The no. 2 fan hub broke and severed all three hydraulic systems. The crew used the remaining 1 & 3 engines to skid the plane through turns. They lined the airplane up with the runway, but as they were going 250 mph and one wing was dipped, the plane rolled upside down (not cartwheel) on impact and broke into 3 pieces. 184 survived, 112 perished. Responsible: General Electric (engine maker). United couldn't have detected the fracture in the fan disk. It was caused when the engine was manufactured, and remained hidden for 18 years, until July 19, 1989.