Cessna 182 N3267S

Summary

On 27 October 2018 at about 14:50 local time, a Cessna 182 registered N3267S was involved in an accident near Burns, Oregon, United States. 3 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

27 October 2018 at 14:50

Classification

Accident

Location

Burns, Oregon, United States

Coordinates

42.3325, -118.3158

Aircraft

Cessna 182

Registration

N3267S

Category

Airplane

Year built

1964

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Caldwell → Burns

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR19LA020

Nobody was injured.

The failure of the left main landing gear due to fatigue cracking of a bolt that initiated at a corrosion pit, which formed in the absence of a required protective cadmium coating.

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

Read the full NTSB narrative

Upon approaching the intended landing area, the pilot performed a high reconnaissance to assess the wind conditions. The airplane touched down and, during the landing roll, the left wing dipped downward. The left wing made contact with the ground before coming to rest with the left main landing gear sheared off. The attachment bolt that connected the left main landing gear leg bracket exhibited a fatigue crack that had progressed through about one third of the bolt cross-section. This fatigue crack initiated at multiple fatigue crack initiation sites along the thread root. This thread root exhibited corrosion pitting that had penetrated the outer cadmium plating, which had led to fatigue cracking. When the remainder of the bolt could no longer support the stress at landing, the remaining cross section fractured in overstress. As this crack had propagated through about one third of the cross section without a discernible transition or mixed fracture zone between the fatigue crack and subsequent stress, the final fracture occurred at a high load event, such as the accident landing. The bolts had been plated with cadmium, a corrosion inhibitor. However, corrosion pitting was observed along the threads, which led to fatigue cracking in both bolts. Although the cadmium plating can provide protection to the underlying alloy steel, corrosion such as in the form of pitting can still occur. This may be due to the operational environment, including locations near saltwater, as well as from a crevice corrosion mechanism. With the fatigued bolt having fractured, the bracket would be able to flex or slide out the side. With these components able to flex, the bottom of the support housing could not support the downward forces from the gear spring, which led to its fracture. This would allow a cantilever force on the inboard support, which would have been enough force to fracture the attachment bolt on that support and the upper support frame. Although a hard landing would have caused this bolt to fracture, the fatigue crack diminished the amount of stress it could withstand.

Quoted verbatim from the NTSB record.