# NTSB SEA89FA111: Oregon Helicopters UH-1L, N157LC, Baring, WA, June 14, 1989

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: June 14, 1989, 11:50 local (18:50 UTC)
- Place: Baring, WA
- Coordinates: 47.729724, -121.490196 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=47.7297&lon=-121.4902&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious, 1 minor
- Status: Completed, report June 26, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 40922
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA89FA111
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/40922/pdf
- Page: https://openairdocs.org/ntsb/SEA89FA111

## Probable cause

FATIGUE FAILURE OF THE TAIL ROTOR 42 DEGREE GEAR BOX DUE TO PILOT INDUCED OVERSTRESS. NAVY DATA AND FAA TYPE CERTIFICATE LIMITATIONS WERE NOT ADHERED TO.

## Sequence of events

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

- Airframe/component/system failure/malfunction, hover
  - rotor drive system,intermediate gearbox(42 deg) - overtorque (cause)
  - design stress limits of aircraft - exceeded, pilot in command (cause)
  - instructions,written/verbal - not followed, company/operator management (cause)
  - rotor drive system,intermediate gearbox(42 deg) - fatigue (cause)
- Loss of control - in flight, hover
- Hard landing, landing - flare/touchdown
  - autorotation - performed, pilot in command
- Roll over, landing - flare/touchdown

## Analysis

WHILE LIFTING A LOG THE CREW HEARD UNUSUAL NOISES & FELT VIBRATIONS. THEY RELEASED THE LOG & FLEW TO A LANDING SITE TO CHECK THE AIRCRAFT. WHILE AT A HIGH HOVER THE AIRCRAFT BEGAN SPINNING AND THE PILOT EXECUTED A HOVERING AUTOROTATION. THE AIRCRAFT LANDED HARD AND ROLLED DOWN A HILL. INVESTIGATION REVEALED A FAILED TAIL ROTOR 42 DEG GEARBOX. THE BOARD'S METALLURGICAL EXAMINATION SHOWED THAT THE GEARBOX'S INPUT SPIRAL BEVEL GEAR HAD FAILED IN FATIGUE. THE ENG N2 TORQUE WAS RED-LINED AT 55 LBS. PILOT STATED THAT A DASH-5 TRANSMISSION WAS INSTALLED RATED FOR 60 LBS, BUT OBSERVED MARKED 55 LB LIMIT. NAVY OPERATORS MANUAL AND FAA TYPE CERTIFICATE BOTH LIST N2 TORQUE LIMIT AS 50 LBS.

## Aircraft

- Registration: [N157LC](https://openairdocs.org/deregistered/N157LC-2017-09-19), registration cancelled 2017-09-19, S/N 157856, built 1969 (OpenAirDocs)
- Reported make and model: OREGON HELICOPTERS UH-1L
- Registry model: [Bell UH-1L](https://openairdocs.org/model/bell-uh-1l) (registry code 1181401) (OpenAirDocs)
- Registry engine: [Lycoming T53-L-13](https://openairdocs.org/engine/lycoming-t53-l-13) (registry code 41551, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 157856
- Airframe hours: 8299
- Engines: LYCOMING T53-L13B 1400 horsepower turbo shaft
- Damage: Destroyed
- Flight: Other work use, Part 133
- Registered owner: Timberline Air Service, Inc.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: 100 hour, June 11, 1989, 16 hours before
- Departed: BARING, WA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 44; commercial, flight instructor; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 15,000 total, 1,500 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 340° at 10 knots
- Visibility: 20 statute miles
- Lowest ceiling: 5,500 ft broken
- Temperature: 61 °F, dew point 54 °F
- Altimeter: 30.00 inHg
- Observed at: PAE, 33 nm away

## 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 19890614015569A](https://openairdocs.org/incident/19890614015569A), Jun 14, 1989: Bell UH1L, Baring, WA, Destroyed. Vibration. Dropped load, hovered prior landing. Began right spin autorotated and crashed. Tail rotor gears stripped

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.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.