# NTSB SEA90LA023: Hughes 369D, N446TN, Stayton, OR, November 29, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: November 29, 1989, 11:45 local (19:45 UTC)
- Place: Stayton, OR
- Coordinates: 44.809211, -122.719383 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.8092&lon=-122.7194&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report June 25, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 41153
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA90LA023
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41153/pdf
- Page: https://openairdocs.org/ntsb/SEA90LA023

## Probable cause

THE MAINTENANCE PERSONNEL FAILED TO RECORD THE PREVIOUS FLIGHT TIME FOR THE OVERRUNNING CLUTCH ON AIRWORTHINESS CERTIFICATION DOCUMENTS WHEN THE ASSEMBLY WAS OVERHAULED. ALSO, CAUSAL TO THE ACCIDENT WAS THE OPERATION OF THE AIRCRAFT BY THE OPERATOR FOR 175 HOURS AFTER MANDATORY RETIREMENT TIME FOR THE SPRAGUE ASSEMBLY.

## 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,freewheeling sprag unit - failure,total (cause)
  - maintenance,recordkeeping - improper, other maintenance personnel (cause)
  - maintenance,replacement - not performed, company maintenance personnel (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

WHILE HOVERING TO PICK UP AN EXTERNAL LOAD, THE PILOT EXPERIENCED LOSS OF ROTOR RPM AND EXECUTED A HOVERING AUTOROTATION. THE ACFT IMPACTED THE GROUND AND WAS SUBSTANTIALLY DAMAGED. EXAMINATION OF THE OVERRUNNING CLUTCH REVEALED FATIGUE FAILURE OF THE OVERRUNNING CLUTCH ASSY. WHEN THE CLUTCH WAS OVERHAULED, THE PREVIOUS TIME WAS LISTED AS UNKNOWN. IT WAS INSTALLED ON THE ACCIDENT ACFT AND OPERATED 175 HOURS PAST MANDATORY REPLACEMENT.

## Aircraft

- Registration: [N446TN](https://openairdocs.org/deregistered/N446TN-1990-07-09), registration cancelled 1990-07-09, S/N 1211037D (OpenAirDocs)
- Reported make and model: HUGHES 369D
- Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1211037D
- Airframe hours: 3688
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Other work use, Part 133
- Operator: Associated Helicopter Svcs
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, November 26, 1989, 15 hours before
- Departed: NONE, STAYTON, OR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 43; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 10,780 total, 1,720 in this make and model, 10,750 as pilot in command, 130 in the last 90 days, 112 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Instrument (IMC), Day
- Wind: calm
- Visibility: 1 statute miles
- Lowest ceiling: 200 ft overcast
- Temperature: 37 °F, dew point 37 °F
- Altimeter: 30.00 inHg
- Observed at: SLE, 13 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 19891129047789A](https://openairdocs.org/incident/19891129047789A), Nov 29, 1989: Hughes 369D, Stayton, OR, Substantial damage. Loud bang lost rotor RPM, settled, chopped tail boom. Spray clutch failed.

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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