At what RPM does the APU Starter disengage?

The APU starter disengages at 50% RPM, which is crucial for preventing damage to the starter motor and the APU itself. When the APU reaches this threshold, the fuel control unit is able to manage the fuel flow to maintain stable operation, allowing the APU to take over the role of supplying power independently. This disengagement point is specifically designed for optimal performance; it ensures that the APU can reliably provide power without putting unnecessary strain on the starter system.

Understanding the importance of this disengagement helps in operational efficiency and maintenance of the APU while preventing unnecessary wear. Recognizing the RPM at which this occurs is vital for proper procedure adherence during the startup sequence, ensuring smooth transitions and minimizing the likelihood of mechanical issues.