Unsuccessful APU starts are limited to 2 consecutive start attempts, then 1 hour off.

Unsuccessful APU starts are limited to 2 consecutive start attempts, then 1 hour off.

• A. 3 consecutive attempts, then 20 minutes off
• B. 2 consecutive start attempts, then 1 hour off
• C. 4 consecutive attempts, then 2 hours off
• D. 1 consecutive start attempt, then 2 hours off

Answer: (B)

Unsuccessful APU starts are limited to two consecutive attempts, then a one-hour off period. This rule protects the APU and its starting system from excessive wear and potential overheating when initial starts fail. If the APU doesn’t start after two tries, the one-hour rest gives the system time to cool and any transient faults to clear before retrying, reducing the risk of damage to the starter, electrical components, or fuel/air systems. The other start patterns don’t align with this safety/protection guideline. They either shorten or remove the mandated cooling period or allow more start attempts than is safe after a failed start, which could lead to increased wear or undetected faults. If two consecutive starts fail, you’d typically pause, inspect aspects like fuel, ignition, and air supply, and involve maintenance if the issue isn’t immediately resolvable.

Unsuccessful APU starts are limited to two consecutive attempts, then a one-hour off period. This rule protects the APU and its starting system from excessive wear and potential overheating when initial starts fail. If the APU doesn’t start after two tries, the one-hour rest gives the system time to cool and any transient faults to clear before retrying, reducing the risk of damage to the starter, electrical components, or fuel/air systems.

The other start patterns don’t align with this safety/protection guideline. They either shorten or remove the mandated cooling period or allow more start attempts than is safe after a failed start, which could lead to increased wear or undetected faults. If two consecutive starts fail, you’d typically pause, inspect aspects like fuel, ignition, and air supply, and involve maintenance if the issue isn’t immediately resolvable.