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A B737-800 was released from a contract maintenance facility 'C' check with #2 engine N1 compressor vibrations out of 'C' check limits. Requires fan balance.
| Attributes | |
| ACN | 677007 |
| Time | |
| Date | 200510 |
| Local Time Of Day | 0001 To 0600 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | agl single value : 0 |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Person 1 | |
| Affiliation | other |
| Function | maintenance : inspector |
| Qualification | technician : powerplant technician : inspection authority technician : airframe |
| ASRS Report | 677007 |
| Person 2 | |
| Affiliation | other |
| Function | oversight : supervisor |
| Events | |
| Anomaly | aircraft equipment problem : critical maintenance problem : improper maintenance maintenance problem : improper documentation non adherence : published procedure non adherence : far |
| Independent Detector | other other : 1 |
| Resolutory Action | none taken : detected after the fact |
| Factors | |
| Maintenance | contributing factor : manuals contributing factor : schedule pressure performance deficiency : scheduled maintenance performance deficiency : repair performance deficiency : non compliance with legal requirements |
| Supplementary | |
| Problem Areas | Maintenance Human Performance Chart Or Publication Aircraft |
| Primary Problem | Maintenance Human Performance |
| Situations | |
| Publication | Maint Manual |
Narrative:
While performing a vibration survey maintenance manual task on a B737-800 on the #2 engine during a 'C' check maintenance visit the indicated vibes were above the 'C' check recommended level for N1 compressor. An interpretation error of the maintenance manual was made and the aircraft was released for service without performing the recommended fan trim balance task. The vibration level that was indicated on the vibration survey task was within levels that would permit the aircraft to fly in service with applied deferral status for monitoring the engine vibrations. My write-up for the deferral status was not written for the aircraft out of the 'C' check maintenance visit. Making revisions to the maintenance manual to give more direct guidance of operator's processes and procedures; when third party maintenance is being performed; would greatly help reduce the likelihood of this error recurring.
Original NASA ASRS Text
Title: A B737-800 WAS RELEASED FROM A CONTRACT MAINT FACILITY 'C' CHK WITH #2 ENG N1 COMPRESSOR VIBRATIONS OUT OF 'C' CHK LIMITS. REQUIRES FAN BAL.
Narrative: WHILE PERFORMING A VIBRATION SURVEY MAINT MANUAL TASK ON A B737-800 ON THE #2 ENG DURING A 'C' CHK MAINT VISIT THE INDICATED VIBES WERE ABOVE THE 'C' CHK RECOMMENDED LEVEL FOR N1 COMPRESSOR. AN INTERP ERROR OF THE MAINT MANUAL WAS MADE AND THE ACFT WAS RELEASED FOR SVC WITHOUT PERFORMING THE RECOMMENDED FAN TRIM BAL TASK. THE VIBRATION LEVEL THAT WAS INDICATED ON THE VIBRATION SURVEY TASK WAS WITHIN LEVELS THAT WOULD PERMIT THE ACFT TO FLY IN SVC WITH APPLIED DEFERRAL STATUS FOR MONITORING THE ENG VIBRATIONS. MY WRITE-UP FOR THE DEFERRAL STATUS WAS NOT WRITTEN FOR THE ACFT OUT OF THE 'C' CHK MAINT VISIT. MAKING REVISIONS TO THE MAINT MANUAL TO GIVE MORE DIRECT GUIDANCE OF OPERATOR'S PROCESSES AND PROCS; WHEN THIRD PARTY MAINT IS BEING PERFORMED; WOULD GREATLY HELP REDUCE THE LIKELIHOOD OF THIS ERROR RECURRING.
Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.