difference between Spit's and Bf 109's wing is only in a magnitude of 0.05), and the Bf-109's wing has higher aspect ratio than the Spit's...
Spit's wing uses the exact same NACA 2300 root profile as Bf 109's wing, but with only 13 % thickness ratio, while Bf 109 has 14.2 % thickness ratio. Lower thickness ratio translates to lower Cl max. Bf 109 uses the same NACA 2300 with thickness ratio of 11%, but Spit's wing profile gradually changes along the span to NACA 2200 (more symmetric profile with smaller Cl max) with thickness ratio of only 9 %.
All the above leaves the Spit's lower wingloading as the only even theoretical advantage for Spit's wing, but even that is somewhat negated by wingprofile that has less Cl max and Cl in general.

Now to add even one more disadvantage to the Spit, "It has NO wing-slats", wich the 109's already superior wings have. So whenever a turn of sufficient AoA is made, low or high speed, the slats deploy on the 109 and it turns even tighter. (Some novice LW pilots didnt know this though)

You miss the point behind the eliptical wing. It's not supposed to improve lift characteristics, it's supposed to improve alierlon efficiency.

But in this point we agree, the gains were minimal and the production cost high - the eliptical wing was not worth it.

The higher thickness ratio of the 109 wing also implies higher drag and a lower mach number.

My point all along has been that the Spitfire and the 109 were generally well matched planes. The 109E was probably a little bit better than the Spit I. The 109F was about equal to the Spit V. The 109G was slightly inferior to the Spitfire IX. The 109G-10/K-4 were more noticeably inferior to the Spit XIVe.

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Lunatic

[cheddar cheese]

Thats something I can agree with.

[The Jug Rules!]

I'd say the Tempest is the best british fighter.

[The Jug Rules!]

I thought that the laminar flow wing was the best.


By the way, what is so special about the laminar flow wing???

Originally Posted by The Jug Rules!

I thought that the laminar flow wing was the best.


By the way, what is so special about the laminar flow wing???

Well, the laminar flow wing has advantages and disadvantages.

The key thing about the laminar flow wing is that the point of maximum thickness is about at the center of the wing (measuring leading to trailing edge), as opposed to about 2/3 to 3/4 of the way toward the front, and it has curvature on both sides though usually a little less on the bottom than the top (conv. wings tend to be rather flat on the bottom).

There are two advantages to this. First, the airflow over the wing climbs a shallower grade as it passes over the wing, which reduces drag and increases the mach number (as compared to a conv. wing of equal thickness). The second advantage is the inside of the wing has more capacity for fuel and weapons.

The disadvantage of the laminar flow wing is for a given wing area there is less lift, though this is not so critical a factor at high speeds. The laminar flow wing is actually advantagous in high-speed turning as long as the angle of attack is kept within what is called the "laminar flow bucket", as such a turn will induce almost no added drag. However beyond that angle of attack, outside the "bucket" the drag is worse than a conventional wing - so the pilot has to be careful about how tight he turns.

It should be noted that on the P-51 the inner parts of the wing, from about the crook in (on the D) are conventional in design, the outer parts are what is termed "near laminar flow" because the top has a little more curvature than the bottom and the whole shape has a (extremely mild) S to it (imagine the points of the "S" are the leading and trailing edges). Also, in practice, the laminar flow properties of the P-51 wing were considered to last only about 50-70 flight hours before the shape became too distorted to support laminar flow.

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Lunatic

[Soren]

You miss the point behind the eliptical wing. It's not supposed to improve lift characteristics, it's supposed to improve alierlon efficiency.

No I don't miss the point, i just disproved the claim about the eliptical wings of the spitfire providing more lift.

But in this point we agree, the gains were minimal and the production cost high - the eliptical wing was not worth it.

Exactly.

The higher thickness ratio of the 109 wing also implies higher drag and a lower mach number.

Yet the 109 was always faster, until the Spit XIV. Anyway combined with superior speed the 109 had greater lift-loading, wich equals better turning ability ! (Not to mension its slats)

My point all along has been that the Spitfire and the 109 were generally well matched planes. The 109E was probably a little bit better than the Spit I.

I would actually say those two were very equal, but the 109 had the slats and fuel-injection wich made it superior. However range was a real downside for the 109.

The 109F was about equal to the Spit V.

Now here I disagree, the 109F was both faster, and a better T&B fighter, plus it had equal roll rate. The F series turned tighter than the E series, as both Wing-loading and Lift-loading were lower in the F series. I must also remind you that against the F series the Spit didnt do good a job, they were beaten badly by the 109F !

The 109G was slightly inferior to the Spitfire IX.

Yeah the G-6 was, but by NO means at all the G-10 or 14, they were noticably superior !

The 109G-10/K-4 were more noticeably inferior to the Spit XIVe.

I agree, the Spit XIV was Superior, but also inferior in some ways, you must remember that the G-10 and K-4 had almost eleminated the aileron and Elevator problems at high speed for the 109 ! In a T&B fight the Spit XIV would be equal at best, but overall it was a better aircraft though. So here we agree.

Originally Posted by Soren

Yet the 109 was always faster, until the Spit XIV. Anyway combined with superior speed the 109 had greater lift-loading, wich equals better turning ability ! (Not to mension its slats)

On paper maybe (and this is quite debatable), but in fact the Spitfires, after the 109E, were always rated as having better rates of turn. Time and time again, both British and the bulk of German sources credit the Sptifire as having been the superior turning plane.

Originally Posted by Soren

I agree, the Spit XIV was Superior, but also inferior in some ways, you must remember that the G-10 and K-4 had almost eleminated the aileron and Elevator problems at high speed for the 109 ! In a T&B fight the Spit XIV would be equal at best, but overall it was a better aircraft though. So here we agree.

And how did the G-10 and K-4 eliminate elevator and aileron problems? I've never seen anything to indicate this. The 109K was a bad rolling plane at even moderately high speed.

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Lunatic