Which instrument indication is used when trimming turbine engines?

• A. Torque
• B. Exhaust gas temperature
• C. Oil pressure
• D. RPM

Answer: (D)

Trimming a turbine engine means adjusting fuel flow to reach and hold a target engine speed. The RPM indicator is the best reference because it directly shows how fast the engine core is turning, which directly controls thrust and how the engine responds to fuel changes. When you tweak fuel flow, you’re trying to settle the engine at a specific speed, so watching RPM lets you know exactly when you’ve hit that target and can maintain it. Other indicators serve as safety or performance checks—exhaust gas temperature tells you about combustion temperature, oil pressure shows lubrication health, and torque relates to load but isn’t the direct measure used to set engine speed. So, the instrument used for trimming is the RPM gauge.