Flight 724 · McDonnell Douglas DC-8-71F

The captain stated that during the landing rollout, while the airplane was at a speed of about 100-120 knots, and while the thrust reversers were deployed, the airplane began to lean and veer to the right. He said that he initially thought it may have been due to the crosswind, but he soon realized that the landing gear had collapsed. The captain estimated that when the airplane began to lean and veer it was positioned in the vicinity of taxiway T-2, and the airplane stopped in the vicinity of taxiway U. The flight crew then evacuated the airplane onto the taxiway via the L1 door slide. The digital flight data recorder (DFDR) and cockpit voice recorder (CVR) were examined by the NTSB. All pertinent parameters on the DFDR were noted to be consistent with those of a normal landing having been performed. When the CVR was auditioned, all conversations were in Spanish and proved to be consistent with a normal landing having occurred. Disassembly of components of the right main landing gear torque tube showed that the outboard torque tube attach bolt had backed out from the piston prior to the incident. The torque tube is attached to the piston by an attach bolt, which is threaded and has a hole drilled in the end. The attach bolt is threaded into the piston and then torqued to 475 ft-lbs. The next step is to install the lockbolt, which retains the attach bolt in place. According to the operators Manager of Quality Assurance, the attach bolt was not properly torqued and the lockbolt was installed, but not through the hole in the end of the attach bolt. As a result, after 11 cycles, the attach bolt backed out of the threaded area of the piston and the right main landing gear collapsed. According to the QA Manager, during installation of the right main landing gear, a maintenance personnel shift change had occurred, and the new shift was not informed by the outgoing shift what work still needed to be accomplished, which resulted in the right main landing gear being reassembled incorrectly. Damaged landing gear parts were collected and sent to the NTSB's Metallurgical Laboratory, Washington DC, where they were examined optically. The examination revealed that the damaged parts exhibited signatures consistent with that of overstress separations. No preexisting cracks or corrosion were noted.

Verbatim NTSB analysis and probable cause from the NTSB dataset