An aircraft that crashed in flames in Kentucky in November had a structural flaw that had been identified by Boeing on similar planes 15 years ago, according to investigators.
The MD-11F freighter operated by UPS crashed after one of its engines separated from the wing as it was preparing to take off from Louisville.
The plane briefly lifted off from the runway before hurtling out of control into an industrial area. Fifteen people were killed including three crew and 12 on the ground.
In an update, the US National Transportation Safety Board (NTSB) revealed that cracks found in the engine mounting assembly had previously occurred on several other aircraft.
At the time the manufacturer responsible for the aircraft, Boeing, concluded that the issue would not result in a safety of flight condition.
The MD-11 is a relatively elderly design initially produced by McDonnell Douglas. Boeing acquired the company in 1997, and the last MD-11 came off the production line in 2001, but the company has continued to provide parts and service support.
In the aftermath of the Kentucky disaster, the NTSB issued a preliminary report highlighting cracks in the engine attachment mechanism. Its latest update elaborates on fractures due to fatigue in a critical bearing and the mounting it is meant to sit in.
Boeing was found to have previously identified failures of the same part on four occasions affecting three different aircraft. In 2011, the company sent a service letter to operators warning them of its findings, advising visual inspections of the part every five years.
Tim Atkinson, a former air accident investigator, expressed concern over Boeing’s conclusion, stating, The structure concerned is not decorative; it's essential for attaching the engine to the wing.
Boeing's internal processes have faced scrutiny following past incidents, including the tragic 737 Max accidents that claimed 346 lives due to flawed software.
In a statement, Boeing said, We continue to support the investigation led by the NTSB. Our deepest condolences go out to the families who lost loved ones and our thoughts remain with all those affected. The NTSB's investigation is ongoing, and no firm conclusions about the cause of the crash have yet been issued.
