09/16/19
Message Overview:
Fault Message:
APU SHUT DOWN- FAILED RELIGHT
Fault Code:
4960146APU
Associated CAS:
| Reporting LRU: | Full-Authority Digital Engine-Controller (FADEC) |
| System Description: | 49-40-00 |
| Schematic Diagram: | 49-61-00 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Wiring Diagram: | 49-12-00 [ Global Express ] [ G5000 ] [ Global XRS ] 49-61-01 [ Global Express ] [ G5000 ] [ Global XRS ] |
Fault Description:
After the Auxiliary Power Unit (APU) blows out, relight of the APU has not occurred before the speed decreases to 45%. In this condition, the Full-Authority Digital Engine-Controller (FADEC) will cause an APU shutdown.
| Fault | See * below | Description |
|---|---|---|
| FADEC FAILURE | ECU internal failure (CPU, watchdog timer, O/S circuit failure, loss of O/S protection, etc.) | |
| O/SPD | (Hardware/Software) overspeed circuits tripped (at 106%) | |
| LOSS OF SPEED | Both monopoles failed | |
| LOSS OF O/SPD | FADEC overspeed circuit/FCU fuel output solenoid failed | |
| OVERTEMP | * | EGT limit exceeded during i) start ii) on-speed operation |
| FIRE EMERG | * | Fire signal is received by the FADEC |
| REVERSE FLOW | * | T2 temp. limit (176.6°C/350°F) has been exceeded for 5 secs |
| HIGH OIL TEMP | * | Oil temp limit of >148.9°C exceeded for 10 seconds |
| LOW OIL PRESS | * | Oil pressure has fallen below lower limit of 30 psig for 15 seconds, with rpm > 95% |
| LOSS OF EGT DETECTION | * | Both EGT thermocouples have failed (NOTE: In Essential Mode, FADEC programs an EGT of 260°C to maintain the APU running) |
| NO FLAME | EGT rise has not been detected within 17 seconds of fuel solenoid being commanded open by FADEC or rpm >18% for 5 seconds | |
| NO ACCEL | Acceleration is < 0.05% of the prescheduled rate (normal acceleration is 2.5% per seconds) | |
| SLOW SPEED | Starter timer expired-APU rpm > 5% and less than starter cut out for 30 seconds | |
| UNDER SPEED | * | Speed has reached 100%, drops below 80% for 5 secs |
| NO CRANK | rpm does not rise above 5% within: i) 2 secs. when oil temp is warmer than minus 23°C ii) 50 secs. when oil temp is minus 23°C or lower |
|
| INLET DOOR | Inlet door position indicates closed 30 secs before starter engagement or 600 msecs. after starter engagement | |
| LOSS OF DC POWER | Loss of 28 VDC power for 200 milliseconds | |
| LOP SW FAIL | * | Oil pressure switch has failed open when rpm is <7% (NOTE: This switch is normally closed during prestart BITE) |
| FALLBACK | APU drop below 25% rpm after starter cutout | |
| APU GCU HIGH OIL TEMP | * | APU Generator oil temperature above 215°C |
| NOTE: An asterisk mark (*) in any row above means that the automatic protection shut down on that row is inhibited if the associated fault occurs in flight. The respective CAS message or an advisory message reading APU FAULT will be displayed in the CAS window and the APU will not shut down automatically in flight. However the pilot may select to shut down the APU manually by placing the APU control switch to OFF. | ||
Possible Causes:
- Combustor
- Ignition Exciter
- Fuel Control Torque Motor
- Fuel Solenoid Valve (V2)
- Inlet Pressure Sensor (MT1)
- Inlet Temperature Sensor (MT3)
- Exhaust Gas Temperature Sensor
- Impending Bypass Valve and Switch (S4)
- Inlet-Duct
- Igniter Plugs
- Igniter Plug Leads
- Fuel Control Unit (FCU) (A3)
- Fuel Flow-Divider Valve
- Auxiliary Power Unit (APU)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin:
- Honeywell Service Bulletin - SIL-APU-106 - Implementation of a Combustor Wash Program
- Honeywell Service Bulletin - SIL-APU-80 - Uncommanded shutdowns of APU
Forum Articles/Infoservice/Newsletter: None
If CAS message is not active, verify stored faults on CAIMS.
Quick Links:
| Access to Active Faults | AMM 45-45-00-970-802 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Access to Stored Faults | AMM 45-45-00-970-803 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the APU | AMM 49-10-00-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the APU | AMM 49-10-00-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Engine Branched Wiring-Harness | AMM 49-12-01-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Engine Branched Wiring-Harness | AMM 49-12-01-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Operational Test of the Inlet Door | AMM 49-14-01-710-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Cleaning of the Auxiliary Power Unit (APU) Combustor | AMM 49-21-00-170-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Fuel Control Unit | AMM 49-30-01-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Fuel Control Unit | AMM 49-30-01-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Fuel Solenoid Valve | AMM 49-30-17-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Fuel Solenoid Valve | AMM 49-30-17-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Fuel Flow-Divider Valve | AMM 49-30-21-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Fuel Flow-Divider Valve | AMM 49-30-21-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Ignition Exciter | AMM 49-41-01-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Ignition Exciter | AMM 49-41-01-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Igniter Plug Leads | AMM 49-41-05-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Igniter Plug Leads | AMM 49-41-05-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Removal of the Igniter Plugs | AMM 49-41-09-000-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Installation of the Igniter Plugs | AMM 49-41-09-400-801 [ Global Express ] [ G5000 ] [ Global XRS ] |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 [ Global Express ] [ G5000 ] [ Global XRS ] |
Troubleshooting Recommendations:
- Verify active and stored faults on CAIMS.
- If faults are found, perform fault isolation as required.
- If faults are not found, continue with next step.
- Inspect APU combustor for clogging.
- Inspect the wiring and connectors on the APU for any damage.
- If there is damage, repair or replace as required and do close out.
- If there is no damage, continue with next step.
- Verify that the APU air intake inlet door opens fully per AMM TASK 49-14-01-710-801. (DO NOT START THE APU, put the APU control panel knob in the run position only and verify door position visually and on APU DATA status page).
- Inspect the APU air inlet duct for FOD or signs of blockage.
- Replace Fuel control unit
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace Fuel solenoid valve
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace fuel flow divider valve
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace igniter plugs
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace igniter plug leads
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace APU
- Do close out.