Tuesday at 10:09 PM2 days 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 ?
Wednesday at 12:51 PM1 day Staff Solution 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. Vrishabh Sehgal ( @Richboy2307 ) Community Team Member & Tester iniBuilds Ltd. | inibuilds.com
5 hours ago5 hr Author On 6/3/2026 at 8:51 AM, richboy2307 said: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.Hello,Unless the Tristar has a different design, the EPR normally compares exhaust and intake total pressure, not ambiant pressure, just like a pitot probe. That means that this intake total pressure will be higher, at speed.You will observe values around 0.90 EPR during idle descent on modern turbofans such as the A320.Edit: That does look like a typical total pressure probe on the Tristar's intake:Uploading Attachment... Edited 5 hours ago5 hr by Genista
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