20120316006359A

An aircraft that was registered to, and operated by a local flight school, experienced a total loss of engine power while in cruise flight near Pensacola, Florida. The pilot subsequently made an off airport forced landing into the Pensacola bay. The certificated flight instructor and student pilot were not injured. A passing boat picked them up after a short time in the water. The airplane sustained impact damage and was submerged in salt water for 12 hours. The aircraft had departed from the Pensacola gulf coast regional airport (pns), Pensacola, FL about 0915 CST. A borescope inspection was preformed on all cylinders and all cylinders moved normally. As the propeller was turned, there was no fire on the impulse coupling. The right magneto was removed to have access to the aft accessory drive gears. The propeller was turned and no movement was observed on the accessory gears. Internal engine failure was suspected due to results of field examination to the engine. Aircraft was transported to atlanta salvage, in griffin, Georgia for further investigation. The engine, after removal of the accessories was rotated by hand utilizing the undamaged propeller. Continuity was not obtained to the rear accessory pad, removal of the accessory pad revealed that the crankshaft gear lockplate and screw were absent and the crankshaft gear rotated smoothly revealing that the stepped dowel was fractured flush with the crankshaft. No defects were noted on the crankcase and the two crankcase halves. The four cylinders were removed and the lifters, cylinder heads, and inside of the cylinders were examined with no defects noted. The crankcase was disassembled and the crankshaft and camshaft were removed and examined with no defects noted. The oil pan exhibited no damage and a small amount of oil remained with saltwater. The missing crankshaft gear lockplate and screw were not found in the oil pan. The dowel and crankshaft gear were retained and sent to the NTSB materials laboratory for examination.