EPR
 

what do you mean by Engine Pressure Ratio?How do the know the intake pressure and the exhaust pressure?
What type of engine is used on Boeing 727-100?

As I understand it, It is the difference between Intake and exhuast Pressure in a gas turbine engine. It is measured by Pressure switches similar to that on a piston engine for measuring oil pressure, the pressure is controled by bleed valves in the fore and aft stages of the engine. I believe one of the main reasons for measurment is to prevent blade stalling in the engine....
If I am wrong then please let me know..

Mike

engine is the P&W JT8D .... a relatively low by-pass turbofan. EPR is a simple differential dynamic pressure measurement which, if the system is working properly .. correlates well with engine thrust levels ..by giving a measure of velocities and hence momentum changes ... can get pilots into trouble if they forget to double check the real thrust indicators like N1 .. see the Patuxent River crash ...