The NTSB has released an update on the UPS McDonnell Douglas MD-11 cargo aircraft, operating as Flight 2976, that crashed on departure from Louisville International Muhammad Ali Airport (SDF) on Nov. 4.
The MD-11 was scheduled to fly to Daniel K Inouye International Airport (HNL) in Honolulu, when it crashed into the primary hub for UPS Airlines, known as Worldport. Flight-data recorder (FDR) logs show the plane did not get more than around 30 feet above ground level, that the plane cleared a blast fence past the end of the runway, but that its left main landing gear sheared the roof of a UPS warehouse at the southern edge of SDF. The aircraft’s left engine mount separated from the wing after take-off and a fire broke out on the wing. The crash claimed the lives of all three crew members and 11 people on the ground in the subsequent fire in an industrial area immediately south of the airport.
The preliminary report states that fatigue cracks were discovered on the left engine mount components that were recovered from the runway, including the spherical bearing assembly. It also stated that there was evidence of overstress failures.
The NTSB states that the aft-mounted bulkhead spherical assembly matched part number S00399-1, which was the subject of a Boeing Service Letter from Feb. 7, 2011. The letter reports four bearing failures caused by a fracture splitting the bearing race in two. The pieces would then separate toward the forward and aft directions. According to the Service Letter, a review of the spherical bearing failure by Boeing determined it would not result in a safety-of-flight condition. Inspection of the part should be included in the general 5-year visual inspection and a new spherical bearing part was released that eliminated the risk of splitting. While Boeing recommended replacing unserviceable bearings with the new part, it did not prohibit installing S00399-1.
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The NTSB is continuing its investigation into the inclusion of the bearing inspection in Boeing’s maintenance planning documents and manuals. It is also investigating the correspondence between Boeing and the FAA, leading up to the Service Letter’s release and afterwards.
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