Incident Overview
On July 17, 2013, at approximately 1300 eastern daylight time, a Piper PA-34-200 (registration N767PE) operated by Phoenix East Aviation experienced in-flight tail vibrations near Palm Coast, Florida. The aircraft was engaged in a local instructional flight under 14 CFR Part 91, having departed Daytona Beach International Airport (DAB). Visual meteorological conditions prevailed. The flight instructor and the private pilot receiving multi-engine instruction were not injured.
Sequence of Events
According to the flight instructor, the airplane was initially at about 5,000 feet in a clean configuration while the student pilot was recovering from a minimum control airspeed condition. Two "kicks" were felt in the rudder system, which neither pilot initiated. The student then heard a "snap," and the rudder pedals began to pump to full deflection in both directions. The instructor took control but found that full rudder application or using both feet could not neutralize the deflections. The aircraft was diverted to Flagler County Airport (XFL), where it landed with 25-degree flaps without further incident. Rudder control was minimal during the approach, with pedals still pumping. Once on the ground, full rudder control returned.
Post-Flight Examination
On the ground, the rudder trim tab control rod was found fractured near the trim tab end. The control rod was replaced, and subsequent flights revealed no further rudder anomalies.
Laboratory Findings
Remnants of the fractured control rod end were sent to the NTSB Materials Laboratory. The fracture morphology was cone-shaped, concave toward the bearing head, with local deformation in the adjacent thread. Four thread roots adjacent to the fracture surface exhibited cracking. Both halves showed smearing damage consistent with post-failure impacts, with mirrored damage patterns 180° apart. After ultrasonic cleaning to remove rust, scanning electron microscope inspection revealed a rough, tortuous fracture surface with high peaks and valleys, generally concave downward. The fracture morphology was consistent with dimple rupture; no other fracture types were observed. The dimple rupture shape, cup-and-cone mating surfaces, and secondary thread root cracks indicated failure from overstress in tension. No evidence of fatigue or pre-fracture corrosion was found. Chemical analysis via energy dispersive x-ray spectroscopy identified the material as low-alloy 1000-series carbon steel. Piper Aircraft's investigator reported the correct material should have been 4130 gr1 (4000-series steel). According to Phoenix East Aviation's Director of Safety, the aircraft logbooks showed the rod had not been replaced since PEA acquired the airplane in 2005. The aircraft, manufactured in 1972, had a total time of 11,575 hours at the time of the incident.