27-31-00
 ALL  ú ú 01 Page 6 ú Jun 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL

 3.  Inboard Elevators (Fig. 3)
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 A.  The inboard elevators are similar in construction to the outboard elevators. Each elevator attaches to the horizontal stabilizer trailing edge at four points. The attachments are similar to those provided for the outboard elevators. The inboard elevators are not mass balanced. Seven panels in the lower skin provide access to the interior.
 4.  Control Columns (Fig. 2)
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 A.  The two control columns transmit commands to control the airplane about the pitch and roll axes. Forward and aft motion of the control columns actuates the elevators to control the airplane about its pitch axis. Rotating a control wheel on either column operates the ailerons and spoilers to control the airplane about its roll axis.
 B.  The control columns are rigidly mounted on a torque tube located just below the control cabin floor. Crank assemblies on each end of the torque tube transmit motion aft by pushrods to the forward quadrant and crank. Stops on the left torque tube crank and its bearing housing limit control column fore and aft movement and, hence, elevator control input travel. Access to the torque tube and to the forward quadrant and crank is gained from the bottom through the main deck ceiling.
 5.  Forward Elevator Control Quadrant and Crank (Fig. 2)
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 A.  The forward elevator control quadrant and crank are located beneath the control cabin just aft of the control column torque tube. A pushrod connects each component to a lever arm on each end of the control column torque tube, and separate pairs of cables connect them to the common rear quadrant.
 B.  The forward quadrant incorporates a tension regulator to regulate the control cable tension. The tension regulator mechanically compensates for the effects of temperature variation and structural deflections on the elevator system left-hand body control cables. A position indicator with a graduated scale provides information convertible to cable tension for the existing temperature, with appropriate markings to show the acceptable operating limits. The range of regulator tension compensation is limited by positive stops.
 6.  Elevator Aft Quadrant (Fig. 2)
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 A.  A common aft quadrant receives the cable-transmitted input from the forward quadrant and crank. The aft quadrant is mounted on a torque tube located on the stabilizer hinge bulkhead. A lever arm and linkage on the torque tube transmit centering forces and artificial feel from the feel unit to the cable system. Another lever arm conveys input through linkages to the input controls on each inboard power control package. Three cranks mounted on the top of the torque tube convey input from the three autopilot servo modules mounted on the stabilizer hinge bulkhead.
 7.  Outboard Elevator Controls (Fig. 2)
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 A.  The mechanical control to each outboard elevator PCP is transmitted mechanically through a slave system from the corresponding inboard elevator. A control rod connected to the inboard elevator front spar operates a control linkage, which is connected by control rods to the corresponding outboard elevator PCP.
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 27-31-00
 ALL  ú ú 01 Page 7 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 8.  Inboard Elevator Power Control Package
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 A.  The inboard elevator PCPs are hydraulic power units used to actuate the inboard elevators. Each PCP drives its associated inboard elevator independently. The two inboard PCPs are identical to each other, but different from the two outboard PCPs. The differences stem chiefly from the load output requirements. The inboard elevator PCPs contain many components which are functionally similar to outboard elevator PCP components, as well as unique components reflecting their function as master units with dual hydraulic inputs.
 B.  The inboard elevator PCPs receive mechanical inputs through linkage from the rear elevator control quadrants. The left PCP is powered by hydraulic systems No. 1 and 2; and the right PCP by hydraulic systems No. 3 and 4.
 9.  Outboard Elevator Power Control Packages
　
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