What happens once the engine reaches self sustaining speed?

• A. The starter is disengaged
• B. Fuel flow increases
• C. Oil pressure rises
• D. The throttle locks

Answer: (A)

When an engine reaches self-sustaining speed, the starter has done its job of getting the engine to rotate; at that point, the engine can keep turning on its own with the mixture, ignition, and compression providing the necessary power. To protect the starter from damage and to avoid being driven by the engine, the drive to the starter is disengaged automatically once the RPM threshold for self-sustaining operation is reached. After that moment, normal operation continues with the engine running on its own, with fuel and ignition controlled for steady operation. Fuel flow increasing, oil pressure behavior, or throttle locking aren’t the defining change at this instant.