During a VNAV approach, what should be monitored closely by the pilot?

Monitoring the aircraft's adherence to the VNAV path and altitude constraints is crucial during a VNAV approach. This is because VNAV procedures are designed to provide vertical guidance to ensure that the aircraft maintains the correct altitude and descent profile throughout the approach. By closely following the VNAV path, pilots can ensure safe and efficient descent while adhering to air traffic control requirements and avoiding terrain or obstacles.

Maintaining the correct altitude not only helps in optimizing fuel efficiency but is also essential for ensuring compliance with published procedures, which may be dictated by airspace restrictions or traffic conditions. Deviations from the VNAV path can lead to unsafe situations, such as excessive altitude changes or conflicts with other aircraft, and could result in the need for sudden corrections that may compromise safety. Therefore, careful monitoring of the VNAV path is fundamental for a successful and safe approach.