National Transportation Safety Board
Aviation Accident Final Report
Date & Time:
08/04/2008, 1550 AKD
Powerplant sys/comp malf/fail
1 Serious, 2 Minor, 5 None
Flight Conducted Under:
Part 135: Air Taxi & Commuter - Scheduled
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.
Turbocharger - Failure (Cause)
Rough terrain - Contributed to outcome (Factor)
On August 4, 2008, about 1550 Alaska daylight time, a twin engine Piper PA-31 airplane, N40YR, sustained substantial damage following a loss of engine power during takeoff/initial climb, about 1/2 mile north of Aniak, Alaska. The airplane was being operated as a visual flight rules (VFR) scheduled domestic commuter flight under Title 14, CFR Part 135, when the accident occurred. The airplane was operated as Flight 8606, by Frontier Flying Service Inc., Fairbanks, Alaska. The airline transport certificated pilot was not injured. One passenger received serious injuries, 2 passengers received minor injuries, and 4 passengers were not injured. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect. The flight was en route to Shageluk, Alaska.
During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on August 4, the director of operations for the operator reported that the airplane had just departed runway 28 at Aniak. The airplane 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 the airplane was descending, and he elected to make an emergency landing on a gravel bar with the landing gear extended. During the touchdown, the nose landing gear collapsed. The airplane received structural damage to the fuselage and wings.
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 airplane's left engine, which was equipped with a turbocharger, was examined at the engine repair 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 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 the turbine shaft and blades were damaged. One thrust bearing had fractured and one half of the bearing was missing.
History of Flight
Powerplant sys/comp malf/fail (Defining event)
Loss of engine power (total)
Off-field or emergency landing
Airline Transport; Commercial
Multi-engine Land; Single-engine Land
Other Aircraft Rating(s):
Second Pilot Present:
Class 1 Without Waivers/Limitations
Last FAA Medical Exam:
Last Flight Review or Equivalent:
3941 hours (Total, all aircraft), 98 hours (Total, this make and model), 2846 hours (Pilot In Command, all aircraft), 293 hours (Last 90 days, all aircraft), 92 hours (Last 30 days, all aircraft), 5 hours (Last 24 hours, all aircraft)
Aircraft and Owner/Operator Information
Year of Manufacture:
Landing Gear Type:
Retractable - Tricycle
Date/Type of Last Inspection:
Certified Max Gross Wt.:
Time Since Last Inspection:
Airframe Total Time:
10047 Hours at time of accident
Installed, not activated
Frontier Flying Service Inc.
Frontier Flying Service Inc.
Operating Certificate(s) Held:
Commuter Air Carrier (135)
Operator Does Business As:
Operator Designator Code:
Meteorological Information and Flight Plan
Conditions at Accident Site:
Condition of Light:
Observation Facility, Elevation:
PANI, 88 ft msl
Distance from Accident Site:
1 Nautical Miles
Direction from Accident Site:
Lowest Cloud Condition:
Overcast / 3000 ft agl
6 knots /
Turbulence Type Forecast/Actual:
Turbulence Severity Forecast/Actual:
30.11 inches Hg
13°C / 7°C
Precipitation and Obscuration:
Aniak, AK (PANI)
Type of Flight Plan Filed:
Shageluk, AK (PAHX)
Type of Clearance:
Type of Airspace:
Runway Surface Type:
Runway Surface Condition:
6000 ft / 150 ft
Wreckage and Impact Information
1 Serious, 2 Minor, 4 None
1 Serious, 2 Minor, 5 None
Investigator In Charge (IIC):
Scott R Erickson
Additional Participating Persons:
Victor Hutchings; FAA-AL-ANC FSDO 03; Anchorage, AK
Erin Talbott; Frontier Flying Service Inc.; Fairbanks, AK
NTSB accident and incident dockets serve as permanent archival information for the NTSB’s investigations. Dockets released prior to June 1, 2009 are publicly available from the NTSB’s Record Management Division at firstname.lastname@example.org, or at 800-877-6799. Dockets released after this date are available at http://dms.ntsb.gov/pubdms/.