Incident Summary
During the initial climb phase of a flight, the certified flight instructor (CFI) observed very little resistance from the stabilator. Despite this, the CFI was able to land the airplane uneventfully using the stabilator trim. The incident did not result in any reported injuries or damage beyond the component failure.
Examination Findings
A post-incident examination of the airplane revealed that the stabilator control cable turnbuckle terminal fitting had failed. The failure was attributed to corrosion on the terminal fitting.
Background on Recommendations
More than six years prior to the incident, the National Transportation Safety Board (NTSB) had issued a recommendation to the Federal Aviation Administration (FAA). The recommendation called for the FAA to issue an airworthiness directive (AD) requiring recurrent visual inspections for evidence of corrosion on control cable terminals. The inspections were to be performed after removal of any safety wire or safety clips on the terminals. At that time, the airplane manufacturer had committed to revising its maintenance manuals to include similar instructions.
Maintenance Inspection
At the time of the incident, the airplane manufacturer had issued a service letter but had not yet updated its maintenance manuals. The FAA had issued a non-mandatory Special Airworthiness Information Bulletin (SAIB) in lieu of an AD. A mechanic performed an annual inspection of the incident airplane 21 days prior to the incident and returned it to service. The mechanic stated that he inspected the incident airplane's control cables for damage during the annual inspection, but believed he missed the corrosion on the turnbuckle terminal fitting because a safety wire covered it. The mechanic added that he was not aware of the manufacturer's service letter or the FAA SAIB regarding the inspection for corrosion at the time of the annual inspection.