Fault Message:

H STAB MOT DR UNIT [CH2]/WRG FAULT

Fault Code:

27661262SX

Associated CAS Message:

STAB TRIM
(Caution)

SPLRS STAB BIT
(Advisory)

STAB CH1 FAIL
(Advisory)

There is a Horizontal Motor Drive Unit failure or the interface wiring is defective between the Flight Control Unit (FCU) 2 and the Motor Drive Unit (MDU).

• Pitch Trim Actuator Motor Motor Drive Unit (MDU) (A184)
• Flight Control Unit (FCU) 2 (A66)
• Pitch Trim Actuator (B44)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

This fault may sometime be cleared by performing the flight control system reset procedure. If the message comes back more then once within 10 flight legs, troubleshooting is required.

1. Swap FCU 2 with FCU 1 and check for the failure transfer over to Channel 1?

   1. If YES, replace FCU 2. Reset FCUs latched faults and do close out.
   2. If NO, continue with next step.

2. Use Ground Support Equipment 27X-41-09 'MDU INVERTING HARNESS' if available. Confirm the failure with the inverting harness installed. If the MDU INVERTING HARNESS is not available, continue with step 3.

   1. If the fault is now on Channel 1, it means that the MDU CH 2 is defective. Replace the MDU and do close out.
   2. If the fault remains on Channel 2, the failure could be with the HSTA motor or the wiring interface. Continue with next step.

3. Disconnect FCU 2 connector A66DP1 and A66BP1. Disconnect MDU connector A184P7. Perform a continuity check as follows:

   From	To	Result
   A66DP1-3H	A184P7-37
   A66DP1-3J	A184P7-23
   A66DP1-6G	A184P7-6
   A66DP1-5K	A184P7-7
   A66DP1-5J	A184P7-8
   A66DP1-3G	A184P7-24
   A66BP1-14F	A184P7-28
   A66BP1-14E	A184P7-29
   A66BP1-15F	A184P7-16
   A66BP1-15E	A184P7-17

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

4. Disconnect MDU connectors A184P7 and A184P6. Disconnect Pitch Trim Actuator connectors B44P4 and B44P3. Perform a continuity check as follows:

   From	To	Result
   A184P6-A	B44P3-A
   A184P6-B	B44P3-B
   A184P6-C	B44P3-C
   A184P7-20	B44P4-13
   A184P7-19	B44P4-14
   A184P7-3	B44P4-12
   A184P7-4	B44P4-11
   A184P7-2	B44P4-26
   A184P7-1	B44P4-34
   A184P7-10	B44P4-32
   A184P7-25	B44P4-33

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

5. Swap HSTA motor 2 with motor 1. Is the fault still present on the same side?

   1. If YES, continue with next step.
   2. If NO, replace defective motor and do close out.

6. Replace the MDU.
7. Replace the Pitch Trim Actuator.
8. Do close out.