How can pilots monitor the amount of thrust produced by an engine?

• A. Vertical speed indicator
• B. Airspeed indicator
• C. Altimeter
• D. EPR (Engine Pressure Ratio)

Answer: (D)

Engine thrust is not measured directly; pilots gauge it using engine indicators. The Engine Pressure Ratio shows how much thrust the engine is producing by comparing the pressure of the air leaving the compressor to the pressure entering the engine. As you advance the throttle, the pressure at the compressor inlet and the turbine discharge both rise, increasing the pressure ratio. That higher ratio correlates with higher thrust, making it a straightforward readout for how hard the engine is working.

The other indicators don’t reflect engine power. A vertical speed indicator shows climb or descent rate, not thrust. An airspeed indicator measures how fast the aircraft is moving through the air. An altimeter shows altitude. While modern jets also monitor parameters like N1 and ITT, the Engine Pressure Ratio is the primary instrument among the options for indicating thrust output.