What is a requirement for cold soaked engines?

The correct answer pertains to the procedure for cold soaked engines, which are those that have been exposed to very low temperatures, often while at high altitude or in cold weather conditions. Motoring the engine for 60 seconds while monitoring N1 fan speed is a critical step in ensuring that the engine components are functioning correctly before an actual start-up.

This process allows technicians to check for proper operation of the engine's systems and indications, confirming that there are no unusual characteristics that could affect performance or safety during engine start-up. The focus on monitoring the N1 fan speed is particularly important, as it helps verify that the engine's components are engaging correctly and provides insight into the overall health of the engine after it has been cold soaked.

In contrast, the other choices do not align with standard operational practices for cold soaked engines. Regularly servicing the engines every hour, warming them for 30 minutes, or starting them directly without checks do not adequately account for the critical need to assess the engine's functionality in these specific conditions. This highlights the importance of procedure and safety in aviation operations.