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A DC9-50 standby horizon indicator was replaced and checked ok but voltage to indicator was 60 volts AC. Wire diagram indicates 120 volts AC input.
| Attributes | |
| ACN | 661284 |
| Time | |
| Date | 200506 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | agl single value : 0 |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 50 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : maintenance |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Qualification | technician : powerplant technician : fcc technician : airframe |
| Experience | maintenance avionics : 2 maintenance technician : 21 |
| ASRS Report | 661284 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Events | |
| Anomaly | aircraft equipment problem : critical maintenance problem : improper documentation non adherence : far non adherence : published procedure |
| Independent Detector | other other : 1 |
| Resolutory Action | none taken : detected after the fact |
| Consequence | other |
| Factors | |
| Maintenance | contributing factor : engineering procedure contributing factor : manuals performance deficiency : non compliance with legal requirements |
| Supplementary | |
| Problem Areas | Maintenance Human Performance Aircraft Chart Or Publication |
| Primary Problem | Maintenance Human Performance |
Narrative:
Aircraft X log #X had an inoperative standby horizon (red flag). Previous mechanic #X replaced faulty indicator and then mechanic #Y confirmed indicator checks good in accordance with manual; but discovered voltage reading at indicator to be '60 vac.' wiring diagram states should be 120 vac. He checks another aircraft and found same 60 vac. I took over at shift change and confirmed 60 vac also on another aircraft. After consulting with other technicians; I was comfortable that 60 vac is normal and 120 vac is a misprint. Upon further review; I think that a better action on my part would have been to contact engineering and have an engineering authority/authorized written to correct the drawing; even though the standby horizon passed all functional tests. I'm confident that the discrepancy was corrected; it's just that I should have followed it up one more step.
Original NASA ASRS Text
Title: A DC9-50 STANDBY HORIZON INDICATOR WAS REPLACED AND CHKED OK BUT VOLTAGE TO INDICATOR WAS 60 VOLTS AC. WIRE DIAGRAM INDICATES 120 VOLTS AC INPUT.
Narrative: ACFT X LOG #X HAD AN INOP STANDBY HORIZON (RED FLAG). PREVIOUS MECH #X REPLACED FAULTY INDICATOR AND THEN MECH #Y CONFIRMED INDICATOR CHKS GOOD IN ACCORDANCE WITH MANUAL; BUT DISCOVERED VOLTAGE READING AT INDICATOR TO BE '60 VAC.' WIRING DIAGRAM STATES SHOULD BE 120 VAC. HE CHKS ANOTHER ACFT AND FOUND SAME 60 VAC. I TOOK OVER AT SHIFT CHANGE AND CONFIRMED 60 VAC ALSO ON ANOTHER ACFT. AFTER CONSULTING WITH OTHER TECHNICIANS; I WAS COMFORTABLE THAT 60 VAC IS NORMAL AND 120 VAC IS A MISPRINT. UPON FURTHER REVIEW; I THINK THAT A BETTER ACTION ON MY PART WOULD HAVE BEEN TO CONTACT ENGINEERING AND HAVE AN ENGINEERING AUTH WRITTEN TO CORRECT THE DRAWING; EVEN THOUGH THE STANDBY HORIZON PASSED ALL FUNCTIONAL TESTS. I'M CONFIDENT THAT THE DISCREPANCY WAS CORRECTED; IT'S JUST THAT I SHOULD HAVE FOLLOWED IT UP ONE MORE STEP.
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.