NTSB Identification: ANC08LA097
Scheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Monday, August 04, 2008 in Aniak, AK
Probable Cause Approval Date: 04/15/2009
Aircraft: PIPER PA-31-350, registration: N40YR
Injuries: 1 Serious,2 Minor,5 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airline-transport-certificated pilot was departing in a twin-engine airplane that was about 130 pounds below its maximum gross weight. About 200 feet above the ground, the pilot reported a loss of engine power in the left engine and smoke was seen coming from the left engine by ground witnesses. The pilot indicated that he feathered the left engine, but that the airplane was descending and he elected to make an emergency landing on a gravel bar about .5 mile from the airport. Following the accident, the operator's maintenance personnel removed the left engine from the airframe and shipped it to an engine repair facility for examination. The airplane's left engine, which was equipped with a turbocharger, was placed on a test stand where it was started and ran, but it would not produce power (measured in manifold pressure) above ambient pressure. The engine's turbocharger was removed and replaced. A second engine run, with the new turbocharger installed, resulted in the engine developing full power. The original turbocharger was disassembled and inspected. The inspection revealed that one of the turbine shaft bearings had failed and that the turbine shaft and blades were damaged. One thrust bearing had fractured, with half of the bearing missing.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A partial loss of engine power during takeoff due to a failure of the left engine's turbocharger as a result of the failure of a turbine shaft bearing. Contributing to the accident was unsuitable terrain for a forced landing. Full narrative available
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