Narrative:

While cruising at FL330 en route from sjc to dfw, our autoplt and autothrottles disconnected, also the mach trim inoperative and yaw damper inoperative annunciator lights came on. The altitude select window went blank and the airspeed bug went to 300 KTS and stayed there. We requested a lower altitude and completed the appropriate checklists. The aircraft was initially difficult to control. It would yaw and roll excessively. Unable to restore any of our lost components, we decided to declare an emergency and divert to las. During the approach, the aircraft was still very unstable. We made a normal landing in las. We stopped on the runway to let the fire crew check the aircraft out. There was no structural damage. Callback conversation with reporter revealed the following information: the problem was suspected to be a bus power problem, but has not been confirmed by maintenance. The reporter said with the number of system inoperative, it had to be a power problem. The reporter stated 1 circuit breaker was found tripped.

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Original NASA ASRS Text

Title: AN MD80 IN CRUISE AT FL330 DECLARED AN EMER AND DIVERTED DUE TO AUTOPLT, AUTOTHROTTLES, MACH TRIM AND YAW DAMPER FAILURE. SUSPECT ELECTRICAL BUS FAILURE.

Narrative: WHILE CRUISING AT FL330 ENRTE FROM SJC TO DFW, OUR AUTOPLT AND AUTOTHROTTLES DISCONNECTED, ALSO THE MACH TRIM INOP AND YAW DAMPER INOP ANNUNCIATOR LIGHTS CAME ON. THE ALT SELECT WINDOW WENT BLANK AND THE AIRSPD BUG WENT TO 300 KTS AND STAYED THERE. WE REQUESTED A LOWER ALT AND COMPLETED THE APPROPRIATE CHKLISTS. THE ACFT WAS INITIALLY DIFFICULT TO CTL. IT WOULD YAW AND ROLL EXCESSIVELY. UNABLE TO RESTORE ANY OF OUR LOST COMPONENTS, WE DECIDED TO DECLARE AN EMER AND DIVERT TO LAS. DURING THE APCH, THE ACFT WAS STILL VERY UNSTABLE. WE MADE A NORMAL LNDG IN LAS. WE STOPPED ON THE RWY TO LET THE FIRE CREW CHK THE ACFT OUT. THERE WAS NO STRUCTURAL DAMAGE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE PROB WAS SUSPECTED TO BE A BUS PWR PROB, BUT HAS NOT BEEN CONFIRMED BY MAINT. THE RPTR SAID WITH THE NUMBER OF SYS INOP, IT HAD TO BE A PWR PROB. THE RPTR STATED 1 CIRCUIT BREAKER WAS FOUND TRIPPED.

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.