What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) The captain reported that en route from ewr to orf, the "auto trim fail" and the "pit trim #1 fail" icas captions illuminated, and approx. 15 minutes later, the backup trim system #2 also failed. No pitch trim was then available, and trim stuck at +1. Detailed troubleshooting by company maintenance personnel, and assisted by Embraer tech reps, determined that the pitch trim actuator had failed. The actuator was replaced with a p/n 362200-1011 unit, the system functionally checked, and the aircraft returned to service. The dfdr was removed, and a complete download data file was provided to the NTSB. The failed trim actuator was delivered to the NTSB Washington headquarters, for further investigation. (.4) during cruise flight, the horizontal stabilizer jammed in the (-1)-degree trim position. After an uneventful landing, the elevator trim actuator was forwarded to the manufacturer for examination under the supervision of a safety board investigator. The elevator trim actuator contained a primary and back-up clutch gear, and each gear had a respective torque nut and lock washer. The examination revealed that that the tabs on the lock washers w ere not bent over into the locked position. Additionally, there was no evidence that the tabs had ever been bent into the locked position. The back-up clutch torque nut had backed off and down the shaft, coming to rest against the clutch gear cluster bearing outer race. The backed-off nut exhibited a scratch around the outer edge of the face, consistent with fouling against the clutch gear cluster bearing outer race, subsequently jamming the unit. The manufacturer identified the isolated error in the production process.
As the FAA filed it
(-23) THE CAPTAIN REPORTED THAT EN ROUTE FROM EWR TO ORF, THE "AUTO TRIM FAIL" AND THE "PIT TRIM #1 FAIL" ICAS CAPTIONS ILLUMINATED, AND APPROX. 15 MINUTES LATER, THE BACKUP TRIM SYSTEM #2 ALSO FAILED. NO PITCH TRIM WAS THEN AVAILABLE, AND TRIM STUCK AT +1. DETAILED TROUBLESHOOTING BY COMPANY MAINTENANCE PERSONNEL, AND ASSISTED BY EMBRAER TECH REPS, DETERMINED THAT THE PITCH TRIM ACTUATOR HAD FAILED. THE ACTUATOR WAS REPLACED WITH A P/N 362200-1011 UNIT, THE SYSTEM FUNCTIONALLY CHECKED, AND THE AIRCRAFT RETURNED TO SERVICE. THE DFDR WAS REMOVED, AND A COMPLETE DOWNLOAD DATA FILE WAS PROVIDED TO THE NTSB. THE FAILED TRIM ACTUATOR WAS DELIVERED TO THE NTSB WASHINGTON HEADQUARTERS, FOR FURTHER INVESTIGATION. (.4) DURING CRUISE FLIGHT, THE HORIZONTAL STABILIZER JAMMED IN THE (-1)-DEGREE TRIM POSITION. AFTER AN UNEVENTFUL LANDING, THE ELEVATOR TRIM ACTUATOR WAS FORWARDED TO THE MANUFACTURER FOR EXAMINATION UNDER THE SUPERVISION OF A SAFETY BOARD INVESTIGATOR. THE ELEVATOR TRIM ACTUATOR CONTAINED A PRIMARY AND BACK-UP CLUTCH GEAR, AND EACH GEAR HAD A RESPECTIVE TORQUE NUT AND LOCK WASHER. THE EXAMINATION REVEALED THAT THAT THE TABS ON THE LOCK WASHERS W ERE NOT BENT OVER INTO THE LOCKED POSITION. ADDITIONALLY, THERE WAS NO EVIDENCE THAT THE TABS HAD EVER BEEN BENT INTO THE LOCKED POSITION. THE BACK-UP CLUTCH TORQUE NUT HAD BACKED OFF AND DOWN THE SHAFT, COMING TO REST AGAINST THE CLUTCH GEAR CLUSTER BEARING OUTER RACE. THE BACKED-OFF NUT EXHIBITED A SCRATCH AROUND THE OUTER EDGE OF THE FACE, CONSISTENT WITH FOULING AGAINST THE CLUTCH GEAR CLUSTER BEARING OUTER RACE, SUBSEQUENTLY JAMMING THE UNIT. THE MANUFACTURER IDENTIFIED THE ISOLATED ERROR IN THE PRODUCTION PROCESS.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.
Other reports on N29917 · 1
Matched to the same aircraft by N-number and date.