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NTSB Report
October 2, 1991 · Piper PA-31-350 · N200AK
Fairbanks, AK
Overview
Report Status
Probable Cause
Event Type
Incident
Date
October 2, 1991
Injury Outcomes
No injuries (5 uninjured)
Location
Fairbanks, AK
Aircraft
Piper PA-31-350
Tail Number
N200AK
Operator
Frontier Flying Service
Injuries
None
Aircraft Damage
Minor
NTSB Number
ANC92IA001
DURING CRUISE FLIGHT, THE LEFT ENGINE LOST POWER AND OIL PRESSURE. AN ENGINE TEARDOWN ANALYSIS SHOWED THAT THE CRANKSHAFT COUNTERWEIGHTS HAD TWO INCORRECT OF THE FOUR INSTALLED ROLLERS. ALL FOUR ROLLERS WERE PART NO. 73648. ACCORDING TO TEXTRON LYCOMING, THE CORRECT ROLLER CONFIGURATION SHOULD HAVE BEEN 'TWO PART NO. 73648 5.1 ORDER AND TWO PART NO. 76788 6.3 ORDER ROLLERS.' AS CONFIGURED, THE ENGINE WOULD EXPERIENCE UNACCEPTABLE 6TH ORDER TORSIONAL VIBRATIONS.
NTSB Probable Cause
INCORRECT INSTALLATION OF CRANKSHAFT COUNTERWWEIGHT ROLLERS BY THE MANUFACTURER DURING REMANUFACTURE OF THE ENGINE. FACTOR WAS THE INADEQUATE SURVEILLANCE OF THE ENGINE ASSEMBLY PROCESS BY THE MANUFACTURER.
Full Narrative
DURING CRUISE FLIGHT, THE LEFT ENGINE LOST POWER AND OIL PRESSURE. AN ENGINE TEARDOWN ANALYSIS SHOWED THAT THE CRANKSHAFT COUNTERWEIGHTS HAD TWO INCORRECT OF THE FOUR INSTALLED ROLLERS. ALL FOUR ROLLERS WERE PART NO. 73648. ACCORDING TO TEXTRON LYCOMING, THE CORRECT ROLLER CONFIGURATION SHOULD HAVE BEEN 'TWO PART NO. 73648 5.1 ORDER AND TWO PART NO. 76788 6.3 ORDER ROLLERS.' AS CONFIGURED, THE ENGINE WOULD EXPERIENCE UNACCEPTABLE 6TH ORDER TORSIONAL VIBRATIONS.
Flight
Event TypeIncident
Event Time13:20 AKDT
Nearest Airport0nm N
Runway0
Flight Plan FiledVFR
Aircraft FireIflt
Aircraft ExplosionIflt
Aircraft
AircraftPiper PA-31-350
Tail NumberN200AK
Aircraft CategoryAir
DamageMinor
OperatorFrontier Flying Service
Operating RulePart 135
Engines2
Engine TypeReciprocating
Engine DetailsLycoming · TIO-540J2BD · Reciprocating · 350
Seats10
People & Injuries
Injury SummaryNo injuries (5 uninjured)
Fatal0
Serious0
Minor0
Uninjured5
Total5
Crew 1Age 35 · First Class
Conditions
ConditionsVMC
LightDaylight
WindCalm
Visibility99 sm
CeilingNone
Temperature / Dew Point39 C / 0 C
Altimeter30.00 inHg
Weather SourcePILO