Spit/109 sea level speed comparisons in 1.08 beta patch

[MiG-3U]

Originally Posted by TomcatViP

@Mig

Always the same, always bragging ... When did I post my "stuff" ? Tell me.

Post #516

Originally Posted by TomcatViP

Your Holtzauge did not post detailed calculation or discuss his method. I pointed one source of error. Tht's it.

Exactly the same calculation is used on the Mtt test on the prototype V15a to calculate speed at higher power at sealevel (blatt 5) posted several times here. I used the same calculation for demonstration on the post #448 and noted that it's a crude, unaccurate and partially wrong way to calculate it. However, it's good enough for small differences.

Originally Posted by TomcatViP

This is the basis in Sciences. Put it down and submit to what ppl think.

Yes, of course. But why do you complain about Holtzauge's calculation now but not about Mtt calculation which has been here much longer (or mine which was posted 3 weeks ago)?

Originally Posted by TomcatViP

ANd you just hve to open a NACA chart to see the drag rise for the specific airfoil. You don't hve to pick bit of info here and there. It's free and available.

Actually I'm refering tests of entire airframe, tunnel and flight tests. And yes, many are available. For Hoerner's Bf 109G analysis, get his Fluid Dynamics book. Some are freely available, here is one for few aircraft including Spitfire I. Below is also a Cd/mach number chart from that report attached, you can see that up to Mach 0.5-0,6 there is rather minimal drag rise due to compressibility.

Originally Posted by TomcatViP

And by the way, 10% of drag raise (outsourced from my memory) is equal to what a fully open rad will do on Seversky P-35.

Hoerner's number 10% is for entire speed range from mach 0.3 up to 0.55 ie speed changes 250-300kmh while we are talking here about 15kmh speed difference around mach 0.4, that means that drag rise is certainly certainly less than 2%, probably less than 1%.