微软模拟飞行2020波音747-8自动驾驶使用指南

VNAV

The Vertical NAVigation (VNAV) uses the vertical profile of the flight plan and guides the aircraft towards it. The aircraft can only climb towards the target altitude when the selected altitude is higher than the current altitude and it can only descent if the selected altitude is lower.

Note - VNAV requires the route to be near by and it is typically used together with LNAV to fly along the route and climb and descent on profile.

During the climb the target speed from the flight management system (FMS) is uses and VNAV SPD is displayed. In the descent the geometric vertical path of the flight plan is flown in VNAV PATH. When ever the aircraft is leveling off at the selected MPC altitude the mode VNAV ALT engages.

When the selected altitude matches the cruise altitude of the flight plan VNAV ALT is not engaged but VNAV PATH engages since the vertical profile is correctly intercepted. When the aircraft is in cruise and VNAV PATH has engaged the selected altitude can be decreased and the aircraft will descent automatically when the top of descent (TOD) is reached.

To summarize a typical VNAV profile looks like this: VNAV SPD to the selected MCP altitude (crz alt). VNAV PATH engages when the cruise altitude is captured. At the top of descent the aircraft automatically descents when the selected altitude is lower.

垂直导航(VNAV)使用飞行计划的垂直计划，并将飞机按照其飞行。只有当选定的高度高于当前高度时，飞机才能朝目标高度爬升;如果选定的高度较低，则飞机只能下降。

注意 -VNAV需要路线在附近，并且通常与LNAV一起沿路线飞行并在轮廓上下降。

在爬升过程中，将使用来自飞行管理系统(FMS)的目标速度，并显示VNAV SPD。在下降中，飞行计划的几何垂直路径在VNAV PATH中飞行。每当飞机在选定的MPC高度稳定下来时，VNAV ALT就会进入模式。

当选定的高度与飞行计划的巡航高度匹配时，由于垂直高度计划被正确拦截，因此不启用VNAV ALT，但启用VNAV PATH。当飞机处于巡航状态且VNAV PATH已接合时，可以降低所选的高度，并且当到达下降高度(TOD)时，飞机将自动下降。

总结典型的VNAV计划如下所示：VNAV SPD到选定的MCP高度(crz alt)。捕获巡航高度后，VNAV PATH会接合。在下降高度TOD处，当选定的高度为低高度时，飞机会自动下降。