A/P STATUS
  CMD  (G)
  FD (G)

CWS PITCH ENGAGED   CWS P (Y)
CWS ROLL ENGAGED  CWS R (Y) SINGLE CHANNEL  1 CH (Y)
ROLL ARMED MODE   VOR/LOC (W)
(G)
- Green

(W)
- White

(Y)
- Yellow

Airplanes with Top FMA
As installed

Copyright . The Boeing Company. See title page for details.
December 7, 2001   4.10.21
Automatic Flight -Controls and Indicators 737 Operations Manual

(yellow)
- CWS PITCH
Airplanes with Bottom FMA

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

737 Operations Manual

General
The automatic flight system (AFS) consists of the autopilot flight director system (AFDS) and the autothrottle (A/T). The flight management computer (FMC) provides N1 limits and target N1 for the A/T and command airspeeds for the A/T and AFDS.
The AFDS and A/T are controlled using the AFDS mode control panel (MCP) and the FMC. Normally, the AFDS and A/T are controlled automatically by the FMC to fly an optimized lateral and vertical flight path through climb, cruise and descent.
AFS mode status is displayed on the flight mode annunciation on each pilot’s EADI.
Autopilot Flight Director System
The AFDS is a dual system consisting of two individual flight control computers (FCCs) and a single mode control panel.
The two FCCs are identified as A and B. For A/P operation, they send control commands to their respective pitch and roll hydraulic servos, which operate the flight controls through two separate hydraulic systems.
For F/D operation, each FCC positions the F/D command bars on the respective ADI.
MCP Mode Selector Switches
The mode selector switches are pushed to select desired command modes for the AFDS and A/T. The switch illuminates to indicate mode selection and that the mode can be deselected by pressing the switch again. While a mode is active, deselection can be automatically inhibited, indicated by the switch being extinguished.
When engagement of a mode would conflict with current AFS operation, pushing the mode selector switch has no effect. All AFDS modes can be disengaged either by selecting another command mode or by disengaging the A/P and turning the F/Ds off.
Automatic Flight -System Description 737 Operations Manual

Autopilot Engagement Criteria
Each A/P can be engaged separately in CMD or CWS. A/P engagement in CMD or CWS is inhibited unless both of the following pilot–controlled conditions are met:
.  
No force is being applied to the control wheel

.  
The STAB TRIM AUTOPILOT cutout switch is at NORMAL.

Only one A/P can be engaged at a given time unless the approach (APP) mode is engaged. Approach mode allows both A/Ps to be engaged at the same time. Dual A/P operation provides control through landing flare and touchdown or an automatic go–around.
In single A/P operation, full automatic flare and touchdown capability and A/P go–around capability are not available.
If an autopilot is engaged in CMD with one or both F/Ds operating in command modes and the F/D command bars are not within approximately 1/2 scale of being centered, the A/P automatically engages in CWS for pitch and/or roll, and the F/D command bars retract.
Autopilot Disengagement
The A/P automatically disengages when any of the following occurs:
.  
Pushing either A/P disengage switch

.  
Pushing either Takeoff/Go–around (TO/GA) switch with a single A/P
engaged in CWS or CMD below 2000 feet RA

.  
Pushing either TO/GA switch after touchdown with both A/Ps engaged in
CMD

.  
Moving the A/P engage paddle to OFF

.  
Activating either pilot’s control wheel trim switch

.  
Moving the STAB TRIM AUTOPILOT cutout switch to CUTOUT

.  
Loss of respective hydraulic system pressure

.  
Repositioning the EFI transfer switch

.  
Either left or right IRS system failure or FAULT light illuminated

.  
Loss of electrical power or a sensor input which prevents proper operation
of the engaged A/P and mode.

Note: Loss of the system A engine-driven hydraulic pump and a heavy demand on system A may cause A/P A to disengage.
AFS Failures
Power interruption or loss may cause disengagement of the AFDS and/or A/T. Re-engagement is possible after power is restored.
Dual channel A/P operation is possible only when two generators are powering the busses.
　
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本文鏈接地址：737-300機組操作手冊Flight Crew Operations Manual FCOM 2(28)