Narrative:

Passenger requested that cabin temperature be increased. Cabin temperature knob was increased to the 6 O'clock position. Smell of smoke was apparent a few mins later. It then progressed to visual white smoke coming out beneath the pilot and copilot sub-panel. In addition; one of the passenger alerted the PIC of smoke coming out of the floorboard near the wing spar. Oxygen was donned and emergency was declared with center. Emergency descent was cleared to 12000 ft. On the descent; the bleed was turned off in an attempt to eliminate the smoke coming into the cockpit. To increase cockpit visibility; the cabin was placed on dump mode at 15000 ft. Smoke was still entering the cockpit and cabin despite all attempts. The battery; generators; and inverter were turned off in a further attempt to extinguish the source of smoke if it were electrically related. For fear that the situation would escalate into fire; the PIC descended below 12000 ft in an attempt to land off field. A dirt field was selected and on final; the approach was abandoned due to power lines and fences. As the plane was leveled off; it was noticeable that the smoke was no longer entering the cockpit and cabin. PIC climbed to a safe altitude and decided to reinitiate ATC communication. The battery was turned on first. Still without luck in getting the word in with center; the other generator was turned on. Finally; communication was re-established with center. The PIC requested ATC for the nearest airport. ATC advised of ZZZ which was located 30 mi to the east (GPS bearing of 115 degrees). The plane landed at ZZZ safely. Maintenance idented the source of smoke in the cockpit and forward cabin was caused by a burnt blower motor under the pilot seat. Under normal conditions; the blower turns on when additional heat is required as adjusted by the cabin temperature rheostat. The situation could possibly have been remedied early on; had the rheostat been turned down at the first sign of smoke (sense of smell).

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Original NASA ASRS Text

Title: BE90 FLT CREW SUFFERS SMOKE IN CABIN AND COCKPIT AND CONSIDERS AN OFF AIRPORT EMERGENCY LANDING. ATTEMPT IS ABANDONED WHEN SMOKE FINALLY DISSIPATES AND THEY PROCEED TO THE NEAREST SUITABLE AIRPORT FOR A SAFE LANDING.

Narrative: PAX REQUESTED THAT CABIN TEMP BE INCREASED. CABIN TEMP KNOB WAS INCREASED TO THE 6 O'CLOCK POS. SMELL OF SMOKE WAS APPARENT A FEW MINS LATER. IT THEN PROGRESSED TO VISUAL WHITE SMOKE COMING OUT BENEATH THE PLT AND COPLT SUB-PANEL. IN ADDITION; ONE OF THE PAX ALERTED THE PIC OF SMOKE COMING OUT OF THE FLOORBOARD NEAR THE WING SPAR. OXYGEN WAS DONNED AND EMER WAS DECLARED WITH CTR. EMER DSCNT WAS CLRED TO 12000 FT. ON THE DSCNT; THE BLEED WAS TURNED OFF IN AN ATTEMPT TO ELIMINATE THE SMOKE COMING INTO THE COCKPIT. TO INCREASE COCKPIT VISIBILITY; THE CABIN WAS PLACED ON DUMP MODE AT 15000 FT. SMOKE WAS STILL ENTERING THE COCKPIT AND CABIN DESPITE ALL ATTEMPTS. THE BATTERY; GENERATORS; AND INVERTER WERE TURNED OFF IN A FURTHER ATTEMPT TO EXTINGUISH THE SOURCE OF SMOKE IF IT WERE ELECTRICALLY RELATED. FOR FEAR THAT THE SITUATION WOULD ESCALATE INTO FIRE; THE PIC DSNDED BELOW 12000 FT IN AN ATTEMPT TO LAND OFF FIELD. A DIRT FIELD WAS SELECTED AND ON FINAL; THE APCH WAS ABANDONED DUE TO PWR LINES AND FENCES. AS THE PLANE WAS LEVELED OFF; IT WAS NOTICEABLE THAT THE SMOKE WAS NO LONGER ENTERING THE COCKPIT AND CABIN. PIC CLBED TO A SAFE ALT AND DECIDED TO REINITIATE ATC COM. THE BATTERY WAS TURNED ON FIRST. STILL WITHOUT LUCK IN GETTING THE WORD IN WITH CTR; THE OTHER GENERATOR WAS TURNED ON. FINALLY; COM WAS RE-ESTABLISHED WITH CTR. THE PIC REQUESTED ATC FOR THE NEAREST ARPT. ATC ADVISED OF ZZZ WHICH WAS LOCATED 30 MI TO THE E (GPS BEARING OF 115 DEGS). THE PLANE LANDED AT ZZZ SAFELY. MAINT IDENTED THE SOURCE OF SMOKE IN THE COCKPIT AND FORWARD CABIN WAS CAUSED BY A BURNT BLOWER MOTOR UNDER THE PLT SEAT. UNDER NORMAL CONDITIONS; THE BLOWER TURNS ON WHEN ADDITIONAL HEAT IS REQUIRED AS ADJUSTED BY THE CABIN TEMP RHEOSTAT. THE SITUATION COULD POSSIBLY HAVE BEEN REMEDIED EARLY ON; HAD THE RHEOSTAT BEEN TURNED DOWN AT THE FIRST SIGN OF SMOKE (SENSE OF SMELL).

Data retrieved from NASA's ASRS site as of May 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.