.
FLARE (engaged) – during a dual A/P ILS approach, flare engages at 50
feet radio altitude. FLARE accomplishes the autoland flare maneuver.
Roll Modes
. LNAV – the AFDS intercepts and tracks the active FMC route. Either of
the following capture criteria must be met:
. on any heading and within 3 NM of the active route segment
.
if outside of 3 NM of active route segment, airplane must be on an intercept course of 90 degrees or less and intercept the route segment before the active waypoint.
.
HDG SEL – the airplane is turning to, or is on the heading selected in the
MCP Heading Display
.
VOR/LOC (armed) – AFDS is armed to capture selected VOR or LOC
COURSE
.
VOR/LOC (engaged) – AFDS tracks selected VOR course or tracks
selected localizer course along the inbound front course bearing.
Autopilot Control Wheel Steering
CWS Engage Switch Selected
Pushing a CWS engage switch engages the A/P pitch and roll axes in the CWS mode and displays CWS P and CWS R on the FMAs.
With CWS engaged, the A/P maneuvers the airplane in response to control pressures applied by either pilot. The control pressure is similar to that required for manual flight. When control pressure is released, the A/P holds existing attitude.
Copyright . The Boeing Company. See title page for details.
4.20.6 March 28, 2005
Automatic Flight -System Description
737 Flight Crew Operations Manual
If aileron pressure is released with 6 degrees or less bank, the A/P rolls the wings level and holds existing heading. This heading hold feature with bank less than 6 degrees is inhibited when any of the following conditions exists:
.
below 1,500 feet RA with the landing gear down
.
after F/D VOR capture with TAS 250 knots or less
.
after F/D LOC capture in the APP mode.
Pitch CWS with a CMD Engage Switch Selected
The pitch axis engages in CWS while the roll axis is in CMD when:
.
a command pitch mode has not been selected or was deselected
.
A/P pitch has been manually overridden with control column force. The
force required for override is greater than normal CWS control column
force. This manual pitch override is inhibited in the APP mode with both
A/Ps engaged.
CWS P is annunciated on the FMAs while this mode is engaged. Command pitch modes can then be selected.
When approaching a selected altitude in CWS P with a CMD engage switch selected, CWS P changes to ALT ACQ. When at the selected altitude, ALT HOLD engages.
If pitch is manually overridden while in ALT HOLD at the selected altitude, ALT HOLD changes to CWS P. If control force is released within 250 feet of the selected altitude, CWS P changes to ALT ACQ, the airplane returns to the selected altitude, and ALT HOLD engages. If the elevator force is held until more than 250 feet from the selected altitude, pitch remains in CWS P.
Roll CWS with a CMD Engage Switch Selected
The roll axis engages in CWS while the pitch axis is in CMD when:
.
a command roll mode has not been selected or was deselected
.
A/P roll has been manually overridden with control wheel force. The
force required for override is greater than the normal CWS control wheel
force.
CWS R is annunciated on the FMAs while this mode is engaged.
CWS R with a CMD engage switch illuminated can be used to capture a selected radio course while the VOR/LOC or APP mode is armed. Upon intercepting the radial or localizer, the F/D and A/P annunciations change from CWS R to VOR/LOC engaged, and the A/P tracks the selected course.
Autothrottle System
The A/T system provides automatic thrust control from the start of takeoff through climb, cruise, descent, approach and go–around or landing. In normal operation, the FMC provides the A/T system with N1 limit values.
Copyright . The Boeing Company. See title page for details.
Automatic Flight -System Description
737 Flight Crew Operations Manual
The A/T moves the thrust levers with a separate servo motor on each thrust lever. Following manual positioning, the A/T may reposition the thrust levers to comply with computed thrust requirements except while in the THR HLD and ARM modes.
The A/T system operates properly with the EECs ON or in ALTN. In either case, the A/T uses the FMC N1 limits. During A/T operation, it is recommended that both EECs be ON or both be in ALTN, as this produces minimum thrust lever separation.
Autothrottle Engagement
Moving the A/T Arm switch to ARM, arms the A/T for engagement in the N1, MCP SPD or FMC SPD mode. The A/T Arm switch is magnetically held at ARM and releases to OFF when the A/T becomes disengaged.
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