EPR is the ratio of which two measurements?

EPR, or Engine Pressure Ratio, is a crucial performance metric used in turbojet and turbofan engines. It represents the ratio of the pressure of the gas exiting the turbine to the pressure of the air entering the engine. Specifically, this measurement involves comparing the turbine discharge pressure, which is measured at the outlet of the turbine section, to the engine inlet pressure at the point where air enters.

This ratio is significant because it provides insights into the efficiency and performance of the engine during various phases of flight. A higher EPR indicates that the engine is effectively converting the energy from the inlet air into thrust, implying better performance.

In contrast, the other choices do not accurately define EPR. For example, while fuel flow to air intake involves the combustion process, it does not address pressure measurements. Thrust to weight relates to aircraft performance in terms of acceleration and lifting capability rather than engine efficiency. Lastly, the comparison of pressure to temperature does not pertain specifically to EPR but instead relates to thermodynamic principles, which are separate from the pressure ratio essential for understanding engine performance in operational contexts.