What are the APU start limits?

• A. Three attempts in one hour with two minute delays
• B. Two attempts in one hour with five minute delays
• C. Five attempts in two hours with one minute delays
• D. Three attempts in one hour with three minute delays

Answer: (A)

APU start limits govern how many times you can attempt to start the APU within a given period to protect the unit from thermal stress and excessive wear. The standard rule is three start attempts in one hour, with at least a two-minute delay between attempts. That two-minute pause allows cooling and reduces stress on the starter, motor, and turbine components, helping prevent damage from rapid successive starts.

Other options don't align with typical published limits: starting more times than the standard window or with shorter delays would increase the risk of overheating or component wear, while longer delays or fewer attempts would unnecessarily restrict APU availability. So, the best choice matches the three attempts in one hour with two-minute delays.