Air Crash Investigations - Hidden Danger

On 3 March 1991, a Boeing 737 operating as United Airlines Flight 585 suddenly rolls into a dive and crashes within eight seconds, killing all 25 people on board. On 8 September 1994, USAir Flight 427 also rolls and crashes within thirty seconds, killing all 132 people on board. On 9 June 1996, Eastwind Airlines Flight 517 also rolls unexpectedly in similar circumstances, but the crew successfully regains control of the aircraft and lands safely. The cause of all three incidents was a design flaw with the rudder's control system which allowed the rudder to suddenly and unexpectedly go to full deflection and jam due to thermal shock of the hydraulic control valve.