PA12 PILOT REPORTS NOSING OVER AFTER LANDING ON A SAND BAR IN THE RIVER.

Narrative

SEQUENCE OF EVENTS: 2 TUNDRA-TIRE (31 INCH ALASKA BUSHWHEEL TIRES) EQUIPPED ACFT LANDED UNEVENTFULLY ON THE SANDBAR. AFTER THEY TAXIED OUT OF THE WAY I LANDED IN THE SAME AREA; FOLLOWING THEIR ROLLOUT PATH. AS MY ROLLOUT WAS COMING TO AN END AND WHILE THE ACFT WAS MOVING SLOWLY; THERE WAS A LOUD NOISE FROM THE R GEAR AND SHORTLY AFTERWARDS ACFT GENTLY NOSED OVER; CAUSING A PROP STRIKE AND SUDDEN ENG STOPPAGE. THE ELT DID NOT ACTIVATE; THERE WERE NO INJURIES; AND THERE WAS NO PROPERTY DAMAGE OTHER THAN TO THE ACFT. AFTER EXITING THE ACFT AND EXAMINING THE TIRE TRACKS IN THE SAND IT APPEARED THAT 1) THE R GEAR STRUCK A 1 1/2 INCH DIAMETER TREE BRANCH PROTRUDING VERTICALLY FROM THE SAND AND APPARENTLY CAUSED THE LOUD NOISE HEARD DURING ROLLOUT; 2) THE TAILWHEEL WAS ALLOWED TO COME OFF THE SAND AS THE ACFT SLOWED DOWN; AND 3) THE SAND WAS DEEP AND SOFT. APART FROM CAUSING A MOMENTARY DISTR; THE TREE BRANCH DID NOT APPEAR TO HAVE PLAYED A ROLE IN THE NOSE-OVER. THE CAUSE APPEARED TO BE PLT ERROR: FAILURE TO KEEP THE CTL STICK FULL AFT DURING ROLLOUT. THE PROB COULD HAVE BEEN AVOIDED BY 1) RECEIVING INSTRUCTION FROM AN EXPERIENCED LCL PLT ON HOW TO RECOGNIZE AND TEST SAND CONDITIONS PRIOR TO ATTEMPTING A LNDG; 2) LNDG ON FIRMER SAND; 3) HOLDING THE STICK BACK AT ALL TIMES AFTER TOUCHDOWN; 4) FITTING THE ACFT WITH 31 INCH ALASKA BUSHWHEEL TIRES. AFTER THE NOSE-OVER; THE ACFT WAS INSPECTED. DAMAGE TO THE PROP APPEARED MINOR (MINOR LEADING EDGE NICKS; BUT NO BENDING; TWISTING OR DEFORMATION). NO DAMAGE TO THE GEAR; FIREWALL; BULKHEADS; COWLING; ENG MOUNT; WING STRUTS; OR WINGS WAS NOTED. THE SMALL NICKS IN THE PROP WERE DRESSED WITH A FILE. THE ENG WAS RUN UP AND THE PROP CYCLED AND NO ABNORMAL CONDITIONS OR VIBRATIONS WERE NOTED. THE ACFT WAS UNEVENTFULLY FLOWN BACK TO ITS HOME BASE FOR MAINT.