What happens if the ignition does not automatically shut off at 55% N2 due to a fault?

What happens if the ignition does not automatically shut off at 55% N2 due to a fault?

• A. It will shut off at 60% N2
• B. It will never shut off
• C. It may require manual intervention
• D. It will shut off at 50% N2

Answer: (C)

The ignition system includes an automatic shutoff around the point where the engine has started and is self-sustaining, roughly at 55% N2. If that automatic stop fails because of a fault, the igniters can stay energized even though they aren’t needed. In that case the crew must intervene manually to shut ignition off once the start is complete and the engine is stable. This manual action—turning the ignition switch to OFF (for both channels if required)—prevents unnecessary spark energy, igniter wear, and potential issues from keeping ignition on when it isn’t needed.

The ignition system includes an automatic shutoff around the point where the engine has started and is self-sustaining, roughly at 55% N2. If that automatic stop fails because of a fault, the igniters can stay energized even though they aren’t needed. In that case the crew must intervene manually to shut ignition off once the start is complete and the engine is stable. This manual action—turning the ignition switch to OFF (for both channels if required)—prevents unnecessary spark energy, igniter wear, and potential issues from keeping ignition on when it isn’t needed.