Narrative:

Flight departed and climbed to 9500 ft. Approximately 40 mins into flight we heard a loud noise with immediate severe vibration from engine. I pulled throttle and mixture; but propeller was still turning about 600 RPM. I believe I also turned off the ignition switch; but I am not sure. I called an emergency on 121.5. 'Guard' responded as well as someone else; I chose to follow 'guard' instructions. After giving them the details and location; they gave me xyz approach frequency. Xyz approach gave me a choice of airports to land at. I chose ZZZ. I landed on runway 24 and turned onto taxiway lima. The propeller stopped and then we saw that the propeller was broken and about half of the blade was missing. Further inspection of engine revealed minor damage; abrasion of cowl from baffles; exhaust pipe support brackets cracked; and cowl airseal fabric abrasion. Still not sure if break was caused by bird strike or fatigue. Propeller had 649 hours. Callback conversation with reporter revealed the following information: the reporter stated the propeller was made of wood and it was manufactured by aymac-demuth. Rptedly when the manufacturer was contacted and informed me of the failure; it was acknowledged that 'they had a few failures.' the reporter advised the manufacturer the engine power had been increased but only slightly by the installation of new pistons. The manufacturer stated this was the cause of the propeller failure; ie; the increase in engine power. The reporter stated he knows of two other propeller failures on the rv-6A aircraft using this manufacturer's propeller. The propeller had a normal preflight inspection and appeared normal with no discrepancies noted.

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Original NASA ASRS Text

Title: AN RV-6A EXPERIMENTAL AT 9500 FT DECLARED AN EMER AND DIVERTED DUE TO PROPELLER FAILURE. HALF OF ONE BLADE DEPARTED ACFT.

Narrative: FLT DEPARTED AND CLBED TO 9500 FT. APPROX 40 MINS INTO FLT WE HEARD A LOUD NOISE WITH IMMEDIATE SEVERE VIBRATION FROM ENG. I PULLED THROTTLE AND MIXTURE; BUT PROP WAS STILL TURNING ABOUT 600 RPM. I BELIEVE I ALSO TURNED OFF THE IGNITION SWITCH; BUT I AM NOT SURE. I CALLED AN EMER ON 121.5. 'GUARD' RESPONDED AS WELL AS SOMEONE ELSE; I CHOSE TO FOLLOW 'GUARD' INSTRUCTIONS. AFTER GIVING THEM THE DETAILS AND LOCATION; THEY GAVE ME XYZ APCH FREQ. XYZ APCH GAVE ME A CHOICE OF ARPTS TO LAND AT. I CHOSE ZZZ. I LANDED ON RWY 24 AND TURNED ONTO TXWY LIMA. THE PROP STOPPED AND THEN WE SAW THAT THE PROP WAS BROKEN AND ABOUT HALF OF THE BLADE WAS MISSING. FURTHER INSPECTION OF ENG REVEALED MINOR DAMAGE; ABRASION OF COWL FROM BAFFLES; EXHAUST PIPE SUPPORT BRACKETS CRACKED; AND COWL AIRSEAL FABRIC ABRASION. STILL NOT SURE IF BREAK WAS CAUSED BY BIRD STRIKE OR FATIGUE. PROP HAD 649 HRS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE PROPELLER WAS MADE OF WOOD AND IT WAS MANUFACTURED BY AYMAC-DEMUTH. RPTEDLY WHEN THE MANUFACTURER WAS CONTACTED AND INFORMED ME OF THE FAILURE; IT WAS ACKNOWLEDGED THAT 'THEY HAD A FEW FAILURES.' THE RPTR ADVISED THE MANUFACTURER THE ENG POWER HAD BEEN INCREASED BUT ONLY SLIGHTLY BY THE INSTALLATION OF NEW PISTONS. THE MANUFACTURER STATED THIS WAS THE CAUSE OF THE PROPELLER FAILURE; IE; THE INCREASE IN ENG POWER. THE RPTR STATED HE KNOWS OF TWO OTHER PROPELLER FAILURES ON THE RV-6A ACFT USING THIS MANUFACTURER'S PROPELLER. THE PROPELLER HAD A NORMAL PREFLT INSPECTION AND APPEARED NORMAL WITH NO DISCREPANCIES NOTED.

Data retrieved from NASA's ASRS site as of January 2009 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.