During a normal NG start, at approximately what N2 speed is power removed from the solenoid holding the engine start switch in GND?

During a normal NG start, at approximately what N2 speed is power removed from the solenoid holding the engine start switch in GND?

• A. 56%
• B. 60%
• C. 70%
• D. 40%

Answer: (A)

During an NG start, the solenoid that holds the engine start switch in GND keeps the start circuit energized while the core is accelerated to a speed where ignition can be sustained. The N2 speed is used as the indicator of readiness because it reflects sufficient compressor airflow and fuel flow for a light-off. When N2 reaches about 56%, the engine control removes power from the solenoid, releasing the hold and allowing the starter circuit to drop out. This transition is timed to ensure the engine can light off reliably and then continue to accelerate without overstressing the starter. The exact value can vary by engine, but around mid-50s percent N2 is the typical threshold used to accomplish a smooth, self-sustaining start.

During an NG start, the solenoid that holds the engine start switch in GND keeps the start circuit energized while the core is accelerated to a speed where ignition can be sustained. The N2 speed is used as the indicator of readiness because it reflects sufficient compressor airflow and fuel flow for a light-off. When N2 reaches about 56%, the engine control removes power from the solenoid, releasing the hold and allowing the starter circuit to drop out. This transition is timed to ensure the engine can light off reliably and then continue to accelerate without overstressing the starter. The exact value can vary by engine, but around mid-50s percent N2 is the typical threshold used to accomplish a smooth, self-sustaining start.