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NTSB Investigates Pylon Fatigue Cracks in UPS Flight 2976 Engine Separation

NTSB Investigates Fatigue Cracks in UPS Flight 2976 Engine Separation
The National Transportation Safety Board (NTSB) has identified fatigue cracking in the left engine pylon structure as a critical element in its investigation into the fatal crash of UPS Flight 2976. The MD-11F cargo aircraft crashed shortly after takeoff from Louisville Muhammad Ali International Airport (KSDF) on November 4, resulting in the deaths of all three crew members aboard and 11 individuals on the ground. A preliminary report released on Thursday details the circumstances surrounding the accident and the ongoing investigative efforts.
Engine Separation and Initial Findings
Airport surveillance footage reviewed by investigators reveals that the No. 1 engine and its pylon separated from the wing moments after the aircraft rotated during takeoff. The report notes that a fire ignited near the left pylon’s attachment point to the wing and persisted until the aircraft impacted the ground. Flight data recorder (FDR) information indicates that the aircraft briefly climbed but did not exceed an altitude of 30 feet before crashing.
The NTSB’s materials laboratory has uncovered clear evidence of fatigue cracking on multiple fracture surfaces of the left pylon’s aft-mount lugs. Specifically, fatigue cracks were observed where the aft lug bore met the forward face, as well as along the forward lug bore. However, the forward lug’s outboard fracture exhibited only overstress failure without signs of fatigue. Additionally, a circumferential fracture was documented in the spherical bearing connecting the aft mount to the wing, although the bearing and associated hardware remained attached to the recovered wing clevis.
Wreckage was dispersed across buildings and a storage yard south of the airport, with separated pylon lugs and fan-blade fragments found on or near Runway 17R. The aircraft had accumulated approximately 92,992 flight hours and 21,043 cycles. The most recent visual inspection of the left pylon aft mount was conducted in October 2021, and lubrication of thrust links and spherical bearings was performed in October 2025. Certain detailed inspections linked to higher cycle thresholds had not yet been required for this airframe.
Industry Response and Regulatory Actions
The engine separation resulted in an uncontained failure that prompted swift action from regulators and operators. Following a recommendation from Boeing, UPS grounded its entire MD-11 fleet on November 7. FedEx, another major operator of the MD-11, also suspended operations of its fleet as a precautionary measure. The Federal Aviation Administration (FAA) subsequently issued two emergency airworthiness directives: initially grounding all MD-11 aircraft, then expanding the order to include DC-10 models due to their similar pylon configurations. The FAA is collaborating closely with Boeing and supporting the ongoing NTSB investigation.
These groundings have raised concerns about operational disruptions and financial consequences for both UPS and FedEx, given their reliance on these aircraft for cargo transport. Industry analysts are closely monitoring how competitors respond and the potential ripple effects on global logistics networks.
Historical Context and Continuing Investigation
The NTSB’s preliminary report draws parallels to the 1979 crash of American Airlines Flight 191, in which a DC-10 experienced a comparable separation of the left engine and pylon assembly during takeoff. Both the cockpit voice recorder (CVR) and flight data recorder from UPS Flight 2976 were recovered with usable data, providing critical information for the investigation.
The NTSB emphasizes that its inquiry remains ongoing and that all preliminary findings are subject to revision as further analysis is conducted.

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