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[1] VNAV is a vertical guidance mode of operation for the DFCS. vertical flight profile guidance is supplied from the FMCS based on the navigation and the performance data bases and the active flight plan. VNAV is normally used with the A/P but is also available for F/D guidance.
Fig. 40-1 VNAV climb
Figure 40-1 illustrates an example of the climb phase:
A. Initial condition ------- after TAKEOFF, LNAV and VNAV are pressed to engage the FMC for lateral and vertical guidance. Only the VNAV mode is discribed.
B. Climb one --------- after engaging LNAV and VNAV, engage the A/P to CMD. Target speed is given by FMC, and the airspeed cursor on MASI is driven to FMC target speed.
C. Level off at MCP altitude ------- If the MCP altitude is below the FMCS cruise altitude, the A/P acquires and holds the MCP altitude. An altitude alert system provides the pilots with a visual and aural alert when the airplane at the approach of the MCP altitude. The altitude alert system also provides a warning if the airplane departs from the MCP altitude. Approach altitude alerting consists of an aural tone and steady illumination of the alert lights when the airplane has approached within 900 feet of MCP altitude. The alert lights remain until 300 feet, at which time they extinguish. The ALT ACQ mode is a transition mode between climb or descent and altitude hold. To reduce altitude overshoot, entry into altitude acquire is by adaptive capture. That is, entry is controlled by altitude rate. At higher altitude rates, capture occurs further from the selected altitude.
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本文链接地址：第31课 大气数据系统 LESSON 31 AIR DATA SYSTEM(43)
