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vertical navigation (VNAV)
A function of area navigation (RNAV) equipment that calculates, displays, and provides vertical guidance to a profile or path. Vertical navigation descent information appears in the profile view of selected non-precision approaches with charts printed after December 3, 1999. The information indicates the geometric descent path with a descent angle from the final approach fix to the threshold-crossing height at the approach end of the runway. The inclusion of the VNAV descent does not change or modify existing non-precision approach requirements, and the usage of the MDA (minimum decision altitude) and the MAP (missed approach point) remains unchanged. This implies that a descent below the MDA cannot be continued unless required visual references are available. Similarly, the prescribed missed approach procedure should not be initiated until the aircraft has reached the published MAP.