Narrative:

FL310 we encountered cirrus with visible ice crystals under the wipers. Anti-ice was selected on; engine and wing. The cabin temperature had been stable to that point. Not long after selecting anti ice we were called that it was getting warm in the back of the cabin. The cabin temp was adjusted lower. Probably 7-10 minutes elapsed and we were called to cool off the back more as it was too warm in the aft cabin. The temperature was adjusted again. Then we got a call in cirrus with anti-icing on. The flight attendants notified us of a hot area on the floor from [row] 22 to 27 and that there was a lady in one of the 'a' seats forward of the back galley that was in tears as the floor was so hot it was burning her feet through her shoes; along with a hot burning smell similar to a clothing iron burning on a shirt; electrical; and paper burning smell. Several conversations passed back and forth. As heat increased on the floor the passengers were moved from those seats to other vacant seats. Both air conditioning systems were selected full cold. There was a commuting pilot in the cabin that confirmed to the flight attendants that the heat was not normal and they advised us of that. There were no abnormal cockpit indications. No cargo fire indication or anything showing any system anomalies. No odor in the cockpit. The recirculation fan; and galley power were turned off. The odor intensified; a ground service individual checked the floor and determined temp was increasing. No cargo fire indication. Concurrently we started the smoke/fire/fumes checklist; [notified ATC of the situation]; and diverted. We did a left descending 360 and landed. We were in icing conditions in the descent until lower 20's as I remember and anti ice was procedurally turned off. We turned into a wide high speed exit area and parked the aircraft. Arff checked the aircraft after we came to a stop and found no active/increasing heat on the exterior or in the cargo compartments. According to the flight attendants the temperature started to decrease just prior to landing. We then taxied to the gate. Station chief met us at the gate. On gate arrival the area on the floor showed higher temp than the surrounding area; but had cooled substantially from its peak airborne. As passengers exited the aircraft another air carrier md-80 [pilot] that was a passenger stopped and told us we did have a problem; but didn't interrupt the flight attendants as he could tell we were diverting and knew we were busy. The entire elapsed time from the call of excess floor temp to the descent and touch down was not very long and quite busy.

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Original NASA ASRS Text

Title: A MD-80 developed a dangerously overheated cabin floor between rows 22 to 27 with anti-ice ON. The flight diverted where Maintenance discovered an anti-ice duct seal separation.

Narrative: FL310 we encountered Cirrus with visible ice crystals under the wipers. Anti-ice was selected on; engine and wing. The cabin temperature had been stable to that point. Not long after selecting anti ice we were called that it was getting warm in the back of the cabin. The cabin temp was adjusted lower. Probably 7-10 minutes elapsed and we were called to cool off the back more as it was too warm in the aft cabin. The temperature was adjusted again. Then we got a call in cirrus with anti-icing on. The flight attendants notified us of a hot area on the floor from [row] 22 to 27 and that there was a lady in one of the 'A' seats forward of the back galley that was in tears as the floor was so hot it was burning her feet through her shoes; along with a hot burning smell similar to a clothing iron burning on a shirt; electrical; and paper burning smell. Several conversations passed back and forth. As heat increased on the floor the passengers were moved from those seats to other vacant seats. Both air conditioning systems were selected full cold. There was a commuting pilot in the cabin that confirmed to the flight attendants that the heat was not normal and they advised us of that. There were no abnormal cockpit indications. No Cargo fire indication or anything showing any system anomalies. No odor in the cockpit. The recirculation fan; and galley power were turned off. The odor intensified; a ground service individual checked the floor and determined temp was increasing. No cargo fire indication. Concurrently we started the smoke/fire/fumes checklist; [notified ATC of the situation]; and diverted. We did a left descending 360 and landed. We were in icing conditions in the descent until lower 20's as I remember and Anti ice was procedurally turned off. We turned into a wide high speed exit area and parked the aircraft. ARFF checked the aircraft after we came to a stop and found no active/increasing heat on the exterior or in the cargo compartments. According to the flight attendants the temperature started to decrease just prior to landing. We then taxied to the gate. Station Chief met us at the gate. On gate arrival the area on the floor showed higher temp than the surrounding area; but had cooled substantially from its peak airborne. As passengers exited the aircraft another air carrier MD-80 [pilot] that was a passenger stopped and told us we did have a problem; but didn't interrupt the flight attendants as he could tell we were diverting and knew we were busy. The entire elapsed time from the call of excess floor temp to the descent and touch down was not very long and quite busy.

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.