What is the cool-down time after starting engines 3rd to 5th in flight?

The correct answer indicates that the cool-down time after starting engines 3rd to 5th in flight is 5 minutes. This timeframe is crucial for ensuring that the engines operate efficiently and maintain their integrity after being started during flight operations. The short cool-down period helps in managing the thermal stress on the engines, allowing for a safe operation while reducing the risk of overheating or unnecessary wear caused by immediate high thrust demands after start-up.

It is important to have precise guidelines for engine management in aviation, as these practices are designed to maximize performance and safety. While other options might suggest longer cool-down periods, 5 minutes is generally sufficient under typical operational circumstances to ensure the engines stabilize after starting.