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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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01/10/22

Message Overview:

Message Name:

APU SHUTS DOWN AFTER APU GEN on-line OR EHP ACTIVATED

Message Code: 496OBS004
Effectivity: All
System: Auxiliary Power Unit (APU) Automatic Control System
System Description: 49-60-00
Schematic Diagram: 49-61-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 49-61-01 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Message Description:

The Auxiliary Power Unit (APU) starts normally but shuts down soon after the APU Generator comes on-line, an Electric Hydraulic Pump (EHP) is activated or an important electrical load is applied.

Possible Causes:

  • DC Power Center (DCPC) (A63)
  • Auxiliary Power Unit (APU) Full-Authority Digital Engine-Controller (FADEC) (A108)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

Forum Articles/Infoservice/Newsletter:

  • Honeywell SIL APU-99 - Electronic Control Unit (ECU) "No Fault Found" Removals
  • Honeywell SIL APU-137 - AIRBORNE AUXILIARY POWER-GAS TURBINE ENGINE-Introduction of a field cleaning procedure for the RE220 APU starter PN: 2704554

Quick Links:

Removal of the Transformer Rectifier Units AMM 24-31-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Transformer Rectifier Units AMM 24-31-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the DC Power Center (DCPC) L-Series Contactor AMM 24-61-53-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the DC Power Center (DCPC) L-Series Contactor AMM 24-61-53-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
APU Safety Precautions AMM 49-00-00-910-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
APU Shutdown (Normal) AMM 49-10-00-866-802 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Full-Authority Digital Engine-Controller (FADEC) AMM 49-61-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Full-Authority Digital Engine-Controller (FADEC) AMM 49-61-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Start the APU making sure the APU Generator is not selected "ON".
  2. Make sure that the APU does not shut down.

    1. If the APU shuts down without any electrical load applied, perform the troubleshooting for APU NO START and do close out.
    2. If the APU does not shut down, continue with next step.

  3. Using the PMAT, access CAIMS System Diagnostics, select ATA 49, CONTROLLER FADEC, LRU TEST and view APU DATA STATUS - PAGE 1. Monitor the APU parameters during this task. If one of the parameters seems abnormal, troubleshoot the affected sensor, component and associated wiring accordingly.
  4. Select the APU Generator on-line. Does the APU shut down?

    1. If YES, go to step 7.
    2. If NO, continue with next step.

  5. Select one or more Electric Hydraulic Pump (EHP) to "ON". Does the APU shut down?

    1. If YES, go to step 7.
    2. If NO, continue with next step.

  6. Apply more electrical loads to the Aircraft to try and reproduce the APU shut down condition.

    1. If you are unable to reproduce the condition, go to step 11.
    2. If you are able to reproduce the APU shut down condition, continue with next step.
      NOTE: Make sure you check CAIMS for any ATA 49 related fault codes.

  7. Start the APU once more with the APU Gen "OFF" and without any EHP or electrical loads applied.
  8. On the copilot Circuit Breaker panel, set the ESS TRU 2 circuit breaker to "OUT". This will force TRU 2 to feed the Battery Bus via TTC 4 (K4) in the DCPC.
  9. Set the APU generator "ON" and reproduce the same condition that made the APU shut down in the previous steps. Does the APU still shut down?

    1. If NO, go to step 11.
    2. If YES, continue with next step.

  10. Perform a wiring check as follows:

    From To Result
    A108BP1-114 A63P3-P

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, continue with next step.

  11. Replace DCPC K3 contactor.
  12. Do close out.

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