by Nexus » Sun Jan 02, 2005 5:53 pm
You're not a rebel, infact using N1 is a much better way, and I still don't understand why Pratt & Whitney and Rolls Royce continues to use EPR as thrust reference, not in the days of hi-bypass engines where some 75-85% of the total thrust is generated by the fan
It's also easier to measure N1 readings than EPR, since you have to blend the core and by-pass airflow to get a true EPR setting. For accurate N1 readins all you need is a tachometer :)
And to add...as the compressor efficiency detoriates, the engine will require an increase in Fuel flow in order to maintain the commanded N2 (which is the thrust lever angle). The fuel flow will obviously drive the N1 faster. So you can easily see if the engine gets old when you have a high N1 reading relative to a low thrust lever angle.