Hello. Currently descending thru FL300 with throttles at idle in MACH hold. Surprised to see that EPR is still 1.1.

In a turbofan engine shouldn't the value be around 0.8-0.9 at idle since the engine are causing more drag than thrust ?

Hi,

No even at IDLE when stationary, a running engine can't give an EPR below 1.0 - which indicates that the total exhaust pressure precisely matches the ambient intake pressure. A flight idle of ~1.100 is pretty typical.