# NTSB NYC90FA156: Bell 206 B3, N73LM, Teterboro, NJ, July 10, 1990

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Field investigation · Final report
- Date: July 10, 1990, 16:59 local (20:59 UTC)
- Place: Teterboro, NJ
- Location: 40.8501° N, 74.0608° W: Placed by OpenAirDocs at TETERBORO (TEB), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=40.8501&lon=-74.0608&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 3 uninjured
- Status: Completed, report November 23, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 36539
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC90FA156
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/36539/pdf
- Page: https://openairdocs.org/ntsb/NYC90FA156

## Probable cause

FAILED POWER TURBINE SHAFT. FACTORS IN THE ACCIDENT WERE CORROSION ON THE POWER TURBINE SHAFT AND INADEQUATE MANUFACTURER'S SERVICE BULLETINS.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of engine power(total) - mech failure/malf, hover
  - turboshaft engine,free turbine shaft - corroded (contributing factor)
  - maintenance,service bulletin/letter - inadequate, manufacturer (contributing factor)
  - turboshaft engine,free turbine shaft - failure,total (cause)
  - turbine assembly,turbine wheel - overspeed (cause)
  - turbine assembly,turbine wheel - failure,total (cause)
- Forced landing, descent - emergency

## Analysis

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.

## Aircraft

- Registration: N73LM (not matched to a registry record)
- Reported make and model: BELL 206 B3
- Category: Helicopter
- Serial number: 2835
- Airframe hours: 2146
- Engines: ALLISON 250-C20B 317 horsepower turbo shaft
- Damage: Substantial damage
- Fire: In-Flight
- Flight: Part 135
- Operator: Annapolis Aviation, doing business as Freedom Air
- Registered owner: Annapolis Sea Going Institute
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, June 28, 1990, 19 hours before
- Departed: TEB
- Destination: BWI, BALTIMORE, MD
- Flight plan: VFR
- Airport: TEB, Teterboro

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 40; commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 3,458 total, 3,000 in this make and model, 3,176 as pilot in command, 74 in the last 90 days, 47 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 300° at 10 knots
- Visibility: 15 statute miles
- Lowest ceiling: 10,000 ft broken
- Temperature: 84 °F, dew point 63 °F
- Altimeter: 29.00 inHg
- Observed at: TEB

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19900710027779A](https://openairdocs.org/incident/19900710027779A), Jul 10, 1990: Bell 206B, Teterboro, NJ, Substantial damage. Engine whine torque varied hovering. Explosion. Autorotated. Turbine shaft failed due corrosion. Inadequate sb.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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