BRAKE 50% DEGRADED
(Caution)

A discrepancy is detected between both Inboard or Outboard Brakes and the Brake Control Unit (BCU) has switched one of the Brake Shut-Off Valves (SOV) to OFF.

• Left Outboard Brake Control Valve (BCV) (MT53)
• Right Outboard Brake Control Valve (BCV) (MT56)
• Left Inboard Brake Control Valve (BCV) (MT153)
• Right Inboard Brake Control Valve (BCV) (MT169)
• Inboard Brake Shut-Off Valve (SOV) (L13)
• Outboard Brake Shut-Off Valve (SOV) (L14)
• Brake Control Unit (BCU) (A71)
• Pilot Left Brake Pedal Position Transducer (MT57)
• Pilot Right Brake Pedal Position Transducer (MT58)
• Copilot Left Brake Pedal Position Transducer (MT59)
• Copilot Right Brake Pedal Position Transducer (MT60)
• Left Inboard (L INBD) Wheel Speed Transducer (WST) (P16)
• Left Outboard (L OUTBD) Wheel Speed Transducer (WST) (P17)
• Right Inboard (R INBD) Wheel Speed Transducer (WST) (P18)
• Right Outboard (R OUTBD) Wheel Speed Transducer (WST) (P19)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW700-32-0359 - Brake Control System - Data Gathering to Reduce the Brake Control Unit (BCU) No-Fault-Found (NFF) rate
• AW700-32-0513 - Wheel Speed Transducer - Brake System Nuisance Fault Messages
• AW700-32-0573 - Main Landing Gear Trailing Arm Water Ingress Survey
• SB700-31-020 - MODIFICATION - FLIGHT DATA RECORDING (FDR) SYSTEM - INSTALLATION OF THE FORCE TRANSDUCER UNITS (FTU) AND ACTIVATION OF THE CREW FORCE MEASURING SYSTEM (CFMS) 2002

Full Throttle Blog/Forum Articles/Infoservice/Newsletter:

• Forum Article - Brake system troubleshooting (BCU top NFF)

Flight Operation Notifications Manual (FONM): None

Brake Control System (BCS) NFF Action:

• To support the technical investigation, FSRs and Service Centers are requested to perform an NVM download, complete a condition report and fill a BCS questionnaire

NOTES:

• Prior to troubleshooting, perform a bleeding of the Brake associated with the closed SOV (Indb or Outb) as the fault could be induced by air in the system.

  • Bleeding of the Inboard Brakes AMM 32-43-00-870-801 [ G5000 ]  [ Global Express ]  [ Global XRS ]
  • Bleeding of the Outboard Brakes AMM 32-43-00-870-802 [ G5000 ]  [ Global Express ]  [ Global XRS ]

• Download and complete this Water Ingress Survey Form
• To avoid unnecessary replacement of BCS part due to Brake related CAS nuisance message, before troubleshooting, follow AW700-32-0513 instructions.

  • Proceed to a QAR (if available) download of the last three flights (Aircraft meeting FAR part 135.172.), SB700-31-020
  • BCU NVM download
  • IAC CAS messages download

• If the BRAKE 50% degraded is posted intermittently or goes away after Brake application, perform the following:

  1. Pressurize the No. 2 and No. 3 hydraulic systems.
  2. Using CAIMS, Access BRAKE CONTROL SYSTEM DATA PAGE under ATA 32 "BCU".
  3. Apply the brakes. In CAIMS, monitor the brake pressure at each brake position.
  4. Release the brake pedals and monitor the brake pressures, all four brake pressures must decrease at almost the same rate. If one of the brake pressures holds longer, that brake control valve is defective.
  5. Perform the Pressure Test of the Brake System (AMM 32-43-00-780-801). If the residual brake pressure after brake pedal release is more than 100 psig (689.48 kPa), interchange the associated Brake Control and Shut-Off valve to confirm faulty valve and replace if required.
  6. If the above tests are not conclusive, do a NVM download of the BCU and send it to the Customer Response Center (CRC) for analysis.

1. Perform Outboard Brake Shut-off Valve (SOV) (L14) inspection.
2. Using the PMAT, access the Active Faults/Stored Faults as per AMM Tasks.
3. Select related CAIMS message below:
   Select an CAIMS message3245316HA - SHUTOFF VALVE OUTBD/BCU/WRG3245317HA - SHUTOFF VALVE INBD/BCU/WRG3245414HA - WHEEL SPEED XDCR OUTBD L/BCU/WRG3245415HA - WHEEL SPEED XDCR INBD L/BCU/WRG3245416HA - WHEEL SPEED XDCR INBD R/BCU/WRG3245417HA - WHEEL SPEED XDCR OUTBD R/BCU/WRG3245418HA - PEDAL POS XDCR PILOT L/BCU/WRG3245419HA - PEDAL POS XDCR PILOT R/BCU/WRG3245420HA - PEDAL POS XDCR COPILOT L/BCU/WRG3245421HA - PEDAL POS XDCR COPILOT R/BCU/WRG3245426HA - BRAKE CONTROL VALVE OUTBD L/BCU/WRG3245427HA - BRAKE CONTROL VALVE INBD L/BCU/WRG3245428HA - BRAKE CONTROL VALVE INBD R/BCU/WRG3245429HA - BRAKE CONTROL VALVE OUTBD R/BCU/WRG
4. Do close out.