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American Airlines Flight 191 was a flight that flew from O' Hare International Airport in Chicago, Illinois to Los Angeles International Airport in Los Angeles, California.
The flight crashed on May 25, 1979, killing everyone on board. The flight was being performed on N110AA, a Douglas DC-10-10 aircraft on that day.
Having taken off that day from O' Hare, the plane carried 258 passengers and 13 crew members for its flight. Two people on the ground would die in the upcoming incident. At 3:02 PM CDT, the aircraft began its takeoff down Runway 32R (Right).
Shortly after the takeoff roll began, tower controllers witnessed the number one engine separate from the aircraft and fly up and over the left wing. The aircraft continued in a normal climb momentarily, as fuel and leaking hydraulic fluid spewed in a vapor trail behind the doomed plane. The pilots aimed to reduce speed to the recommended engine-out climb speed of 153 knots, but the engine separation had severed the hydraulic lines that controlled the aircraft's leading-edge wing slats (retractable devices that increase a wing's lift during takeoff and landing). Further damage to the aircraft's warning systems meant that the pilots were unaware of the aircraft's true configuration. As the hydraulic fluid bled away, the slats retracted on the left wing, raising that wing's stall speed from 124 knots to 159 knots. As the aircraft slowed the left wing stalled, and the aircraft quickly entered an uncontrollable 112-degree bank [1] (http://www.airdisaster.com/photos/aa191/photo.shtml) and pitched nose-down from an altitude of 400 feet, slamming into a nearby mobile home park and an open field. All 271 persons on board were fatally injured during the impact and explosion. In addition, two residents of the mobile home park also perished.
The resulting investigation by the National Transportation Safety Board (NTSB) revealed the probable cause to be attributable to damage to the left wing engine pylon that occurred during an earlier engine change at American's aircraft overhaul facility in Tulsa, Oklahoma. The pylon was damaged due to a incorrectly executed engine removal procedure. The correct procedure called for removal of the engine prior to the removal of the engine pylon. To save time and costs, American Airlines instructed its mechanics to remove the engine together with the pylon all at one time. A large fork lift was used to hold the engine up while it was detached from the wing. During the procedure a crew shift change occurred, leaving the fork lift unmonitored for a period of time. A problem in the fork lift's hydraulic system caused it to tilt the engine while still under the wing. This exerted enough pressure on the engine pylon to create a large indentation and a serious fracture in its body. The fracture went unnoticed for several flights, getting worse with each flight that the plane had taken. During flight 191's takeoff, enough force was generated to finally cause the pylon to fail. With the failure of the rear pylon, the left engine detached from under the wing and tore away. With the loss of the engine and the position of the slats, the plane was destined for disaster. The NTSB concluded that given the circumstances of the situation, the pilots were not in any way to blame for the resulting accident.
Many problems with DC-10s were discovered as a cause of the accident, including problems in the wings and engines areas. Since this tragedy happened just after a Western Airlines DC-10 had crashed in Mexico City and six years after a Turkish Airlines DC-10 crashed in Paris, the FAA quickly ordered all DC-10s to be stored until all problems were solved. The result of the problem solving was an arguably more efficient and safe DC-10.
The crash in Chicago remains the largest single-aircraft air crash in United States history. Another flight with the same number, Delta Air Lines Flight 191, crashed at Dallas/Fort Worth International Airport in 1985. Neither company has ever used the 191 flight number again. In addition, Puerto Rican airline Prinair also had a fatal flight numbered flight 191.
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