MT. ST. HELENS, WA, USA
N58397
HUGHES 269C
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.
Source: NTSB Aviation Accident Database
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