What happened
Following major engine work, an aircraft was released for an engine ground test run. The airplane had not yet been returned to service or cleared for flight. Approximately one minute after takeoff, the pilot reported the need to return for landing and was cleared for right traffic on runway 33. About two minutes later, the pilot requested to turn onto the base leg. Shortly after this request, the aircraft was observed to roll over and impact the ground in an inverted position.
The investigation
The investigation focused on the failure of the left elevator horizontal tube, which extends outboard from the bellcrank. Upon inspection, corrosion particles were removed from inside the tube. Measurements taken outboard of the corrosion area revealed a tube thickness of only 0.035 inch.
Additionally, the director of maintenance noted that the aircraft was due and scheduled for its annual inspection before being released for flight testing.