The pilot completed his third aerial application sortie of the day in the Grumman G164-A, and was returning for landing on a paved private airstrip near Caruthers, Calif. On touchdown, he heard a “huge bang,” and the airplane began to roll right wing down.He tried to correct with aileron, but as the plane slowed, its right wing hit the ground. The plane veered to the right, departed the paved surface, and hit an embankment that bordered the runway, which caused the airplane to nose over. It came to rest inverted, partially down the embankment.
Examination revealed that the right main landing gear leg had fractured and separated near the upper bend just below the fuselage.
Laboratory analysis revealed that the leg failure was the result of a fatigue crack that went undetected until the remaining material was insufficiently strong to sustain the landing load.
The fatigue crack originated at the site of electrical arc damage to the gear leg. Possible mechanisms for the arc damage included a power line strike, a lightning strike, improper grounding during weld repairs to the airframe, or processing damage during overhaul of the landing gear.
Because the gear leg was heat-treated, the airplane manufacturer prohibited welding of the leg. The presence and condition of paint on the gear leg’s surface at the site of the arc damage indicated that the damage occurred before the paint was applied and that the gear leg had not been painted in the recent past.
Finding paint covering the damage raises questions about what inspections were performed on the gear leg and the efficacy of the inspections, however, because the maintenance records were not available, the history of the gear leg could not be determined.
The NTSB determined the probable cause as an undetected fatigue crack in the landing gear leg, which initiated at an electrical arc-induced damage site of undetermined origin and resulted in landing gear failure. Contributing to the severity of damage was the close proximity of an embankment to the runway.
NTSB Identification: WPR14LA130
This February 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.