Narrative:

At cruise, we had an electrical problem and almost simultaneously suffered an uncommanded yaw input. Emergency checklist items we did (yaw damper 'off'). An emergency was declared. I diverted into ind. An overweight landing was uneventful. Callback conversation with reporter revealed the following information: the reporter was the captain and trip started out at pit where it was snowing and the RVR was 4000 ft. The B737-300LR aircraft was deiced at the new aircraft deicing facility at pit. The engines were left running but the APU was shut off as per procedure. After the deice process was complete, the APU was restarted to be available as a back up on the low visibility takeoff. On takeoff, the cockpit went black. A generator failed. Due to low visibility at pit, the decision was made to continue having a good engine generator and the APU generator. At cruise, a power interruption occurred on the main AC bus and the yaw damper gave a hard kick. The maneuver caused the aircraft to gain 200 ft and lose 900 ft and bank 20 to 40 degrees and a flight attendant was injured. The yaw damper was shut off and an emergency was declared and a landing was made at the nearest suitable airport which was ind. During the recovery, the aircraft was observed by ARTCC when it was 700 ft below the assigned altitude and the controller asked the pilots to say their altitude whereupon the emergency was declared. On approach the APU failed and a one generator landing was made at ind. The WX at ind was 300 degree overcast and 1 mi visibility. This crew earned their pay that day!

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Original NASA ASRS Text

Title: FLC HAD AN ELECTRICAL PROB AND A YAW DAMPER PROB.

Narrative: AT CRUISE, WE HAD AN ELECTRICAL PROB AND ALMOST SIMULTANEOUSLY SUFFERED AN UNCOMMANDED YAW INPUT. EMER CHKLIST ITEMS WE DID (YAW DAMPER 'OFF'). AN EMER WAS DECLARED. I DIVERTED INTO IND. AN OVERWT LNDG WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE CAPT AND TRIP STARTED OUT AT PIT WHERE IT WAS SNOWING AND THE RVR WAS 4000 FT. THE B737-300LR ACFT WAS DEICED AT THE NEW ACFT DEICING FACILITY AT PIT. THE ENGS WERE LEFT RUNNING BUT THE APU WAS SHUT OFF AS PER PROCEDURE. AFTER THE DEICE PROCESS WAS COMPLETE, THE APU WAS RESTARTED TO BE AVAILABLE AS A BACK UP ON THE LOW VISIBILITY TKOF. ON TKOF, THE COCKPIT WENT BLACK. A GENERATOR FAILED. DUE TO LOW VISIBILITY AT PIT, THE DECISION WAS MADE TO CONTINUE HAVING A GOOD ENG GENERATOR AND THE APU GENERATOR. AT CRUISE, A PWR INTERRUPTION OCCURRED ON THE MAIN AC BUS AND THE YAW DAMPER GAVE A HARD KICK. THE MANEUVER CAUSED THE ACFT TO GAIN 200 FT AND LOSE 900 FT AND BANK 20 TO 40 DEGS AND A FLT ATTENDANT WAS INJURED. THE YAW DAMPER WAS SHUT OFF AND AN EMER WAS DECLARED AND A LNDG WAS MADE AT THE NEAREST SUITABLE ARPT WHICH WAS IND. DURING THE RECOVERY, THE ACFT WAS OBSERVED BY ARTCC WHEN IT WAS 700 FT BELOW THE ASSIGNED ALT AND THE CTLR ASKED THE PLTS TO SAY THEIR ALT WHEREUPON THE EMER WAS DECLARED. ON APCH THE APU FAILED AND A ONE GENERATOR LNDG WAS MADE AT IND. THE WX AT IND WAS 300 DEG OVCST AND 1 MI VISIBILITY. THIS CREW EARNED THEIR PAY THAT DAY!

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.