Fault Message:

APU NO FLAME

Fault Code:

4960133APU

Associated CAS:

APU SHUTDOWN
(Advisory)

Light off has not occurred 17 seconds after fuel solenoid has been energized and Auxiliary Power Unit (APU) speed has been greater that 18% for 5 seconds. In this condition, the Full Authority Digital Engine Control (FADEC) will cause an APU shutdown.

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.

• Ignition Exciter (A2)
• Fuel Control Torque Motor
• Fuel Solenoid Valve (V2)
• Inlet Pressure Sensor (MT1)
• Inlet Temperature Sensor (MT3)
• Exhaust-Gas Temperature (EGT) sensor (TC1)
• Igniter Plugs
• Igniter Plug Leads
• Fuel Control Unit (A3)
• Fuel Flow Divider Valve
• Auxiliary Power Unit (APU) Full-Authority Digital Engine-Controller (FADEC) (A108)
• Auxiliary Power Unit (APU)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

If CAS message is not active, verify stored faults on CAIMS.

It would be recommended to use CAIMS data pages to confirm sequence of events during start. Go to System diagnostic/ ATA 49/ Controller (FADEC)/ LRU test/ APU Data status page 2 and APU Status. In these pages one can see Fuel flow, and signal active as command given by FADEC.

Attempt APU start and look at data pages to see sequence of events: Starter voltage, Ignition and Fuel at 5%rpm, starter cut out at 45%rpm, then should ramp to 100%. If you hang around 80% rpm is because you don't have your secondary fuel (Fuel Flow Divider).

1. Look for residual fuel in the exhaust duct.
2. Examine the APU wiring and connectors for bare wiring, kinks, worn areas and other damage.

   1. If there is bare wiring, kinks, worn areas or other damage, repair or replace as required and do close out.
   2. If there is no bare wiring, kinks, worn areas or other damage, continue with next step.

3. Verify that the APU air intake inlet door opens fully (Do not start the APU, put the APU control panel control knob in the run position only and verify door position visually and on APU DATA status page).
4. Inspect the APU air inlet duct for FOD or signs of blockage.

   1. If blockage is found, remove the blockage and do close out.
   2. If blockage is not found, continue with next step.

5. Re-rack FADEC and verify both the tray and FADEC connectors for damage or FOD.

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

6. Attempt an APU start and observe data pages mention above to confirm if sequences of event are observed.
7. Swap igniter plugs.

   1. If system checks are good, replace defective igniter plug and do close out.
   2. If fault remains, continue with next step.

8. Swap igniter plug leads.

   1. If system checks are good, replace defective igniter plug and do close out.
   2. If fault remains, continue with next step.

9. Swap fuel control units.

   1. If system checks are good, replace defective fuel control unit and do close out.
   2. If fault remains, continue with next step.

10. Swap fuel solenoid valves.

    1. If system checks are good, replace defective fuel solenoid valve and do close out.
    2. If fault remains, continue with next step.

11. Swap fuel flow divider valves.

    1. If system checks are good, replace defective fuel flow divider valve and do close out.
    2. If fault remains, continue with next step.

12. Swap FADECs.

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

13. Replace APU.
14. Close out.