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MAINTENANCE MANUAL
(g) Localizer Active Mode 1) The LOC active mode provides aileron commands to acquire and track the centerline of the localizer beam during all phases of single or multi-channel approach. The A/P yaw channel provides rudder commands during multi-channel approaches to maintain runway alignment during rollout. 2) Localizer mode is armed by pressing the LOC switch/light on the MCP and may be disarmed by pressing the LOC switch/light a second time. LOC is displayed white on the PFDs while it is armed. The LOC arm mode has no effect on the current roll axis mode. Once the LOC capture criteria are satisfied the LOC mode is engaged and LOC is displayed green on the PFDs.
3) Once the localizer mode is engaged it can be disabled if the following modes are selected: HDG HLD, HDG Select, or LNAV.
(h) Vertical Speed Mode (V/S) 1) Vertical speed is the basic pitch axis mode. When the V/S switch/light is pressed with the A/P in CMD or the F/D on, the vertical speed command acquires the selected vertical speed. The existing V/S mode is automatically acquired when the F/D is initially turned on or the F/D is overridden by engaging the A/P in CMD.
2) Once V/S mode is engaged, it can be disabled if CMD is disabled or the F/D is turned off. The V/S mode will also be disabled by the selection of the following modes: ALT HLD, FL CH, VNAV, APP, or GA.
(i) Flight Level Change
1) The flight level change mode is manually selected by pressing the FLCH switch/light on the MCP. The mode uses software programmed elevator control laws to generate pitch attitude A/P or F/D commands. The pitch attitude commands control the airplane to obtain and maintain an MCP selected airspeed or Mach. The FLCH mode provides flap placard and minimum speed limit protection. When limits are encountered, corresponding annunciation is provided on the PFD.
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MAINTENANCE MANUAL
2) Once flight level change is engaged it can be disabled if the following modes are selected: ALT HOLD, VS, VNAV, G/S, or GA.
Vertical Navigation Mode (VNAV)
1) The mode is manually selected by pressing the VNAV switch/light on the MCP. The A/P or F/D responds to pitch steering commands from the FMC. Pitch steering commands are generated in the FMC as necessary to acquire and track a vertical path along a preplanned flight route.
2) Once VNAV MODE is engaged it will be disabled if any of the following modes are selected: ALT HLD, V/S, FL CH.
Glideslope Active Mode (Approach)
1) The mode is manually selected by pressing the APP switch/light on the MCP. Pitch commands are generated for A/P or F/D control to acquire and maintain capture of the glideslope. The A/P channels can be used for single channel or multi-channel ILS approaches.
2) Once the approach mode is engaged, it can be disabled when the following modes are selected: HDG HLD, HDG Select, or LNAV.
Altitude Mode Active (Altitude Sel/Hold)
1) The ALT HOLD mode is manually requested by pressing the HOLD switch/light on the MCP. A valid request is indicated by the lighting of the dot-bar matrix on the lower half of the switch cover. The ALT HOLD mode is automatically selected when in the vertical speed mode and V/S is zero. (The V/S light will remain lighted.)
2) The ALT HOLD mode is also selected automatically when in the VNAV mode and the FMC has commanded a target altitude in a direction away from the MCP selected altitude. Under these conditions, VNAV disengages and the VNAV switch/light extinguishes. ALT HOLD is active in CMD ENG or F/D on.
3) Altitude select arm and altitude select engage are not manually selectable on the MCP. Altitude select occurs at altitude capture, which is determined by capture criteria, and may be entered from any of the following modes: V/S, FL CH, VNAV, T/O (in F/D only), and GA. Altitude select may not be entered from the G/S mode.
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