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NTSB Report
July 10, 1990 · Bell 206 B3 · N73LM
Teterboro, NJ
Overview
Report Status
Probable Cause
Event Type
Accident
Date
July 10, 1990
Injury Outcomes
No injuries (3 uninjured)
Location
Teterboro, NJ
Aircraft
Bell 206 B3
Tail Number
N73LM
Operator
Annapolis Aviation
Injuries
None
Aircraft Damage
Substantial
NTSB Number
NYC90FA156
THE PILOT WAS HOVERING WHEN HE HEARD A WHINE IN THE ENGINE THAT INCREASED IN INTENSITY. HE SAW TORQUE FLUCTUATIONS, HEARD AN EXPLOSION, AND AUTOROTATED TO THE RAMP. INVESTIGATION SHOWED THE POWER TURBINE INNER SHAFT FAILED IN TORSION DUE TO CORROSION ON THE INNER SURFACE AND THIS ALLOWED THE THIRD STAGE TURBINE WHEEL TO GO INTO OVERSPEED AND FAIL. ALLISON ISSUED THREE SERVICE BULLETINS ON THE POWER TURBINE INNER SHAFT. NONE OF THEM USED CALENDAR TIME FOR COMPLIANCE, ONLY ENGINE TOTAL TIME. THE HELICOPTER WAS 11 YEARS OLD WITH 2146 HRS TT AIRFRAME AND ENGINE. THE FIRST SCHEDULED WORK ON THE POWER TURBINE OCCURS AT 3550 HRS.
NTSB Probable Cause
FAILED POWER TURBINE SHAFT. FACTORS IN THE ACCIDENT WERE CORROSION ON THE POWER TURBINE SHAFT AND INADEQUATE MANUFACTURER'S SERVICE BULLETINS.
Full Narrative
THE PILOT WAS HOVERING WHEN HE HEARD A WHINE IN THE ENGINE THAT INCREASED IN INTENSITY. HE SAW TORQUE FLUCTUATIONS, HEARD AN EXPLOSION, AND AUTOROTATED TO THE RAMP. INVESTIGATION SHOWED THE POWER TURBINE INNER SHAFT FAILED IN TORSION DUE TO CORROSION ON THE INNER SURFACE AND THIS ALLOWED THE THIRD STAGE TURBINE WHEEL TO GO INTO OVERSPEED AND FAIL. ALLISON ISSUED THREE SERVICE BULLETINS ON THE POWER TURBINE INNER SHAFT. NONE OF THEM USED CALENDAR TIME FOR COMPLIANCE, ONLY ENGINE TOTAL TIME. THE HELICOPTER WAS 11 YEARS OLD WITH 2146 HRS TT AIRFRAME AND ENGINE. THE FIRST SCHEDULED WORK ON THE POWER TURBINE OCCURS AT 3550 HRS.
Flight
Event TypeAccident
Event Time16:59 EDT
Nearest AirportTeterboro (0nm N)
Runway0
Flight Plan FiledVFR
Aircraft FireIflt
Aircraft ExplosionNo
Aircraft
AircraftBell 206 B3
Tail NumberN73LM
Aircraft CategoryHeli
DamageSubstantial
OperatorAnnapolis Aviation
Operating RulePart 135
Engines1
Engine TypeTurboshaft
Engine DetailsAllison · 250-C20B · Turboshaft · 317
Seats5
People & Injuries
Injury SummaryNo injuries (3 uninjured)
Fatal0
Serious0
Minor0
Uninjured3
Total3
Crew 1Age 40 · Second Class
Conditions
ConditionsVMC
LightDaylight
Wind300° @ 10 kt
Visibility15 sm
CeilingBroken clouds 10000 ft
Temperature / Dew Point63 F
Altimeter29.00 inHg
Observation Time20:50
Weather SourceWFAC