# NTSB DEN82DA089: Enstrom F-28C, N8617J, Marmath, ND, May 17, 1982

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Final report
- Date: May 16, 1982, 18:30 local (May 17, 1982, 00:30 UTC)
- Place: Marmath, ND
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report May 16, 1983
- Report: Approved by Office Director
- NTSB case key (mKey): 71592
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN82DA089
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/71592/pdf
- Page: https://openairdocs.org/ntsb/DEN82DA089

## 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, cruise
  - engine assembly,valve,intake - fatigue (cause)
  - powerplant controls - improper use of (cause)
- Forced landing, landing - flare/touchdown
  - autorotation - not performed, pilot in command

## Analysis

THE PILOT REPORTED THAT WHILE HE WAS IN FLIGHT AT ABOUT 75 TO 80 FT AGL, THE ENGINE LOST POWER. DURING AN AUTOROTATIVE LANDING IN AN OPEN PASTURE, A SKID DUG INTO THE GROUND AND THE HELICOPTER ROLLED OVER. A SUBSEQUENT ENGINE TEARDOWN REVEALED EVIDENCE THAT THE ENGINE HAD BEEN OPERATED IN AN OVERSPEED CONDITION OVER A PROLONGED PERIOD OF TIME. THERE WAS EVIDENCE OF HIGH VALVE SEATING VELOCITIES AND BOUNCING, THE UPPER SPRING SEATS HAD BEEN STRIKING THE TOPS OF THE VALVE GUIDES, FATIGUE FAILURE OF THE KEEPERS HAD OCCURRED, AND SUBSEQUENTLY, A VALVE FAILED FROM FATIGUE.

## Aircraft

- Registration: [N8617J](https://openairdocs.org/deregistered/N8617J-1989-10-03), registration cancelled 1989-10-03, S/N 5162 (OpenAirDocs)
- Reported make and model: ENSTROM F-28C
- Registry model: [Enstrom F-28C](https://openairdocs.org/model/enstrom-f-28c) (registry code 3300407) (OpenAirDocs)
- Category: Helicopter
- Serial number: 516-2
- Airframe hours: 483
- Engines: LYCOMING HIO-360-E1BD 205 horsepower reciprocating
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Operator: Douglas Duffield
- Registered owner: Douglas Duffield
- Departed: 3U6, BAKER, MT
- Destination: ELLIS, WI

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 33; student; medical: class 3, valid medical--no waivers/lim.; flight hours: 51 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 25 statute miles
- Temperature: 135 °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 19820516019399A](https://openairdocs.org/incident/19820516019399A), May 16, 1982: Enstrm F28C, Marmarth, ND, Substantial damage. Engine quit at low altitude. Crashed on autorotation landing. Valves failed due to present and prior overspeed.

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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