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Atlas / NTSB / LAX90LA186

NTSB CAROL · Event

Event LAX90LA186

1990-05-23 LA VERNE, California, United States Airport · POC Minor 1 aircraft Status: Completed

Aircraft involved

Probable cause & findings

GROUND RESONANCE DUE TO AN INADEQUATELY MAINTAINED STRUT.

Factual narrative

THE PILOT HAD BEEN ASKED BY THE OPERATOR TO FLY THE HELICOPTER PRIOR TO THE OPERATORS SIGNING A LEASEBACK AGREEMENT WITH THE REPORTED OWNER. THE INITIAL AIR TAXI TO A HELIPAD WAS ABORTED WHEN THE HELICOPTER BEGAN TO OSCILLATE DURING A GROUND RESONANCE EVENT. PRIOR TO THIS ATTEMPT THE OLEO STRUTS APPEARED TO BE OF EQUAL EXTENSION. AFTER THE EVENT, THE OLEO STRUTS WERE LOW AND ONE WAS FLAT. ABOUT 18 DAYS LATER, AND AFTER THE PILOT HAD BEEN TOLD THAT THE STRUTS HAD BEEN TAKEN CARE OF AND THAT THE OWNER HAD BEEN FLYING THE HELICOPTER AFTER A PLANNED AIR TAXI TO A HELIPAD. THE HELICOPTER AGAIN EXPERIENCED A GROUND RESONANCE EVENT WITH SEVERE OSCILLATIONS TO THE POINT OF DESTRUCTION. THE PILOT SAID HE LOWERED THE COLLECTIVE AND DECREASED THE THROTTLE WHEN THE OSCILLATIONS BEGAN. ATTEMPTS TO OBTAIN THE MAINTENANCE RECORDS AND COMPONENTS OF THE HELICOPTER FOR TESTING WERE UNSUCCESSFUL. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12

Verbatim from NTSB's published report. Source file NTSB_1990_LAX90LA186.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.

Related research

What the literature says.

Academic papers and agency reports matching this event's aircraft type or causal vocabulary (maintenance). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.

Browse the full corpus — academia portal ↗