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A B737-300, during descent, crew noted stabilizer trim wheel jerking with abnormal noise. Trim wheel jammed electrically and manually. Caused by failing trim wheel bearings.
| Attributes | |
| ACN | 598268 |
| Time | |
| Date | 200311 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : mco.airport |
| State Reference | FL |
| Altitude | msl single value : 10000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : mco.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Route In Use | approach : visual arrival : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 200 flight time total : 22000 flight time type : 17000 |
| ASRS Report | 598268 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : stabilizer trim wheel other flight crewa other flight crewb |
| Resolutory Action | flight crew : overcame equipment problem |
| Consequence | other |
| Supplementary | |
| Problem Areas | Company Flight Crew Human Performance Chart Or Publication Aircraft |
| Primary Problem | Aircraft |
Narrative:
During descent noticed stabilizer trim wheel jerking and making unusual noise during autoplt trimming. Disengaged autoplt and used electric trim to activate trim. As trim wheel turned, it sounded different than normal. Reengaged autoplt and continued descent. As we started our speed reduction to 250 KTS at 10000 ft, stabilizer wheel again began to bind as autoplt trim motor tried to trim aircraft. Again, autoplt was disengaged, cycled main electric/autoplt trim cut out switches and stabilizer trim override switch. Decided to fly aircraft without autoplt and used main electric trim. Trim wheel would turn, but still sounded as if something was binding. Then turning vectors to airport, stabilizer wheel jammed and would not trim electrically or manually. As aircraft was slowed to 220 KTS, flaps 5 degrees was selected. At this point, trim wheel resumed normal operation. Visual approach without autoplt flown to normal landing. The point is that there existed a malfunction which has no specific non-normal checklist that applies. Subsequent maintenance action revealed that the bearings on the stabilizer wheel trim mechanism had or were in the process of failure.
Original NASA ASRS Text
Title: A B737-300, DURING DSCNT, CREW NOTED STABILIZER TRIM WHEEL JERKING WITH ABNORMAL NOISE. TRIM WHEEL JAMMED ELECTRICALLY AND MANUALLY. CAUSED BY FAILING TRIM WHEEL BEARINGS.
Narrative: DURING DSCNT NOTICED STABILIZER TRIM WHEEL JERKING AND MAKING UNUSUAL NOISE DURING AUTOPLT TRIMMING. DISENGAGED AUTOPLT AND USED ELECTRIC TRIM TO ACTIVATE TRIM. AS TRIM WHEEL TURNED, IT SOUNDED DIFFERENT THAN NORMAL. REENGAGED AUTOPLT AND CONTINUED DSCNT. AS WE STARTED OUR SPD REDUCTION TO 250 KTS AT 10000 FT, STABILIZER WHEEL AGAIN BEGAN TO BIND AS AUTOPLT TRIM MOTOR TRIED TO TRIM ACFT. AGAIN, AUTOPLT WAS DISENGAGED, CYCLED MAIN ELECTRIC/AUTOPLT TRIM CUT OUT SWITCHES AND STABILIZER TRIM OVERRIDE SWITCH. DECIDED TO FLY ACFT WITHOUT AUTOPLT AND USED MAIN ELECTRIC TRIM. TRIM WHEEL WOULD TURN, BUT STILL SOUNDED AS IF SOMETHING WAS BINDING. THEN TURNING VECTORS TO ARPT, STABILIZER WHEEL JAMMED AND WOULD NOT TRIM ELECTRICALLY OR MANUALLY. AS ACFT WAS SLOWED TO 220 KTS, FLAPS 5 DEGS WAS SELECTED. AT THIS POINT, TRIM WHEEL RESUMED NORMAL OP. VISUAL APCH WITHOUT AUTOPLT FLOWN TO NORMAL LNDG. THE POINT IS THAT THERE EXISTED A MALFUNCTION WHICH HAS NO SPECIFIC NON-NORMAL CHKLIST THAT APPLIES. SUBSEQUENT MAINT ACTION REVEALED THAT THE BEARINGS ON THE STABILIZER WHEEL TRIM MECHANISM HAD OR WERE IN THE PROCESS OF FAILURE.
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.