Unsuccessful APU starts are limited to 3 consecutive attempts, then 20 minutes off.

• A. 3 consecutive attempts, then 20 minutes off
• B. 2 consecutive attempts, then 1 hour off
• C. 4 consecutive attempts, then 30 minutes off
• D. 5 consecutive attempts, then 15 minutes off

Answer: (A)

APU start attempt limits protect the APU and its starter from thermal and mechanical stress during power-up. If the APU fails to start after three consecutive attempts, you must pause for twenty minutes before trying again. That cooldown lets the starter and APU cool, reduces battery draw, and prevents repeated strain on the electrical system when starting in marginal conditions. Following this limit helps you avoid masking a developing issue with rapid retries and keeps you aligned with proper procedures. The other possible limits would either permit too rapid retries that risk overheating and wear or impose longer pauses that unnecessarily delay operations; the standard practice is three consecutive unsuccessful starts, then a twenty-minute break.