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.

垂直導(dǎo)航(VNAV)使用飛行計(jì)劃的垂直計(jì)劃，并將飛機(jī)按照其飛行。只有當(dāng)選定的高度高于當(dāng)前高度時(shí)，飛機(jī)才能朝目標(biāo)高度爬升;如果選定的高度較低，則飛機(jī)只能下降。

注意 -VNAV需要路線在附近，并且通常與LNAV一起沿路線飛行并在輪廓上下降。

在爬升過程中，將使用來自飛行管理系統(tǒng)(FMS)的目標(biāo)速度，并顯示VNAV SPD。在下降中，飛行計(jì)劃的幾何垂直路徑在VNAV PATH中飛行。每當(dāng)飛機(jī)在選定的MPC高度穩(wěn)定下來時(shí)，VNAV ALT就會(huì)進(jìn)入模式。

當(dāng)選定的高度與飛行計(jì)劃的巡航高度匹配時(shí)，由于垂直高度計(jì)劃被正確攔截，因此不啟用VNAV ALT，但啟用VNAV PATH。當(dāng)飛機(jī)處于巡航狀態(tài)且VNAV PATH已接合時(shí)，可以降低所選的高度，并且當(dāng)?shù)竭_(dá)下降高度(TOD)時(shí)，飛機(jī)將自動(dòng)下降。

總結(jié)典型的VNAV計(jì)劃如下所示：VNAV SPD到選定的MCP高度(crz alt)。捕獲巡航高度后，VNAV PATH會(huì)接合。在下降高度TOD處，當(dāng)選定的高度為低高度時(shí)，飛機(jī)會(huì)自動(dòng)下降。