Narrative:

I was the first officer. 30 mins west of ZZZ; the purser notified the flight deck of an odor of unknown origin. Moments later; the captain and I also smelled it. The odor appeared electrical in nature. We performed the qrc. The captain coordination with the purser while I requested a return to ZZZ. An emergency was declared. The flight attendants were advised to perform a 'cabin advisory.' dispatch was advised via ACARS and landing performance was requested. The captain flew a visual approach into ZZZ. The aircraft was 28500 pounds over maximum landing weight. The landing was gentle. We cleared the runway and shut down both engines so the fire department could inspect the tires and brakes. Nothing unusual was noted by the fire department. We restarted both engines and taxied to the gate.

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Original NASA ASRS Text

Title: A B757'S PLTS AND FLT ATTENDANTS SMELLED AN ELECTRICAL ODOR INFLT. AN EMER WAS DECLARED WITH A RETURN TO LAND OVERWT AT THE DEP ARPT.

Narrative: I WAS THE FO. 30 MINS W OF ZZZ; THE PURSER NOTIFIED THE FLT DECK OF AN ODOR OF UNKNOWN ORIGIN. MOMENTS LATER; THE CAPT AND I ALSO SMELLED IT. THE ODOR APPEARED ELECTRICAL IN NATURE. WE PERFORMED THE QRC. THE CAPT COORD WITH THE PURSER WHILE I REQUESTED A RETURN TO ZZZ. AN EMER WAS DECLARED. THE FLT ATTENDANTS WERE ADVISED TO PERFORM A 'CABIN ADVISORY.' DISPATCH WAS ADVISED VIA ACARS AND LNDG PERFORMANCE WAS REQUESTED. THE CAPT FLEW A VISUAL APCH INTO ZZZ. THE ACFT WAS 28500 LBS OVER MAX LNDG WT. THE LNDG WAS GENTLE. WE CLRED THE RWY AND SHUT DOWN BOTH ENGS SO THE FIRE DEPT COULD INSPECT THE TIRES AND BRAKES. NOTHING UNUSUAL WAS NOTED BY THE FIRE DEPT. WE RESTARTED BOTH ENGS AND TAXIED TO THE GATE.

Data retrieved from NASA's ASRS site as of May 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.