(5)  
Display Test

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(a)  This test illuminates all segments of the BITE display in a sequence. The operator determines whether the test passes or fails. The YDC does not determine or display any faults.
G.  Other Functions
(1) 
 System Configuration

(a)  When the System Configuration option is selected, the YDC displays a list of configuration parameters. These are software version number, airplane type as determined by the program pins and program pin test, yaw damper actuator limit as determined by the servo test, elapsed time indication in hours, as stored in NVM, and the number of power cycles that the YDC has experienced.

(2)  
I/O Monitor

(a)  When the I/O Monitor option is selected the YDC displays a list of options, Analog Inputs/Outputs or Discrete Inputs/Outputs. 1) Analog Inputs and Outputs
a)  When the Analog Inputs/Outputs option is selected, the YDC displays a list of analog type YDC inputs and outputs in engineering units. The values are updated at a rate of 1 Hz. If a particular input parameter is currently unknown due to a detected input fault, it is displayed as invalid instead. Only inputs and outputs that are relevant to the current airplane type are displayed.
2)  Discrete Inputs and Outputs
a)  When the Discrete Inputs/Outputs option is selected, the YDC displays a list of discrete type YDC inputs and outputs in engineering units. The values are updated at a rate of 1 Hz. If a particular input parameter is currently unknown due to a detected input fault, it is displayed as invalid instead. Only inputs and outputs that are relevant to the current airplane type are displayed.
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(3)  Output Control
(a)  
When the Output Control option is selected, the YDC displays a list of the output control functions. The control functions are yaw damper servo control, yaw damper engage switch, pressure reducer, and hydraulic lamp control for the A system low pressure warning.

(b)  
The purpose of this function is to provide direct control of the YDC outputs to assist in airplane system installation and troubleshooting. This supplements the I/O monitoring provided elsewhere. Note that all control outputs except the autopilot warning lights are selectable. The Ground Maintenance mode (Autopilot Warning Lights) can simply be toggled by going in and out of BITE.  1) Yaw Damper Servo Control

a)  When the Yaw Damper Servo Control option is selected, the operator can change the yaw damper actuator position using the up-arrow and down-arrow keys in steps of 0.05 deg. If a key is held pressed for more than one second, the command changes by 0.5 deg. The command can be moved over a range exceeding the largest actuator authority. The actuator command is displayed on the upper display segment and the actuator position is displayed on the lower display segment.
2)  Yaw Damper Engage Switch Control
a)  When the Yaw Damper Switch Control option is selected, the operator is able to enable or energize the yaw damper engage switch solenoid by pressing the up-arrow and down-arrow keys.
3)  Pressure Reducer Control
a)  When the Pressure Reducer Control option is selected, the operator is able to energize the pressure reducer solenoid using the up-arrow and down-arrow keys.
4)  Low Hydraulic Pressure Lamp Control
a)  When the Hydraulic Lamp Control option is selected, the operator is able to turn the A system Low Pressure Warning lamp on and off using the up-arrow and down-arrow keys.
b)  Since this lamp can be driven by the A system flight controls low hydraulic Pressure switch, the YDC will not be able to extinguish the lamp if the A-System is not pressurized.
(4)  BITE Control Panel Deactivation
(a)  At any time when the BITE control panel is in use, the operator can press the ON-OFF button to exit BITE and ground maintenance state. Confirmation is requested before the exit actually occurs. Any test or other operation that was in progress at the time is stopped before BITE is exited. If the operator does not provide confirmation, the YDC displays the last menu option that was selected and waits for further input.
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YAW DAMPER SYSTEM - TROUBLE SHOOTING

EFFECTIVITY
Aircraft with Yaw Damper Coupler P/N 4084042 (after 27A1206)
1. General
A.  The following trouble shooting procedures are intended to help trouble shoot the yaw damper system down to a component level.
　
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