The Federal Aviation Administration yesterday ordered changes in the McDonnell Douglas DC10 jumbo jet to prevent the kind of sudden control failure that was partly blamed for the nation's worst aviation accident almost three years ago.
The accident, on May 25, 1979, in Chicago, killed 273 people. The American Airlines plane, en route to Los Angeles, crashed almost immediately after takeoff from O'Hare International Airport.
The system the FAA ordered modified concerns control surfaces called slats, large metal plates on the front edge of the wing that are extended out and down from the wing during takeoff. That extension gives the wing added lift at low speeds and makes it possible to take off and land on relatively short runways.
As the DC10 was lifting off the ground, an engine and its support mountings broke loose. Vital electrical wiring and hydraulic fluid lines were ripped from the wing, and the slats on the left wing retracted while those on the right wing remained extended.
That gave the Chicago pilot a condition called asymmetrical slats, where the right wing had substantially greater lifting ability than the left. The plane rolled to the left and crashed to the ground. Test pilots "flying" a simulator after the accident learned how to safely fly with the condition, but all but one "crashed" the simulator in his first flight.
In ordering the modification to prevent asymmetrical slats the FAA did not cite the Chicago crash, but two other incidents. In the most recent one, an Air Florida DC10 safely aborted its takeoff in Miami after the right-wing engine failed. Flying parts from the engine severed a cable and the right-wing slats retracted.
Top technical experts from the FAA and the Douglas Aircraft Co. have been meeting in recent weeks to hammer out the final details of the change. Parts have been ordered and must be installed on all U.S. DC10s by Jan. 31, 1983. The cost of the change will be "less than $10,000 an airplane," according to a McDonnell Douglas spokesman, and will be borne primarily by the individual airlines.
The FAA ordered several changes in the DC10 after the Chicago crash, including added redundancy in warning systems, but the slats were not changed. "The kind of damage done in Chicago was totally unpredictable," a McDonnell Douglas spokesman explained. An American Airlines maintenance procedure was blamed by the National Transportation Safety Board as the reason the engine and its mountings separated from the wing in the first place. But the NTSB said the probable cause of the accident was the asymmetrical slats and the resulting roll of the aircraft.