NTSB: Did Boeing's 2011 Warning Fail to Prevent Fatal UPS MD-11 Crash?

The National Transportation Safety Board (NTSB) released a factual update. This report concerns the fatal UPS Flight 2976 crash last November. The cargo jet, a Boeing MD-11 freighter, crashed shortly after takeoff. It departed from Louisville Muhammad Ali International Airport (SDF). The accident tragically killed all three crew members. It also killed at least 11 people on the ground.

Investigation Focus: The Spherical Bearing

Investigators quickly focused on the left engine. The engine and pylon separated from the wing. The NTSB found extensive fatigue cracking. This was on a spherical bearing race component. This race is part of the MD-11 engine pylon separation assembly. It helps attach the engine to the wing structure. The fatigue accounted for about 75% of the fracture.

Manufacturer's Prior Knowledge

The NTSB report revealed a critical detail. Boeing had known about this issue for almost 15 years. Boeing inherited the MD-11 line from McDonnell Douglas. In 2011, Boeing issued a service letter. The letter was dated February 7, 2011. It informed operators of four prior bearing race failures. All failures started at a design recess groove.

Despite this history, Boeing's review concluded the issue “would not result in a safety of flight condition.” The company recommended visual inspections. These checks were part of the routine 60-month maintenance cycle. This is a general visual inspection (GVI).

The Optional Upgrade and Regulatory Oversight

The 2011 Boeing service letter also mentioned an upgraded part. This new bearing design eliminated the failure-prone groove. Boeing recommended installing the new part. This was only if an original bearing was found unserviceable. Crucially, the letter did not prohibit replacing a faulty part with an original design. The upgrade was optional, not a mandatory fix.

Investigators are now examining maintenance records. They are checking how UPS incorporated the 2011 guidance. The last detailed inspection on the accident aircraft was in 2021. The aircraft was not due for another check for thousands of flight cycles. This timeline is now a key part of the inquiry.

Impact on Aviation Safety and Aging Fleets

This incident raises serious questions about advisory guidance. It questions if a service letter is enough for known failures. The alternative is an enforceable airworthiness directive from the FAA. The aging widebody freighters fleet is under scrutiny. The MD-11 that crashed was 34 years old. Many MD-11 aircraft remain in cargo service worldwide. Following the crash, Boeing urged operators to ground their MD-11s. The FAA then mandated a temporary grounding. The NTSB investigation update highlights the need for vigilance. It shows the challenges of managing legacy design issues. This affects manufacturers, operators like UPS, and regulators.

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