FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesMedium
During a normal turbine engine start, the starter begins rotating the compressor. At approximately what point in the sequence should the fuel and ignition systems typically be energized?
- AOnly after the starter has been disengaged and rotation has stopped
- BAfter the starter has accelerated the engine to a specified minimum N2 (or N1) speed
- CSimultaneously with generator paralleling after the engine reaches idle
- DImmediately when the starter switch is first engaged, before any rotation begins
Show answer & explanationAnswer & explanation
Correct answer: B. After the starter has accelerated the engine to a specified minimum N2 (or N1) speed
A normal start sequence first uses the starter to establish airflow through the compressor by rotating the gas generator to a specified minimum speed; fuel and ignition are then introduced to achieve light-off, avoiding a hot start caused by insufficient airflow.
Why the other options are wrong
- A. The starter continues assisting rotation through light-off, not after it stops.
- C. Generator paralleling occurs well after the start sequence is complete.
- D. Introducing fuel before adequate airflow risks a hot start or torching.
Turbine Engine Start Sequence
Fuel and ignition are introduced only after the starter has rotated the engine to a specified minimum speed, ensuring adequate airflow for proper light-off and preventing hot starts.
- Starter rotates compressor first
- Fuel/ignition introduced at min N2/N1 speed
- Light-off produces EGT rise
- Starter disengages at self-sustaining speed
Memory trick: Spin first, then spark — airflow before fire