This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
VNAV
Vertical Navigation
VNAV is an autopilot and FMS mode that automatically manages the aircraft’s vertical profile - including climbs, cruise altitude, descents, and altitude constraints - based on the flight plan programmed into the Flight Management System. The FMS calculates an optimised vertical path from origin to destination using the programmed route, performance data, aircraft weight, cost index, and the altitude constraints embedded in the SIDs, STARs, and airways. When VNAV is engaged, the autopilot follows this computed profile, adjusting thrust and pitch to meet each constraint in sequence.
VNAV operates in several sub-modes depending on the phase of flight and the aircraft manufacturer’s implementation. In climb, VNAV typically uses economy speed (ECON CLB) or a selected speed to reach the cruise altitude. During cruise, it maintains the selected flight level. In descent, VNAV PATH follows the geometric descent angle required to meet all downstream constraints, while VNAV SPEED adjusts the descent speed to maintain the path. If ATC issues an instruction that deviates from the VNAV path - such as a speed restriction or a step-down altitude - the crew may need to intervene manually and re-engage VNAV once the constraint is satisfied. VNAV is distinct from LNAV, which manages lateral navigation along the route.