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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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08/09/21

Message Overview:

Message Name:

NO OFV RS422 BUS OUTPUT

Message Code:

B3-007272

Associated CAS:

AUTO PRESS FAIL
(Caution)

Reporting LRU: OUTFLOW VALVE
System Description: 21-31-00
Schematic Diagram: 21-31-00
Wiring Diagram: 21-31-05

Message Description:

The OUTFLOW VALVE does not send any RS422 data to both IASCs.

Possible Causes:

  • Junction Box 2 (JB2)
  • Cabin Pressure Control System Outflow Valve (MPE1)
  • Integrated Air System Controller (IASC) (A56)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • AW300-21-0047 - No MDC Report upon "AUTO PRESS FAIL" CAS Message (20003 - 20500)

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Operational Test of the Cabin Pressure Control System AMM 21-31-00-710-801
Removal of the Integrated Air System (IAS) Controller AMM 21-31-01-000-801
Installation of the Integrated Air System (IAS) Controller AMM 21-31-01-400-801
Operational Test of the Integrated Air System (IAS) Controller AMM 21-31-01-710-801
Removal of the Outflow Valve AMM 21-31-05-000-801
Installation of the Outflow Valve AMM 21-31-05-400-801
Removal of the Junction Box JB2 AMM 24-63-05-000-803
Installation of the Junction Box JB2 AMM 24-63-05-400-803
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Wire Repair SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset Outflow Valve circuit breakers CB3-D6 and CB4-D6.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  2. Do wiring checks from the Outflow Valve to the IASCs. Repair as required.

    1. If wiring checks passes, go to step 4.
    2. If wiring checks fails, continue with next step.

    NOTE: Dual transmit and receive signals from the IAS Controllers and the outflow enable signal pass through Junction Box #2.

  3. Replace Junction Box #2.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  4. Confirm proper operation of the Outflow Valve by doing the Section (2) of the Operational Test of the Cabin Pressure Control System.

    1. If test passes, do close out.
    2. If test fails, continue with next step.

  5. Replace Outflow Valve.
  6. Do close out.

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