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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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For AOG assistance contact:

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Quick Links

11/04/24

Message Overview:

AT FAIL
(Advisory)

DDG Reference: None
Effectivity: Post SB350-22-002
Aircraft 20937 and Subs
Pilot Action (QRH): None
System Description: 22-30-00 - Autothrottle System
Schematic Diagram: 22-30-00 - Autothrottle System
Wiring Diagram: 22-30-00 - Autothrottle System

Message Description:

The Autothrottle (AT) computer has detected a failure or the AT system data is lost or is invalid for a minimum of 500 ms and the Right Main Bus is powered.

Possible Causes:

  • Autothrottle (AT) computer (A252)
  • Integrated Avionics Processing System (IAPS) (A4)
  • IAPS Input/Output Concentrator (IOC) card
  • Power source
  • Servo Motor Clutch Pack (SMCP) (B205)
  • Throttle Quadrant Assembly (TQA) (A51)

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: Review the Auto Throttle "AT Diagnostic Information" document, to find details about the MDC Data Reader Labels & bits.

Quick Links:

Standard Aircraft Configuration for Maintenance AMM 12-00-00-867-803
Removal of the Auto Throttle Computer AMM 22-30-01-000-801
Installation of the Auto Throttle Computer AMM 22-30-01-400-801
Operational Test of the Auto Throttle System AMM 22-30-00-710-801
Functional Test of the Auto Throttle Computer AMM 22-30-01-720-801
Safety Precautions - Maintenance Practices - ALL SPM 20-00-01-02-01
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02-01

Troubleshooting Recommendations:

  1. Interrogate the MDC as follows:

    1. On the cursor control panel, ensure the toggle switch is to the right and select Anti-Ice, ECS and Fuel buttons simultaneously. The MDC main menu should now be displayed on Display Unit #3.
    2. Using the joystick, select Current Faults (if the fault is active) or Aircraft History to research stored faults. From Aircraft History you can then select Fault Message History and locate the system fault logged.
    3. Select displayed fault message from menu below:

45_advance_diagnostics

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