EXPERIMENTAL HOMEBUILT WITH PUSHER PROP HAD A SMALL PORTION OF EXHAUST SYS BREAK OFF AND IT PASSED THROUGH PROP; CAUSING PROP BLADE FAILURE.

Narrative

PROP FAILURE; PART OF 1 BLADE OF WOODEN PROP BROKE OFF CAUSED BY FAILURE OF EXHAUST SYS. ABOUT 6 INCHES OF R EXHAUST PIPE WAS MISSING. I THINK THAT EXHAUST PIPE PIECE BROKE OFF; WENT THROUGH PROP ARC; STRIKING PROP CAUSING A FRACTURE WHICH RAPIDLY GREW CAUSING ABOUT 1/3 OF 1 PROP BLADE TO DEPART. WE WERE IN CRUISE FLT ENRTE GPS DIRECT FROM CEDAR RAPIDS TO HUTCHINSON AT 4500 FT MSL. I WAS MONITORING DSM APCH SINCE WE WOULD PASS JUST S OF THEIR AIRSPACE. ABOUT 12 MI E OF KNOXVILLE WE EXPERIENCED A VIBRATION WHICH QUICKLY BECAME VERY SEVERE. I CLOSED THE THROTTLES; MOVED MIXTURE TO IDLE CUTOFF AND SWITCHED OFF MAGNETOS. I PULLED UP TO BLEED OFF AIRSPD TO GET THE PROP STOPPED. THIS HAPPENED AT 58 KIAS. ESTABLISHED BEST GLIDE AND CONTACTED DSM APCH FOR VECTORS TO NEAREST ARPT. THEY ESTABLISHED RADAR CONTACT AND GAVE ME A VECTOR TO KNOXVILLE ARPT. IT BECAME APPARENT WE COULD NOT REACH THE ARPT SO LOOKED FOR POSSIBLE SITES AND SELECTED A PORTION OF HWY 92. MADE A R PATTERN AND LANDED ABOUT 10 MI E OF KNOXVILLE. NO DAMAGE TO ACFT OR GND VEHICLES OR PEOPLE. REMOVED ACFT TO KNOXVILLE ARPT FOR REPAIR.