ASN Wikibase Occurrence # 226165
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| Date: | Thursday 13 June 2019 |
| Time: | 12:20 LT |
| Type: | Experimental Cub |
| Owner/operator: | Private |
| Registration: | N9WU |
| MSN: | 0003 |
| Year of manufacture: | 2013 |
| Engine model: | Lycoming O-320-B2C |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | near Stanley, Custer County, ID -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Burley Municipal Airport, ID (BYI/KBYI) |
| Yellow Pine, ID (3U2) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While overflying mountainous terrain, the airplane encountered turbulence. The pilot heard a 'pop' from the right wing and shortly thereafter, the wing began to shake violently. The pilot was maneuvering the airplane to a forced landing site when the airplane encountered turbulence again and subsequently entered a spin that continued until impact with terrain.
The accident site was adjacent to a mountain range where strong thermals likely existed as well as an unstable low-level pressure system. This is likely the cause of the localized turbulence that was encountered by the flight.
Examination of the wing spar revealed in-plane fractures consistent with tensile overstress failure. The fracture sequence started with the fracture of the wing spar, which led to subsequent spar fractures, and eventual buckling and fracture of the connected supporting members and struts. It is likely that the turbulence encounter resulted in excessive loads on the wing and subsequent overstress failure.
Probable Cause: Overstress failure of the right-wing spar due to an encounter with turbulence.
Accident investigation:
 |
|
Sources:
NTSB WPR19LA170
FAA register: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=9WU
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Jun-2019 20:07 | Captain Adam | Added |
| 14-Jun-2019 22:07 | RobertMB | Updated [Time, Aircraft type, Registration, Cn, Operator, Nature, Source, Narrative] |
| 14-Jun-2019 23:51 | Captain Adam | Updated [Total occupants, Narrative] |
| 02-Jul-2022 08:36 | ASN Update Bot | Updated [Time, Other fatalities, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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