Flight 191 DC-10 Takeoff Crash from Chicago

Flight 191, a DC-10, departed on May 25th, 1979 from O'Hare airport in Chicago, heading for Los Angeles. Just prior to takeoff, some pieces of the port engine fell off the aircraft. After the aircraft took off, the entire engine and pylon assembly tore free. The resulting crash killed all 271 onboard.

Eight weeks prior to the accident, both the pylon and the engine were removed during scheduled maintenance. The normal procedure is to remove the engine and the pylon separately, but alternate procedures had been adopted involving removing both simultaneously.

After the crash, fatigue cracks and fractures were found on the pylon, and a crescent shaped deformation was found on the Lipper flange of the pylon bulkhead. It is believed that the deformations occurred during removal or replacement of the pylon.

The operational envelope for an aircraft not only includes how it is flown, but also how it is maintained. Changing procedures had invalidated the safety argument for the aircraft.

As a result of the crash and the incident investigation, the Federal Aviation Authority (FAA) grounded all DC-10 registered in the USA and began inspections. On six aircraft, belonging to two airlines, similar fractures were found. Both of these airlines had adopted procedures to remove both the engine and the pylon simultaneously.


The Flight 123 crash was also caused by fatigue through incorrect maintenance.