02/26/21
Message Overview:
Message Description:
Motor Control Unit (MCU) Fault detected by Horizontal Stabilizer Electronic Control Unit (HST ECU). Verify MCU, wiring or HST ECU. Consequently failures described above will trigger in the MDC the corresponding HST ECU Label 352 bit 13.
Possible Causes:
- Motor Control Unit (MCU) (A131)
- Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) (A130)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin:
- AW300-27-0315 - PRI STAB TRIM FAIL EICAS message caused by CPLD U27
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| Removal of the Horizontal Stabilizer-Trim Actuator (HSTA) | AMM 27-41-05-000-801 |
| Installation of the Horizontal Stabilizer-Trim Actuator (HSTA) | AMM 27-41-05-400-801 |
| Operational Test of the Horizontal Stabilizer-Trim Actuator (HSTA) Full Range Trimming | AMM 27-41-05-710-801 |
| Functional Test of the HSTA Torque Limiter | AMM 27-41-05-720-801 |
| Functional Test of the Horizontal Stabilizer Trim Actuator (HSTA) Brake System | AMM 27-41-05-720-803 |
| Removal of the Motor and Brake Unit | AMM 27-41-09-000-801 |
| Installation of the Motor and Brake Unit | AMM 27-41-09-400-801 |
| Removal of the Motor Control Unit (MCU) | AMM 27-41-13-000-801 |
| Installation of the Motor Control Unit (MCU) | AMM 27-41-13-400-801 |
| Removal of the Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) | AMM 27-41-21-000-801 |
| Installation of the Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) | AMM 27-41-21-400-801 |
| Operational Test of the Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) | AMM 27-41-21-710-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Aircraft on Ground: Pull the circuit breakers that follow and reset after a few seconds:
- PRI STAB TRIM/RUD LIM, CB1 - B15
- SEC STAB TRIM/RUD LIM, CB2 - B13
- PRI STAB MOTOR, LCDPC - A4
- SEC STAB MOTOR, RDCPC - A5
- Do the MCU power check as per table below:
- If power is there, go to step 4.
- If there is no power, continue with next step.
Circuit Breaker Label Connector A131P1 Pins Location Reading (+) (-) CB Closed CB Open CB1-B15 Trim Prim Stab/Rudd Lim B GND Center Pedestal 28 ±2 VDC 0 ±2 VDC - Troubleshoot power source. Repair/replace as required.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Remove HST ECU from the avionics rack (LHS).
- Do wiring check between MCU connector A131P1 pins D, C to Ground; MCU connector A131P2 pins D, C to Ground. Repair as required.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Do wiring check between MCU connector A131P3 pins 15, 13 and HST ECU connector A130AP1 pins 5K, 5J. Repair as required.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Do wiring check between MCU A131 connector and HSTA MPE44 connector as follow: Repair as required.
- A131P3 pins 1, 2, 4, 5, 6 and MPE44P1 pins 7, 8, 9, 10, 11.
- A131P5 pins B, C, D and MPE44P1 pins A, D, B.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace HST ECU.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace the primary motor and Brake Unit if the MDC has the corresponding Label 352 bit 13 and the Label 352 bit 19.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace the MCU.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace HSTA.
- Do close out.