In the context of VNAV, what is a "profile descent"?

A "profile descent" in the context of VNAV refers to a descent path that provides a gradual reduction in altitude over a specific distance. This technique is especially beneficial for optimizing fuel efficiency and ensuring a smooth transition for the aircraft as it approaches its destination. By maintaining a controlled descent, pilots can manage airspeed and altitude more effectively, which is crucial for ensuring safety and compliance with air traffic control directives.

This approach contrasts with a steep descent, which is not characteristic of a profile descent as it would involve a more abrupt change in altitude over a shorter distance. Additionally, a constant altitude flight segment does not represent a descent at all; it simply describes maintaining the same altitude. A level flight segment, too, focuses on maintaining specific altitude and speed parameters without any descent, which diverges from the concept of reducing altitude gradually. The essence of a profile descent lies in its ability to balance the need for altitude reduction with efficiency and safety during the landing approach.