737 Flight Crew Operations Manual
Automatic Flight -
System Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
4.20.14 D6-27370-866-EGP
Other pitch modes available are:
• altitude hold (ALT HOLD)
• level change (MCP SPD)
• vertical speed (V/S).
Automatic Flight Approach and Landing
The AFDS provides guidance for single A/P non–precision approaches. The
VOR/LOC switch arms the AFDS for VOR or localizer tracking. Descent may be
accomplished using VNAV, LVL CHG, or V/S. VOR/LOC, LNAV, or HDG SEL
may be used for the roll mode.
The AFDS provides guidance for single or dual A/P precision approaches. The
approach mode arms the AFDS to capture and track the localizer and glideslope.
Approach (APP) Mode Dual A/Ps
Approach mode allows both A/Ps to be engaged at the same time. Dual A/P
operation provides fail–passive operation through landing flare and touchdown or
an automatic go–around. During fail passive operation, the flight controls respond
to the A/P commanding the lesser control movement. If a failure occurs in one
A/P, the failed channel is counteracted by the second channel such that both A/Ps
disconnect with minimal airplane maneuvering and with aural and visual
warnings to the pilot.
One VHF NAV receiver must be tuned to an ILS frequency before the approach
mode can be selected. For a dual A/P approach, the second VHF NAV receiver
must be tuned to the ILS frequency and the corresponding A/P engaged in CMD
prior to 800 feet RA.
YK981 - YQ456
If the pilot is flying manually but not following the approach flight director
guidance and then selects an autopilot CMD engagement, the autopilot reverts to
CWS for the pitch and roll mode.
YW273, YW274
If the pilot is flying manually but not following the approach flight director
guidance and then selects an autopilot CMD engagement, the autopilot reverts to
CWS for the pitch and roll mode. The approach mode(s) will then re-arm.
Localizer and Glideslope Armed
After setting the localizer frequency and course, pushing the APP switch selects
the APP mode. The APP switch illuminates and VOR/LOC and G/S annunciate
armed. The APP mode permits selecting the second A/P to engage in CMD. This
arms the second A/P for automatic engagement after LOC and G/S capture and
when descent below 1500 RA occurs.
The localizer can be intercepted in the HDG SEL, CWS R or LNAV mode.
September 15, 2016
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