Incident Overview
A Citabria 7GCBC aircraft was observed performing a loop maneuver. As the aircraft reached the bottom of the loop and began recovering to level flight, the left wing bent upward at the strut attachment point. Subsequently, the aircraft entered a right spiral descent and did not recover before colliding with the ground.
Structural Findings
Post-accident examination revealed an improper manufacturing condition in the left forward wing spar. The forward wing spar failed with tension on the top and compression on the bottom, while the rear wing spar exhibited tension on the bottom and compression on the top. The left wing outboard of the strut attachment point separated from the aircraft prior to impact. The left aileron was bent upward 90 degrees at the middle hinge point, which corresponded to the strut attachment point.
Manufacturing Defects
Further investigation identified that the slope of the grain in the forward wing spar exceeded specifications. Additionally, two areas of poor bonding were found in the spar structure. No problems were noted on the left rear wing spar. The aircraft log books were not located during the investigation.