Narrative:

We departed and were climbing through 13000 ft MSL when we experienced a loss of both left and right electrical buses. The emergency power system automatically pwred the emergency bus; which restored some of the captain's flight instruments; but all of my instruments were dead; and we lost cabin pressurization control; causing the cabin altitude to begin climbing. The captain directed me to level off; and then we quickly coordinated a descent to 10000 ft. We elected not to don our oxygen masks since we were at a safe altitude and descending rapidly back down to 10000 ft; and we felt that flying the airplane and coordinating with ATC were our most important immediate priorities. I flew 'cross-cockpit' for a few moments while the captain talked with ATC and the crew; and then he took the controls and I began to perform the abnormal checklist procedures. We were able to restore electrical power to the left bus; which enabled the captain to fly normally; and we proceeded back to ZZZ; declaring an emergency en route. We flew a visual approach; but on final; we discussed the runway length and our aircraft weight; and decided to instead circle to the longest runway at ZZZ. We completed all normal checklists and were cleared to land. After performing an uneventful overweight landing; we returned to the gate. After landing; I took another look at the abnormal checklist; and realized that I had missed a step in the checklist that likely would have allowed us to restore power to the right bus as well; which could have been a vital step at night or in bad WX. Distrs during the return to ZZZ; and a confusing checklist format (this is a fairly involved procedure; with lots of conditional boxed items that require the user to skip around from one section to another) contributed to my omitting a potentially important step in the checklist. I will be especially vigilant in the future to make sure that I do not overlook any steps in abnormal procedures.

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Original NASA ASRS Text

Title: MD90 FLT CREW HAS ELECTRICAL FAILURE DURING DEP; DECLARES AN EMER AND DIVERTS FOR LNDG.

Narrative: WE DEPARTED AND WERE CLBING THROUGH 13000 FT MSL WHEN WE EXPERIENCED A LOSS OF BOTH L AND R ELECTRICAL BUSES. THE EMER PWR SYS AUTOMATICALLY PWRED THE EMER BUS; WHICH RESTORED SOME OF THE CAPT'S FLT INSTS; BUT ALL OF MY INSTS WERE DEAD; AND WE LOST CABIN PRESSURIZATION CTL; CAUSING THE CABIN ALT TO BEGIN CLBING. THE CAPT DIRECTED ME TO LEVEL OFF; AND THEN WE QUICKLY COORDINATED A DSCNT TO 10000 FT. WE ELECTED NOT TO DON OUR OXYGEN MASKS SINCE WE WERE AT A SAFE ALT AND DSNDING RAPIDLY BACK DOWN TO 10000 FT; AND WE FELT THAT FLYING THE AIRPLANE AND COORDINATING WITH ATC WERE OUR MOST IMPORTANT IMMEDIATE PRIORITIES. I FLEW 'CROSS-COCKPIT' FOR A FEW MOMENTS WHILE THE CAPT TALKED WITH ATC AND THE CREW; AND THEN HE TOOK THE CTLS AND I BEGAN TO PERFORM THE ABNORMAL CHKLIST PROCS. WE WERE ABLE TO RESTORE ELECTRICAL PWR TO THE L BUS; WHICH ENABLED THE CAPT TO FLY NORMALLY; AND WE PROCEEDED BACK TO ZZZ; DECLARING AN EMER ENRTE. WE FLEW A VISUAL APCH; BUT ON FINAL; WE DISCUSSED THE RWY LENGTH AND OUR ACFT WT; AND DECIDED TO INSTEAD CIRCLE TO THE LONGEST RWY AT ZZZ. WE COMPLETED ALL NORMAL CHKLISTS AND WERE CLRED TO LAND. AFTER PERFORMING AN UNEVENTFUL OVERWT LNDG; WE RETURNED TO THE GATE. AFTER LNDG; I TOOK ANOTHER LOOK AT THE ABNORMAL CHKLIST; AND REALIZED THAT I HAD MISSED A STEP IN THE CHKLIST THAT LIKELY WOULD HAVE ALLOWED US TO RESTORE PWR TO THE R BUS AS WELL; WHICH COULD HAVE BEEN A VITAL STEP AT NIGHT OR IN BAD WX. DISTRS DURING THE RETURN TO ZZZ; AND A CONFUSING CHKLIST FORMAT (THIS IS A FAIRLY INVOLVED PROC; WITH LOTS OF CONDITIONAL BOXED ITEMS THAT REQUIRE THE USER TO SKIP AROUND FROM ONE SECTION TO ANOTHER) CONTRIBUTED TO MY OMITTING A POTENTIALLY IMPORTANT STEP IN THE CHKLIST. I WILL BE ESPECIALLY VIGILANT IN THE FUTURE TO MAKE SURE THAT I DO NOT OVERLOOK ANY STEPS IN ABNORMAL PROCS.

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.