What conditions must be met for Advisory VNAV to be valid?

For Advisory VNAV (Vertical Navigation) to be valid, several conditions must be met. These include the selection of the Flight Management System (FMS) and ensuring that the flight plan contains a valid altitude. Specifically, having the FMS selected and set to the Performance (PERF) menu allows the system to utilize the necessary parameters for calculating vertical flight paths.

Additionally, the flight plan must not only include a valid altitude but also must be active and include a destination waypoint. This ensures that the system can calculate appropriate vertical navigation paths based on both the current and future waypoints along the route, as well as any altitude constraints that apply.

By requiring all these elements—FMS selection on the PERF menu, a valid altitude in the flight plan, and an active flight plan with a destination waypoint and preselected altitude—Advisory VNAV can accurately guide the aircraft in managing its vertical flight profile, thus enhancing safety and efficiency during flight operations.