FAA History Lesson -- May 25

From the FAA Historical Chronology, 1926-1996...

”May 25, 1979: An American Airlines DC-10 crashed into an open field near Chicago's O'Hare airport after its left engine and pylon assembly separated from the aircraft on takeoff. The engine and pylon rotated up and over the left wing, taking part of the wing’s leading edge with them and damaging the control system. The ensuing crash and fire killed all 272 persons aboard the flight and two people on the ground, an unprecedented toll for an airline accident within U.S. airspace.

Early in its investigation, the National Transportation Safety Board discovered the presence of a fatigue fracture of a pylon forward thrust link attach bolt. On May 28, FAA Administrator Langhorne Bond ordered all airlines to keep their DC-10s on the ground until they had completed certain visual inspections. The next day, after learning that these checks were turning up potentially dangerous deficiencies in the pylon mountings, Bond grounded the entire U.S. DC-10 fleet pending a more comprehensive inspection. His order included U.S.-certificated Airbus A-300s because of the similarity of their pylon to the DC-10's.

As these inspections progressed, evidence mounted that the problem might lie in American Airline's non-standard use of a forklift to dismount and remount engine and pylon as a single unit during maintenance. Similar cracks had been found on DC-10s operated by Continental Airlines, the only other carrier using the forklift method. On Jun 5, however, the discovery of cracks that appeared unrelated to the forklift procedure strengthened evidence that seemed to suggest the existence of some more fundamental problem. On Jun 6, Bond suspended the DC-10's type certificate indefinitely. He then ordered three parallel investigations into the DC-10 issue.

Thirty-seven days later, FAA's investigative teams concluded that the aircraft destroyed in Chicago had indeed been damaged by the forklift procedure. This was also the cause of the other cracks found in the pylons of DC-10s operated by American and Continental. (The two airlines later received civil penalties of $500,000 and $100,000 respectively for using the procedure.) Other findings of the teams supported the conclusion that the DC-10 should be returned to service, and FAA therefore lifted the grounding order. The agency required a stringent program of inspections, however, and directed the manufacturer to redesign certain engine mount components. ”

The accident investigation was quite complicated and centered on the maintenance procedure used by American. You might be interested in the side issue of the controllers working the flight. When it comes to aviation, controllers often have front-row seats to disasters no one wants to witness.

Witness to American Airlines Flight 191

I’m glad I worked in a Center.

Don Brown
May 25, 2008