Originally Posted by hawk37
there seems no reason to program the engine to decrease it's thrust output.
Hawk
If engine thrust were not flat rated, imagine the chaos on a cold clear day with OAT, say 0*C and the a/c certification done at, say 25*C. The engine at full throttle would probably deliver considerably more thrust, so where is the relevance of certification trials and, more to the point, how are you, captain, going to control the beast when an engine fails at V1 +1kt. It may well be worth watching from a safe distance, though!!
IMHO, flat rating is about the engine manufacturers supplying the airframers with a known level of thrust and maintained to as high an OAT as possible so that they can do all their sums about control moments etc., etc. There's the rub, though, the engine gives more thrust than you really need at low density alts when it's not too critical and gives less at high DAs just when you need it most. Ain't life a pi55er sometimes?