UPS cargo aircraft maintenance protocols for MD-11 freighters failed to include mandatory enhanced inspections for engine pylon bearings, despite earlier warnings from Boeing regarding potential failure risks. According to documents released by the National Transportation Safety Board (NTSB), this oversight occurred because Boeing incorrectly assured operators that bearing failures would not jeopardize flight safety, leading to a fatal crash in Louisville, Kentucky, last November.
Why were critical bearing inspections omitted?
Maintenance records indicate that while Boeing identified the need for enhanced inspection procedures for the spherical bearings in MD-11 engine pylons, the manufacturer simultaneously maintained that existing inspection intervals were sufficient. According to Chris Hentz, Vice President of STE San Antonio Aerospace, Boeing stated in writing that while current requirements for the aft bulkhead were adequate, changes were warranted to ensure that “migration of the outer race would be reliably detected and identified during inspection.”
UPS informed the NTSB that it relied on these representations from Boeing. Because the planemaker did not move the enhanced procedures into the federally approved maintenance schedule, UPS determined that no further changes to its own maintenance program were necessary. Consequently, mechanics were instructed to check for general corrosion rather than specific signs of bearing failure.
Before the fatal Louisville crash, at least 10 instances of bearing or pylon component failures were reported by other MD-11 operators, including FedEx.
How did inspection schedules impact safety?
The regulatory framework governing these inspections faced scrutiny after Boeing successfully petitioned the Federal Aviation Administration (FAA) to extend inspection intervals. According to NTSB records, the FAA allowed the interval to increase from 19,900 cycles of takeoffs and landings to 29,260 cycles. This extension was granted even though Boeing had already received reports of seven bearing flaws before the aircraft reached the original limits.
The UPS aircraft involved in the November accident had logged 21,043 cycles. Under the original, more frequent inspection schedule, the faulty components would have undergone a thorough review before the crash occurred. Guzzetti, who used to investigate crashes for both the NTSB and FAA, noted that safety is a shared responsibility, stating that the NTSB’s current task is to apportion that responsibility.
What happens next for MD-11 operations?
Following the crash, which killed all three pilots and 12 people on the ground, the landscape for MD-11 maintenance has shifted significantly. FedEx resumed operations of its MD-11 fleet in May after the FAA approved a new safety plan. These updated requirements mandate that spherical bearings be replaced regularly, specifically after every 4,000 cycles of takeoffs and landings.
UPS has taken a different path, announcing its decision to retire its entire fleet of MD-11 freighters earlier than planned. While the NTSB’s final report on the cause of the Louisville accident is not expected until late this year or early next, UPS stated in its submission that “once the pylon separated from the aircraft, the crash was inevitable.”
For the latest updates on aviation safety directives, always consult the official National Transportation Safety Board database and the Federal Aviation Administration Airworthiness Directives.
Frequently Asked Questions
Were there previous warnings about the MD-11 bearings?
Yes. According to investigative documents, Boeing had reports of at least seven bearing flaws prior to the inspection interval extension, and other operators reported at least 10 additional failures over the years.
Why did UPS not perform the enhanced inspections?
UPS stated that it relied on Boeing’s representations that the bearing issue did not jeopardize flight safety and that existing maintenance manual requirements were sufficient.
When will the final crash report be released?
The NTSB expects to publish its final report on the Louisville crash by late this year or early next year, according to agency disclosures.
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