United Airlines Flight 232: Hydraulic Failure

United Airlines Flight 232 On July 19, 1989, a McDonnell Douglas DC-10-10 operated by United Airlines experienced a catastrophic failure of the number 2 tail-mounted engine during cruise flight. The catastrophic failure led to engine debris severing all three flight control hydraulic lines resulting in total hydraulic loss. The pilots were subsequently unable to control the airplane, except by manipulation of the throttles to vary engine thrust, resulting in a crash landing. The NTSB determined that the probable cause of the accident was the inadequate consideration given to human factors limitations in the inspection and quality control procedures used by United Airlines’ engine overhaul facility which resulted in the failure to detect
The failure involved disintegration of the disc causing metal fragmentation and discharge which destroyed the engine and severed all three hydraulic system lines leading to total loss of airplane flight controls. The pilots attempted to fly the airplane but found the control columns had no effect on aircraft movement. Without hydraulics, the crew was forced to attempt a landing without flaps, slats, flight controls, or landing gear. The crew was eventually able to deploy landing gear, which managed to manually lock into place.

Failure of the stage 1 fan rotor assembly was attributed to the development of a fatigue crack in the titanium alloy which developed over 17 years. A metallurgist inspector with the NTSB found the titanium alloy piece, which unimaginably broke into two pieces, had elements of nitrogen and oxygen contained within the titanium. When those impurities are present, they increase the ferociousness of each engine start and stop on the metal. Every time the defected area was loaded, the crack became progressively