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Atlas / NTSB / SEA91LA128

NTSB CAROL · Event

Event SEA91LA128

1991-06-07 BAGGS, Wyoming, United States None 1 aircraft Status: Completed

Aircraft involved

Probable cause & findings

EXHAUST VALVE FAILURE, RESULTING IN A PARTIAL POWER LOSS. CONTRIBUTING FACTORS WERE LOW ALTITUDE AND ROUGH/UNEVEN TERRAIN.

Factual narrative

THE PILOT OF THE ENSTROM F280C STATED THAT HE HEARD A LOUD NOISE WHILE FLYING AT 50-100 FEET AGL. HE THEN DESCENDED TO A FORCED LANDING AS THE ENGINE RPM DECREASED. HE SET THE AIRCRAFT DOWN HARD IN TALL SAGEBRUSH, CAUSING THE DOWNHILL SKID TO COLLAPSE. AS A RESULT OF THE HARD IMPACT THE MAIN ROTOR BLADES DROOPED AND SHEARED OFF THE TAIL BOOM. LATER INSPECTION OF THE ENGINE REVEALED THAT THE NUMBER THREE EXHAUST VALVE STEM HAD BROKEN AND THAT PARTS OF THIS VALVE HAD DESTROYED THE TURBOCHARGER AND BOTH SPARK PLUGS IN THE NUMBER THREE CYLINDER. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12

Verbatim from NTSB's published report. Source file NTSB_1991_SEA91LA128.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.