The National Transportation Safety Board says fatigue cracking within the left engine pylon structure is a key focus of its investigation into the crash of UPS Flight 2976, according to a preliminary report released Thursday.
The MD-11F went down shortly after takeoff from Louisville, Kentucky (KSDF), on November 4, killing all three crewmembers and 11 people on the ground.
Airport surveillance video reviewed by NTSB investigators shows the No. 1 engine and pylon separating from the wing moments after rotation.
“A fire ignited near the area of the left pylon attachment to the wing, which continued until ground impact,” the report states.
The aircraft climbed briefly but “did not get higher than about 30 ft above ground level,” according to flight-data recorder (FDR) information.
Fatigue Cracking
The NTSB’s materials laboratory found evidence of fatigue cracking on multiple fracture surfaces of the left pylon’s aft-mount lugs. According to the report, “examination of the left pylon aft mount lug fractures found evidence of fatigue cracks in addition to areas of overstress failure.”
On the aft lug, investigators observed a “fatigue crack…where the aft lug bore met the aft lug forward face.” The forward lug’s inboard fracture surface also showed that “fatigue cracks were observed along the lug bore,” while the forward lug’s outboard fracture consisted entirely of overstress with no fatigue indications.
Investigators also documented a circumferential fracture of the spherical bearing that connects the aft mount to the wing. The report notes that the “spherical bearing outer race had fractured circumferentially, exposing the ball element,” though the bearing and hardware remained attached to the wing clevis recovered at the site.
Wreckage from the aircraft was scattered across buildings and a storage yard south of the airport, with the separated upper portions of the pylon lugs and fan-blade fragments recovered on or near Runway 17R.
The aircraft had accumulated approximately 92,992 hours and 21,043 cycles. Visual inspections of the left pylon aft mount were last completed in October 2021, and required lubrication of the thrust links and spherical bearings was completed in October 2025. Certain special detailed inspections tied to higher cycle thresholds were not yet due for this airplane.
UPS grounded its MD-11 fleet on November 7 following a recommendation from Boeing. The FAA subsequently issued two emergency airworthiness directives—initially grounding all MD-11 aircraft, then expanding the order to include DC-10 models because of their similar pylon configuration.
American 191 Accident
In the preliminary report, the NTSB also references the 1979 crash of American Airlines Flight 191, noting that the DC-10 involved in that accident experienced a separation of the left engine and pylon assembly during takeoff. The agency highlights the event as a “similar” historical case in which the engine-pylon structure detached from the wing.
Both the cockpit voice recorder (CVR) and FDR were recovered with usable data. The NTSB says its investigation remains ongoing and that all preliminary findings are subject to change.
