The NTSB’s preliminary report on the UPS crash of 2976 states that the accident was caused by the left engine and its pylon separating from the wing during takeoff, which was caused by fatigue cracks and overstress failure in the pylon structure. Airport surveillance video captured the engine and pylon separating from the wing just after the plane took off, leading to a fire and the subsequent crash. The NTSB also issued emergency airworthiness directives for similar MD-11 and DC-10 models due to this issue.
The report goes on to say the left engine and pylon detached from the left wing of the MD-11F aircraft shortly after takeoff. The separation was linked to evidence of fatigue cracks and areas of overstress failure in the pylon structure. This separation led to a fire and the aircraft losing control and crashing.
“The left pylon aft mount’s forward and aft lugs were both found fractured near their 2 o’clock (inboard fracture) and 9 o’clock (outboard fracture) positions when in the aft-looking-forward frame of reference. The fractured and separated upper portions of the forward and aft lugs were found adjacent to runway 17R. The left wing clevis, aft mount spherical bearing, and aft mount attachment hardware were found with a portion of the left wing at the accident site. The bolt, spherical bearing, and associated hardware remained attached to the wing clevis. The spherical bearing outer race had fractured circumferentially, exposing the ball element.The right engine remained attached to the right wing pylon, both found at the accident site. The right wing pylon-to-wing forward and aft mounts had separated from the right wing pylon but were found about 87 ft from the right engine. The right pylon aft mount remained attached to the right wing clevis,” the report says.
In response to the findings, the NTSB and FAA issued emergency airworthiness directives for similar MD-11 and DC-10 models, which have comparable pylon configurations.