Designed for Disaster: The DC-10 Airliner, Part 3

December 07, 2009

No Way Out - American Airlines Flight 191.

Five years had passed since the crash of Turkish Air flight 981 outside Paris. In the intervening years, there had been several incidents involving the DC-10 and one accident with fatalities - a Continental Airlines flight in Los Angeles.

In the L.A. accident, the crew heard a loud sound during the takeoff roll and aborted the takeoff. Due to their speed, they couldn’t stop the airplane before running out of runway and the landing gear had been torn off, followed by a fire, which destroyed the airplane. The sound had been caused by a tire blowing out.

After the disaster in France, each time there was an unflattering story about the DC-10 in the media, the flying public noticed. And they didn’t see a difference between an accident caused by a design problem and any other accident.  All they knew was DC-10 airplanes seemed to have a lot of problems.

On May 25 th, 1979, any remaining confidence seasoned travelers may have had in the DC-10 would be shattered when American Airlines flight 191 crashed immediately after take off in Chicago. An iconic photograph of a crashing DC-10, with one engine missing, would be seared into the consciousness of newspaper readers everywhere.

A Slow Motion Tragedy

To be fair to McDonnell-Douglas, it has to be pointed out that the aircraft was certified by the FAA and met all of the certification rules in force at the time. Still, there were decisions made that were not based on good engineering practices.

And a few of the decisions were based on requests made by end users whose motives may have been more related to profit than safety.

The first bad decision was simple enough.  American Airlines, the launch customer for the DC-10, wanted to delete something called the stick shaker from the co-pilot’s flight controls, presumably to save weight and money.

A stick shaker is a device that causes an impossible-to-ignore vibration and buzzing noise in the flight controls if the aircraft’s wing is about to stall and to delete it from either pilot’s controls is impossible to understand from a safety standpoint.

But certification standards in effect at the time allowed the fitting of such a device only on the captain’s controls so McDonnell-Douglas accommodated the customer - apparently not having learned a lesson from agreeing to American’s earlier request to change the design of the cargo door.

Design mistake number 2 involved how the remaining stick shaker was powered.

The device drew its power only from the number 1 engine, the engine on the captain’s side. There was no automatic cut-over to another source. In the event the number 1 engine failed, power for the stick shaker could be switched manually by the flight engineer to another source. But the engineer could not reach the appropriate switch while seated at his station.

The next poor decision was related to the wing’s leading edge slats.

When aircraft wings are pulled or pushed through the air, the air accelerates as it moves over the curved,

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