CEN19LA166

The pilots were performing an instructional flight with multiple takeoffs and landings when, during one takeoff, the pilots heard a loud noise, and the right main landing gear (MLG) wheel assembly departed the airplane. The pilots elected to perform an emergency landing at another airport due to its larger runways and emergency personnel and equipment. The airplane landed and came to rest upright on the runway surface. Examination of the airplane after landing revealed that the right main wheel/tire and lower shock absorber assembly departed the upper shock absorber assembly. The separated assembly, which was located near the departure airport, impacted the right horizontal stabilizer after separation, which sustained substantial damage. Metallurgical examination of the assembly revealed that the MLG fractured at the connection between the upper and lower torque knees. Fatigue was identified on a fractured piece of the upper torque knee, and other fractures on the torque knee were consistent with overload. Corrosion assisted in crack initiation, and the crack propagated through fatigue until a critical crack length was reached. It is likely that the fatigue area fractured first and the other connections experienced an increase in loading, which caused them to separate from the MLG assembly.

On June 12, 2019, about 1725 central daylight time, a Beech E90 airplane, N176TW, experienced a right main landing gear (MLG) failure during takeoff from Majors Airport (GVT), Greenville, Texas, and an emergency landing was performed at Fort Worth Alliance Airport (AFW), Fort Worth, Texas. The two airline transport pilots and a company check pilot were not injured, and the airplane sustained substantial damage to the right horizontal stabilizer. The airplane was registered to Sierra American Corporation, Wilmington, Delaware, and operated by Ameristar Jet Charter, Inc., Addison, Texas, as a Title 14 Code of Federal Regulations Part 91 instructional flight. Day visual meteorological conditions prevailed at the time of the accident, and a visual flight rules flight plan was filed. The flight was originating from GVT. According to the operator, the pilots were performing an instructional flight with multiple takeoffs and landings at GVT. During the accident takeoff, the pilots heard a loud noise, and with the assistance of ground witnesses, determined the right MLG wheel assembly departed the airplane. The separated wheel assembly and fractured components were located near the runway at GVT. The pilots elected to perform an emergency landing at AFW due to large runways and emergency personnel and equipment. The airplane landed and came to rest upright on the runway surface (see Figure 1. Airplane on runway at AFW) Figure 1. Airplane on runway at AFW Examination of the airplane revealed the right main wheel/tire and lower shock absorber assembly departed the upper shock absorber assembly. The separated assembly then impacted the right horizontal stabilizer, and the stabilizer sustained substantial damage. The lower shock absorber assembly was recovered at GVT and retained for further materials examination. (See Figure 2. Right Main Wheel Assembly) Figure 2. Right Main Wheel Assembly On June 27, 2019, at Textron Aviation, Wichita, Kansas, the right MLG assembly was examined by Textron Aviation engineers under the supervision of a Federal Aviation Administration (FAA) engineer. According to the Textron engineering report, the MLG was found to have fractured at the connection between the upper and lower torque knees (part numbers 50-810032-4, 50-810295-17), and at two other connection points in the upper torque knee. The examination resulted in the following findings: 1. The upper torque knee was found to have fractured at all three connection points. 2. Fatigue was identified on a fractured piece of the upper torque knee, and all other fractures were consistent with overload. 3. Corrosion was found to have assisted in crack initiation. The crack propagated through fatigue until a critical crack length was reached. 4. Material chemistry, tensile properties, conductivity, and microstructure of the upper torque link was consistent with aluminum alloy 2014 in the T6 condition. The Textron engineering report was reviewed and approved by the NationalTransportation Safety Board materials laboratory chief engineer. According to Textron, due to historical evidence of this occurrence, a mandatory service bulletin (SB 32-3134) was released in July 1999 requiring non-destructive inspection of the torque knees at reduced intervals. Per the SB, the mandatory inspection was to be accomplished within the next 100 cycles (1 cycle = 1 landing) or next scheduled inspection for MLG torque knees with accumulated time in service of 1,000 hours. Recurring inspections were required every 1,000 cycles or 2 years, which ever occurred first. An additional service bulletin (SB 32-3116) was released in October 1999 recommending a steel torque knee replacement for the upper and lower torque knees and removed the 1,000 cycle/2-year inspection requirement for SB 32-3134. On February 22, 2002, the FAA issued airworthiness directive 2002-01-10 which required the repetitive inspection and/or replacement of the torque knees per the SBs. A review of the aircraft records revealed the upper torque knee underwent florescent penetrant inspection on March 25, 2016; airframe total time: 11,230.4/Landings 10,505, and on February 10, 2017; time and landings unknown. At the time of the accident, the airframe total time was 11,423.5 hours and 10,715 landings.