Narrative:

At cruise flight FL230 we noticed a faint smell emanating from the aircraft. We thought there was a possibility that a passenger might be smoking. We verified that no one was smoking. We also thought the smell might be coming from the environmental system. We turned off the mode controled and the smell dissipated without a trace. We advised ZBW we would like to proceed to alb for a precautionary landing. We discussed the possibility of donning the oxygen masks as a precaution and quickly agreed this was not necessary as the smell was down to a trace. We proceeded to alb and made an uneventful emergency landing. The fire trucks were rolled as a precaution. We thought of the possibility of evacuating the aircraft but again decided this was not necessary. We taxied to the gate and deplaned the passenger without further incident. Upon closer inspection by mechanics, it was determined that the cause of the smell was a faulty sensor board in the overhead cabin that had burned out. Callback conversation with reporter revealed the following information: the reporter stated the cause of the smoke and burning odor was a small fan on the autotemp controller that draws cabin ambient air across a temperature sensor. The reporter said the fan was completely burned up. The reporter stated the circuit breaker for the fan never tripped. The reporter said the circuit breaker is not accessible to the crew in-flight being located in a cabin closet under the floorboard. The reporter said the FAA has made contact with the crew.

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Original NASA ASRS Text

Title: A BE1900D IN CRUISE AT FL230 DECLARED AN EMER AND DIVERTED DUE TO SMELL OF ELECTRICAL BURNING ODOR IN CABIN AND COCKPIT CAUSED BY A CABIN TEMP SENSOR FAN.

Narrative: AT CRUISE FLT FL230 WE NOTICED A FAINT SMELL EMANATING FROM THE ACFT. WE THOUGHT THERE WAS A POSSIBILITY THAT A PAX MIGHT BE SMOKING. WE VERIFIED THAT NO ONE WAS SMOKING. WE ALSO THOUGHT THE SMELL MIGHT BE COMING FROM THE ENVIRONMENTAL SYS. WE TURNED OFF THE MODE CTLED AND THE SMELL DISSIPATED WITHOUT A TRACE. WE ADVISED ZBW WE WOULD LIKE TO PROCEED TO ALB FOR A PRECAUTIONARY LNDG. WE DISCUSSED THE POSSIBILITY OF DONNING THE OXYGEN MASKS AS A PRECAUTION AND QUICKLY AGREED THIS WAS NOT NECESSARY AS THE SMELL WAS DOWN TO A TRACE. WE PROCEEDED TO ALB AND MADE AN UNEVENTFUL EMER LNDG. THE FIRE TRUCKS WERE ROLLED AS A PRECAUTION. WE THOUGHT OF THE POSSIBILITY OF EVACUATING THE ACFT BUT AGAIN DECIDED THIS WAS NOT NECESSARY. WE TAXIED TO THE GATE AND DEPLANED THE PAX WITHOUT FURTHER INCIDENT. UPON CLOSER INSPECTION BY MECHS, IT WAS DETERMINED THAT THE CAUSE OF THE SMELL WAS A FAULTY SENSOR BOARD IN THE OVERHEAD CABIN THAT HAD BURNED OUT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE SMOKE AND BURNING ODOR WAS A SMALL FAN ON THE AUTOTEMP CTLR THAT DRAWS CABIN AMBIENT AIR ACROSS A TEMP SENSOR. THE RPTR SAID THE FAN WAS COMPLETELY BURNED UP. THE RPTR STATED THE CIRCUIT BREAKER FOR THE FAN NEVER TRIPPED. THE RPTR SAID THE CIRCUIT BREAKER IS NOT ACCESSIBLE TO THE CREW INFLT BEING LOCATED IN A CABIN CLOSET UNDER THE FLOORBOARD. THE RPTR SAID THE FAA HAS MADE CONTACT WITH THE CREW.

Data retrieved from NASA's ASRS site as of July 2007 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.