Techman:
I understand that. It's the primary qualification run to achieve the FAA acceptance which is interesting to me.
The manufacturer states that we have a 50000 lbs engine here. How does he prove that? He sets it up in a rig and lets it run through the FAA approved qualification (rating) process.
If the mfg of the engine could choose test conditions himself he would set it up in a more favourable condition. That's my understanding of why set (ISA) conditions are needed to validate test results. Can't compare apples and oranges...