FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesHard
A turbofan engine's Engine Pressure Ratio (EPR) is defined as turbine discharge total pressure (Pt7) divided by compressor inlet total pressure (Pt2). If Pt7 is 34.8 psi and Pt2 is 14.5 psi, what is the EPR?
- A1.8
- B2.0
- C2.4
- D2.9
Show answer & explanationAnswer & explanation
Correct answer: C. 2.4
EPR = Pt7 / Pt2 = 34.8 / 14.5 = 2.4. EPR is used as a thrust-setting parameter, comparing turbine discharge pressure to compressor inlet pressure.
Why the other options are wrong
- A. 1.8 does not match the calculated ratio of 34.8/14.5.
- B. 2.0 is an incorrect division result.
- D. 2.9 overstates the actual pressure ratio.
Engine Pressure Ratio (EPR)
A thrust indicator on many turbofan engines, calculated as the ratio of turbine discharge total pressure (Pt7) to compressor/fan inlet total pressure (Pt2).
- EPR = Pt7 / Pt2
- Displayed in cockpit as a thrust setting parameter
- Alternative to N1 for setting thrust on some engines
Memory trick: 'EPR: End over Entry' - discharge pressure over inlet pressure