YAW DAMPER SERVOS RUDDER PCA'S Yaw Damper and Rudder PCAs Figure 22
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(b) All PCA control valves are driven by the PCA control levers, while all are interconnected. The primary input rod from the yaw damper assembly and ratio changer is connected to the center PCA. The secondary input rod is connected to the lower PCA. The PCAs cause movement of the rudder about the hinge line in opposition to the reaction link. The rudder position transmitter provides an output to the control surface position indicator on the lower EICAS display unit status page.
AD. High Lift System - Introduction (Fig. 23)
(1)
Leading Edge Slats
(a)
Five leading edge slat segments are on each wing. Control is by movement of the flap lever on the center section of the control stand (P10). Control cables from the flap lever operate the slat and flap Power Drive Units (PDUs), which use hydraulic or electrical power. Primary control is hydraulic.
(b)
The flap lever also enables the Flap/Slat Electronic Unit (FSEU), which controls the hydraulic shutoff valve for each PDU. The PDUs drive a gearbox and rotary actuator at each slat segment. Slat position is transmitted to the FSEU for fault detection and annunciation.
(c)
Alternate control is via the alternate flaps control panel on the pilots center instrument panel (P3-1). This panel controls the FSEU which provides electrical output signals that cause the PDUs to extend or retract slats (or flaps) to the selected position.
(2)
Trailing Edge Flaps
(a)
Two trailing edge flap segments are on each wing. The outboard flap is composed of two flap surfaces.
(b)
The flap lever controls flap PDUs and the FSEUs as previously described. Hydraulic power for the flap PDUs is enabled by the FSEU. Flap position is sent to FSEU for fault detection and annunciation. It is also sent to the FSEU for interfacing with other autoflight systems.
(c)
Alternate control is via the alternate flaps control panel, as previously described.
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FLAP
LEVEROUTBOARDSLAT
INBOARD
FLAP LEVER
POSITION
SLAT
TRANSMITTER
OUTBOARD SEAT
DRIVE UNIT
OUTBOARDFLAP OFFSET GEAR BOX
INBOARDAND ROTARY ACTUATOR
FLAP DRIVE UNITTE FLAP
YFMM-22-00-04
FLAP POSITIONTRANSMITTER(TYPICAL)
High Lift System
Figure 23
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757 MAINTENANCE MANUAL
(d) The primary drive is powered from the left hydraulic system.
The alternate drive uses 115 vac. AE. Flap Lever/Flap-Slats Positions (Fig. 24)
(1) The flap lever can be positioned between 0 and 30 units. The units do not necessarily relate to degrees of flap extension. Detents are at 0, 1, 5, 15, 20, 25 and 30 units. Trailing edge flap and inboard and outboard leading edge slat relative positions are indicated.
(a)
Position 0 fully retracts the flaps and slats.
(b)
Position 1 results in partial slat extension with the slats still sealed (no gap). The flaps remain fully retracted.
(c)
Position 5 results in the flaps extending to 5 degrees after the slats are partially extended (no gap).
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