The initial investigation found cracks in the engine pylon structure and inspections found similar cracks on other DC-10s. 12 days after the accident, on 6 June 1979, the FAA issued an Emergency Order of Suspension for the DC-10's Type Certificate (A22WE), grounding the DC-10. The suspension order was lifted on 13 July 1979, concurrent with several Airworthiness Directives (ADs) mandating inspections before further flight of DC-10s. Images of the grounded DC-10 fleet at the start of the busy summer flying season is darkly echoed by similar photographs today of the grounded 737 MAX fleet.
The probable cause of the accident from the NTSB's accident report:
The National Transportation Safety Board determines that the probable cause of this accident was the asymmetrical stall and the ensuing roll of the aircraft because of the uncommanded retraction of the left wing outboard leading edge slats and the loss of stall warning and slat disagreement indication systems resulting from maintenance-induced damage leading to the separation of the No. 1 engine and pylon assembly at a critical point during takeoff. The separation resulted from damage by improper maintenance procedures which led to failure of the pylon structure.
Contributing to the cause of the accident were the vulnerability of the design of the pylon attach points to maintenance damage; the vulnerability of the design of the leading edge slat system to the damage which produced asymmetry; deficiencies in Federal Aviation Administration surveillance and reporting systems which failed to detect and prevent the use of improper maintenance procedures; deficiencies in the practices and communications among the operators, the manufacturer, and the FAA which failed to determine and disseminate the particulars regarding previous maintenance damage incidents; and the intolerance of prescribed operational procedures to this unique emergency.
Today's Featured Map shows the intended route of AA 191 and the location of the crash just northwest of O'Hare.
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Karl L. Swartz.
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