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An MD80 'yaw damper off' warning light was discovered inoperative shortly after an FGS test had been made. Test procedure does not require yaw damper off light test.
| Attributes | |
| ACN | 650490 |
| Time | |
| Date | 200503 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Series (DC-9-80) Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : maintenance |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| ASRS Report | 650490 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | aircraft equipment other aircraft equipment : yaw damper 'off' light other other : 2 |
| Resolutory Action | none taken : detected after the fact |
| Consequence | other other |
| Factors | |
| Maintenance | contributing factor : work cards performance deficiency : scheduled maintenance performance deficiency : repair performance deficiency : testing performance deficiency : inspection |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Maintenance Human Performance Aircraft Chart Or Publication |
| Primary Problem | Chart Or Publication |
Narrative:
I performed a successful return to service check on both #1 and #2 dfgc's (both system passed with no failures) per MD80 amm 22-01-05. This was done as part of the chkout procedure following the installation of a GPS FMS on the subject aircraft. After several flts; it was discovered that the 'yaw damper off' annunciation was inoperative due to a broken wire. How the checked items contributed to the close-up event error: if the wire was broken at the time I performed the return to service check; a confirmation of the 'yam damper off' annunciation during the initial setup of the return to service check test would have brought the discrepancy to light. Currently; the amm doesn't require a xchk of the light when the yaw damper switch is placed in the off position at the beginning of the test. A revision of the MD80 amm would possibly correct this problem. Made suggestion to revise MD80 amm.
Original NASA ASRS Text
Title: AN MD80 'YAW DAMPER OFF' WARNING LIGHT WAS DISCOVERED INOP SHORTLY AFTER AN FGS TEST HAD BEEN MADE. TEST PROC DOES NOT REQUIRE YAW DAMPER OFF LIGHT TEST.
Narrative: I PERFORMED A SUCCESSFUL RETURN TO SVC CHK ON BOTH #1 AND #2 DFGC'S (BOTH SYS PASSED WITH NO FAILURES) PER MD80 AMM 22-01-05. THIS WAS DONE AS PART OF THE CHKOUT PROC FOLLOWING THE INSTALLATION OF A GPS FMS ON THE SUBJECT ACFT. AFTER SEVERAL FLTS; IT WAS DISCOVERED THAT THE 'YAW DAMPER OFF' ANNUNCIATION WAS INOP DUE TO A BROKEN WIRE. HOW THE CHKED ITEMS CONTRIBUTED TO THE CLOSE-UP EVENT ERROR: IF THE WIRE WAS BROKEN AT THE TIME I PERFORMED THE RETURN TO SVC CHK; A CONFIRMATION OF THE 'YAM DAMPER OFF' ANNUNCIATION DURING THE INITIAL SETUP OF THE RETURN TO SVC CHK TEST WOULD HAVE BROUGHT THE DISCREPANCY TO LIGHT. CURRENTLY; THE AMM DOESN'T REQUIRE A XCHK OF THE LIGHT WHEN THE YAW DAMPER SWITCH IS PLACED IN THE OFF POS AT THE BEGINNING OF THE TEST. A REVISION OF THE MD80 AMM WOULD POSSIBLY CORRECT THIS PROB. MADE SUGGESTION TO REVISE MD80 AMM.
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.