Narrative:

On taxi out we had a strong odor that was reminiscent of chicken cooking. Thought it was possibly from chicken sandwich flying first officer had brought on board; as did the relief first officer. When odor did not dissipate after a time; it was presumed to be from the galley(south); so we queried the galley; and they said they had nothing cooking at the time. The odor was strong; but we did not associate it with a known malfunction; and I presumed it would pass. Upon takeoff; the odor appeared to dissipate very quickly. Soon thereafter; however; we started receiving numerous calls from the flight attendants indicating a strong; acrid; burning smell in the cabin; and throughout the mid to aft cabin area. The relief first officer inquired as to specifics; and we waited a brief period to see if it would dissipate. It did not; and we received a number of confusing calls from the cabin; haze; smoke from a lavatory waste bin; a waste bin fire extinguisher discharge. Most of these calls proved later to be either unfounded; or unverifiable; though there was a consensus regarding the odor in the cabin; and the flight attendant at door 3R insisted she saw a smoky haze in the cabin. As the calls were numerous; and could not be specifically located; I decided I had to consider the possibility of an unknown; undetermined fire; and opted to return to ZZZ. We did not prepare the cabin as things were quite hectic; but declared an emergency and returned to ZZZ. We were delayed in our return due to miscoms due to wrongly assigned frequencys; but once initiated; return was expeditious. Landing runway 14R; we were met and escorted by emergency equipment to the gate after an exterior inspection by rescue personnel for signs of smoke or fire; none of which was found. An interior of the aircraft revealed no fire or problem source. The nearest thing to probable cause was a maintenance person suggesting oil or grease in the pack system; though this was not verified by the time we departed the aircraft.

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Original NASA ASRS Text

Title: A B777-200 FLT ATTENDANT CREW DEPARTING ORD NOTICED STRONG BURNING SMELL IN CABIN. FLT CREW DECLARED AN EMER AND RETURNED.

Narrative: ON TAXI OUT WE HAD A STRONG ODOR THAT WAS REMINISCENT OF CHICKEN COOKING. THOUGHT IT WAS POSSIBLY FROM CHICKEN SANDWICH FLYING FO HAD BROUGHT ON BOARD; AS DID THE RELIEF FO. WHEN ODOR DID NOT DISSIPATE AFTER A TIME; IT WAS PRESUMED TO BE FROM THE GALLEY(S); SO WE QUERIED THE GALLEY; AND THEY SAID THEY HAD NOTHING COOKING AT THE TIME. THE ODOR WAS STRONG; BUT WE DID NOT ASSOCIATE IT WITH A KNOWN MALFUNCTION; AND I PRESUMED IT WOULD PASS. UPON TKOF; THE ODOR APPEARED TO DISSIPATE VERY QUICKLY. SOON THEREAFTER; HOWEVER; WE STARTED RECEIVING NUMEROUS CALLS FROM THE FLT ATTENDANTS INDICATING A STRONG; ACRID; BURNING SMELL IN THE CABIN; AND THROUGHOUT THE MID TO AFT CABIN AREA. THE RELIEF FO INQUIRED AS TO SPECIFICS; AND WE WAITED A BRIEF PERIOD TO SEE IF IT WOULD DISSIPATE. IT DID NOT; AND WE RECEIVED A NUMBER OF CONFUSING CALLS FROM THE CABIN; HAZE; SMOKE FROM A LAVATORY WASTE BIN; A WASTE BIN FIRE EXTINGUISHER DISCHARGE. MOST OF THESE CALLS PROVED LATER TO BE EITHER UNFOUNDED; OR UNVERIFIABLE; THOUGH THERE WAS A CONSENSUS REGARDING THE ODOR IN THE CABIN; AND THE FLT ATTENDANT AT DOOR 3R INSISTED SHE SAW A SMOKY HAZE IN THE CABIN. AS THE CALLS WERE NUMEROUS; AND COULD NOT BE SPECIFICALLY LOCATED; I DECIDED I HAD TO CONSIDER THE POSSIBILITY OF AN UNKNOWN; UNDETERMINED FIRE; AND OPTED TO RETURN TO ZZZ. WE DID NOT PREPARE THE CABIN AS THINGS WERE QUITE HECTIC; BUT DECLARED AN EMER AND RETURNED TO ZZZ. WE WERE DELAYED IN OUR RETURN DUE TO MISCOMS DUE TO WRONGLY ASSIGNED FREQS; BUT ONCE INITIATED; RETURN WAS EXPEDITIOUS. LNDG RWY 14R; WE WERE MET AND ESCORTED BY EMER EQUIP TO THE GATE AFTER AN EXTERIOR INSPECTION BY RESCUE PERSONNEL FOR SIGNS OF SMOKE OR FIRE; NONE OF WHICH WAS FOUND. AN INTERIOR OF THE ACFT REVEALED NO FIRE OR PROB SOURCE. THE NEAREST THING TO PROBABLE CAUSE WAS A MAINT PERSON SUGGESTING OIL OR GREASE IN THE PACK SYS; THOUGH THIS WAS NOT VERIFIED BY THE TIME WE DEPARTED THE ACFT.

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.