What is the interval between consecutive successful APU starts?

What is the interval between consecutive successful APU starts?

• A. 5 minutes
• B. 10 minutes
• C. 15 minutes
• D. 20 minutes

Answer: (B)

The interval is about giving the APU time to cool and stabilize between starts. The APU runs a turbine and generates heat quickly; starting it again too soon can cause thermal stress and wear on the turbine, bearing, and lubrication system. Waiting 10 minutes ensures the hot sections have cooled enough and the lubrication pressure has recovered, reducing the risk of damage or faults when the next start is attempted. That’s why the correct interval is 10 minutes. Shorter times risk overheating or stress; longer times aren’t in line with the specified operating limits.

The interval is about giving the APU time to cool and stabilize between starts. The APU runs a turbine and generates heat quickly; starting it again too soon can cause thermal stress and wear on the turbine, bearing, and lubrication system. Waiting 10 minutes ensures the hot sections have cooled enough and the lubrication pressure has recovered, reducing the risk of damage or faults when the next start is attempted. That’s why the correct interval is 10 minutes. Shorter times risk overheating or stress; longer times aren’t in line with the specified operating limits.