Related Accidents / Incidents

On July 19, 1989 a United Airlines DC-10-10 experienced an in-flight separation of the stage 1 (titanium) fan disk in the No. 2 tail-mounted General Electric CF6-6 engine. The failure led to the loss of the three hydraulic systems that powered the airplane's flight controls and subsequent loss of control during an attempted landing at Sioux Gateway Airport, Sioux City, Iowa. The accident killed 111 passengers and 1 crewmember. The NTSB determined that the stage 1 titanium fan rotor disk assembly failure was caused by a fatigue crack that initiated from a Type I hard alpha metallurgical defect on the surface of the disk bore. The NTSB further concluded that the defect, or inclusion, was formed in the titanium alloy material during manufacture of the ingot from which the disk was forged.

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