WHEN REDUCING ENG PWR IN PREPARATION FOR LNDG; THE ENG STOPPED AS THE RESULT OF A FAILED CAMSHAFT DRIVE GEAR. EMER LNDG ON A BEACH COMPLETED WITH SOME DAMAGE AND NO INJURY.

Narrative

I WAS SCHEDULED TO FLY AN INTRODUCTORY FLT. WE PREFLTED THE AIRPLANE; INCLUDING STICKING THE FUEL TANKS FOR QUANTITY; WHICH WAS MORE THAN ADEQUATE (19 GALLONS) FOR THE PROPOSED 40 MIN FLT. WE DEPARTED ZZZ AND PROCEEDED TO THE MARSH TO PRACTICE TURNS AND COORD MANEUVERS AT 1500 FT. AFTER FLYING FOR ABOUT 1/2 HR; I DECIDED TO RETURN TO THE ARPT TO DEMONSTRATE THE TFC PATTERN AND LNDG. AT THE TIME; WE WERE OVER THE MARSH. SHORTLY AFTER REDUCING ENG PWR TO 2000 RPM; THE ENG STOPPED WITHOUT WARNING. THERE WAS NO ROUGHNESS; BACKFIRING; OR UNUSUAL NOISE. I MADE AN IMMEDIATE CHK OF THE ENG CTLS; FINDING NO DISCREPANCY. I DECLARED AN EMER OVER THE RADIO (REPEATED TWICE); AND INCLUDED MY INTENTION TO LAND ON THE BEACH. THE ENG CONTINUED TO WINDMILL UNTIL SLOWING THE AIRSPD JUST PRIOR TO TOUCHDOWN. THE ACFT ROLLED FOR ABOUT 300 FT UNTIL THE NOSEWHEEL DUG INTO SOFT SAND; AT WHICH TIME THE NOSEWHEEL SEPARATED FROM THE AIRFRAME. THE OCCUPANTS DEPLANED; ASCERTAINED THAT NEITHER WAS INJURED; AND CALLED FOR ASSISTANCE ON A PORTABLE TELEPHONE. SUBSEQUENT INVESTIGATION DETERMINED THAT THE ENG FAILURE WAS CAUSED BY A FAILURE OF THE CAMSHAFT DRIVE GEAR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ACFT INVOLVED WAS A C152 WITH THE ENG DUE FOR ITS NEXT OVERHAUL IN APPROX 400 HRS. SO FAR; IT WAS DETERMINED THAT THE DRIVE GEAR HAD BECOME LOOSE SO THAT IT WAS NO LONGER ENGAGED. THE INVESTIGATION CONTINUES AT THE MANUFACTURER.