(2)  
The AP/FD roll cruise modes are compatible with each other and with any of the longitudinal and vertical cruise modes. The AP/FD pitch cruise modes are only compatible with the A/T modes (SPEED, PDC Speed and EPR) in prescribed combinations based primarily upon the relationship between the current altitude and the selected altitude.

(3)  
The AP Pitch CWS mode, in cruise, is compatible with either A/T Speed or A/T EPR with a Climb EPR limit regardless of the altitude relationship.

(4)  
The AP/FD level change (LVL CHG) speed mode is only compatible with the A/T EPR mode if the selected altitude is above the current altitude and with throttles at aft limit if the selected altitude is below the current altitude.

(5)  
The AP/FD PDC Speed mode is only compatible with the A/T EPR mode with the PDC Climb Target EPR as a limit if the selected altitude is above the current altitude and with thrust levers at aft limit if the selected altitude is below the current altitude. This mode will automatically transition to PDC Speed on A/T when the A/P or F/D captures and holds the selected altitude via the ALT ACQ mode.

(6)  
The AP/FD Altitude Acquire (ALT ACQ) mode provides automatic capture of the selected altitude with a 0.05g maneuver. The only compatible A/T modes are the A/T Speed or A/T PDC Speed (only if AP or F/D were in PDC Speed mode upon engagement of ALT ACQ) modes.

(7)  
The AP/FD Altitude Hold (ALT HLD) (at the selected altitude) mode is entered after the ALT ACQ mode. The only compatible A/T modes are the A/T Speed or A/T PDC Speed. Selection of a new altitude will cause a reversion to the ALT HOLD (not at selected altitude) mode, reversion from A/T PDC Speed mode (if engaged) to A/T Speed mode and, in addition, will automatically arm the V/S mode.

(8)  
The AP/FD (ALT HLD) (not at selected altitude) mode is entered either by selecting a new altitude when in the ALT HOLD (at the selected altitude) mode or by capturing the existing altitude when the ALT HOLD pushbutton is pressed and the existing altitude is not the selected altitude. The only compatible A/T mode is A/T Speed mode.

(9)  
The A/T Speed and A/T EPR pushbutton on the MCP have a very limited function. If the A/T is in the A/T Speed mode, pressing the A/T Speed pushbutton will cause the A/T to go to the ARM mode, allowing manual speed control via the thrust levers. If the A/T is not in the A/T Speed mode and this mode is compatible with the existing AP or F/D mode, pressing the A/T Speed pushbutton will cause engagement of this mode. If the A/T is in an A/T EPR mode, pressing the A/T EPR pushbutton will cause the A/T to go to the ARM mode, allowing EPR control via the thrust levers. If the A/T is not in an A/T EPR mode and an A/T EPR mode is compatible with the existing AP or F/D mode, pressing the A/T EPR pushbutton will cause engagement of the A/T EPR mode. If the A/T has been put in the ARM mode, the next compatible A/T mode request, either manual or automatic, will take the A/T out of the ARM mode and put it in the appropriate compatible mode.

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Feb 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  22-11-01 Page 45 

J.  Single Channel Autopilot Approach
(1)  
Automatic ILS approach to FAA Category II Lower Weather Minimums (LWM) may be conducted single channel by the AFCS.

(2)  
The single channel system configuration is only one computer engaged and only one set of pitch and roll servos engaged. Both flight director may be operated with either the A and B autopilot channels engaged. In this configuration, autopilot off, or with autopilot engaged in CWS, the captain's ADI command bars are driven by A channel and the first officer's ADI commandbars are driven by the B channel.

(3)  
The roll control channel uses the difference between the actual and commanded bank angle to develop the command to drive the control surfaces. The bank angle command is derived from a lateral accelerometer, vertical gyro, ILS receiver, and course error (except in AOC).

(4)  
The pitch control channel uses altitude rate feedback which is generated by the air data computer and smoothed by normal acceleration, longitudinal acceleration, and derived rate. The ILS receiver in combination with the signals described above provide the error signals for glide slope beam tracking.

(5)  
The radio altimeter provides for gain programming of the beam error signals and is also used with altitude rate in computing the flare command.

(6)  
Single Channel Approach Localizer and Glide Slope Arm (Precapture ILS)

(a)  
During the precapture phase of an automatic autopilot coupled approach, the autopilot MCP is engaged in single channel A or B CMD mode. The system may be engaged in ALT HLD, V/S or HDG HOLD as required. Navigation receivers are tuned to ILS frequencies and the inbound runway course is dialed in on the A and B channel course windows. The APP button is pressed to arm the LOC and G/S Modes. This is indicated white on black on the FMA. The autopilot status annunciation is set to SINGLE CHANNEL, black on amber.
　
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