Engine Pressure Ratio (EPR) is commonly used to estimate which parameter on some engines?

• A. Fuel flow
• B. Exhaust gas temperature
• C. Thrust
• D. Oxygen content

Answer: (C)

Engine pressure ratio acts as a quick indicator of thrust, because it compares the air pressure produced by the compressor to the pressure in the exhaust. As the engine produces more thrust, the compressor discharge pressure rises while the exhaust pressure is kept relatively lower, increasing the EPR. This provides a practical way to gauge how much power the engine is delivering, especially on engines where direct thrust measurement isn’t available in flight. Fuel flow is related to power but isn’t what EPR directly estimates, and exhaust gas temperature indicates turbine inlet temperature rather than thrust. Oxygen content in the exhaust isn’t used to estimate thrust either.