During which condition is the pilot required to monitor the engine RPM closely?

Monitoring the engine RPM closely is particularly crucial when the primary governor is subjected to failure. The primary governor plays an essential role in regulating engine speed and maintaining optimal performance during various phases of flight. If the governor fails, the pilot must take immediate action to manage the engine's RPM manually. This involves monitoring the RPM closely to prevent overspeed conditions, which can lead to serious mechanical failure, or underspeed conditions, which can affect aircraft control and performance.

In scenarios such as when air conditioning is off, at cruising altitude, or during final approach for landing, while engine RPM is still important to observe, the urgency and critical nature of monitoring arise primarily during a governor failure situation. The pilot's attention to engine RPM during this condition helps ensure safety and maintain control of the aircraft under adverse operational circumstances.