Originally Posted by mustafagander
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.
Look at it this way: if the plane is at a low density altitude, then the thrust of a Full Rated engine increases with air density. But so do aerodynamic forces on fins and rudders at a given airspeed!
Thus, the more asymmetric yaw an engine out produces, the more compensating authority is available for a given airspeed.
However, it seems that the mechanical strength of the engine, engine mountings, wings, rudder and fin is not improved by low temperature or low pressure altitude...