What is the cooldown after 3 consecutive unsuccessful APU start attempts?

What is the cooldown after 3 consecutive unsuccessful APU start attempts?

• A. 5 minutes
• B. 20 minutes
• C. 40 minutes
• D. 60 minutes

Answer: (B)

When you have three consecutive unsuccessful APU start attempts, you must observe a twenty-minute cooldown before trying again. This pause gives the APU and its starter motor a chance to cool and dissipate residual heat, reducing thermal stress on the turbine, bearings, and electrical components. The cooldown helps prevent heat-related failures on the next start and protects the overall health of the APU. After the period, recheck the system conditions and any fault indications, then proceed with the start procedure per the checklist.

When you have three consecutive unsuccessful APU start attempts, you must observe a twenty-minute cooldown before trying again. This pause gives the APU and its starter motor a chance to cool and dissipate residual heat, reducing thermal stress on the turbine, bearings, and electrical components. The cooldown helps prevent heat-related failures on the next start and protects the overall health of the APU. After the period, recheck the system conditions and any fault indications, then proceed with the start procedure per the checklist.