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757 MAINTENANCE MANUAL
(b) The INOP indicator illuminates under the following conditions:
1) When the yaw damper module associated with the INOP is not installed (the opposite module must be installed and functioning properly)
2) When the yaw damping function is lost
3) During the pre-flight test (the YAW DMPR test switch initiates a pre-flight YDS test, provided the airplane is on ground)
4) During the power-up test
B. AIRPLANES WITH YDM DASH NUMBERS -101 THRU -121; Yaw Damper Module
(1)
Each yaw damper module consists of two digital computing channels (control and monitor) and a servo amplifier. The module contains a total of ten printed circuit assemblies.
(2)
The control computing channel consists of five assemblies as follows:
(a)
Monitor Receiver Assembly - provides three high-speed and two low-speed ARINC 429 receiver interfaces for the control microprocessor.
(b)
Control Microprocessor Assembly - provides the digital computing function for the yaw damper.
(c)
Control In/Out Assembly - provides input and output discrete signal conditioning for the control microprocessor.
(d)
Diode Board Assembly - provides transient suppression for the module fault balls.
(e)
EMI Filter Assembly - provides EMI filtering for signal inputs, signal outputs, and electrical power inputs for the control channel.
(3)
The monitor computing channel consists of four assemblies as follows:
(a)
Monitor Receiver Assembly - provides three high-speed and two low-speed ARINC 429 receiver interfaces for the monitor microprocessor.
(b)
Monitor Microprocessor Assembly - provides the digital computing function for the yaw damper, duplicating the computing of the control channel.
(c)
Monitor In/Out Assembly - provides input and output discrete signal conditioning for the monitor microprocessor.
(d)
EMI filter Assembly - provides EMI filtering for signal inputs, signal outputs, and electrical power inputs for the monitor channel.
(4)
The servo amplifier provides rudder command signals to the yaw damper electrohydraulic servo-valve. Feedback from the Linear Variable Differential Transducer (LVDT) position sensor is received by the actuator position demodulator assembly to close the servo loop. The assembly also provides servo loop monitoring which operates the automatic solenoid disengagement relay when a failure affecting operation is detected.
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(5)
(6)
(7)
(8)
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757
MAINTENANCE MANUAL
One connector with three inserts is on the rear panel of each module. Two inserts contain the YDS signal pins and low voltage power pins. One insert contains the ground reference pins. Cooling is provided by air from the rack plenum being forced from the bottom to the top of the modules. A hinged top provides access to the interior of the module.The 28 vdc engage servo solenoid power is routed from the control panel, through the module auto-disengage relay contacts, to the servo. Separate 28 vdc is used to drive the yaw damper module fault ball indicators. Module operating power (+5 vdc and |15 vdc) and the 26 vac LVDT demodulator reference is provided by the Control System Electronics Unit (CSEU) power supply modules (Ref 27-09-00).The fault logic in the modules is designed to isolate faults to the LRU level within the YDS and interfacing LRUs. The front panel contains seven fault ball indicators and a maintenance reset switch. If a fault is detected, the fault ball is yellow (fault ball set). The fault ball is black if no fault is detected. The following fault ball indications are provided: 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：757 AMM 飛機維護手冊 自動飛行 AUTOFLIGHT 2(24)
