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747-400 MAINTENANCE MANUAL
(d)
The inboard ailerons operate at all airspeeds. The outboard ailerons are used at low airspeeds or when flaps are extended. Outboard ailerons are locked out (disabled) at cruise speeds. This prevents overcontrol and application of unnecessary loads at the wing tip which may damage the structure. The aileron lockout mechanism is motor-operated and is controlled by the stabilizer trim/rudder ratio module (SRM).
(e)
An aileron position transmitter at each aileron drives the pointers, which indicate the surface position of the inboard and outboard ailerons, displayed on the auxiliary EICAS display when the Flight Controls Maintenance Page is selected.
(2) Autopilot Input
(a)
Autopilot inputs from the Flight Control Computers (FCCs) are made through the LAS and autopilot servos which are part of each CLCP. These servos are connected to the trim and feel mechanism. When the autopilot is engaged, the servos move the same point in the control as the pilot's manual input. The control wheels are also back-driven.
(b)
The autopilot servos for aileron control are connected together for two reasons. First, it provides the capability for any one autopilot channel to control the airplane about its roll axis. Second, it provides the method of multi-channel autopilot control known as mechanical voting.
(c)
In mechanical voting, differences between the command from each autopilot channel are detected and resolved. In the case of dual-channel operation, small differences are resolved by using the smaller (or least) value of the command inputs from the two autopilot channels. Large differences will result in disengagement of both autopilot channels since it is not possible to determine which command input is correct.
(d)
In the case of triple-channel operation, small differences are resolved by using the middle value of the command inputs from the three autopilot channels. Large differences will result in disengagement of the autopilot channel with a command input which is different from the command inputs from the other two channels. This allows multi-channel operation to continue and assumes the difference is due to a failure in the disengaged channel.
B. Elevator Control System (Fig. 15)_______________________
(1) Manual Input
(a)
Manual input for pitch control is from the captain's or first officer's control column. Control column input is transmitted to the aft quadrant through parallel cables. Control inputs are conditioned to provide a sense of feel and centering.
(b)
Feel is introduced by a feel actuator and feel unit. Inputs are from the neutral shift and a feel computer. The feel computer uses dynamic pressure (CAS) and stabilizer position to vary the feel. The feel unit includes the centering device.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
VERTICAL STABILIZER SEE A
UPPER RUDDER POWER CONTROL MODULE
SEE B
UPPER RUDDER THIRD ACTUATOR
AFT
LOWER RUDDER
POWER CONTROL
MODULE
SEE C
A
Rudder Power Control Module Figure 11 (Sheet 1)
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ALL ú ú 02 Page 22 ú Feb 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
UPPER RUDDER
UPPER ACTUATOR
UPPER RUDDER
FRONT SPAR
UPPER RUDDER CENTER ACTUATOR
UPPER RUDDER UPPER RUDDER POWER CONTROL RATIO CHANGER MODULE
(RCPM)
UPPER RUDDER THIRD ACTUATOR
AFT
FEEL,TRIM,AND
CENTERING MECHANISM
B
LOWER RUDDER LOWER RUDDER
UPPER ACTUATOR FRONT SPAR
LOWER RUDDER
POWER CONTROL
MODULE
LOWER RUDDER (RPCM)
RATIO CHANGER
AFT
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