Narrative:

My fourth leg of the day; first with first officer and first with aircraft that had just come out of maintenance. Events from pre-departure through climbout were normal. I always monitor the service intercom during flight and; during climb; I heard the 'a' flight attendant ask one of the others if she smelled anything burning. They confirmed an odor but stated it wasn't too bad at the time. I could initially detect a stale smelling odor from the air conditioning unit. As we just reached cruise altitude; the 'a' flight attendant rang me to say the odor was getting stronger. She described it as a burning electrical smell; we could definitely smell something burning at that time. I directed the first officer to don oxygen. We were only 50 NM away from the departure airport so I contacted ATC to declare an emergency and request vectors back to the departure airport for landing. I directed the first officer to keep flying while I told company we were returning and then ran the QRH for fumes in the cabin and set up for an ILS approach back to 31L. I was still trying to complete the fumes removal checklist as we were descending to 6;000 ft. Once at 6;000 ft; I elected to stop running the QRH and complete the preparations for landing. The approach and landing; while expeditious; was stable and uneventful. We cleared the runway and stopped. The 'a' told me the fumes were dissipating and crash/fire rescue also could not see any evidence of fire so I elected to taxi to the gate with crash fire rescue equipment in tow. Passengers deplaned. I did not observe anyone with issues as they deplaned. I found out the right engine had just been changed. But; I don't know if maintenance could have found the cause of the problem with just an engine run.

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Original NASA ASRS Text

Title: After reaching cruise altitude; the flight attendants reported a burning electrical odor which the pilots then detected; so an emergency was declared; oxygen masks donned; and the flight returned to the departure airport while the QRH was being accomplished.

Narrative: My fourth leg of the day; first with First Officer and first with aircraft that had just come out of maintenance. Events from pre-departure through climbout were normal. I always monitor the service intercom during flight and; during climb; I heard the 'A' Flight Attendant ask one of the others if she smelled anything burning. They confirmed an odor but stated it wasn't too bad at the time. I could initially detect a stale smelling odor from the air conditioning unit. As we just reached cruise altitude; the 'A' Flight Attendant rang me to say the odor was getting stronger. She described it as a burning electrical smell; we could definitely smell something burning at that time. I directed the First Officer to don oxygen. We were only 50 NM away from the departure airport so I contacted ATC to declare an emergency and request vectors back to the departure airport for landing. I directed the First Officer to keep flying while I told Company we were returning and then ran the QRH for fumes in the cabin and set up for an ILS approach back to 31L. I was still trying to complete the Fumes Removal Checklist as we were descending to 6;000 FT. Once at 6;000 FT; I elected to stop running the QRH and complete the preparations for landing. The approach and landing; while expeditious; was stable and uneventful. We cleared the runway and stopped. The 'A' told me the fumes were dissipating and crash/fire rescue also could not see any evidence of fire so I elected to taxi to the gate with CFR in tow. Passengers deplaned. I did not observe anyone with issues as they deplaned. I found out the right engine had just been changed. But; I don't know if Maintenance could have found the cause of the problem with just an engine run.

Data retrieved from NASA's ASRS site 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.