The Ram Ratio compares total pressure to static pressure at which location?

• A. At the air intake
• B. Within the combustion chamber
• C. In the exhaust nozzle
• D. At the compressor

Answer: (A)

The Ram Ratio measures how much extra pressure the incoming air gains from the aircraft’s motion, by comparing the air’s stagnation (total) pressure to the ambient static pressure. This ratio is defined at the engine’s air intake, where the air first enters the engine and is slowed down, converting dynamic pressure into stagnation pressure while the static pressure remains essentially the ambient value. Measuring at the intake captures the ram effect of forward speed and how it affects the pressure seen by the engine. Inside the combustion chamber, exhaust, or after the air has been through the compressor, you’re no longer assessing the ram effect on the incoming air, so those locations aren’t used for this ratio.