Accident Details
A pilot was practicing takeoffs and landings in a recently-purchased airplane. During the practice session, he performed one landing that he described as "a pretty good jolt," but "not extraordinary." Following the flight, the pilot noticed damage to the left wing's upper skin.
Inspection Findings
Further examination of the aircraft revealed that a portion of the left wing rib cap was fractured. Additionally, two sets of double-drilled, overlapping rivet holes were present, which matched up with holes partially drilled into a false spar. The false spar was covered with a green preservative paint, while the partially-drilled holes were not painted. The fracture surface of the rib cap exhibited fatigue cracking that did not extend into the overlapping rivet holes.
Maintenance History
A review of the airplane's maintenance logs revealed no evidence of any prior repair to the affected area. The airplane was manufactured in 1971 and had accumulated 5,529 hours of operating time at the time of the event.