[ACE-OF-ACES]

Originally Posted by JtD

Historical performance data for climb typically comes with a climb speed information.

Typically? Well I have not counted all the test reports that included BCS vs. those that did not include BCS, but based on my memory I have seen more test reports without BCS than with

Originally Posted by JtD

This climb speed hardly ever is constant.

Same is true wrt altitude in top speed testing.. It is impossible to maintain a 'constant' altitude.. But the NAVY test documents say the altitude must be held within a 'range'.. If I remember correctly it was something like +/-100ft or 150ft. Same goes for BCS.. It is impossible for a human to maintain a constant BCS. The goal of each is to keep both as constant as humanly possible during the test from one second to the next. Some if not most planes ROC performance required the BCS to be adjusted as altitude increased, but the change was done such that the transition was smooth and within that +/- acceptable range such that the IAS could still be considered constant from one second to the next.

Originally Posted by JtD

Often, TAS increases while IAS decreases. This has an effect on climb performance, and it is measurable.

Often? Actually TAS 'always' increases with altitude.. But in WWII TAS gauges were the exception to the rule, that is to say most if not all fighters only had IAS gauges. Thus the test pilot focus was on the IAS, but not because he didn't have a TAS gauge as much as the stall speed is realities to IAS, not TAS. Thus they would keep the IAS as 'constant' during the ROC test from one second to the next, While TAS increased during the test due to the increase in altitude.

Originally Posted by JtD

Il-2 compare does not take the planes acceleration into account,

That is good news wrt ROC testing because as in real life the goal was to keep the BCS as constant as humanly possible. And as any high school physics book will tell you, when velocity is constant acceleration is ZERO. So another way of putting it, you could say that during a ROC test the goal is to keep acceleration as close to ZERO as humanly possible, even during the transitions in BCS

Originally Posted by JtD

and the climb performance in Il-2 compare is a little bit higher than what is achievable in game or would be, even if perfectly modelled, with the real plane.

Maybe.. I guess it really depends on ones definition of 'a little bit' but based on the +/-5% acceptance the IL-2Compare data falls well within (matches) the manually flown (3rd party test pilot) test results that I have done.