The National Transportation Safety Board’s investigation into a UPS MD-11 crash in Louisville has focused on how a maintenance inspection schedule was changed with less frequent checks of hard-to-access engine mount components, and how key safety information did not appear to be shared in a way that would have prompted closer scrutiny before the crash.
In testimony during a two-day hearing, NTSB investigators questioned how an engine mount problem could develop without being caught by the inspection intervals that Boeing and federal regulators approved. The NTSB’s case described bearing and metal sheath issues inside the engine mount area near the plane’s pylons—locations where mechanics would need detailed, engine removal work to spot the problems.
The NTSB said the change began with Boeing’s request to extend the inspection schedule in 2015, and that the Federal Aviation Administration approved the request after a month’s review. Aviation safety expert Jeff Guzzetti told the hearing that the NTSB is trying to determine how responsibilities are divided among the airline, the manufacturer and the regulator.
Testimony also said Boeing relied on older data when it sought the extension, and that it did not account for instances on other MD-11s of the same model in which key engine mount parts were failing. Boeing officials and the FAA acknowledged they misunderstood the risks involving a steel bearing and metal sheath in the engine mount, which could lead to the lugs that secure the engine to the wing breaking.
Boeing’s request was designed to reduce airline downtime by allowing airlines to complete more major maintenance tasks at the same time. According to testimony, Boeing succeeded in extending the required inspections from once every 19,900 cycles of takeoffs and landings to once every 29,260 cycles, allowing longer intervals between the more detailed checks.
Investigators said the company sought the schedule extension even after it received reports of seven flaws in the bearings well before the planes reached their original inspection limits. After the inspection schedule was relaxed, testimony said three more instances were discovered before the Louisville crash.
The hearing testimony tied the schedule question to the particular aircraft involved in the crash. The plane that lost an engine while accelerating down the runway at Louisville’s Muhammad Ali International Airport had flown 21,043 cycles—an amount the NTSB said would have put it into a thorough inspection under the original schedule. The crash killed all three pilots and 12 people on the ground, and left 23 others injured.
The NTSB’s investigation also drew attention to the relationship between manufacturer-maintenance guidance and operator compliance. Greg Raiff, who owns aviation maintenance companies and operates a fleet at Elevate Aviation Group, said plane operators aren’t expected to deviate from federally approved maintenance schedules, adding that it was not up to individual airlines to “reinvent the inspection program” for the MD-11.
NTSB Chairwoman Jennifer Homendy said the FAA should have done more to challenge Boeing’s request in 2015, pointing to the fact that even if regulators didn’t know about all the flaws, they knew Boeing had sent a service letter about them and had previously reported two of them. Homendy said she was “confused on why you wouldn’t ask for more information, more testing” and why the FAA would accept information Boeing provided during certification decades earlier.
Boeing’s director of airframe service engineering, Justin Konopaske, said Boeing lacked records about what it considered at the time because McDonnell Douglas originally designed and built the MD-11 and its predecessor DC-10 before merging with Boeing in 1997. Konopaske said Boeing should have shared details of the problems it knew about with the FAA when it applied to extend the inspection schedule.
Konopaske told the hearing, “I believe transparency is critical in that process,” and added that he did not know what engineers were considering or whether bearing failures had been considered in the discussion, given the record gaps at the company.
The NTSB said it will continue investigating other factors that may have contributed to the crash before issuing its final report, likely later this year or sometime next year. In the meantime, testimony said FedEx resumed flying its MD-11 aircraft earlier this month after the FAA approved Boeing’s plan to ensure their safety, with the engine mounts closely inspected after the November crash and spherical bearings replaced regularly after every 4,000 cycles of takeoffs and landings.
Homendy said the problems documented from 2002 to 2009 all happened between 6,058 cycles and 13,650 cycles, underscoring the focus on whether the relaxed schedule left insufficient time for the issues to be discovered before the Louisville crash.