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| Date: | Wednesday 20 September 2023 |
| Time: | 14:45 |
| Type: |  Cessna U206C Super Skywagon |
| Owner/operator: | Middle Fork Aviation Inc |
| Registration: | N3923G |
| MSN: | U206-0923 |
| Year of manufacture: | 1967 |
| Total airframe hrs: | 10473 hours |
| Engine model: | Continental IO-550 |
| Fatalities: | Fatalities: 0 / Occupants: 4 |
| Other fatalities: | 0 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Bernard USFS Airport (U54), Challis, ID -
 United States of America
|
| Phase: | Take off |
| Nature: | Executive |
| Departure airport: | Bernard USFS Airport, ID (U54) |
| Challis Airport, ID (CHL/KLLJ) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot was in the process of taking off when the left main gear spring assembly fractured. The airplane veered off the runway and ground contact substantially damaged the left horizontal stabilizer and elevator.
Metallurgical examination of the failed gear spring assembly revealed it failed due to fatigue cracking and overload stresses. Further examination revealed corrosion underneath the primer paint and inside the dimples of the shot-peened area, which likely initiated the development of the fatigue crack.
A records review revealed that in March of 2010, the left and right main gear spring assemblies were inspected, heat treated, shot peened and painted with a zinc-rich primer. It is likely that corrosion existed on the landing gear before the application of the primer paint, and that the inadequate removal of the corrosion allowed fatigue cracking to propagate until the left assembly failed in overstress.
Probable Cause: The failure of the left main landing gear spring assembly due to a fatigue crack. Contributing to the accident was the improper maintenance on the landing gear spring assembly which allowed corrosion to develop.
Accident investigation:
 |
|
Sources:
NTSB WPR23LA350
https://data.ntsb.gov/Docket?ProjectID=193112
Location
Images:
Photo: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 01-Mar-2025 12:44 | ASN Update Bot | Added |
| 02-Mar-2025 20:32 | Captain Adam | Updated [Time, Aircraft type, Location, Departure airport, Source, Narrative, Photo, ] |
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