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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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Quick Links

01/28/21

Message Overview:

OUTBD BRAKES FAIL
(Caution)

DDG Reference: None
Pilot Action (QRH): GEAR 10-7
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 'OUTBD BRAKES FAIL' caution CAS message indicates both outboard 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:

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

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

42_bcu_nvm_download

Possible Causes:

  • Brake Control Unit (BCU) (A67)
  • Brake Control Unit (BCU) (A67) Connectors
  • Brake Shut-off Valve (BSOV) (MPE27)
  • Brake Control Valve (BCV) (MPE23)
  • Wheel Speed Transducer
  • Pressure Transducer
  • Brake Pedal LVDT
  • Hydraulic Leak
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

Forum Articles/Infoservice/Newsletter: None

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

    • Wheel Speed Transducer
    • Both Outboard Pilot and Copilot LVDT
    • Hydraulic Fuse
    • Shuttle Valves

  • If only one of the two failures is rectified, one of the following CAS messages will be displayed; "L OUTBD BRAKE FAIL" or "R OUTBD BRAKE FAIL".

Download the MDC for fault isolation.

Download the BCU NVM for the Outboard 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 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 "OUTBD BRAKE PRESS LO" is also displayed on the EICAS.

    1. If message is displayed, troubleshoot this message first.
      NOTE: It is normal to have an 'OUTBD 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. Access the MDC to view fault messages. Select displayed message from menu below:

    1. If none of these fault messages are displayed, continue with next step.

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

    1. If messages are present, select from dropdown menu and troubleshoot accordingly.
    2. If no messages are present, continue with next step.

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

    1. If at least one outboard brake pressure is higher than 130 psi, go to step 12.
    2. If outboard brake pressure is below 130 psi, continue with next step.

  6. Apply full brake pedal deflection.
  7. Verify that pressure at the outboard 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.

  8. Release the brakes.
  9. Verify that pressure at the outboard brakes is lower than 130 psi.

    1. If the brake pressure is higher than 130 psi, go to step 12.
    2. If the brake pressure is lower than 130 psi, continue with next step.

  10. Verify if both hydraulic fuses on the outboard brakes are set at the flow position.

    1. If both hydraulic fuses are tripped (closed), reset them and redo the procedure starting at step 5.
    2. If both hydraulic fuses are not tripped, continue with next step.

  11. Replace the Outboard Brake SOV and do close out.
  12. Replace the BCV.
  13. Do close out.

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