Horizontal Stabilizer Motor Drive Unit reported a loss of AC power going to Motor Drive Unit (MDU) Channel 2 or a failure of the internal power supply.

• Cockpit Circuit Breaker Panel (CCBP) (A35)
• Pitch Trim Actuator Motor Drive Unit (MDU) (A184)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

NOTES:

• This CAIMS fault is posted when the following thermal breaker is pulled.

•  This fault may sometime be cleared by performing the flight control system reset procedure.

1. Check status of STAB TRIM CH2 thermal (CCBP-E5).

   1. If circuit breaker tripped, go to step 3.
   2. If circuit breaker did not trip, continue with next step.

2. Physically inspect the CCBP-E5 and then measure for 115 VAC at the MDU connector A184P5, pins A, B, C and pin D to aircraft ground.

   From	To	Expected Result	Result
   A184P5-A	Ground	115 VAC
   A184P5-B	Ground	115 VAC
   A184P5-C	Ground	115 VAC
   A184P5-D	GND	0 Ω

   1. If checks are good continue with next step.
   2. If checks are not good repair as required and do close out.

3. Slave in a MDU and see if Active Fault clears.
4. Use the Ground support Equipment 27X-41-09 "MDU INVERTING HARNESS" to isolate the fault to the MDU or Pitch Trim Actuator, prior to replacing any units.
5. 

   1. If the fault is isolated to the MDU, replace the MDU and do close out.
   2. If the fault is isolated to the HSTA, continue with the next step.

6. Replace HSTA, do close out.
   NOTE: The Pitch Trim Motors can be interchanged for confirmation before replacing a component.
7. Do close out.

NOTE: The MDU status can be verified via CAIMS

1. SYSTEM DIAG
2. 27-00 FLIGHT CONTROLS
3. FLIGHT CONTROL UNIT #2
4. LRU TEST
5. DISPLAY ADVANCED EFCS DATA
6. Go to page 5 of 8