What happened
The pilot reported that during the initial climb phase of takeoff, the aircraft reached an altitude of approximately 100 feet above ground level. While reducing power and retracting the flaps from the takeoff setting, the pilot felt the aircraft suddenly give way. In response, he re-extended the flaps, applied full throttle, and jettisoned the fuel load to reduce weight. Despite these efforts, the aircraft continued to lose both altitude and airspeed until it impacted the top of a tree and crashed.
The investigation
A post-accident examination revealed that the top member of the right wing tubular rear spar was broken at the cluster joint where the spar attaches to the fuselage stub wing. Analysis of the fracture surfaces showed they were severely rusted. The fracture occurred specifically where the wing had been welded. It was reported that the right wing tip had sustained damage approximately three years prior and was subsequently repaired.
Findings
The structural integrity of the aircraft was compromised by severe rust within the wing spar assembly. This corrosion weakened the metal at the weld joint, leading to catastrophic failure under the stress of takeoff operations. The history of previous damage and repair to the wing tip suggests a long-standing issue that ultimately resulted in structural failure during flight.