Case Study Aa191

Case Study Analysis

Activity Title: American Airlines Flight 191

Name:

Date: 16 March 2013

Cause(s) of Accident

On May 25, 1979, American Airlines (AA) flight 191, a DC-10, experienced a number one (left wing) engine/strut failure, and subsequent engine and strut separation, on takeoff from Chicago, O’Hare Airport. During rotation, the left engine and strut assembly separated from the wing, and went over the top of the wing, severing hydraulic lines, with an associated loss of hydraulic pressure. The damage to the hydraulic lines subsequently caused a retraction of the outboard leading edge slats on the left wing.

The resulting lift asymmetry caused an uncontrollable left roll and loss of control of the airplane. The airplane continued to roll (112 degrees of roll at impact) and crashed in a trailer park near the airport. All 271 passengers and flight crew and two persons on the ground were killed.

According to the National Transportation Safety Board (NTSB) determined that the probable cause of the accident was the asymmetric stall and ensuing roll following the uncommanded retraction of the wing outboard leading edge-slats (FAA, n.d.).

Structural and Mechanical Factors

When McDonnell Douglas designed the DC-10-10 they did not consider the effects on maintenance of the very small tolerances existent in the engine-pylon subassembly. The design of the pylon complied with strength requirements of the Federal Aviation Administration (FAA) regulations, but the design did not adequately consider the vulnerability of the structure to damage during maintenance.

In the document presented to the Studies of Ethics, Safety, and Liability for Engineers, University of Texas at Austin, Hoover and Fowler (n.d.) cites, according to the NTSB, when the pylon is installed, only a .080-inch clearance was present between the bolt heads on the flange assembly and the clevis. These clearances, in several places were unnecessarily small...