APU starter duty cycle: what is the required OFF time after starter attempts 1 and 2?

APU starter duty cycle: what is the required OFF time after starter attempts 1 and 2?

• A. 30 sec OFF
• B. 60 sec OFF
• C. 90 sec OFF
• D. 2 min OFF

Answer: (B)

Understanding how the APU starter duty cycle works: after each start attempt, there is a required cooling/off period to protect the starter and the APU from overheating. For the ERJ 175, that cooling interval is 60 seconds between attempts. So, after the first start attempt and after the second start attempt, you must wait 60 seconds before trying again. This 60-second pause ensures the starter motor and APU have time to dissipate heat. The shorter 30 seconds wouldn’t provide adequate cooling, while longer intervals (like 90 seconds or 2 minutes) aren’t required for the first two attempts and would unnecessarily delay the next start unless specified for a different scenario.

Understanding how the APU starter duty cycle works: after each start attempt, there is a required cooling/off period to protect the starter and the APU from overheating. For the ERJ 175, that cooling interval is 60 seconds between attempts. So, after the first start attempt and after the second start attempt, you must wait 60 seconds before trying again. This 60-second pause ensures the starter motor and APU have time to dissipate heat. The shorter 30 seconds wouldn’t provide adequate cooling, while longer intervals (like 90 seconds or 2 minutes) aren’t required for the first two attempts and would unnecessarily delay the next start unless specified for a different scenario.