What does trimming a turbine engine mean?

• A. Optimizing the engine fuel mixture to reach idle and trim speed RPM.
• B. Shutting down the engine during idle.
• C. Increasing exhaust gas temperatures.
• D. Adjusting fuel control to achieve idle and trim speed RPM.

Answer: (D)

Trimming a turbine engine means fine‑tuning the fuel metering so the engine runs at the correct idle speed and maintains a defined trim speed. The fuel control (or FADEC) sets how much fuel is delivered to the turbine, and trimming calibrates that delivery so the engine settles at the intended idle RPM and holds a steady, target speed when the aircraft is in its trimmed operating condition. This is about precise fuel control to achieve predictable engine speeds, not about changing air‑fuel mixtures like in piston engines. It also isn’t about shutting the engine down or purposely driving exhaust gas temperatures higher.