Narrative:

As the flight was descending out of FL350, the captain noticed the smell of smoke in the cockpit. I (captain) asked the if he smelt it and he responded 'yes.' I immediately turned around and asked the passenger if anyone in the airplane was smoking. I asked because a few of the passenger were smokers. The response was 'no.' I then saw smoke coming out of the overhead vents in the cockpit. Since these vents receive their air from the aft baggage area, I then asked one of the passenger to look over the back seat to see if there was any smoke or fire in the area. The response was 'no.' I also asked the passenger to turn the overhead light system off just in case the smoke was originating in the ceiling area. The flight then requested radar vectors to the nearest airport since the origin of the smoke at this point was unknown. The emergency procedures were followed. The smoke had the distinct smell of an electrical origin. As the electrical load was reduced the intensity of the smoke seemed to 'level off.' it was neither decreasing nor intensifying. ATC was very cooperative and provided the flight with the assistance it needed to expedite landing. The only problem was the initial vector was to an airport that did not have long enough runways. This only caused a delay of a few mins. The aircraft landed without incident at malden municipal airport, malden, mo. ATC had called the local fire and rescue personnel. The aircraft was taxied in and the passenger and crew exited the aircraft normally and without incident. The emergency equipment arrived and were told their services were not required. The passenger were then driven to their destination and maintenance on the aircraft was started. The culprit was found to be a blower motor that had overheated. This is the same blower that supplies the cockpit overhead vents with air. The circuit breaker that protects the system was found to be in the open position. The blower motor was then removed in accordance with the master equipment list and approved maintenance procedures. The aircraft was then returned to service via the company director of maintenance and the local airframe and power plant mechanic, and the trip was completed without incident.

Related reports:

Google
 

Original NASA ASRS Text

Title: BEGINNING OF DSCNT NOTICED SMOKE DEVELOPING IN COCKPIT AND CABIN AREA. REQUESTED VECTOR AND DSCNT TO NEAREST ARPT. ELECTRICAL LOAD REDUCED, SMOKE BEGAN TO DECREASE. LAND MAW WITH EQUIP STANDING BY. MAINT FOUND BLOWER MOTOR OVERHEATED. REPLACED AND ACFT RETURNED TO SVC. L35A.

Narrative: AS THE FLT WAS DSNDING OUT OF FL350, THE CAPT NOTICED THE SMELL OF SMOKE IN THE COCKPIT. I (CAPT) ASKED THE IF HE SMELT IT AND HE RESPONDED 'YES.' I IMMEDIATELY TURNED AROUND AND ASKED THE PAX IF ANYONE IN THE AIRPLANE WAS SMOKING. I ASKED BECAUSE A FEW OF THE PAX WERE SMOKERS. THE RESPONSE WAS 'NO.' I THEN SAW SMOKE COMING OUT OF THE OVERHEAD VENTS IN THE COCKPIT. SINCE THESE VENTS RECEIVE THEIR AIR FROM THE AFT BAGGAGE AREA, I THEN ASKED ONE OF THE PAX TO LOOK OVER THE BACK SEAT TO SEE IF THERE WAS ANY SMOKE OR FIRE IN THE AREA. THE RESPONSE WAS 'NO.' I ALSO ASKED THE PAX TO TURN THE OVERHEAD LIGHT SYS OFF JUST IN CASE THE SMOKE WAS ORIGINATING IN THE CEILING AREA. THE FLT THEN REQUESTED RADAR VECTORS TO THE NEAREST ARPT SINCE THE ORIGIN OF THE SMOKE AT THIS POINT WAS UNKNOWN. THE EMER PROCS WERE FOLLOWED. THE SMOKE HAD THE DISTINCT SMELL OF AN ELECTRICAL ORIGIN. AS THE ELECTRICAL LOAD WAS REDUCED THE INTENSITY OF THE SMOKE SEEMED TO 'LEVEL OFF.' IT WAS NEITHER DECREASING NOR INTENSIFYING. ATC WAS VERY COOPERATIVE AND PROVIDED THE FLT WITH THE ASSISTANCE IT NEEDED TO EXPEDITE LNDG. THE ONLY PROB WAS THE INITIAL VECTOR WAS TO AN ARPT THAT DID NOT HAVE LONG ENOUGH RWYS. THIS ONLY CAUSED A DELAY OF A FEW MINS. THE ACFT LANDED WITHOUT INCIDENT AT MALDEN MUNICIPAL ARPT, MALDEN, MO. ATC HAD CALLED THE LCL FIRE AND RESCUE PERSONNEL. THE ACFT WAS TAXIED IN AND THE PAX AND CREW EXITED THE ACFT NORMALLY AND WITHOUT INCIDENT. THE EMER EQUIP ARRIVED AND WERE TOLD THEIR SVCS WERE NOT REQUIRED. THE PAX WERE THEN DRIVEN TO THEIR DEST AND MAINT ON THE ACFT WAS STARTED. THE CULPRIT WAS FOUND TO BE A BLOWER MOTOR THAT HAD OVERHEATED. THIS IS THE SAME BLOWER THAT SUPPLIES THE COCKPIT OVERHEAD VENTS WITH AIR. THE CIRCUIT BREAKER THAT PROTECTS THE SYS WAS FOUND TO BE IN THE OPEN POS. THE BLOWER MOTOR WAS THEN REMOVED IN ACCORDANCE WITH THE MASTER EQUIP LIST AND APPROVED MAINT PROCS. THE ACFT WAS THEN RETURNED TO SVC VIA THE COMPANY DIRECTOR OF MAINT AND THE LCL AIRFRAME AND POWER PLANT MECH, AND THE TRIP WAS COMPLETED WITHOUT INCIDENT.

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.