An aircraft that crashed in flames in Kentucky in November had a structural flaw that had been identified by Boeing on similar planes more than a decade earlier, according to investigators. The MD-11F freighter, operated by UPS, crashed after one of its engines separated from the wing as the aircraft was preparing to take off from Louisville, killing 15 people.
The crash involved three crew members on board and 12 people on the ground after the aircraft briefly lifted off the runway and then veered out of control into an industrial area.
Findings From The NTSB Investigation
In an update report, the National Transportation Safety Board said cracks found in the engine mounting assembly had also appeared on several other aircraft in the past. At the time, Boeing concluded that the issue would not result in a safety of flight condition.
The MD-11 design dates back several decades. It was originally produced by McDonnell Douglas before the company was acquired by Boeing in 1997. The final MD-11 left the production line in 2001, although Boeing has continued to provide parts and service support for the aircraft type.
Evidence Of Fatigue In Critical Components
Shortly after the Kentucky crash, the NTSB issued a preliminary report highlighting cracks in the engine attachment mechanism. The latest update provides more detail, citing fractures linked to fatigue caused by repeated stress in a critical bearing and in the mounting structure that supports it.
According to the report, Boeing had previously identified failures of the same component on four occasions involving three separate aircraft. In 2011, the company issued a service letter to operators outlining its findings. Service letters are advisory documents and are not legally binding.
Boeing recommended that the part be added to a general visual inspection every five years. The company also referred operators to changes in inspection procedures contained in the aircraft maintenance manual and noted the availability of a revised bearing assembly that could be installed, although this modification was not mandatory.
Industry Reaction To The Findings
Tim Atkinson, a former air accident investigator who now works as an aviation safety consultant, said the NTSB update raised serious concerns.
He said the structure involved was a critical element that attaches the engine to the wing and carries operational loads such as thrust and drag. He questioned Boeing’s earlier conclusion that failure of the part would not have safety implications.
Broader Scrutiny Of Boeing Processes
Boeing’s internal processes have faced repeated scrutiny in recent years. Critics have pointed to the design of the 737 Max, where flawed software was linked to two crashes in 2018 and 2019 that killed a combined 346 people.
Manufacturing quality has also drawn attention after a door panel detached from a newly delivered 737 Max shortly after take-off in early 2024.
In a statement, Boeing said it continues to support the investigation led by the NTSB and extended condolences to the families of those who died in the Kentucky crash.
The NTSB investigation remains ongoing. The agency has not issued formal conclusions on the cause of the accident and is not expected to do so until the release of its final report.
Featured image credits: Wikimedia Commons
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