What is the engine cooldown limitation prior to shutdown?

What is the engine cooldown limitation prior to shutdown?

• A. Idle for 1 minute prior to shutdown.
• B. Idle for 2 minutes prior to shutdown.
• C. Idle for 3 minutes prior to shutdown.
• D. Idle for 4 minutes prior to shutdown.

Answer: (B)

Cooldown before shutdown serves to protect the engine from thermal stress and to let critical systems settle after operation. The specified procedure is to idle for two minutes prior to shutdown. During that idle period, hot sections have time to cool gradually, reducing the risk of thermal shock to turbines and the accessory drive gear train, while the lubrication and control systems stabilize. Shorter cooldowns wouldn’t provide enough time for these protections, and longer cooldowns don’t add extra benefit for this routine.

Cooldown before shutdown serves to protect the engine from thermal stress and to let critical systems settle after operation. The specified procedure is to idle for two minutes prior to shutdown. During that idle period, hot sections have time to cool gradually, reducing the risk of thermal shock to turbines and the accessory drive gear train, while the lubrication and control systems stabilize. Shorter cooldowns wouldn’t provide enough time for these protections, and longer cooldowns don’t add extra benefit for this routine.