Vampire vs Me 262

[Soren]

Delcyros,

The Me-262's wing has a 11% thickness ratio at the root and 9% at the tip.

You have shown no CLmax info about the Vampires airfoil yet.

[delcyros]

I have already included Your wingroot / wingtip figures.

The Vampire´s wing is also included. See above. For those who understand to read the graph, which is indeed complicated to read, the Vampire´s EC 1240 /0640 appears to have a Cl-max of about 0.75 at Mach= 0.4 are given above in the RAF paper, which concluded them to be little indifferent from the NACA 0012, which in turn is found to be better than the NACA 0009. Note that very low Reynolds numbers have been used for this! It is not before Mach = 0.5 that the graphs for NACA0009 and 0012 close again (another NACA technical report which I have filed down here somewhere) and at Mach = 0.7 the NACA 0009 is superior to the NACA 0012, which has a Cl-max of 0.6 at Mach = 0.7, compared to Cl-max ? 0.8 for the Vampires EC 1240/0640 at Mach = 0.7, which is about the same ballpark of the NACA 0009 for this Mach fraction. The Me-262 wing offers less drag and correspondingly less lift, too.

[Soren]

Delcyros,

The chart is easy to read, you just later added report on the EC1240 without me noticing it, and from it you can also see that the NACA 0012 & EC1240 have VERY similar CL figures at the different Reynolds numbers.

Also keep in mind that these tests were done with a wing of different planform and with a considerably lower AR, and as we all know CLmax increases with increased AR. The AR of ME-262's wing is 7.23.

[drgondog]

Originally Posted by Soren

Delcyros,

The chart is easy to read, you just later added report on the EC1240 without me noticing it, and from it you can also see that the NACA 0012 & EC1240 have VERY similar CL figures at the different Reynolds numbers.

Also keep in mind that these tests were done with a wing of different planform and with a considerably lower AR, and as we all know CLmax increases with increased AR. The AR of ME-262's wing is 7.23.

Induced drag decreases with AR increases all things equal on the airfoil.

Soren, I think CLmax on these charts usually refer to the two dimensional airfoil (only) for the reason that AR is another (separate) design variable for airfoil data as presented. Maybe I misread what was presented? I didn't see the AR reference in the charts.

[Evil_Merlin]

Wow... you know all this bickering back and forth.

the Me-262 had a huge advantage over the Vamp. Experienced pilots who knew how to fly it.

End of story.

[drgondog]

Originally Posted by Evil_Merlin

Wow... you know all this bickering back and forth.

the Me-262 had a huge advantage over the Vamp. Experienced pilots who knew how to fly it.

End of story.

The two engaging in the debate above are bringing facts and opinions sometimes on facts to the table.

What did you just bring?

[DerAdlerIstGelandet]

Originally Posted by drgondog

The two engaging in the debate above are bringing facts and opinions sometimes on facts to the table.

What did you just bring?

A wise man has spoken...

[Evil_Merlin]

Originally Posted by drgondog

The two engaging in the debate above are bringing facts and opinions sometimes on facts to the table.

What did you just bring?

So are you honestly saying that the experience that the Me-262 pilots had flying the tempermental machine isn't an advantage?

PS: it also means I'm not stupid enough to get involved in a conversation that involves nearly as much opinion as it does factual data.

[drgondog]

Originally Posted by Evil_Merlin

So are you honestly saying that the experience that the Me-262 pilots had flying the tempermental machine isn't an advantage?

PS: it also means I'm not stupid enough to get involved in a conversation that involves nearly as much opinion as it does factual data.

EM - I don't assume you are stupid or ill informed. Just curious what your fact base was to determine that the advantage of a 262 was so great as to arrive at your conclusion?

[drgondog]

Originally Posted by Evil_Merlin

So are you honestly saying that the experience that the Me-262 pilots had flying the tempermental machine isn't an advantage?

PS: it also means I'm not stupid enough to get involved in a conversation that involves nearly as much opinion as it does factual data.

EM - The only point I might have been making to you is that you did exactly that (involved in conversation that involves as much opinion as data)?

Further, if you meant advantage that experienced 262 pilots had over 262 pilots that had no experience in the 262, then yes - it is reasonable to make that assumption or express that opinion. But pilot skill prior to Me 262 time a huge factor.

Ditto - advantage of experienced Vampire pilots probably better than Vampire pilots that no experience in the Vampire, then same as above.

So, what is your thesis? That experienced 262 pilots had an advantage over inexperienced Vampire pilots? Or that experienced Me 262 pilots had an advantage over experienced Vampire pilots? Interesting but where are your facts? And how do you factor in prior experience and flight time?

Moving more into subjective opinion - where the answer could be 'it depends' on;

the quality of the time before transitioning into either a/c, the amount of time each had in the a/c (325 'better than 293'?? 5000 better than 3600?), and the quality of the pilots, and the tactical situation (fuel status, who sees whom first, altitude, airspeed in the engagement, etc)

A lot of these dialogues bring opinion, fact based opinion and simple 'I like it" statements - don't confuse me with facts!

So, help us out here. how did you arrive at "End of Story" for your conclusions?

[Soren]

Originally Posted by drgondog

Induced drag decreases with AR increases all things equal on the airfoil.

Yes induced drag is decreased and CLmax in increased, increasing the L/D ratio, that is the effect an increase in AR has.

Soren, I think CLmax on these charts usually refer to the two dimensional airfoil (only) for the reason that AR is another (separate) design variable for airfoil data as presented. Maybe I misread what was presented? I didn't see the AR reference in the charts.

The tests refer to wings with an AR of 6.

[Soren]

With similar CLmax figures let me demonstrate just how important wing AR is;

L/D ratio = Cl / Cd

Cd = Cd0 + Cdi

Cd0 = {Negligable as it always lies in the 0.02 -0.025 area}

Cdi = (Cl^2)/(pi*AR*e)

So for the comparison we assume a Clmax of 1.3 for both and Cd0 of 0.02 for both, now note the difference wing AR alone has on the L/D ratio one of the most crucial factors to high turn performance. (The higher the L/D ratio the better)

Wing with AR of 8

(1.3^2)/(pi*8*.85) = 0.0791093688

0.0791093688 + 0.02

Cd = 0.0991093688

1.3 / 0.0991093688 = 13.1168225

L/D ratio = 13.11

Wing with AR of 6

(1.3^2)/(pi*6*.85) = 0.105479158

0.105479158 + 0.02

Cd = 0.125479158

1.3 / 0.125479158 = 10.3602863

L/D ratio = 10.36
_______________________________

L/D ratio Differential: 35.9 %

Additionally two graphs showing the difference in L/Dmax between a wing with an AR of 4 vs a wing with an AR of 9:

AR 4


AR 9

[delcyros]

The chart is easy to read, you just later added report on the EC1240 without me noticing it, and from it you can also see that the NACA 0012 & EC1240 have VERY similar CL figures at the different Reynolds numbers.

Sorry for doing so but it took time to fully compile this post. However, there is not the information You seem to get from the charts. NACA 0012 and EC1240 have comparable Cl-max figures. But not at different reynold numbers (tests are for same reynold numbers) instead they show similar Clmax at different Mach fractions. Key aspect is that the NACA 0012 has better Cl-max than the Me-262´s basic airfoil at lower speeds (US&german tests. at RE= 5.000.000 and Mach = 0.1, the Cl-max is 1.40 for the NACA 0012 and 1.26 for the NACA 0009). The EC 1240 is comparable to the NACA 0012 and thus better than the Me-262´s airfoil at low speeds. It appears that the influence of the reynolds number is largest at low speeds and lowers towards Mach= 0.5. So the RAF test is reasonable for higher speeds.

Also keep in mind that these tests were done with a wing of different planform and with a considerably lower AR, and as we all know CLmax increases with increased AR. The AR of ME-262's wing is 7.23.

aspect ratio= span^2 / wingarea (for tapered wings)

..and the aspect ratio of the tapered Vampire I wing is 7.08, not much different from the Me-262´s wing (actually 7.21). Note that the computations I use for Cl-approximation is three dimensional (lattice vortex method) and include planform, aspect ratio and other variables, already. This method is not two dimensional! The difference in aspect ratio between Vampire and Me-262 is tiny (ca. 1.9%).


To bring the discussion back on track, our early dispute was whether or not the Me-262 turns as good or better than the Vampire MK I. Soren´s thesis that the LE-slats help to turn the tide for the Me-262 has been questioned by myselfe. It appears that the Me-262´s wing has a lower Cl-max than the Vampire´s wing at maneuvering speeds. This is partly offsetted by the use of LE-slats. It also appears that the wingload for the Me-262 is much higher at combat weight and thrust to weight ratio are in the same ballpark for both planes (slight advantage for the Vampire at combat weight).

[Arsenal VG-33]

When I was a kid, I had a model of the Mistral, the French built version of the Vampire. I vaguely recall on the assembly sheet, the short aircraft history mentioning something about the Vampire/Mistral being capable of carrier takeoff/landing (or could be easily modified to do so). Anyone else heard of this? If it were true, that would be an advantage over the 262.

[Soren]

Delcyros,

Why do you keep talking about the Me-262's wing tip ?? What does that have to do with anything ??

The wing tip always has the lowest Clmax & critical AoA, hence the use of wing twist (Wash out) and slats on outer wing sections.

The Me-262's wing root thickness ratio is 11% from where it gradually decreases along the span to 9% at the wing tip. The Vampire's wing thickness ratio decreases more sharply starting at 14% and ending at 9%.

The automatic LE slats on the Me-262 help increase the lift & critical AoA by 25%.

Furthermore I completely understand the charts and it is clearly illustrated that the CL figures are VERY similar between both airfoils at the different Reynolds numbers and speeds.


As to the Aspect Ratio of the wings, well you totally blew it there Delcyros!

The Aspect Ratio of a wing is calculated likewise: (Span * Span) / Wing Area, very true.


Me-262: A = 21.7 m^2 Span = 12.51 m
DH Vampire. A = 24.34 m^2 Span = 11.58 m

So the Me-262's wing's AR is 7.23, and the Vampire's is 5.5 !

Actually I'm quite surprised you could ever screw that up Delcyros as just by looking at the two wings it should've been very clear to you that the ARs are VERY different!