EPR v. N1 for turbofan power setting

From:         entmlf@cr41.staffs.ac.uk (Martin at Staffs University, UK)
Date:         15 Feb 95 03:42:21 
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A two-part question, and probably a pretty stupid one too:-

a)  RR Engines usually use Engine Pressure Ratio as
the parameter used to set engine power/thrust for
take-off, climb, noise abatement, cruise, etc. Other
manufacturers use N1.

Which is the better parameter to use, ie who has got it
right?   Maybe EPR is harder to gauge than N1 but is more 
meaningful? 

b) On aircraft that use EPR for thrust setting, why is
the range from 0.0 to about 2.3?  On a recent MD81
flight, thrust was set using EPR (I don't know what
engines, but not RR?) and the Go Around limit was about
2.1, and flight-idle during descent was about 0.3.

I can't calculate the actual pressure ratio, but IF
it represents the pressure rise along the engine, and
if flight-idle is 0.3, then I'd have guessed that full
power EPR would have been about 50 on that scale? 

A range of 0.0 to 2.3 representing the thrust range
from idle to TO/GA seems small.

OK, so what have I got wrong?!

Martin
m.fiddler@staffs.ac.uk