Narrative:

A preflight inspection was performed in accordance with the manufacturer's recommendations and the aircraft was found to be airworthy. The weight and balance was calculated and found to be well within the manufacturer's limitations. A run-up system check was performed to the manufacturer's recommendations and found to be normal and within limitations. Takeoff and initial climb out were normal and all engine instruments indicated normal and within limitations. At approximately 7500 ft MSL, engine roughness occurred. Roughness was similar to an excessively rich mixture. The mixtures were leaned slightly and the roughness subsided momentarily. At that point, all engine instruments still indicated normal and within limitations. Engine roughness reoccurred and it was determined not to be related to the fuel/air mixture. Before a magneto check could be performed, the left engine began to expel smoke profusely from the outboard underside of the cowling. The smoke was believed to have come from the exhaust stack, but it was not visible from the pilot's seat. A loss of power was noticed immediately, accompanied by a yaw to the left and decreasing left engine egt and oil pressure indications. The left engine was shut down and secured with the propeller feathered to the manufacturer's recommendations. The engine quit smoking after it was secured and no evidence of fire was found to exist. The aircraft returned to the departure airport (the nearest airport available) and a safe and uneventful landing ensued. Postflt inspection of the aircraft revealed the left propeller was difficult to rotate by hand and was accompanied by 'scraping noises' from within the engine. The left engine was found to have used 2 1/2 gals of oil during a 22 min flight (10 of those mins the engine was not operating). Cause of failure has not been determined at this time.

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Original NASA ASRS Text

Title: A BE18 PLT ON A SKYDIVER'S MISSION HAS TO RETURN WITH ONE ENG SHUT DOWN. ENG WAS RUNNING ROUGH, SPEWED SMOKE AND LOST OIL. POSTFLT FAILED TO DISCLOSE PROB.

Narrative: A PREFLT INSPECTION WAS PERFORMED IN ACCORDANCE WITH THE MANUFACTURER'S RECOMMENDATIONS AND THE ACFT WAS FOUND TO BE AIRWORTHY. THE WT AND BAL WAS CALCULATED AND FOUND TO BE WELL WITHIN THE MANUFACTURER'S LIMITATIONS. A RUN-UP SYS CHK WAS PERFORMED TO THE MANUFACTURER'S RECOMMENDATIONS AND FOUND TO BE NORMAL AND WITHIN LIMITATIONS. TKOF AND INITIAL CLBOUT WERE NORMAL AND ALL ENG INSTS INDICATED NORMAL AND WITHIN LIMITATIONS. AT APPROX 7500 FT MSL, ENG ROUGHNESS OCCURRED. ROUGHNESS WAS SIMILAR TO AN EXCESSIVELY RICH MIXTURE. THE MIXTURES WERE LEANED SLIGHTLY AND THE ROUGHNESS SUBSIDED MOMENTARILY. AT THAT POINT, ALL ENG INSTS STILL INDICATED NORMAL AND WITHIN LIMITATIONS. ENG ROUGHNESS REOCCURRED AND IT WAS DETERMINED NOT TO BE RELATED TO THE FUEL/AIR MIXTURE. BEFORE A MAGNETO CHK COULD BE PERFORMED, THE L ENG BEGAN TO EXPEL SMOKE PROFUSELY FROM THE OUTBOARD UNDERSIDE OF THE COWLING. THE SMOKE WAS BELIEVED TO HAVE COME FROM THE EXHAUST STACK, BUT IT WAS NOT VISIBLE FROM THE PLT'S SEAT. A LOSS OF PWR WAS NOTICED IMMEDIATELY, ACCOMPANIED BY A YAW TO THE L AND DECREASING L ENG EGT AND OIL PRESSURE INDICATIONS. THE L ENG WAS SHUT DOWN AND SECURED WITH THE PROP FEATHERED TO THE MANUFACTURER'S RECOMMENDATIONS. THE ENG QUIT SMOKING AFTER IT WAS SECURED AND NO EVIDENCE OF FIRE WAS FOUND TO EXIST. THE ACFT RETURNED TO THE DEP ARPT (THE NEAREST ARPT AVAILABLE) AND A SAFE AND UNEVENTFUL LNDG ENSUED. POSTFLT INSPECTION OF THE ACFT REVEALED THE L PROP WAS DIFFICULT TO ROTATE BY HAND AND WAS ACCOMPANIED BY 'SCRAPING NOISES' FROM WITHIN THE ENG. THE L ENG WAS FOUND TO HAVE USED 2 1/2 GALS OF OIL DURING A 22 MIN FLT (10 OF THOSE MINS THE ENG WAS NOT OPERATING). CAUSE OF FAILURE HAS NOT BEEN DETERMINED AT THIS TIME.

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.