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SWITCH/LIGHT L NAV HEADING DISPLAY LOCALIZER SWITCH/LIGHT
LNAV Mode
Figure 14
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(e) LNAV and LOC ARM (E)
1) The LOC ARM submode is initiated by pressing the LOC switch/light on the MCP. The roll channel is armed for capture of selected ILS frequency. The EADI displays LOC as the roll armed mode but the AFDS responds to LNAVC until LOC capture. The EADI displays LOC and GS. Localizer mode will be discussed later.
(16)
LNAV Mode Logic (Fig. 10)
(a) When the LNAV switch/light is pressed and accepted, this request is processed by mode transition logic to produce the LAT NAV logic. When the FMC indicates a valid horizontal steering command (LNAV capture) the LAT NAV engage valid logic is produced. This develops the 2 NAV engaged logic. If one or more channels are in CMD ENG, the LNAV command input logic (LNAVIN) is produced. The LNAV engage and LNAVIN logic signals are used in signal processing.
(17)
LNAV Mode Signal Processing (Fig. 11)
(a) The LNAV engage logic applies the horiziontal steering command from the FMC to a summing point where it is summed with the F/D heading command in the development of the roll F/D commands. The LNAVIN logic applies the horizontal steering command to the roll attitude processing chain which generates the aileron servo command. Aileron servo position and surface position LVDTs provide feedback to the processor for nulling the servo command.
(18)
Localizer (LOC) Mode (Fig. 15)
(a)
The MCP controls and displays associated with the LOC mode are the HDG display, the LOC switch/light and the APP switch/light.
(b)
The AFDS acquires and maintains the front course LOC centerline during single or multichannel ILS approach. Localizer control laws generate AFDS commands for control of optimum flight path to the LOC centerline. At LOC capture, continuous tests are started to determine when transition from LOC capture to LOC track should occur. In LOC track, the AFDS commands for optimum tracking of the LOC centerline.
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MAINTENANCE MANUAL
EADI
Localizer Mode Figure 15
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(c)
The FMA on the EADI displays LOC in white as the roll armed mode before LOC capture and LOC in green as the roll engaged mode after LOC capture. At LOC capture, the heading display on the MCP changes from the last selected heading to the selected course (runway heading) on the ILS control panel.
(d)
Single Channel LOC Approach
1) A single channel LOC approach is enabled by pressing the LOC switch. This mode is used when the pilot wishes to fly a different vertical path than that dictated by the glideslope beam, or where no G/S is available. The pitch axis may be controlled using any single channel vertical control mode.
2) The single channel LOC approach mode can be disengaged by: selecting heading hold; arming the approach mode and capturing G/S; sensing an on-ground condition; A/P disconnect; or switching the F/D off.
(e) Single Channel ILS Mode
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