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A B737-400 in cruise at FL350 declared an emergency and diverted due to loss of the standby AC bus caused by a failed standby bus relay.
| Attributes | |
| ACN | 499325 |
| Time | |
| Date | 200101 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : oak.airport |
| State Reference | CA |
| Altitude | msl single value : 35000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zoa.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-400 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Route In Use | enroute airway : j1.airway |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : multi engine pilot : atp pilot : commercial |
| Experience | controller military : 6 controller non radar : 12 controller radar : 12 flight time last 90 days : 180 flight time total : 5500 flight time type : 2500 |
| ASRS Report | 499325 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : bus failure indication other flight crewa other flight crewb |
| Resolutory Action | controller : issued new clearance flight crew : diverted to another airport flight crew : declared emergency |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
At cruise at FL350, we had indications of an electrical malfunction. Primary indications were: captain's primary flight displays inoperative, and standby power off light illuminated. We determined that we had a standby AC power failure. The checklist calls for placing the standby power switch to battery position. This provides 30 mins of power on a fully charged battery. Since we did not know the status of our battery charge and were VMC, we decided to wait until we were on approach to move the switch. We were bound for pdx but decided to divert to oak (we were positioned for a normal descent profile to oak). We coordinated with ZOA and declared an emergency. On extended final for oak, we went to standby battery power which operated properly. Landing and taxi were uneventful. Maintenance determined that the standby power relay had failed.
Original NASA ASRS Text
Title: A B737-400 IN CRUISE AT FL350 DECLARED AN EMER AND DIVERTED DUE TO LOSS OF THE STANDBY AC BUS CAUSED BY A FAILED STANDBY BUS RELAY.
Narrative: AT CRUISE AT FL350, WE HAD INDICATIONS OF AN ELECTRICAL MALFUNCTION. PRIMARY INDICATIONS WERE: CAPT'S PRIMARY FLT DISPLAYS INOP, AND STANDBY PWR OFF LIGHT ILLUMINATED. WE DETERMINED THAT WE HAD A STANDBY AC PWR FAILURE. THE CHKLIST CALLS FOR PLACING THE STANDBY PWR SWITCH TO BATTERY POS. THIS PROVIDES 30 MINS OF PWR ON A FULLY CHARGED BATTERY. SINCE WE DID NOT KNOW THE STATUS OF OUR BATTERY CHARGE AND WERE VMC, WE DECIDED TO WAIT UNTIL WE WERE ON APCH TO MOVE THE SWITCH. WE WERE BOUND FOR PDX BUT DECIDED TO DIVERT TO OAK (WE WERE POSITIONED FOR A NORMAL DSCNT PROFILE TO OAK). WE COORDINATED WITH ZOA AND DECLARED AN EMER. ON EXTENDED FINAL FOR OAK, WE WENT TO STANDBY BATTERY PWR WHICH OPERATED PROPERLY. LNDG AND TAXI WERE UNEVENTFUL. MAINT DETERMINED THAT THE STANDBY PWR RELAY HAD FAILED.
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.