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B737-500 crew found that the yoke trim switches were inoperative. After maintenance fixed them, they became inoperative in the air. This was a chronic problem.
| Attributes | |
| ACN | 608420 |
| Time | |
| Date | 200402 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : den.airport |
| State Reference | CO |
| Altitude | msl single value : 6000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-500 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : takeoff climbout : intermediate altitude climbout : initial |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 13800 flight time type : 5000 |
| ASRS Report | 608420 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical maintenance problem : improper maintenance non adherence : company policies non adherence : far non adherence : published procedure |
| Independent Detector | aircraft equipment other aircraft equipment : trim wheels other flight crewa other flight crewb |
| Resolutory Action | flight crew : overrode automation flight crew : returned to original clearance flight crew : overcame equipment problem |
| Consequence | other other |
| Factors | |
| Maintenance | contributing factor : schedule pressure performance deficiency : repair performance deficiency : testing performance deficiency : non compliance with legal requirements performance deficiency : fault isolation |
| Supplementary | |
| Problem Areas | Maintenance Human Performance Aircraft Company |
| Primary Problem | Company |
Narrative:
During aircraft preflight, found the stabilizer trim switch on both the captain's and the first officer's yoke would not activate stabilizer trim. Maintenance was called. This aircraft had just come out of maintenance for the same problem with several parts replaced. After an hour delay, replacement of the stabilizer actuator, and much testing, we were released with a clean mrd. On takeoff from runway 8, I attempted to trim the stabilizer on the climb out, but there was no movement. I had the first officer try his trim switch and he was unable to trim the stabilizer either. The speed trim feature interfered with my attempts to manually trim the aircraft, so I directed both main and autoplt cutout switches be moved to cutout. The aircraft flew fine with manual trim. During the climb and before we had an opportunity to contact dispatch, I had the cutout switches placed back to normal to check the autoplt trim function. After resetting both switches, the control column switches now worked normal. The autoplt also checked normal. Above 18000 ft, I had the first officer contact maintenance controller through dispatch and discuss the event and all applicable implications that would effect returning or continuing to destination. It was determined that safety would not be compromised and we continued to ord. Appropriate logbook entry was made. The aircraft was taken OTS at ord.
Original NASA ASRS Text
Title: B737-500 CREW FOUND THAT THE YOKE TRIM SWITCHES WERE INOP. AFTER MAINT FIXED THEM, THEY BECAME INOP IN THE AIR. THIS WAS A CHRONIC PROB.
Narrative: DURING ACFT PREFLT, FOUND THE STABILIZER TRIM SWITCH ON BOTH THE CAPT'S AND THE FO'S YOKE WOULD NOT ACTIVATE STABILIZER TRIM. MAINT WAS CALLED. THIS ACFT HAD JUST COME OUT OF MAINT FOR THE SAME PROB WITH SEVERAL PARTS REPLACED. AFTER AN HR DELAY, REPLACEMENT OF THE STABILIZER ACTUATOR, AND MUCH TESTING, WE WERE RELEASED WITH A CLEAN MRD. ON TKOF FROM RWY 8, I ATTEMPTED TO TRIM THE STABILIZER ON THE CLBOUT, BUT THERE WAS NO MOVEMENT. I HAD THE FO TRY HIS TRIM SWITCH AND HE WAS UNABLE TO TRIM THE STABILIZER EITHER. THE SPD TRIM FEATURE INTERFERED WITH MY ATTEMPTS TO MANUALLY TRIM THE ACFT, SO I DIRECTED BOTH MAIN AND AUTOPLT CUTOUT SWITCHES BE MOVED TO CUTOUT. THE ACFT FLEW FINE WITH MANUAL TRIM. DURING THE CLB AND BEFORE WE HAD AN OPPORTUNITY TO CONTACT DISPATCH, I HAD THE CUTOUT SWITCHES PLACED BACK TO NORMAL TO CHK THE AUTOPLT TRIM FUNCTION. AFTER RESETTING BOTH SWITCHES, THE CTL COLUMN SWITCHES NOW WORKED NORMAL. THE AUTOPLT ALSO CHKED NORMAL. ABOVE 18000 FT, I HAD THE FO CONTACT MAINT CTLR THROUGH DISPATCH AND DISCUSS THE EVENT AND ALL APPLICABLE IMPLICATIONS THAT WOULD EFFECT RETURNING OR CONTINUING TO DEST. IT WAS DETERMINED THAT SAFETY WOULD NOT BE COMPROMISED AND WE CONTINUED TO ORD. APPROPRIATE LOGBOOK ENTRY WAS MADE. THE ACFT WAS TAKEN OTS AT ORD.
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.