Accident Details
On August 4, 2008, at approximately 1550 Alaska daylight time, a twin-engine Piper PA-31 airplane, registration N40YR, sustained substantial damage following a loss of engine power during the takeoff and initial climb phase. The aircraft was operating as Frontier Flying Service Inc. Flight 8606, a visual flight rules (VFR) scheduled domestic commuter flight under Title 14 CFR Part 135. The flight was en route from Aniak to Shageluk, Alaska. Visual meteorological conditions prevailed, and company VFR flight following procedures were in effect.
The airline transport certificated pilot was not injured. Among the passengers, one received serious injuries, two received minor injuries, and four were not injured.
Emergency Landing
The aircraft had just departed runway 28 at Aniak, and was approximately 130 pounds below its maximum gross weight. At about 200 feet above ground level, the pilot reported a loss of engine power in the left engine, and ground witnesses observed smoke emanating from that engine. The pilot feathered the left engine, but due to the airplane's descent, he elected to make an emergency landing on a gravel bar with the landing gear extended. During touchdown, the nose landing gear collapsed, resulting in structural damage to the fuselage and wings.
Post-Accident Examination
Following the accident, the operator's maintenance personnel removed the left engine from the airframe and shipped it to an engine repair facility in Anchorage, Alaska. On August 15, 2008, the left engine, which was equipped with a turbocharger, was examined at the facility. The examination was overseen by an NTSB air safety investigator and attended by representatives from the operator and the FAA.
The engine was placed on a test stand and started, but it would not produce power above ambient pressure as measured in manifold pressure. The turbocharger was then removed and replaced. A second engine run with the new turbocharger resulted in the engine developing full power.
Turbocharger Failure
The original turbocharger was disassembled and inspected. The inspection revealed that one of the turbine shaft bearings had failed, causing damage to the turbine shaft and blades. Additionally, one thrust bearing had fractured, and half of that bearing was missing.