Message Name:

GEN4 [DIFF PROTECTION FEEDER]

Message Code:

2424124LPS

Associated CAS:

GEN 4 FAIL
(Advisory)

Variable Frequency Generator (VFG) 4 has tripped off-line or will not come on-line.

• Variable Frequency Generators (VFG) 4 (G4)
• Generator Control Units (GCU) 4 (A59)
• AC Power Center (ACPC) (A54)
• Associated Wiring

Advisory Wire/Service Bulletin: 

• AW700-24-0370 - Variable Frequency Generator (VFG) #4 Feeder Cable Chafing
• AW700-24-0598 - Variable Frequency Generator (VFG) GL511-1103-9 - Failure
• AW700-24-0572 - "GEN FAIL" associated with fault message "Open Circuit TR2/TR3"
• AW700-24-0655 - Variable Frequency Generator Harness Low Clearance to Hydraulic/Fuel Lines

Full Throttle Blog/Forum Articles/Infoservice/Newsletter:

• REFERENCE INSTRUCTION LETTER (RIL) GX-0198 - Return to service following VFG bearing failure and/or VFG housing rupture

Flight Operation Notifications Manual (FONM): None

NOTES:

• Prior to T/S procedures, perform a visual of generator 4 for heat distress. Confirm if the heat exchanger is blocked  with FOD.
• A GCU patch cable (GSE REF # 24X-24-02) can be used to interchange GCUs 1, 4 and 5 into position 2 or 3 (for troubleshooting only).

• The GCU NVMs can only be downloaded at position #2 or #3.

1. Access CAIMS and check if the following faults are active:

   • 2424126LPS - GEN4 OIL OVERTEMP FAULT
   • 2424200LPS - GEN4 DRIVE SHAFT FAIL/INVALID %N2

   Inspect the VFG for the following:

   • VFG oil filter bypass indicator tripped, and/or
   • Metal particles in the oil lines, and/or
   • VFG end frame cracked or breached, and/or
   • Oil sight glass cracked

   1. If there is a combination of the listed CAIMS active fault and VFG condition(s) perform RIL GX-0198
   2. If there is NO combination, continue with next step.

2. Access CAIMS active faults. Are there any ACPC related fault messages?

   1. If YES, troubleshoot these messages first.
   2. If NO, continue with next step.

3. Interchange the GCU 4 with GCU 2 (physically or using the GCU patch cable).
   NOTE: Use PMAT to monitor the fault on GCU.

   1. If system checks are good, replace GCU 4 and do close out.
   2. If fault remains, continue with next step.

4. Disconnect GCU 4 connector A59P2 and VFG 4 connector G4P1. Do a continuity check as follows:

   From	To	Result
   A59P2-41	Ground
   A59P2-42	Ground
   A59P2-50	Ground
   A59P2-40	Ground

   1. If there is continuity, repair defective wiring as required.
   2. If there is NO continuity, continue with next step.

5. Do a continuity check between GCU 4 and VFG 4 as follows:

   From	To	Result
   A59P2-41	G4P1-F
   A59P2-42	G4P1-E
   A59P2-50	G4P1-J
   A59P2-40	G4P1-D

   1. If there is continuity continue with next step.
   2. If there is NO continuity, repair defective wiring as required.

6. Disconnect ACPC connector A54P2. Do a continuity check as follows:

   From	To	Result
   A59P2-49	Ground
   A59P2-57	Ground
   A59P2-63	Ground
   A59P2-62	Ground

   1. If there is continuity continue with next step.
   2. If there is NO continuity, repair defective wiring as required.

7. Do a continuity check between GCU 4 and ACPC as follows:

   From	To	Result
   A59P2-49	A54P2-E
   A59P2-57	A54P2-F
   A59P2-63	A54P2-G
   A59P2-62	A54P2-H

   1. If there is continuity, continue with next step.
   2. If there is NO continuity, repair defective wiring as required.

8. Disconnect VFG #4 (T1, T2 and T3) and ACPC VFG4-A, B and C.
9. Do an Insulation check using a megger as follows:
   Caution: Before using the megger, make sure both sides of cable are disconnected. Failure to do that may damage the equipment

   From	To	Expected Result	Result
   VFG4-T1	Ground	No continuity
   VFG4-T2	Ground	No continuity
   VFG4-T3	Ground	No continuity

   1. If there is continuity repair defective wiring and do close out.
   2. If there is no continuity, continue with next step.

10. Do an Insulation check using a megger as follows:
    Caution: Before using the megger, make sure both sides of cable are disconnected. Failure to do that may damage the equipment

    From	To	Expected Result	Result
    VFG4-T1	VFG4-T2	No continuity
    VFG4-T1	VFG4-T3	No continuity
    VFG4-T1	VFG4-G	No continuity
    VFG4-T2	VFG4-T3	No continuity
    VFG4-T2	VFG4-G	No continuity
    VFG4-T3	VFG4-G	No continuity

    1. If there is continuity repair defective wiring and do close out.
    2. If there is no continuity, continue with next step.

11. Do a continuity check as follows:

    From	To	Expected Result	Result
    VFG4-T1	ACPC VFG4-A	Continuity
    VFG4-T2	ACPC VFG4-B	Continuity
    VFG4-T3	ACPC VFG4-C	Continuity
    VFG4-G	Ground	Continuity

    1. If there is continuity, continue with next step.
    2. If there is no continuity, repair defective wiring as required.

12. Interchange VFG 4 with VFG 3. Is the fault still present?

    1. If YES, continue with next step.
    2. If NO, replace defective VFG.

13. Replace ACPC.
14. Do close out.