CEN25LA086

After the uneventful instructional flight landed, the airplane was shut down on the ramp. A second flight instructor and student pilot then completed a preflight inspection before their planned instructional flight. During their preflight inspection, the lower hinge for the rudder was found fractured from the vertical spar tube. Examination of the rudder and the lower hinge attachment hardware revealed the lower hinge barrel fractured from fatigue cracking that initiated along the toe of the weld that joined the hinge barrel and the rudder post. Cracking started on both the outer and inner surfaces of the lower rudder post, propagating into the post cross section, consistent with reverse-bending fatigue. The inner surface cracking initiated from small corrosion pits on the inside surface, and the outer surface fatigue cracking initiated along geometrical features at the weld toe that acted as stress concentration sites. The fatigue cracking propagated from the top down the left and right sides until the final overstress detached a small downward-facing ligament of the post at an unknown time. A black protective coating had been applied to the frame of the rudder post. This layer was consistent with the prescribed black powder coating from manufacture. A successive series of paint layers were present on top of this black coating: white, red, white, and then blue on the exterior. The white layers were likely primer. The blue and white paint layers covered areas of the post where cracks had developed. However, worn surfaces on the hinge knuckles were also covered with blue paint, indicating the rudder post had operated for some time before the paint was applied. The presence of corrosion pitting suggests that the paint and other coatings were either not sufficient to protect the underlying alloy surfaces or were compromised during the rudder’s life. The rudder is expected to accommodate the variable loads that stress the upper and lower hinge knuckle attachments during normal operation. However, the contact that produced wear at the hinge barrels could have contributed to elevated stress at the attachment locations. The vertical stabilizer carries vertical and lateral loads from rudder accelerations and surface pressures through the upper and lower hinges. The weld toes between the hinge barrels and the rudder post would concentrate these variable stresses at this location; additionally, both hinge barrels' lower surfaces were worn, indicating prolonged surface contact with an associated increase in stress. While fatigue cracking had initiated at both the inner and outer surfaces of the rudder post, the extent of crack growth propagating from the exterior surface indicates the primary initiation area was along the toe of the weld. According to the FAA, where the airplane was based is classified as an area of having moderate corrosive exposure for aircraft structures. Based on the available evidence, the lower hinge barrel likely failed due tofatigue cracking at an unknown time. Contributing to the failure of the lower hinge barrel was increased stress from end face contact likely associated with worn bushings or displaced needle bearings. After the incident, the operator and the airframe manufacturer both expanded their inspection requirements for these areas by using magnification glass visual and dye penetrant inspections, which will likely enhance future crack detection by maintenance personnel.

On January 16, 2025, about 1700 central standard time, an American Champion Aircraft 7ECA airplane, N798L, sustained damage near Longview, Texas. The flight instructor and the student pilot were not injured and the damage was identified during a preflight inspection before the next flight began. Because the timing of the ultimate failure of the barrel could not be identified, and may not have occurred in flight, the event was investigated as an incident. The airplane was to be operated as a Title 14 Code of Federal Regulations (CFR) Part 91 instructional flight. The airplane was to be operated by LeTourneau University, as part of their 14 CFR Part 141 flight training program. The purpose of the flight was for the flight instructor and the student pilot to practice soft field landings. Prior to the discovery of damage, the airplane departed from the East Texas Regional Airport (GGG), Longview, Texas, at 1548, and the flight instructor performed a soft field landing to the grass at the Kilgore Airport (4TX6), Kilgore, Texas. The airplane departed 4TX6 and flew to the Gladewater Municipal Airport (07F), Gladewater, Texas. The student pilot performed a soft field landing to runway 32 and then the airplane departed 07F and returned to GGG. During the approach to runway 18, the student pilot, with the flight instructor “shadowing” the flight controls, performed a “constant forward slip down” to the runway and landed without further incident. The student pilot then taxied to the ramp where the airplane was shut down. A second flight instructor and student pilot then completed a preflight inspection before their planned instructional flight. During their preflight inspection, the lower hinge for the rudder was found fractured from the vertical spar tube. The lower rudder hinge hardware was intact and secured in place. The LeTourneau University College of Aviation and Aeronautical Science is based at GGG, and they operate nine American Champion Aircraft 7ECA airplanes, in addition to other make and model airplanes. According to FAA registration records, LeTourneau University purchased the airplane directly from the American Champion Aircraft Corporation, on April 8, 2005. At the time of the incident, the airframe had accumulated 8,512.6 hours. The most recent airframe inspection, a 100-hour inspection, occurred on November 12, 2024, and 59.4 hours had elapsed since that inspection. The rudder, part number 4-1698, had accumulated 8,420.7 hours when the failure occurred. According to the operator, the rudder was repaired twice prior to the observed failure. According to the American Champion Aircraft Service Manual, the rudder is constructed of steel tubing and is covered with fabric using an adhesive. After the observing the failure, the operator grounded their entire fleet and conducted an inspection of the upper and lower rudder hinges, including utilizing a 10x magnifying glass and a dye penetrant inspection. No fractures or crack indications wereidentified in the rest of their fleet. Examination of the rudder and the lower hinge attachment hardware revealed the lower hinge barrel fractured from fatigue cracking that initiated along the toe of the weld joining the hinge barrel to the rudder post. The fatigue cracking initiated on both the outer and inner surfaces of the rudder post, propagating into the cross section of the post, consistent with reverse bending fatigue. The inner surface cracking initiated from small corrosion pits on the inside surface, and the outer surface fatigue cracking initiated along geometrical differences at the weld toe. The fatigue cracking propagated from the top down the left and right sides until the final overstress detached a small downward-facing ligament of the post at an unknown time. A black protective coating had been applied to the frame of the rudder post. This layer was consistent with the prescribed black powder coating from manufacture. During the investigation, it was determined that a successive series of paint layers were on top of this black coating: white, red, white, and then blue on the exterior. The white layers were likely primer. The blue and white paint layers covered areas of the post where cracks had developed. However, worn surfaces on the hinge knuckles were also covered with blue paint, indicating the rudder post had operated for some time before the paint was applied. The worn surfaces on the hinge knuckles are not normally in contact but can come into contact if bushings are worn or if needle bearings are displaced. After the incident, the operator implemented a removal requirement of the rudder at each 100-hour inspection for their fleet using a 10x magnification glass to inspect for fractures. Additionally, at 300 hours, they implemented a dye penetrant inspection requirement for the upper and lower rudder hinges. The American Champion Aircraft Service Manual states that, during the preflight inspection, the pilot should ensure there is “no external damage, cracks, or operational interference to the control surfaces, wings, or fuselage”. It further states that during a 100-hour inspection interval to “check rudder hinges, stops and attachments for damage and operation” and to “check rudder hinge bolts and bushings for excessive wear, replace as necessary.” American Champion Aircraft published Service Letter 449 Corrosion Inspection and Preventative Maintenance on May 23, 2018. This document references FAA Advisory Circular (AC) 43-4B, Corrosion Control for Aircraft. According to FAA AC 43-4B, the area where the airplane was based is classified as an area of having moderate corrosive exposure for aircraft structures. After the incident, American Champion Aircraft published Service Letter 459 Inspection of Rudder and Vertical Stabilizer Upper and Lower Hinge on April 24, 2025. This document mandates a visual inspection with a 10x magnification glass or dye penetrant inspection of the upper and lower bushings, welds, andattachment hardware on the vertical stabilizer and the rudder at every 100-hour or annual inspection on airplanes that have accumulated more than 2,000 hours of service. Prior to this incident, on April 12, 2024, a different American Champion Aircraft 7ECA airplane also operated by LeTourneau University, N793L, sustained similar damage to the rudder. The NTSB case number is CEN24LA162.