Probable Cause: metal fatigue crack failure
Overhaul interval < OEM’s limit
Why/How did SMS miss this risk?
The NTSB investigated the above-depicted crash at Fort Lauderdale Airport. Its report was its normal, detailed and carefully analyzed assessment of the underlying mechanical/engineering problem. The summary from the Press Release:
Shortly after the FedEx MD-10-10F touched down at the Fort Lauderdale – Hollywood International Airport Oct. 28, 2016, the flight crew reported hearing a “bang” as the brakes were applied. The airplane yawed to the left as it decelerated and came to rest on the left side of the runway, followed by a fuel-fed fire on the left wing. The two crewmembers evacuated the plane with one suffering minor injuries during the egress. The plane was damaged beyond economical repair.
Investigators found the failure of the left main landing gear was the result of a that initiated within the gear. The crack went undetected and gradually progressed until the gear collapsed.
The NTSB also said the interval of nine years between scheduled overhauls of the main landing gear, which exceeded Boeing’s recommendation of eight years, contributed to the accident. Investigators determined the fatigue crack would likely have been detected during an overhaul. The gear failed eight years and 213 days after its last overhaul.
The trail of the probable cause was found in these drawings. The Board also found that the FedEx years between overhauls exceeded the manufacturer’s recommendation.
To have stopped there does not reflect the industry’s SMS approach. If the system worked as expected, variance in the interval between overhaul (as recommended by the manufacturer v. implemented by the carrier), should have been reviewed. It would seem that was should have been a question for FedEx, its SMR committee and the FAA to have reviewed. And a question which the NTSB should have included in its report.
In this period during which SMS is being implemented, benefits found, techniques compared, and results assayed, might it have been appropriate for the Board to ask whether this interval had been the subject of a FedEx SMS review? Whether any data has been identified and if not, why not?
SMS’s rule of confidentiality may circumscribe the degree to which the Board may examine the inner workings of this valuable process, but by raising the issue of SMS’s involvement, the Board might have helped the FAA and the industry to determine whether the otherwise incredibly comprehensive mechanism has any blind spots.
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