AFCS ENGAGE INVAL
(Caution)

The Fault Warning Computer (FWC) senses that the Automatic Flight Control System (AFCS) engages during an incorrect system condition and the EICAS display does not show the Flight Director Information (FDI).

There may be an incorrect relationship between some or all the items that follow:

• ASCB system condition (e.g., power-up mode, test mode)
• AFCS condition (e.g., engaged, disengaged)
• Touch-control steering switches
• AP servo clutch signal
• WOW condition.

• Aileron Parallel Servo (B26)
• Elevator Parallel Servo (B25)
• Integrated Avionic Computer (IAC) 1 (A11)
• IAC 2 (A10)
• IAC 3 (A12)
• Touch Control Steering (TCS) (S46, S47)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW700-22-0333 - Aileron and Elevator Auto-Pilot Servo

Forum Articles/Infoservice/Newsletter: None

1. Access CAIMS active faults. Are there any IAC related faults?

   1. If YES, take down the IMT fault code and access the IMT failure code look-up on the PMAT for further troubleshooting instructions.
   2. If NO, continue with next step.

2. Perform the following tests:

   • Operational test of the Flight Director System.
   • Operational test of the Junction Box JB4.

   1. If defects are found, troubleshoot/rectify as required.
   2. If no defects are found, continue with next step.

3. Remove power from the A/C.
4. Remove JB4, IAC 1, 2 and 3. Perform a continuity check as follows:
   NOTE: Make sure you also check the related shield wires if applicable
   For IAC 1
   

   From	To	Result
   A11CP1-12	JB4CP1-3E
   A11DP1-89	JB4CP1-3A
   A11DP1-87	Ground
   A11DP1-33	Ground

   For IAC 2

   From	To	Result
   A10CP1-12	JB4CP1-3H
   A10DP1-89	JB4CP1-3D
   A10DP1-33	Ground

   For IAC 3

   From	To	Result
   A12DP1-89	JB4CP1-3C
   A12DP1-33	Ground

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

5. Perform a continuity check as follows:
   For IAC 1
   

   From	To	Result
   A11CP1-12	Ground
   A11DP1-89	Ground

   For IAC 2

   From	To	Result
   A10CP1-12	Ground
   A10DP1-89	Ground

   For IAC 3

   From	To	Result
   A12DP1-89	Ground

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

6. Access and disconnect the Aileron (B26) and Elevator (B25) Parallel Servos. Perform a continuity check as follows:
   For the aileron parallel servo:
   

   From	To	Result
   B26P1-11	JB4CP1-3B
   B26P1-12	Ground

   For the elevator parallel servo:

   From	To	Result
   B25P1-11	JB4CP1-4A
   B25P1-14	Ground

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

7. Perform a continuity check as follows:
   For the Aileron parallel servo:
   

   From	To	Result
   B26P1-11	Ground

   For the Elevator parallel servo:

   From	To	Result
   B25P1-11	Ground

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

8. Disconnect the Flight Guidance Panel (FGP) connector A79P1. Perform a continuity check as follows:
   

   From	To	Result
   A79P1-BB	Ground

   1. If there is continuity, investigate the wiring interface and the Touch Control Steering switches. Repair as required.
   2. If there is no continuity, continue with next step.

9. Press and hold the TCS switches on the control column one at a time, checking for continuity to ground each time:
   

   From	To	Result
   A79P1-BB	Ground

   1. If there is continuity for each switch when pressed, continue with next step.
   2. If there is no continuity, investigate the wiring interface and the TCS switches. Repair as required.

10. Check the WOW wiring interface between the FGP connector A79P1-y and the Landing Gear Electronic Control Unit (LGECU) connector A52AP1-J10.

    1. If defects are found, repair defective wiring as required.
    2. If no defects are found, continue with next step.

11. Replace the Elevator parallel servo. Is the fault still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

12. Replace the Aileron parallel servo. Is the fault still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

13. Replace IAC 1. Is the fault still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

14. Replace IAC 2. Is the fault still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

15. Replace IAC 3.
16. Do close out.