National Transportation Safety Board
Aviation Accident Final Report

 

 

Location:

Aniak, AK

Accident Number:

ANC08LA097

Date & Time:

08/04/2008, 1550 AKD

Registration:

N40YR

Aircraft:

PIPER PA-31-350

Aircraft Damage:

Substantial

Defining Event:

Powerplant sys/comp malf/fail

Injuries:

1 Serious, 2 Minor, 5 None

Flight Conducted Under:

Part 135: Air Taxi & Commuter - Scheduled

Analysis

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.

Probable Cause and Findings

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.

Findings

Aircraft

Turbocharger - Failure (Cause)

Environmental issues

Rough terrain - Contributed to outcome (Factor)

Factual Information

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

Initial climb

Powerplant sys/comp malf/fail (Defining event)

Loss of engine power (total)

Emergency descent

Off-field or emergency landing

 

 

Pilot Information

Certificate:

Airline Transport; Commercial

Age:

40, Male

Airplane Rating(s):

Multi-engine Land; Single-engine Land

Seat Occupied:

Left

Other Aircraft Rating(s):

Glider

Restraint Used:

Seatbelt

Instrument Rating(s):

Airplane

Second Pilot Present:

No

Instructor Rating(s):

Glider

Toxicology Performed:

No

Medical Certification:

Class 1 Without Waivers/Limitations

Last FAA Medical Exam:

06/14/2008

Occupational Pilot:

Yes

Last Flight Review or Equivalent:

07/10/2008

Flight Time:

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

Aircraft Make:

PIPER

Registration:

N40YR

Model/Series:

PA-31-350

Aircraft Category:

Airplane

Year of Manufacture:

 

Amateur Built:

No

Airworthiness Certificate:

Normal

Serial Number:

31-7952008

Landing Gear Type:

Retractable - Tricycle

Seats:

8

Date/Type of Last Inspection:

07/25/2008, AAIP

Certified Max Gross Wt.:

7368 lbs

Time Since Last Inspection:

14 Hours

Engines:

2 Reciprocating

Airframe Total Time:

10047 Hours at time of accident

Engine Manufacturer:

Lycoming

ELT:

Installed, not activated

Engine Model/Series:

TIO-54D

Registered Owner:

Frontier Flying Service Inc.

Rated Power:

350 hp

Operator:

Frontier Flying Service Inc.

Operating Certificate(s) Held:

Commuter Air Carrier (135)

Operator Does Business As:

Frontier Alaska

Operator Designator Code:

FFSA

 

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual Conditions

Condition of Light:

Day

Observation Facility, Elevation:

PANI, 88 ft msl

Distance from Accident Site:

1 Nautical Miles

Observation Time:

1556 ADT

Direction from Accident Site:

80°

Lowest Cloud Condition:

 

Visibility

10 Miles

Lowest Ceiling:

Overcast / 3000 ft agl

Visibility (RVR):

 

Wind Speed/Gusts:

6 knots /

Turbulence Type Forecast/Actual:

/

Wind Direction:

300°

Turbulence Severity Forecast/Actual:

/

Altimeter Setting:

30.11 inches Hg

Temperature/Dew Point:

13°C / 7°C

Precipitation and Obscuration:

 

Departure Point:

Aniak, AK (PANI)

Type of Flight Plan Filed:

Company VFR

Destination:

Shageluk, AK (PAHX)

Type of Clearance:

None

Departure Time:

1550 ADT

Type of Airspace:

 

 

Airport Information

Airport:

Aniak (PANI)

Runway Surface Type:

Asphalt

Airport Elevation:

88 ft

Runway Surface Condition:

Dry

Runway Used:

28

IFR Approach:

None

Runway Length/Width:

6000 ft / 150 ft

VFR Approach/Landing:

Forced Landing

 

Wreckage and Impact Information

Crew Injuries:

1 None

Aircraft Damage:

Substantial

Passenger Injuries:

1 Serious, 2 Minor, 4 None

Aircraft Fire:

None

Ground Injuries:

N/A

Aircraft Explosion:

None

Total Injuries:

1 Serious, 2 Minor, 5 None

Latitude, Longitude:

61.581667, -159.543056

 


 


Administrative Information

Investigator In Charge (IIC):

Scott R Erickson

Report Date:

04/15/2009

Additional Participating Persons:

Victor Hutchings; FAA-AL-ANC FSDO 03; Anchorage, AK

Erin Talbott; Frontier Flying Service Inc.; Fairbanks, AK

Publish Date:

04/16/2009

Investigation Docket:

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 pubinq@ntsb.gov, or at 800-877-6799. Dockets released after this date are available at http://dms.ntsb.gov/pubdms/.