SMA HAS ROUGH ENG; MAKES OFF ARPT LNDG.

Narrative

DURING THE 'MESSAGE DROP EVENT' AT THE NIFA COMPETITION HELD IN CLEVELAND; MS; MY PAX AND I WERE MAKING OUR DROP RUN OVER THE ARPT. WE WERE AT 250 FT AGL AND WERE FLYING AT CRUISE PWR (2350 RPM AND 95 KTS). AFTER MY PAX MADE HIS FINAL DROP I APPLIED FULL THROTTLE AND RAISED THE NOSE OF THE PLANE. THE PLANE IS AN SMA. AFTER CLBING TO 400 FT AGL THE ENG ON OUR PLANE BEGAN TO RUN VERY ROUGH AND WAS SHAKING THE FRONT OF THE PLANE VIOLENTLY. I IMMEDIATELY CHKED TO SEE IF MY FUEL VALVE WAS STILL ON (IT WAS); AND IF MY PRIMER WAS IN AND LOCKED (IT WAS). AS MY PLANE BEGAN LOSING ALT; I RADIOED THE TWR AND ASKED FOR AND RECEIVED AN IMMEDIATE CLRNC TO LAND. THE TWR THEN CLRED THE AREA OF TFC (THERE WERE 4 OTHER SMAS IN THE PATTERN). THE TWR THEN INFORMED ME THAT I WOULD HAVE A 10 KT TAILWIND ON FINAL. I TURNED THE PLANE 135 DEGS TO A 45 DEG ENTRY FOR FINAL. AT APPROX 50 FT AGL I TURNED FINAL. BY THIS TIME I HAD PULLED THE THROTTLE TO IDLE AND HAD APPLIED FULL FLAPS. AFTER XING THE NUMBERS I WAS STILL TOO FAST TO LAND ON THE RWY (75-80 KTS). THE TAILWIND I HAD WAS NOT HELPING AS YOU CAN IMAGINE. THE RWY AT CLEVELAND IS APPROX 3000 FT LONG. ABOUT 2/3 OF THE WAY DOWN THE RWY I REALIZED THAT I COULD NOT MAKE A SAFE LNDG. I THEN APPLIED FULL PWR AND BEGAN RAISING THE FLAPS (IT WAS LATER DISCOVERED THAT I HAD LOST 6 OUT OF 8 SPARK PLUGS DUE TO A HVY CONCENTRATION OF LEAD BUILD-UP). I HAD BARELY ENOUGH PWR AND AIRSPD TO CLR THE PWRLINES AT THE S END OF THE RWY. AFTER CLRING THESE LINES; THE AIRPLANE BEGAN TO DSND. I TURNED THE AIRPLANE TO AVOID A TREE IN MY FLT PATH. BY THIS TIME I STILL HAD 10 DEGS OF FLAPS IN. ONCE CLR OF THE TREE THERE WAS ANOTHER SET OF PWRLINES. NOT HAVING THE PWR TO GO OVER THEM I WENT UNDER THEM. ONCE I WAS CLR OF THE LINES I PULLED MY THROTTLE BACK TO IDLE AND BEGAN TO ADD FLAPS. I PERFORMED A SOFT FIELD LNDG AT IDLE PWR AND FULL FLAPS INTO A MUDDY FIELD. NO DAMAGE TO ACFT. NO INJURIES. NO PERSONAL PROPERTY DAMAGE.