Hi Bear,
The DC-10 incident at O'Hare was the result of the #1 engine and nacelle separating from the pylon attachment points to the wing causing the engine to flip over top of the wing. In doing so, major hydraulic and electrical lines were either damaged or severed and the wing itself was damaged. The Captain did not know the engine separated (couldn't be seen from the cockpit) and thought it was just an engine failure and therefore followed an emergency engine out procedure. This procedure called for reduction of air speed from the 165 knots they were at to 153 knots. However, the slats on the damaged wing retracted with the loss of hydraulic fluid and pressure as there was no mechanical lock on the DC-10. When the slats retracted, the stall speed on the wing increased from 124 knots to 159 knots, so that the wing went into a full aerodynamic stall. To make matters worse the Captain's slat disagreement and stick shaker (stall warning) was knocked out by the electrical failure and American Airlines had decided not to include a stick shaker on the FO's control column. So with the loss of left wing lift, the aircraft rolled left and went down. This stick shaker arrangement changed after the accident.
I recall there being Simulator studies conducted which basically indicated, more or less, the aircraft was not recoverable once into the wing stall phenomenon.
It was a black day for AA and the FAA when the NTSB released its findings. The change in engine removal along with the pylon using a forklift truck in place of designed rigging to first remove only the engine to save 200 man-hours of labor (cost reduction) was determined to be the root cause, all accomplished under FAA surveillance or non-surveillance depending on how you want to look at it. The same procedure was incorporated at Continental and UAL where the other damaged pylon to wing mounts were found.