# NTSB SEA84LA153: Hughes 269C, N58397, Mt. St. Helens, WA, July 2, 1984

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: July 2, 1984, 14:45 local (21:45 UTC)
- Place: Mt. St. Helens, WA
- Coordinates: 46.139331, -122.799537 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=46.1393&lon=-122.7995&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor
- Status: Completed, report March 4, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 39954
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA84LA153
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/39954/pdf
- Page: https://openairdocs.org/ntsb/SEA84LA153

## Sequence of events

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

- Loss of engine power(partial) - mech failure/malf, approach - vfr pattern - final approach
  - ignition system,spark plug - worn (cause)
  - maintenance,inspection - inadequate, company maintenance personnel (cause)
  - ignition system,magneto - output low (cause)
- Hard landing, landing - flare/touchdown
  - proper descent rate - not possible, pilot in command
  - remedial action - not possible, pilot in command
- Roll over, landing - flare/touchdown
  - terrain condition - rough/uneven (contributing factor)
  - proper touchdown point - not possible, pilot in command
  - terrain condition - downhill (contributing factor)

## Analysis

THIS ACCIDENT OCCURRED AT THE 5500 FT LEVEL ON MT. ST. HELENS. DENSITY ALT AT THE TIME WAS 7500 FT. AT APRX 40-50 FT AGLENGINE AND ROTOR RPM BEGAN TO DECAY RAPIDLY. THE ACFT LANDED HARD ON A ROCK LEDGE WITH ONE SKID PARTIALLY OFF THE LEDGE.AS ROTOR RPM CONTINUED TO DECAY THE ROTOR DISC COULD NO LONGER SUPPORT THE HELICOPTER AND IT ROLLED 100 FT DOWN THE MOUNTAIN SUSTAINING SUBSTANTIAL DAMAGE. MAINTENANCE INVESTIGATION REVEALED THAT ALL SPARK PLUGS WERE SEVERLY WORN. WHEN TESTED, FOUR OUT OF EIGHT PLUGS FIRED INTERMITTENTLY. THE LEFT MAGNETO ALSO HAD BURNED POINTS.

## Aircraft

- Registration: [N58397](https://openairdocs.org/aircraft/N58397), registered now, S/N 1090833, built 1979 (OpenAirDocs)
- Reported make and model: HUGHES 269C
- Registry model: [Hughes 269C](https://openairdocs.org/model/hughes-269c) (registry code 4470504) (OpenAirDocs)
- Registry engine: [Lycoming HIO-360 series](https://openairdocs.org/engine/lycoming-hio-360-series) (registry code 41524, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1090833
- Airframe hours: 1472
- Engines: LYCOMING HIO-360-D1A 190 horsepower reciprocating
- Damage: Destroyed
- Flight: Business, Part 91
- Registered owner: Transwestern Helicopters
- Airworthiness certificate: Standard, Utility
- Departed: 1S4, SCAPPOOSE, OR
- Destination: MT ST HELENS, WA
- Airport: None

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 653 total, 282 in this make and model, 562 as pilot in command, 101 in the last 90 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 300° at 5 knots
- Visibility: 55 statute miles
- Lowest ceiling: none
- Temperature: 73 °F, dew point 54 °F
- Altimeter: 30.00 inHg
- Observed at: TDO, 25 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 19840702029719A](https://openairdocs.org/incident/19840702029719A), Jul 2, 1984: Hughes 269C, Mount St Helens, WA, Destroyed. Lost engine rpms while trying to land on a ledge. Rolled off ledge on landing. Spark plugs defective and worn.

## Other investigations on N58397 (2)

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.

- [NTSB GAA15CA197](https://openairdocs.org/ntsb/GAA15CA197), Jul 21, 2015: Hughes 269C (N58397), Atlanta, TX, substantial damage. Probable cause: The non-helicopter rated pilot's improper landing flare, which resulted in impact with terrain.
- [NTSB NYC99LA217](https://openairdocs.org/ntsb/NYC99LA217), Sep 1, 1999: Hughes 269C (N58397), Utica, NY, substantial damage. Probable cause: The pilot's failure to maintain control of the helicopter while maneuvering, which resulted in a hard landing. A factor in this accident was the pilot's lack of total experience in helicopters.

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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