What is meant by trimming a turbine engine?

• A. Adjusting the fuel control for proper idle and full throttle RPM.
• B. Adjusting the fuel control for proper specific gravity of the fuel and for the proper idle and full throttle RPM.
• C. Replacing the fuel pump with a calibrated unit.
• D. Changing compressor blade angles.

Answer: (B)

Trimming a turbine engine means calibrating the fuel control so the engine receives the correct fuel flow to reach and maintain the proper idle and full-throttle RPM. Because fuel density (specific gravity) can vary with temperature and fuel batches, the trim adjusts the metering to compensate for those density changes, ensuring the engine speeds match the targets across the operating range. This isn’t about changing hardware like pumps or compressor blades; it’s about tuning the fuel metering so RPM targets are met reliably, even as fuel properties vary.