.  
After F/D LOC capture in the APP mode.

Pitch CWS with a CMD 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

Copyright . The Boeing Company. See title page for details.
4.20.6   December 1, 2000

Automatic Flight -System Description

737 Operations Manual
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.
The A/T moves the thrust levers with a separate servo motor on each thrust lever. Manually positioning the thrust levers does not cause A/T disengagement unless 10 degrees of thrust lever separation is exceeded during a dual channel approach after FLARE armed is annunciated. 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 PMCs ON or OFF. In either case, the A/T computer controls to the FMC N1 limits. During A/T operation, it is recommended that both PMCs be ON or both OFF, as this produces minimum thrust lever separation. A/T takeoffs may be performed with both PMCs OFF.
Automatic Flight -System Description 737 Operations Manual

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.
A general summary of A/T mode engagement is as follows:
.  
A/T SPD or N1 modes automatically engage when AFDS command pitch
modes become engaged

.  
Engaging LVL CHG or VNAV climb modes automatically engages the
A/T N1 mode

.  
Engaging LVL CHG or VNAV descent modes automatically engages the
A/T in RETARD and then ARM when thrust is at idle

.  
If not in a VNAV mode, engagement of ALT ACQ or ALT HOLD
automatically engages the A/T in the MCP SPD mode; otherwise the A/T
remains in FMC SPD.

.  
Engagement of G/S capture automatically engages the A/T in the MCP
SPD mode.

Autothrottle Disengagement
Any of the following conditions or actions disengages the A/T:
.  
Moving the A/T Arm switch to OFF

.  
Pressing either A/T Disengage switch

.  
An A/T system fault is detected

.  
Two seconds have elapsed since landing touchdown

.  
Thrust levers become separated more than 10 degrees during a dual
channel approach after FLARE armed is annunciated.

Additionally, on some airplanes, a thrust split monitor disengages the autothrottle if autopilot roll control requires significant spoiler deployment and thrust levers become separated. The thrust split monitor is active when flaps are less than 15, and the A/T is not engaged in the takeoff or go-around mode.
A/T disengagement is followed by A/T Arm switch releasing to OFF and flashing red A/T Disengage lights. The A/T Disengage lights do not illuminate when the A/T automatically disengages after landing touchdown.
　
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本文鏈接地址：737-300機組操作手冊Flight Crew Operations Manual FCOM 2(31)