# NTSB ANC92FA164: Mcdonnell Douglas 369D, N1096X, Eagle, AK, September 11, 1992

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: September 11, 1992, 09:10 local (17:10 UTC)
- Place: Eagle, AK
- Coordinates: 64.430587, -141.220458 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=64.4306&lon=-141.2205&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 3 fatal
- Status: Completed, report September 17, 1993
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- ADs cited in the narratives: AD 91-17-04 (OpenAirDocs)
- NTSB case key (mKey): 5651
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC92FA164
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5651/pdf
- Page: https://openairdocs.org/ntsb/ANC92FA164

## Probable cause

AN INFLIGHT FATIGUE FAILURE AND SEPARATION OF A MAIN ROTOR BLADE, INADEQUATE OPERATOR MAINTENANCE AND INSPECTION, AND MATERIAL DEFECT.

## Sequence of events

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

- Airframe/component/system failure/malfunction, approach
  - rotor system,main rotor blade - fatigue (cause)
  - inadequate quality control, manufacturer (cause)
  - rotor system,main rotor blade - separation (cause)
  - maintenance,compliance with ad - not performed, company maintenance personnel (cause)
- Loss of control - in flight, approach
- In flight collision with terrain/water, approach

## Analysis

SHORTLY AFTER TAKEOFF THE PILOT RADIOED HE WAS RETURNING DUE TO POOR VISUAL FLIGHT CONDITIONS, AND WAS LAST SEEN CIRCLING THE EAGLE RUNWAY. THE WRECKAGE WAS FOUND APRX 7 HRS LATER 150 YDS NORTH OF THE RUNWAY. THE BLUE M/R BLADE WAS FOUND SEPARATED; THE TRAILING ATTACHMENT LUGS OF BOTH THE UPPER AND LOWER BLADE ROOT FITTINGS WERE FRACTURED THROUGH THE HOLES, AND THE LEAD LAG DAMPENER LUG WAS ALSO FRACTURED. METALLURGICAL EXAMINATION REVEALED FATIGUE PROGRESSION ON ALL FOUR ROOT FRACTURES. OPERATOR MAINTENANCE PERSONNEL STATED THAT THEY WERE NOT AWARE OF AD91-17-04 REQUIREMENT TO REMOVE & INSPECT THE M/R BLADES AT 100-HR INTERVALS.

## Aircraft

- Registration: [N1096X](https://openairdocs.org/deregistered/N1096X-1997-02-19), registration cancelled 1997-02-19, S/N 1100836D (OpenAirDocs)
- Reported make and model: MCDONNELL DOUGLAS 369D
- Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs)
- Category: Helicopter
- Serial number: 110836D
- Airframe hours: 3023
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Destroyed
- Flight: Part 135
- Operator: Tundra Copters Inc.
- Registered owner: Tundra Copters Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, August 14, 1992, 57 hours before
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane, helicopter; medical: class 2, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 3,779 total, 281 in this make and model, 3,644 as pilot in command, 205 in the last 90 days, 61 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 1 statute miles
- Temperature: 34 °F, dew point -0 °F

## 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 19920911036509A](https://openairdocs.org/incident/19920911036509A), Sep 11, 1992: Hughes 369D, Eagle, AK, Destroyed, 3 fatal. Main rotor attach bolts and lead lag links failed in fatigue. Caused blade loss. AD on main rotors not complied.

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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