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A B737-200 after rudder replacement and test flight reported rudder trim with power on was 1 unit and trim with power off was 2 pt 5 units. Was acceptable within maintenance manual limits.
| Attributes | |
| ACN | 356590 |
| Time | |
| Date | 199612 |
| Day | Thu |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : zzz |
| State Reference | US |
| Altitude | agl bound lower : 0 agl bound upper : 0 |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | other personnel other |
| Qualification | other other : other |
| ASRS Report | 356590 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | other personnel other |
| Qualification | other other : other |
| ASRS Report | 356608 |
| Events | |
| Anomaly | aircraft equipment problem : less severe other anomaly other |
| Independent Detector | other flight crewa other other : unspecified cockpit |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | other |
Narrative:
Dec/xx/96 I was maintenance supervisor on duty at the hangar in ZZZ. Aircraft was a B737-200. Just had its rudder replaced due to a lightning strike and required a test flight. The aircraft returned from the test flight with an item concerning the rudder trim. After discussing the item with the flight crew, reviewing the flight test report, and reviewing the maintenance manual, I was convinced that everything discussed with the flight crew was acceptable and within allowable operating limits per the aircraft's maintenance manual. The flight test report indicated the aircraft required 1 unit of left rudder trim with hydraulic power on which is acceptable. Also on the report it stated that during manual reversion, rudder trim went from .2 degrees left to 2.7 degrees left (2.5 degrees total). There is no mention in the maintenance manual to 'zero out' rudder trim prior to hydraulic power off. Had the original 1 unit of trim remained input, then hydraulic power removed the rudder would have deflected an additional 1.5 units which is still acceptable per the maintenance manual. We tried to contact the flight test crew several times to clarify if there was a discrepancy between the maintenance manual and the flight test report. I was unable to contact them. I turned this aircraft over to the oncoming shift manager and explained the flight test results to him and felt the aircraft was airworthy and discussed my findings with an explanation.
Original NASA ASRS Text
Title: A B737-200 AFTER RUDDER REPLACEMENT AND TEST FLT RPTED RUDDER TRIM WITH PWR ON WAS 1 UNIT AND TRIM WITH PWR OFF WAS 2 PT 5 UNITS. WAS ACCEPTABLE WITHIN MAINT MANUAL LIMITS.
Narrative: DEC/XX/96 I WAS MAINT SUPVR ON DUTY AT THE HANGAR IN ZZZ. ACFT WAS A B737-200. JUST HAD ITS RUDDER REPLACED DUE TO A LIGHTNING STRIKE AND REQUIRED A TEST FLT. THE ACFT RETURNED FROM THE TEST FLT WITH AN ITEM CONCERNING THE RUDDER TRIM. AFTER DISCUSSING THE ITEM WITH THE FLC, REVIEWING THE FLT TEST RPT, AND REVIEWING THE MAINT MANUAL, I WAS CONVINCED THAT EVERYTHING DISCUSSED WITH THE FLC WAS ACCEPTABLE AND WITHIN ALLOWABLE OPERATING LIMITS PER THE ACFT'S MAINT MANUAL. THE FLT TEST RPT INDICATED THE ACFT REQUIRED 1 UNIT OF L RUDDER TRIM WITH HYD PWR ON WHICH IS ACCEPTABLE. ALSO ON THE RPT IT STATED THAT DURING MANUAL REVERSION, RUDDER TRIM WENT FROM .2 DEGS L TO 2.7 DEGS L (2.5 DEGS TOTAL). THERE IS NO MENTION IN THE MAINT MANUAL TO 'ZERO OUT' RUDDER TRIM PRIOR TO HYD PWR OFF. HAD THE ORIGINAL 1 UNIT OF TRIM REMAINED INPUT, THEN HYD PWR REMOVED THE RUDDER WOULD HAVE DEFLECTED AN ADDITIONAL 1.5 UNITS WHICH IS STILL ACCEPTABLE PER THE MAINT MANUAL. WE TRIED TO CONTACT THE FLT TEST CREW SEVERAL TIMES TO CLARIFY IF THERE WAS A DISCREPANCY BTWN THE MAINT MANUAL AND THE FLT TEST RPT. I WAS UNABLE TO CONTACT THEM. I TURNED THIS ACFT OVER TO THE ONCOMING SHIFT MGR AND EXPLAINED THE FLT TEST RESULTS TO HIM AND FELT THE ACFT WAS AIRWORTHY AND DISCUSSED MY FINDINGS WITH AN EXPLANATION.
Data retrieved from NASA's ASRS site as of July 2007 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.