At what RPM does the APU starter cut out?

• A. 40%-45%
• B. 46%-60%
• C. 61%-70%
• D. 71%-75%

Answer: (B)

The APU starter is designed to cut out when the APU reaches an operational RPM that is sufficient for it to sustain itself without the need for starter assistance. This cutout typically occurs in the range of 46% to 60%. Once the APU RPM reaches this threshold, the starter disengages, allowing the APU to function independently. This operational range ensures that the APU can produce the necessary pneumatic power and electrical energy for aircraft systems without putting unnecessary strain on the starter. Understanding this RPM range is crucial for ensuring proper operation and startup procedures for the auxiliary power unit.