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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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11/04/24

Message Overview:

Message Name:

INTERNAL FAULT [AT]

Message Code:

B3-681655

Associated CAS:

AT FAIL
(Advisory)

Reporting LRU: Autothrottle (AT) Computer
Effectivity: Post SB350-22-002
Aircraft 20937 and Subs
System Description: 22-30-00 - Auto Throttle System (ATS)
Schematic Diagram: 22-30-00-801 - Auto Throttle System (ATS)
Wiring Diagram: 22-30-00-801 - Auto Throttle System (ATS)

Message Description:

The "INTERNAL FAULT" message is posted if the Autothrottle (AT) computer power-up or continuous built-in tests report an internal fault condition not associated with invalid input data or the Servo Motor Clutch Pack (SMCP). Internal fault reported by the Autothrottle (AT) Computer.

Possible Causes:

  • Autothrottle (AT) Computer (A252)

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: Review the Auto Throttle "AT Diagnostic Information", to find details about the MDC Data Reader Labels & bits.
NOTE: Bombardier recommends referencing the elements one (1) through eleven(11) of the "Wiring & Connections" Troubleshooting Tip document. The intent of the document is to ensure the Maintenance Technician has the information needed to perform a comprehensive check of an aircraft system wiring circuit, while also doing checks found in the From - To tables called out in the Troubleshooting Recommendations element.

From - To Table (Example)
From To Expected Results Results
XXXX-XX XXXX-XX Continuity

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 22-3001-720-801
Data Download from the Maintenance Diagnostic Computer (MDC) AMM 45-45-01-970-802
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. Cycle power to the Autothrottle (AT) Computer.
  2. Allow sufficient time for the unit to perform its power up test.
  3. Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

  4. Replace the AT Computer
  5. Do close out.

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