Narrative:

During aircraft runup, the magneto check, both checks, left and right indicated roughness and excessive drop in RPM. We decided to attempt to clean out any buildup that might be causing it and advanced the throttle, then leaned the mixture. As soon as the mixture started to lean, the engine backfired and attempted to die out. We decided to return to base and advanced mixture and reduced throttle. At this time, I smelled something burning. The smell increased and then I noticed smoke coming over the cowling. We immediately shut the engine down and exited the aircraft to investigate. A large amount of bluish (oil smell) smoke was coming out of the lower area of the cowling, around the nose wheel. We checked the oil filler area (we had added no oil before flight) and other areas as best we could see, and found no evidence of fire or smoke cause. We notified our company and ground control (ground control wanted us to get back in the aircraft and finally agreed to let us stay 'beside' the aircraft when we explained the smoke problem), requesting assistance. Airport security, a fire truck and our maintenance people arrived, about 10, 15 and 20 mins later, in above order. The only error we feel we made was, after the engine was successfully shut down, we realized we had not turned the fuel control knob to off. In our investigative process, we really did not want to reenter the aircraft to do this. It should have been done before we exited the aircraft to investigate. We truly did not realize the seriousness of the problem. No fire was found, and in fact, our maintenance department so far says aircraft is fine.

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Original NASA ASRS Text

Title: INSTRUCTOR PLT AND TRAINEE EVACUATE ACFT ON TXWY AFTER RUNUP ATTEMPT CREATES SMOKE EMANATIONS FROM ACFT ENGINE.

Narrative: DURING ACFT RUNUP, THE MAGNETO CHK, BOTH CHKS, LEFT AND RIGHT INDICATED ROUGHNESS AND EXCESSIVE DROP IN RPM. WE DECIDED TO ATTEMPT TO CLEAN OUT ANY BUILDUP THAT MIGHT BE CAUSING IT AND ADVANCED THE THROTTLE, THEN LEANED THE MIXTURE. AS SOON AS THE MIXTURE STARTED TO LEAN, THE ENG BACKFIRED AND ATTEMPTED TO DIE OUT. WE DECIDED TO RETURN TO BASE AND ADVANCED MIXTURE AND REDUCED THROTTLE. AT THIS TIME, I SMELLED SOMETHING BURNING. THE SMELL INCREASED AND THEN I NOTICED SMOKE COMING OVER THE COWLING. WE IMMEDIATELY SHUT THE ENG DOWN AND EXITED THE ACFT TO INVESTIGATE. A LARGE AMOUNT OF BLUISH (OIL SMELL) SMOKE WAS COMING OUT OF THE LOWER AREA OF THE COWLING, AROUND THE NOSE WHEEL. WE CHKED THE OIL FILLER AREA (WE HAD ADDED NO OIL BEFORE FLT) AND OTHER AREAS AS BEST WE COULD SEE, AND FOUND NO EVIDENCE OF FIRE OR SMOKE CAUSE. WE NOTIFIED OUR COMPANY AND GND CTL (GND CTL WANTED US TO GET BACK IN THE ACFT AND FINALLY AGREED TO LET US STAY 'BESIDE' THE ACFT WHEN WE EXPLAINED THE SMOKE PROB), REQUESTING ASSISTANCE. ARPT SECURITY, A FIRE TRUCK AND OUR MAINT PEOPLE ARRIVED, ABOUT 10, 15 AND 20 MINS LATER, IN ABOVE ORDER. THE ONLY ERROR WE FEEL WE MADE WAS, AFTER THE ENG WAS SUCCESSFULLY SHUT DOWN, WE REALIZED WE HAD NOT TURNED THE FUEL CTL KNOB TO OFF. IN OUR INVESTIGATIVE PROCESS, WE REALLY DID NOT WANT TO REENTER THE ACFT TO DO THIS. IT SHOULD HAVE BEEN DONE BEFORE WE EXITED THE ACFT TO INVESTIGATE. WE TRULY DID NOT REALIZE THE SERIOUSNESS OF THE PROB. NO FIRE WAS FOUND, AND IN FACT, OUR MAINT DEPT SO FAR SAYS ACFT IS FINE.

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.