Muito bom este site...
http://www.virtualpilots.fi/feature/articles/109myths/
Discussão a respeito das verdadeiras capacidades do messerschimit bf-109
Messerschmitt 109 - Mitos e Fatos
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Cobra-Kan
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Cobra-Kan
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Cobra-Kan
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Cobra-Kan
Indice do que é tratado no artigo...
Introduction
Part I: PILOT NOTES ON THE ME 109
General comments on Me 109 | Training to fly the Messerschmitt | Taking off | Landing | 109 undercarriage | Stalling the 109 | Flying Messerschmitt 109 | Climbing in combat | Diving - structural rigidity of 109 in dives | Stick forces and maneuvering in high speeds | Stick force and black outs | 109 needs constant rudder pressure to fly straight? | Trimming | Wing leading edge slats - good or bad? | Fighting in the 109 | Tactics with 109 | Me 109 as gun platform | Me 109 weapon effectiviness | Cannonboot (three cannon) Messerschmitts | Gunsight | Radios | Cockpit | Daimler-Benz engine and engine systems | Luftwaffe fuels | Other systems, radiators | Maintenance | Me 109 fuselage and drag
Part II: Breaking the myths | Forgetting the big picture | Was Me 109 hard or difficult to fly? Comparisons to Spitfire and Hurricane | Why many "western" pilots found it hard to fly the 109? | Various myths debunked | Messerschmitt 109 design features and comparisons by Markus Mikkolainen | Other interesting details on 109
Part III: Other subjects | 109 test flight reports
Primary sources
Introduction
Part I: PILOT NOTES ON THE ME 109
General comments on Me 109 | Training to fly the Messerschmitt | Taking off | Landing | 109 undercarriage | Stalling the 109 | Flying Messerschmitt 109 | Climbing in combat | Diving - structural rigidity of 109 in dives | Stick forces and maneuvering in high speeds | Stick force and black outs | 109 needs constant rudder pressure to fly straight? | Trimming | Wing leading edge slats - good or bad? | Fighting in the 109 | Tactics with 109 | Me 109 as gun platform | Me 109 weapon effectiviness | Cannonboot (three cannon) Messerschmitts | Gunsight | Radios | Cockpit | Daimler-Benz engine and engine systems | Luftwaffe fuels | Other systems, radiators | Maintenance | Me 109 fuselage and drag
Part II: Breaking the myths | Forgetting the big picture | Was Me 109 hard or difficult to fly? Comparisons to Spitfire and Hurricane | Why many "western" pilots found it hard to fly the 109? | Various myths debunked | Messerschmitt 109 design features and comparisons by Markus Mikkolainen | Other interesting details on 109
Part III: Other subjects | 109 test flight reports
Primary sources
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Cobra-Kan
Esse texto aqui é uma part do artigo pra ver se o pessoal interessa:
Spitfire elliptical wings vs 109 wings
(Ok, this is a bit off topic but since the Spit and Me 109 are so close adversaries, I decided to let this stay)
Claim:
"Spitfire has eliptical wings. That means that the lift is spread ellipticaly over the wings... Therefore it is THE MOST EFFICENT WING CONFIGURATION POSSIBLE".
Answer:
The elliptical planform has very small theoretical advantage, but only theoretical, and only valid if the planform is truly 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 a whopping 0.05 improvement in comparison to a trapezoidal planform used in for example 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?
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. In short, the wing twist negated the effect of the elliptical wing. Although the wing was physically elliptical, its lift was not.
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 of magnitude of 0.05), and Bf 109's wing has higher aspect ratio than Spit's...
Spit's wing uses the exactly 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 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.
- Pentti Kurkinen, enthusiast
Another reader responded to the above paragraph with following text but unfortunately did not give his name: - True, eliptical wing has less drag coefficient than other, but not because of "lift is spread ellipticaly over the wings", but because of less induced drag. It is connected with shape of wing tip and wing tip vortex (stronger if you have bigger tip chord - elliptical wing tip chord is 'almost zero', so tip vortex is also weak). Unfortunately elliptical wings are also harder to built, and stalls first at tips (when are usually placed ailerons ), so they are also less safe. Difference in drag coefficient between taper (like 109) and elliptical (Spitfire) wing depends also from aspect ratio (influents to induced drag), not only from wing shape. And 109's wing aspect ratio (about 6 ) is higher than Spitfire's (about 5.4), what can balance Spit's induced drag reduction from wing shape . Of course, it depends also, how is 'taper ratio' (I am not sure how it is called in English) of a taper wing.
Spitfire elliptical wings vs 109 wings
(Ok, this is a bit off topic but since the Spit and Me 109 are so close adversaries, I decided to let this stay)
Claim:
"Spitfire has eliptical wings. That means that the lift is spread ellipticaly over the wings... Therefore it is THE MOST EFFICENT WING CONFIGURATION POSSIBLE".
Answer:
The elliptical planform has very small theoretical advantage, but only theoretical, and only valid if the planform is truly 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 a whopping 0.05 improvement in comparison to a trapezoidal planform used in for example 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?
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. In short, the wing twist negated the effect of the elliptical wing. Although the wing was physically elliptical, its lift was not.
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 of magnitude of 0.05), and Bf 109's wing has higher aspect ratio than Spit's...
Spit's wing uses the exactly 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 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.
- Pentti Kurkinen, enthusiast
Another reader responded to the above paragraph with following text but unfortunately did not give his name: - True, eliptical wing has less drag coefficient than other, but not because of "lift is spread ellipticaly over the wings", but because of less induced drag. It is connected with shape of wing tip and wing tip vortex (stronger if you have bigger tip chord - elliptical wing tip chord is 'almost zero', so tip vortex is also weak). Unfortunately elliptical wings are also harder to built, and stalls first at tips (when are usually placed ailerons ), so they are also less safe. Difference in drag coefficient between taper (like 109) and elliptical (Spitfire) wing depends also from aspect ratio (influents to induced drag), not only from wing shape. And 109's wing aspect ratio (about 6 ) is higher than Spitfire's (about 5.4), what can balance Spit's induced drag reduction from wing shape . Of course, it depends also, how is 'taper ratio' (I am not sure how it is called in English) of a taper wing.
