Narrative:

During flight my flight crew and I experienced smoke in the cockpit and we chose to declare an emergency. The event occurred during a descent from 17000 ft MSL in IFR and icing conditions. Center had given a vector of 090 degrees and a descent from 17000 ft to an altitude of 14000 ft. As we encountered the icing conditions; the captain turned on the appropriate anti-icing equipment. Soon thereafter; we received a cas message for l-hand elevator horn heat fail. Due to the icing conditions; the captain chose to reset the system by turning the l-hand heat off; then on again. Moments later we received the same cas message as previously stated. Soon thereafter; I stated that I smelled smoke and asked the captain if he could smell smoke. He responded yes. The flight attendant at the rear of the cabin also responded that she detected the smell of smoke. Then both the captain and I noticed a light haze of smoke appearing in the cockpit. The captain immediately declared an emergency and asked for a direct vector for our destination which was less than 50 NM from our location. As we started a rapid descent and exited the icing conditions the smoke cleared rapidly from the cockpit. We landed without incident. An aircraft mechanic performed inspections. It was determined that the cause of smoke was a relay located under the captain's seat. The l-hand elevator horn heat was MEL'ed and all appropriate actions were taken by the captain and mechanic to assure a safe and legal operation of the aircraft. The mechanic that repaired the aircraft stated that the electrical relay for the l-hand elevator horn heat had indeed overheated and was damaged. All crew members did experience a burning sensation in the eyes and throat after the event. I believe that this problem can be prevented by not resetting a system until the QRH has been reviewed and followed.

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Original NASA ASRS Text

Title: DO328 TURBOJET ENCOUNTERS SMOKE IN CABIN AND COCKPIT WHEN CIRCUIT BREAKER FOR FAILED ANTI-ICE EQUIP IS RESET DURING ICING CONDITIONS.

Narrative: DURING FLT MY FLT CREW AND I EXPERIENCED SMOKE IN THE COCKPIT AND WE CHOSE TO DECLARE AN EMER. THE EVENT OCCURRED DURING A DSCNT FROM 17000 FT MSL IN IFR AND ICING CONDITIONS. CTR HAD GIVEN A VECTOR OF 090 DEGS AND A DSCNT FROM 17000 FT TO AN ALT OF 14000 FT. AS WE ENCOUNTERED THE ICING CONDITIONS; THE CAPT TURNED ON THE APPROPRIATE ANTI-ICING EQUIP. SOON THEREAFTER; WE RECEIVED A CAS MESSAGE FOR L-HAND ELEVATOR HORN HEAT FAIL. DUE TO THE ICING CONDITIONS; THE CAPT CHOSE TO RESET THE SYS BY TURNING THE L-HAND HEAT OFF; THEN ON AGAIN. MOMENTS LATER WE RECEIVED THE SAME CAS MESSAGE AS PREVIOUSLY STATED. SOON THEREAFTER; I STATED THAT I SMELLED SMOKE AND ASKED THE CAPT IF HE COULD SMELL SMOKE. HE RESPONDED YES. THE FLT ATTENDANT AT THE REAR OF THE CABIN ALSO RESPONDED THAT SHE DETECTED THE SMELL OF SMOKE. THEN BOTH THE CAPT AND I NOTICED A LIGHT HAZE OF SMOKE APPEARING IN THE COCKPIT. THE CAPT IMMEDIATELY DECLARED AN EMER AND ASKED FOR A DIRECT VECTOR FOR OUR DEST WHICH WAS LESS THAN 50 NM FROM OUR LOCATION. AS WE STARTED A RAPID DSCNT AND EXITED THE ICING CONDITIONS THE SMOKE CLRED RAPIDLY FROM THE COCKPIT. WE LANDED WITHOUT INCIDENT. AN ACFT MECH PERFORMED INSPECTIONS. IT WAS DETERMINED THAT THE CAUSE OF SMOKE WAS A RELAY LOCATED UNDER THE CAPT'S SEAT. THE L-HAND ELEVATOR HORN HEAT WAS MEL'ED AND ALL APPROPRIATE ACTIONS WERE TAKEN BY THE CAPT AND MECH TO ASSURE A SAFE AND LEGAL OP OF THE ACFT. THE MECH THAT REPAIRED THE ACFT STATED THAT THE ELECTRICAL RELAY FOR THE L-HAND ELEVATOR HORN HEAT HAD INDEED OVERHEATED AND WAS DAMAGED. ALL CREW MEMBERS DID EXPERIENCE A BURNING SENSATION IN THE EYES AND THROAT AFTER THE EVENT. I BELIEVE THAT THIS PROB CAN BE PREVENTED BY NOT RESETTING A SYS UNTIL THE QRH HAS BEEN REVIEWED AND FOLLOWED.

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.