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A B737-300 with a chronic #2 generator dropping off line was worked by the reporter with no positive fix accomplished. Later found xfer relay failed.
| Attributes | |
| ACN | 723237 |
| Time | |
| Date | 200701 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | agl single value : 0 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : maintenance |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Qualification | technician : airframe technician : powerplant |
| ASRS Report | 723237 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Events | |
| Anomaly | aircraft equipment problem : less severe maintenance problem : improper maintenance maintenance problem : improper documentation non adherence : published procedure non adherence : far |
| Independent Detector | aircraft equipment other aircraft equipment : #2 gen indications other other : 3 |
| Resolutory Action | none taken : detected after the fact |
| Consequence | other |
| Factors | |
| Maintenance | performance deficiency : testing performance deficiency : training performance deficiency : repair performance deficiency : fault isolation |
| Supplementary | |
| Problem Areas | Aircraft Chart Or Publication Maintenance Human Performance |
| Primary Problem | Maintenance Human Performance |
Narrative:
On jan/sun/07; approximately XA00; after completing a fan blade set change on an OTS aircraft; my lead told mr X and I to get a turnover on aircraft with electrical problems and to move it from a to B. Told us the #2 generator drops off line and that he had reconnected the #2 generator which was on MEL. He also told us he did not know the cause of the problem. Mr X talked to maintenance control and discovered that this aircraft has been having electrical problems on originating flts for awhile and that technician foremen have been working on it. At approximately XB00 mr X and I went to a and closed #2 engine cowls and both east&east doors to move aircraft. We pushed back from a and started both engines with a normal start; and put both engine generators on line. On taxi #2 generator dropped off line. At that time we xferred power to APU and back for troubleshooting; #2 generator did not come back on line. We also tried resetting thrust reverser #2 and thrust reverser #3 circuit breakers for troubleshooting from previous problems. We arrived at B and parked the aircraft and shut down engine. We pulled up some wiring diagrams and a little more troubleshooting; but our shift was over at XC00; so did a written turnover about #2 generator dropping off line on taxi and that APU power would power both busses; etc. Mr Y; told me that he did find the problem with the #2 generator. It was the R4 'altitude' xfer relay. I then changed the R4 relay and signed it off with an operations check required.
Original NASA ASRS Text
Title: A B737-300 WITH A CHRONIC #2 GENERATOR DROPPING OFF LINE WAS WORKED BY THE RPTR WITH NO POSITIVE FIX ACCOMPLISHED. LATER FOUND XFER RELAY FAILED.
Narrative: ON JAN/SUN/07; APPROX XA00; AFTER COMPLETING A FAN BLADE SET CHANGE ON AN OTS ACFT; MY LEAD TOLD MR X AND I TO GET A TURNOVER ON ACFT WITH ELECTRICAL PROBS AND TO MOVE IT FROM A TO B. TOLD US THE #2 GENERATOR DROPS OFF LINE AND THAT HE HAD RECONNECTED THE #2 GENERATOR WHICH WAS ON MEL. HE ALSO TOLD US HE DID NOT KNOW THE CAUSE OF THE PROB. MR X TALKED TO MAINT CTL AND DISCOVERED THAT THIS ACFT HAS BEEN HAVING ELECTRICAL PROBS ON ORIGINATING FLTS FOR AWHILE AND THAT TECHNICIAN FOREMEN HAVE BEEN WORKING ON IT. AT APPROX XB00 MR X AND I WENT TO A AND CLOSED #2 ENG COWLS AND BOTH E&E DOORS TO MOVE ACFT. WE PUSHED BACK FROM A AND STARTED BOTH ENGS WITH A NORMAL START; AND PUT BOTH ENG GENERATORS ON LINE. ON TAXI #2 GENERATOR DROPPED OFF LINE. AT THAT TIME WE XFERRED PWR TO APU AND BACK FOR TROUBLESHOOTING; #2 GENERATOR DID NOT COME BACK ON LINE. WE ALSO TRIED RESETTING THRUST REVERSER #2 AND THRUST REVERSER #3 CIRCUIT BREAKERS FOR TROUBLESHOOTING FROM PREVIOUS PROBS. WE ARRIVED AT B AND PARKED THE ACFT AND SHUT DOWN ENG. WE PULLED UP SOME WIRING DIAGRAMS AND A LITTLE MORE TROUBLESHOOTING; BUT OUR SHIFT WAS OVER AT XC00; SO DID A WRITTEN TURNOVER ABOUT #2 GENERATOR DROPPING OFF LINE ON TAXI AND THAT APU PWR WOULD PWR BOTH BUSSES; ETC. MR Y; TOLD ME THAT HE DID FIND THE PROB WITH THE #2 GENERATOR. IT WAS THE R4 'ALT' XFER RELAY. I THEN CHANGED THE R4 RELAY AND SIGNED IT OFF WITH AN OPS CHK REQUIRED.
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.