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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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01/28/21

Message Overview:

INBD BRAKES FAIL
(Caution)

DDG Reference: None
Pilot Action (QRH): GEAR 10-5
System Description: 32-43-00
Schematic Diagram: 32-43-00
Wiring Diagram: 32-43-01
32-43-05
32-43-09
32-43-17
32-43-25
32-43-45

Message Description:

The amber 'INBD BRAKES FAIL' caution CAS message indicates both inboard normal system brakes have failed. This message is posted during or shortly after the brake pressure pulse test. The pressure pulse test is initiated 3 ways:

  1. At power up when hydraulic supply reaches above 1850 psi.
  2. Every time the landing gear is selected down.
  3. Can be initiated through the MDC LRU test page.

The inboard normal brake system is inoperative, either from a BCU fault, pressure loss to the inboard brakes, or dual component failure in the inboard brake system.

Possible Causes:

  • Left Brake Shut-off Valve MPE27 (BSOV)
  • Brake Control Unit A67 (BCU)
  • Left Brake Control Valve MPE23 (BCV)
  • Dual failure on Inboard Brake system components

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

Forum Articles/Infoservice/Newsletter: None

  • Any combination of two failures of the following components on the inboard brakes will trigger an "INBD BRAKES FAIL" CAS message.

    • Wheel Speed Transducer
    • Both Inboard Pilot and Copilot Linear Variable Differential Transducers (LVDT)
    • Hydraulic Fuse
    • Shuttle Valves

  • If only one of the dual failure is fixed the CAS message will be posted as a "L INBD BRAKE FAIL" or "R INBD BRAKE FAIL" CAS message.

Download the MDC for fault isolation.

Download the BCU NVM for the Inboard Channel.

Quick Links:

Data Download from the Maintenance Diagnostic Computer (MDC) AMM 45-45-01-970-802
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 Control Valve AMM 32-43-09-000-801
Installation of the Brake Control Valve AMM 32-43-09-400-801
Removal of the Brake Shutoff Valve AMM 32-43-25-000-801
Installation of the Brake Shutoff Valve AMM 32-43-25-400-801
Removal of Wheel Speed Transducer AMM 32-43-49-000-801
Installation of Wheel Speed Transducer AMM 32-43-49-400-801
Removal of the Brake Pedal Position Transducer AMM 32-43-05-000-801
Installation of the Brake Pedal Position Transducer AMM 32-43-05-401-801
Removal of Hydraulic Fuse AMM 32-43-33-000-801
Installation of Hydraulic Fuse AMM 32-43-33-400-801
Removal of Shuttle Valve AMM 32-43-21-000-801
Installation of Shuttle Valve AMM 32-43-21-400-801

Troubleshooting Recommendations:

  1. Verify if "PK/EMER BRK PRESS LO" or "INBD BRAKE PRESS LO" is showing on EICAS.

    1. If message is associated with CAS from step 1, troubleshoot specific CAS message. Do close out.
      NOTE: It is normal to have an "INBD BRAKE FAIL" CAS message when the brake accumulator pressure is below 1400 PSI.
    2. If message is not associated with CAS from step 1, continue with next step.

  2. If MDC faults from step 2 are showing, use drop down menu and troubleshoot according to specific B3 code.

    1. If MDC faults from step 2 are not showing, continue with next step.

  3. Verify MDC faults for a combination of two of the following messages.

    1. If a combination of MDC faults from step 3 are showing, use drop down menu and troubleshoot according to specific B3 code.

      If MDC faults from step 3 are not showing, continue with next step.

  4. Pressurize hydraulic system.
  5. Enter MDC main menu and select system parameters and record pressure using.
  6. Check the Inboard brake pressure.

    1. If at least one Inboard brake pressure is higher than 130 psi, go to step 13.
    2. If Inboard brake pressure is below 130 psi, continue with next step.

  7. Apply full brake pedal deflection.
  8. Verify pressure to the Inboard brakes is higher than 2640 psi.

    1. If the brake pressure is higher than 2640 psi, do close out.
    2. If the brake pressure is lower than 2640 psi, continue with next step.

  9. Maintain full brake application.
  10. Verify pressure to the Inboard brakes is lower than 130 psi.

    1. If the brake pressure is higher than 130 psi, go to step 13.
    2. If the brake pressure is lower than 130 psi, continue with next step.

  11. Verify if both hydraulic fuses on the inboard brakes are set at the flow position.

    1. If both hydraulic fuses are tripped (closed), re-set them and redo the procedure starting at step 6.
    2. If both hydraulic fuses are not tripped, continue with next step.

  12. Replace Inboard BSOV, do close out.
  13. Replace BCV, do close out.

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