Spit/109 sea level speed comparisons in 1.08 beta patch

[JtD]

OK Tomcat, if he's got it all wrong, then why does it work reasonably well with about all other WW2 aircraft in the same speed league? He's clearly got a point, 500 at sea level and 575 at 5000 m don't add up with the power levels given. Personally I'd be most curious to have that sorted, preferably to a point where the test results make sense.

Can you guys try to be constructive and solve that problem?

[TomcatViP]

I am

[JtD]

Great, so what's your explanation? I seem to have missed it.

[TomcatViP]

Really did you read at least what I wrote on the last page?

(Edited on request).

[JtD]

Yes I did, assuming you are referring to this one. But it only states a few principles of aerodynamics, doesn't quantify them or provides a calculation illustrating that if this is taken into account, the numbers add up. I agree on the trend, but I doubt that they will account for the full difference.

Thank you for editing your post.

[MiG-3U]

Originally Posted by JtD

Yes I did, assuming you are referring to this one. But it only states a few principles of aerodynamics, doesn't quantify them or provides a calculation illustrating that if this is taken into account, the numbers add up. I agree on the trend, but I doubt that they will account for the full difference.

Thank you for editing your post.

Well, the logical problem with Tomcat's argument on Holtzauge's calculation is that Mtt calculated that claimed 498km/h at sea level exactly same way as Holtzauge. So if we prove either of them seriously unaccurate, the other is just as unaccurate.

However, generally there is no steep rise on the Cd until mach numbers well over 0.6 so the error caused by compressibility is very small given the speed differerences around 15kmh talked here.

[TomcatViP]

No Mig Sry but Mach nbr is the local mach, not the plane frwd speed.

At 15% thickness, the speed is in high subsonic when the plane is flying around 600kph.

At this local speed, drag effects are not linear and raise sharply.

Moreover, I think I was one of the first to put the dK/dt=SIGMA(P) eq around on forums. So don't nurse me with it. Thx in advance.

Remind simply that this give only the max speed any increase of pow will give to a plane. At high speed, this is not linear.

Generaly speeking:

Incompressible theo apply only for M<0.3
Btw M0.3 to 0.8 effecst are sharp and results vary btw 6% to 100%
Over 0.8, you hve shock waves and you need to apply according theo.

Of course many guys rely only on incompressible, simply because they never really to get into the others case