Which instrument indicates engine speed?

Which instrument indicates engine speed?

• A. Engine RPM
• B. Turbine inlet temperature
• C. Exhaust gas pressure
• D. Fuel pressure

Answer: (A)

Engine speed is the rotational rate of the compressor/shaft assembly, and the instrument that directly shows that is the RPM gauge (tachometer). It reads revolutions per minute, often fed by a speed sensor from the engine, so you can see exactly how fast the engine is turning. This speed setting governs how much air is drawn in and how the compressor and turbine are matched to deliver power. Turbine inlet temperature measures how hot the gas entering the turbine is, which is about thermal conditions, not rotation. Exhaust gas pressure reflects the flow and backpressure in the exhaust, not how fast the engine is spinning. Fuel pressure indicates how much fuel is being delivered to the combustor, again not the rotational speed. So the instrument that indicates engine speed is the RPM gauge.

Engine speed is the rotational rate of the compressor/shaft assembly, and the instrument that directly shows that is the RPM gauge (tachometer). It reads revolutions per minute, often fed by a speed sensor from the engine, so you can see exactly how fast the engine is turning. This speed setting governs how much air is drawn in and how the compressor and turbine are matched to deliver power. Turbine inlet temperature measures how hot the gas entering the turbine is, which is about thermal conditions, not rotation. Exhaust gas pressure reflects the flow and backpressure in the exhaust, not how fast the engine is spinning. Fuel pressure indicates how much fuel is being delivered to the combustor, again not the rotational speed. So the instrument that indicates engine speed is the RPM gauge.