Accident Summary - continued

American Airlines (AAL) Flight 191, a DC-10, experienced a No. 1 engine strut failure, and subsequent engine separation, on takeoff from Chicago, O'Hare Airport on May 25, 1979.

Loss of actuator pressure allowed several left wing leading edge slats to retract. The hydraulic actuators did not include a "no back" safety feature to prevent inadvertent slat retraction due to loss of hydraulic system pressure.

The AAL flight crew was unaware that the left wing leading edge slats had retracted following takeoff. They interpreted the strut failure and subsequent engine separation as an engine failure and followed prescribed engine failure procedures. The scheduled V₂ (engine-out takeoff climb speed) that was flown was 6 knots below stall speed for a wing with retracted leading edge devices.

The left wing then stalled at 300 feet altitude, and the airplane rolled and crashed inverted. All 271 passengers and crew died in this crash.

Select here to view a Flash animation illustrating how this happened.

Select here to learn more about the stall speeds of the DC-10, how they're affected by slat extension/retraction, and to see an animation illustrating what happens when a wing stalls.

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