Unraveling the Mystery: What Caused the Deadly UPS Cargo Plane Engine Detachment?

Federal safety investigators are convening this week to explore the circumstances surrounding a tragic incident where an engine detached from a UPS cargo plane last year. This malfunction led to a devastating crash that claimed 15 lives. The hearings will also scrutinize why Boeing did not promptly address the fundamental issue.

The disaster unfolded when the engine became dislodged from the MD-11’s wing as the aircraft was accelerating on the runway at Louisville’s Muhammad Ali International Airport in November. This tragic event resulted in the deaths of three pilots on board and an additional 12 individuals on the ground.

Scheduled for Tuesday and Wednesday, the National Transportation Safety Board’s hearings will delve into the reasons behind the catastrophic failure. The board’s comprehensive final report is anticipated to take over a year to complete, as the NTSB thoroughly investigates all potential factors contributing to the crash.

Here’s what you need to know:

What happened in the crash

The ill-fated UPS flight, on its way to Hawaii, was heavily laden with packages and fuel. It barely took off, clearing the airport’s perimeter fence, before crashing into several nearby businesses in Louisville, igniting a massive fireball.

Dramatic photos the NTSB released after the crash showed the engine detaching and flying up and over the wing as flames erupted on the wing. The final images show the plane ablaze as it gets airborne, leaving behind trails of smoke.

The crash was reminiscent of a 1979 crash in Chicago involving a DC-10, which was the predecessor of the trimotor jet that crashed in Louisville. The left engine also fell off in that crash that killed 273 people.

That previous crash led to the worldwide grounding of 274 DC-10s. The airliner returned to the skies because the NTSB determined that maintenance workers damaged the plane that crashed while improperly using a forklift to reattach the engine. That meant the crash wasn’t caused by a fatal design flaw even though there had already been a number of accidents involving DC-10s.

But even at that point the plane’s manufacturer, McDonnell Douglas, raised concerns about the spherical bearing that helps hold the engines to the wings. McDonnell Douglas later merged with Boeing.

Past problems with these planes

The NTSB said shortly after the Louisville crash that investigators had found cracks in some of the parts that held the engine to the wing. Those cracks hadn’t been caught in regular maintenance done on the plane, which raised questions about the adequacy of the maintenance schedule. The last time those key engine mount parts were examined closely was in October 2021, and the plane wasn’t due for another detailed inspection for roughly 7,000 more takeoffs and landings.

Boeing had documented in 2011 there were four previous failures of a part that helps secure the MD-11’s engines to the wings on three different planes, but at that point the plane manufacturer “determined it would not result in a safety of flight condition.”

The service bulletin that Boeing issued didn’t require plane owners to make repairs like an FAA airworthiness directive would, and the agency didn’t issue such a directive. At that point, Boeing just recommended replacing the bearings with a redesigned part that was less likely to fail.

MD-11 planes flying again

Some MD-11s, a workhorse of the cargo fleet, are now back in the air after the FAA approved Boeing’s plan to replace the spherical bearing on each aircraft and increase inspections.

FedEx resumed using the planes to deliver packages on May 10, but UPS has said it plans to retire its fleet of MD-11s. Western Global also uses MD-11s but hasn’t said what it plans to do with the planes.

Some experts speculated after the crash that the MD-11s might never fly again if the repair proved to be more expensive that it was worth in these older planes. But Boeing found a way to address the safety concerns with just replacing the bearing and stepping up inspections.