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.