Narrative:

The right AC bus failed in cruise. The AC crosstie light on checklist was performed. We were unable to reestablish power to the right bus. When the checklist was completed I declared an emergency and requested a vector for phx. Callback conversation with reporter revealed the following information: the reporter stated maintenance reported the right AC bus failure was caused by a malfunctioning generator control relay. The reporter said the relay failure was such as to prevent transfer of AC power from the left bus to the right. The reporter stated the transfer of the auxiliary power unit bus to the right bus was not attempted. The reporter said the emergency checklist was no help in this situation.

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Original NASA ASRS Text

Title: AN MD80 IN CRUISE AT FL 310 DECLARED AN EMER AND DIVERTED DUE TO LOSS OF #2 AC ELECTRICAL BUS CAUSED BY A FAILED GENERATOR CTL RELAY.

Narrative: THE R AC BUS FAILED IN CRUISE. THE AC CROSSTIE LIGHT ON CHKLIST WAS PERFORMED. WE WERE UNABLE TO REESTABLISH PWR TO THE R BUS. WHEN THE CHKLIST WAS COMPLETED I DECLARED AN EMER AND REQUESTED A VECTOR FOR PHX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED MAINT RPTED THE R AC BUS FAILURE WAS CAUSED BY A MALFUNCTIONING GENERATOR CTL RELAY. THE RPTR SAID THE RELAY FAILURE WAS SUCH AS TO PREVENT TRANSFER OF AC PWR FROM THE L BUS TO THE R. THE RPTR STATED THE TRANSFER OF THE AUXILIARY PWR UNIT BUS TO THE R BUS WAS NOT ATTEMPTED. THE RPTR SAID THE EMER CHKLIST WAS NO HELP IN THIS SIT.

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.