Key facts
- UPS did not require detailed inspections of a critical engine bearing and metal sheath.
- Boeing had recommended enhanced inspections for this part years before the crash.
- The failure of this part led to the engine detaching from a UPS MD-11 freighter during takeoff.
- The crash resulted in the deaths of three pilots and 12 people on the ground.
- Boeing and the FAA admitted to misunderstanding the risks associated with the component failure.
- An aviation safety expert indicated shared responsibility among Boeing, UPS, the FAA, and the maintenance company STE San Antonio Aerospace.
UPS never mandated the detailed inspections necessary to detect the problem that caused an engine to detach from one of its planes before it crashed, even though Boeing had recommended them years prior, according to new documents released by crash investigators. The package delivery giant stated that it did not require enhanced bearing inspections within the pylons holding the engines to the wings of its MD-11 freighters because Boeing incorrectly assured that the failure of these bearings would not compromise flight safety.
The plane crashed last fall while accelerating for takeoff at Louisville’s Muhammad Ali International Airport, resulting in the deaths of all three pilots and 12 individuals on the ground, with 23 others injured. The hearing highlighted failures that prevented mechanics from closely examining the critical parts securing the engines to the wings, with Wednesday's documents offering further details.
While the NTSB's final report on the cause of the crash is not expected until late this year or early next, UPS acknowledged that once the pylon separated from the aircraft, the crash was unavoidable. Boeing and FAA officials admitted during hearings that they had misunderstood the risks associated with the failure of a steel bearing and metal sheath in the engine mount, not realizing it could lead to the failure of the lugs securing the engines to the MD-11's wings. These bearings are located deep within the pylons, making detection difficult without removing each engine for thorough inspections.
Aviation safety expert Jeff Guzzetti stated that the actions of Boeing, UPS, the FAA, and the maintenance company STE San Antonio Aerospace all contributed to the crash, emphasizing that safety is a shared responsibility. STE San Antonio Aerospace's Vice President, Chris Hentz, confirmed that UPS mechanics were only instructed to check for corrosion, not signs of bearing failure. Both Hentz and UPS noted that while Boeing suggested changes to inspection requirements for the spherical bearing, it also stated in the same communication that existing inspection requirements were sufficient.
UPS explained that it determined no additional changes to its maintenance program were necessary beyond current practices, relying on Boeing's assurances that the issue was not safety-of-flight related and that existing inspections were adequate. Boeing had previously succeeded in petitioning the FAA to extend the inspection schedule for these bearings from every 19,900 cycles to 29,260 cycles, even after receiving reports of seven flaws in the bearings before they reached their original inspection limits. Three more instances were discovered in the years following this schedule relaxation. The UPS plane that crashed had flown 21,043 cycles, meaning it should have been inspected under the original, more frequent schedule. FedEx and other MD-11 operators reported at least 10 other instances of failures involving these bearings or their securing parts prior to the UPS crash, though their maintenance practices are unclear. FedEx resumed flying its MD-11s in May after the FAA approved Boeing's safety plan, and going forward, spherical bearings will be replaced every 4,000 cycles. UPS chose to retire its entire MD-11 fleet early after the incident.