As a driver, I love the security being driven by an engine that takes EPR as the controlling parameter. I watch N1's to understand what is going on, but I'm assured that at takeoff thrust that is exactly what is being produced.
In an N1 aircraft, at takeoff N1, then we can be assured that the fan is spinning at the correct speed. However, that fan may be nearing the end of its life, as such the thrust produced
may be slightly degraded.
All subject to having the anti ice on as required....
