Spit/109 sea level speed comparisons in 1.08 beta patch

[Glider]

Crumpp
You are reading something into the paper which isn't there and as a result are making an incorrect assumption.

Originally Posted by Crumpp

Once more, the RAE admits that operating a trailing static head is difficult as best. Do you know what you have to do? When installed, you have a tangle of tubes in the cockpit that the pilot must pinch off with an airtight seal on the correct lines at the right time. It is hard enough in cruise flight and would be extremely difficult to do accurately in a high performance fighter at the stall point.

That is why they labeled the values as "assumed values of CLmax".

You are right in some of what you say but have ignored other parts of the quote. The paragraph can be summerised as follows

a) An accurate calculation of the turn performance is dependent on an accurate measure of the CL max in level flight
b) The only way that the CLmax can be accurately measured is the use of the trailing static head.
c) It is difficult to do (this is the part which you highlight)
d) Despite it being difficult it has been successfully done on both the Spitfire and Me109
e) That the method used by the NACA is not as reliable and gave a misleading result

By ignoring the other relevent parts your assumption that the RAE had to calculate the results because they couldn't measure the CL max is fundamentally flawed.

Its because they were able to get an accurate measure of the CL max in a glide and max throttle that an accurate calculation of turn performance was possible

I should add that the RAE did exactly the same with the Me109 so these are by far the best calculations around.