May 25, 1979. American Airlines flight 191, a McDonnell Douglas DC-10, was scheduled for nonstop service from Chicago O'Hare International Airport to Los Angeles International Airport, with 13 crew and 258 passengers on board. Captain Walter Lux, with 22,000 hours in his logbook and eight years' experience flying the DC-10, was in command.

At 3:02 PM, 191 rolled down the runway at O'Hare under the first officer's control. Just before the aircraft rotated, the left underwing engine on the trijet began to loosen from its pylon, and as the aircraft became airborne, it tore off entirely, flew over the wing, and fell to the ground. Despite the air traffic controller's calls, the DC-10 maintained radio silence for the next ten seconds, climbing normally, until it began to bank to the left at an altitude of about 300 feet, keeled over, and slammed into a field adjacent to a trailer park on the airport's outskirts. All 271 people on board were killed, in addition to two on the ground.

"...Because the engine fell off," you're probably saying. Well, not exactly. The DC-10 was designed to withstand the loss of an engine. In fact, when the engine fell off, Lux did exactly what he was supposed to do in such a situation: he kept the plane's flaps and slats extended for maximum lift, and reduced power on the right engine so that the plane would remain stable, adding rudder and aileron input to compensate. Indeed, the DC-10 did remain stable... albeit for only ten seconds.

So what happened? Unbeknownst to anyone in the cockpit, when the engine took off over the wing, it tore off the left wing's slats and flaps. Once the left wing had lost its extra lift, it couldn't keep the left side of the airplane up at reduced speed. So the left side began to fall while the right side was still rising: the airplane fell over and crashed.

Every DC-10 in the United States was overhauled after Flight 191's crash to strengthen the underwing engine pylons. Apparently, the pylon on Flight 191's left engine was damaged when the engine was being replaced. McDonnell Douglas, in their infinite wisdom, had told airlines it was okay to replace the engine and pylon at the same time, but in reality, the combined weight of the two made replacements riskier and damages more likely.

Combine that with the fact that the engine was designed to fly over the wing if it became severed, and that the separation disconnected the display in the cockpit that would tell the pilots whether the slats and flaps were deployed or not... well, needless to say, there was a blatant design flaw in the DC-10.

American chose to write off Flight 191, blaming their mechanics instead of the airplane's manufacturer. McDonnell Douglas thanked American several years later by giving them a sweet deal on a fleet of McDonnell Douglas MD-80 aircraft. However, pylon strength remained a niggling issue on both the DC-10 and its successor, the MD-11. Flight 191 helped spell the beginning of the end of McD's venture in widebody aircraft production.

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