On July 19, 1989, United Airlines Flight 232, a McDonnell Douglas DC-10 flying from Denver to Chicago, suffered an uncontained failure of its tail-mounted No. 2 engine while cruising at 37,000 feet. Debris from the disintegrating engine severed all three of the aircraft’s hydraulic systems — a failure the DC-10’s design had assumed to be practically impossible — leaving the crew with no working flight controls except the throttles of the two remaining engines.
For some 45 minutes, Captain Alfred Haynes and his crew, joined by Dennis Fitch, a United DC-10 training pilot who had been riding as a passenger, steered the crippled jet by adjusting engine power alone, fighting its constant tendency to roll, and guided it toward an emergency landing at Sioux City, Iowa.
The aircraft reached Sioux Gateway Airport but came down short of a stable landing, striking the runway at high speed, cartwheeling and breaking apart in a cornfield. Of the 296 people aboard, 112 died and 184 survived — a survival outcome investigators credited to the crew’s airmanship and to the emergency services waiting on the ground.
The National Transportation Safety Board (report AAR-90/06) found that the engine’s stage 1 fan disk had shattered because a fatigue crack, originating in a metallurgical defect in the titanium from which the disk was forged, had gone undetected. The Board determined the probable cause was the inadequate consideration given to human-factors limitations in the inspection and quality-control procedures used by United’s engine overhaul facility.
The accident led to fleet-wide inspection directives for fan disks, new requirements to protect hydraulic lines from debris, and lasting changes in aircraft certification. Flight 232 is still taught as a landmark example of crew resource management.
Download NTSB Aircraft Accident Report AAR-90/06 (3.7 MB file)