APU start limits specify how many attempts in one hour with what delays?

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

Answer: (A)

The idea being tested is how APU start limits control cycling: you’re allowed a certain number of start attempts within a set time window, with minimum delays between attempts to prevent heat buildup and wear.

The correct setting is three start attempts allowed in one hour, with at least two minutes between each attempt. This pattern protects the APU by limiting rapid cycling and giving a brief cooling interval between tries. If you’ve used up those three attempts, you’d need to wait for the window to reset before trying again, which typically means waiting until the hour is up or following the maintenance procedure.

Other options either reduce or extend the window, or increase the required delay, which would change how often you can attempt a start and wouldn’t align with the standard practice of three attempts per hour with a two-minute pause between attempts.