ANC12LA058

The scheduled passenger flight was about 11 miles from its destination airport when the airplane's engine began to lose power and vibrate. After completing the "Engine Power Loss In-Flight" emergency checklist, and with no improvement in engine power or the vibration, the pilot elected to shut down the engine and performed a forced landing on a beach. During the landing, the airplane's nose landing gear folded back under the airplane, and the engine firewall sustained substantial damage. An examination of the engine revealed that the crankshaft fractured forward of the #6 bearing journal on the crankshaft through the counterweight web. The fracture surfaces were all consistent with fatigue; however, the cause of the fatigue crack initiation could not be determined.

On June 25, 2012, about 0940 Alaska daylight time, a Piper PA-32 airplane, N8908N, sustained substantial damage during a forced landing after a loss of engine power about 5 miles southeast of the Gustavus Airport, Gustavus, Alaska. The airplane was being operated by Air Excursions, Gustavus, as a visual flight rules (VFR) scheduled commuter flight under 14 Code of Federal Regulations Part 135. The pilot and three passengers were not injured. Visual meteorological conditions prevailed at the time of the accident, and company flight following procedures were in effect. The flight originated from the Juneau International Airport, Juneau, Alaska about 0923, and was destined for Gustavus. In a written statement to the National Transportation Safety Board (NTSB) investigator-in-charge, the pilot stated that the departure and initial portion of the flight were uneventful. About 11 miles from Gustavus, the engine began to lose power, and the airplane started shaking. He performed the emergency procedures checklist for "Engine Power Loss In-Flight," but the power loss and shaking continued to worsen. About 8 miles from Gustavus, he elected to shut the engine down, and performed a forced landing on a beach. During the landing, the airplane's nose landing gear folded back under the airplane, and the engine firewall sustained substantial damage. Initial examination of the engine by a Federal Aviation Administration inspector revealed that there was a bulge in the engine crankcase, and the propeller was difficult to rotate by hand. Maintenance record entries indicate that the operator was troubleshooting engine vibration problems in the accident airplane since at least March 10, 2012. The airplane was equipped with a Lycoming IO-540 engine. A postaccident examination of the engine's internal components was performed by a Materials Research Engineer at the NTSB Materials Laboratory. The tests revealed that the crankshaft fractured forward of the #6 bearing journal on the crankshaft through the counterweight web. The fracture surfaces were all consistent with fatigue. No other indications of other failure modes were found, and damage to the other internal engine components were consistent with overstress damage sustained after the crankshaft failed. The cause of the fatigue crack initiation could not be determined. A copy of the Materials Laboratory report can be found in the public docket for this accident.