James EXPERIMENTAL CUB N9WU

Summary

On 13 June 2019 at about 19:20 local time, a James EXPERIMENTAL CUB registered N9WU was involved in an accident near Stanley, Idaho, United States. 2 people were on board and 2 were seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

13 June 2019 at 19:20

Classification

Accident

Location

Stanley, Idaho, United States

Coordinates

44.1783, -114.8917

Aircraft

James EXPERIMENTAL CUB

Registration

N9WU

Category

Airplane

Year built

2013

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Burley → Yellow Pine

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR19LA170

2 people were seriously injured.

Overstress failure of the right-wing spar due to an encounter with turbulence.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.