Originally Posted by
Zar_1
Yeah N1 is definitely easier to calculate, since it's kinda a Tachometer by design... and yes, EPR is the more accurate of the 2.
An innovation that I've seen (ig in the A350) is the presence of 'calculated thrust' gauges which are meant to be more intuitive to use.
So, the PW4000, if given inadequate bleed... would give you a nasty Hot Start or the FADECs would auto-cut the fuel and turn the start into a Dry Crank Motoring phase?
"Calculated Thrust" is simply measured EPR compared to the max rated EPR for those conditions. Perhaps slightly more intuitive, but still has all the potential issues as EPR. I had some friends that spent a lot of time working on a "0-100" thrust measurement. They finally decided that - while there were various ways to make it dimensionless, in the end it really wasn't any better than simply using N1 and/or EPR.
Autostart wasn't basic on the PW4000/747-400 - autostart was an add-on box called an SCU (Supplemental Control Unit). It didn't work very well though...
Junkman - I'd still have to make all the effort to write the darned thing...