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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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03/16/21

Message Overview:

Message Name:

IB ARINC PRESS DISAGREE

Message Code:

B3-224428

Associated CAS:

BRAKE FAULT
(Advisory)

Reporting LRU: IB PRESS SWITCH
System Description: 32-43-00
Schematic Diagram: 32-43-00
Wiring Diagram: 32-43-01

Message Description:

The BCU detects a discrepancy between the left hydraulic system pressure and the inboard brake pressure switch (S99).

Possible Causes:

  • Brake Pressure Switch (LH) (S99)
  • Brake Control Unit (BCU) (A67)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Brake Control Unit AMM 32-43-01-000-801
Installation of the Brake Control Unit AMM 32-43-01-400-801
Removal of the Brake Pressure Switch AMM 32-43-45-000-801
Installation of the Brake Pressure Switch AMM 32-43-45-400-801
Data Download from the Maintenance Diagnostic Computer (MDC) AMM 45-45-01-970-802
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Electrical Wiring-Continuity Test - Adjustment/Test SPM 20-12-01-05
Standard Practices - Wire Repair SPM 20-12-10-02

Troubleshooting Recommendations:

NOTE: A failure of pressure switch S99 does not affect the hydraulic synoptic page inboard brakes 'PRESS NORM' and pressure value indications which are supported by the inboard brakes accumulator pressure transducer MT102.

  1. Reset LCBP-C15 (INBD BRAKES).

    1. If the 'BRAKE FAULT' CAS message did not reappeared, do close out.
    2. If the 'BRAKE FAULT' CAS message still posted, continue with next step.

  2. Disconnect the inboard brakes pressure switch S99.
  3. Pressurize the Left Hydraulic system.
  4. Verify continuity between pins 2 and 3 of pressure switch S99.

    1. If the is continuity, replace pressure switch S99.
    2. If there is no continuity, continue with next step.

  5. Verify wiring for a short circuit per the following table:

    From (PRESS SWITCH) Pin To (BCU) Pin
    S99P1 2 A67P2 40
    S99P1 3 A67P2 43

    1. Repair as required.
    2. If wiring is found serviceable, replace BCU.

  6. Do close out.

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