Cessna 172A N7810T accident near Payson, Arizona

Probable cause

The stress corrosion cracking of the nose gear landing fork, which resulted in the fork's failure during landing.

NTSB analysis

The pilot reported that, as the airplane touched down, the nose gear separated and the airplane veered to the left before coming to rest on the runway. During the event the right wing was substantially damaged. Postaccident examination of the separated nose landing gear fork indicated that the alloy used for forging the part was 2014 series aluminum, which is susceptible to stress corrosion cracking (SCC) given the proper environment and a continuous stress state. A Safety Board metallurgist concluded that the fracture characteristics were consistent with SCC, with slow crack growth over time. The crack appeared to have originated from a point on the surface of the bolt hole bore and propagated upwards and outwards. The last annual inspection of the airplane was conducted about two weeks prior to the accident, although the investigation was unable to determine if the crack would have been visible to the unaided eye during a routine inspection.

Text from the NTSB. Open the NTSB docket for WPR10LA004 for the full record.