What happened
On July 19, 1989, United Airlines Flight 232, a McDonnell Douglas DC-10, departed Denver-Stapleton International Airport for Chicago and Philadelphia. The flight proceeded normally until approximately one hour into the journey when an explosion was heard within the cabin, accompanied by significant airframe vibrations. The crew identified that the No. 2 tail-mounted engine had failed.
Following the engine failure, the aircraft experienced a total loss of all hydraulic systems. This rendered the primary flight control surfaces inoperable, leaving the crew unable to steer the aircraft using standard inputs. To maintain control, the crew relied on differential thrust from the remaining engines. An off-duty training check airman joined the cockpit to assist with throttle manipulation to manage pitch and roll.
The crew declared an emergency and was vectored toward Sioux Gateway Airport in Sioux City, Iowa. During the approach, the aircraft's descent rate increased significantly, and the crew struggled to maintain a stable glidepath without flaps or slats. The aircraft touched down on runway 22 with a high sink rate, causing the right wing to strike the ground first. The plane subsequently skidded, rolled onto its back, and caught fire. The accident resulted in 111 fatalities, along with 47 serious and 125 minor injuries.
Findings
Investigations revealed that a fatigue crack developed in a critical component of the engine's fan disk. This failure was caused by inadequate quality control and inspection procedures at the engine overhaul facility, which failed to identify an underlying metallurgical defect.