Parallels Between the 737 Max 8 and the DC-10 Crashes of the Late 1970s

There are strong parallels between the McDonnell Douglas DC-10 in the late 1970s and the Boeing 737 Max planes of today.

Parallels Between the 737 Max 8 and the DC-10 Crashes of the Late 1970s
McDonnell Douglas DC-10 commons.wikimedia.orgMcDonnell Douglas DC-10

On May 25, 1979, Judith Wax, a 47-year-old suburban Chicago housewife was on a high. She and her husband, 52-year-old Sheldon Wax, the managing editor of Playboy magazine, were on their way to the American Booksellers Convention in Los Angeles where Mrs. Wax was going to promote her first book entitled, "Starting in the Middle."

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Along with 256 other passengers and 13 crew members, the Waxes settled into their roomy seats on board American Airlines Flight 191, a double aisle McDonnell Douglas DC-10 with three engines – one under each wing and one at the back. As the big plane lumbered into the sky, observers on the ground noticed something odd. Just 300 feet off the ground, the plane had keeled over onto its left side until it was almost flying inverted.

On O'Hare's Airport's observation deck, Canadian amateur photographer Michael Laughlin was able to grab a shot of the plane before there was a deafening roar and a huge fireball. 271 people on the plane perished along with two workers at a repair garage on the ground, making it the deadliest aviation accident to have occurred in the United States. Of the passengers, 262 were American, four were from Saudi Arabia, and one each were from South Korea, Austria, Belgium and The Netherlands.

What Went Wrong?

An American Airlines employee on the ground had seen what had gone wrong. He witnessed the engine under the left wing separate from its connecting pylon and fly up and over the left wing, before it plummeted to the ground. The engine had behaved as if it still had lift, and it followed the path of the airflow over the wing. As it flipped over the wing, the engine severed the hydraulic fluid lines responsible for locking the wing's leading-edge slats in place, and it damaged the wing's leading edge. It is this leading edge that creates the aerodynamic forces that keep an airplane in the sky.

An investigation by the U.S. National Transportation Safety Board traced the fate of Flight 191 to an American Airlines maintenance facility in Tulsa, Oklahoma. There, between March 29 and 30, 1979, the airplane, tail number N110AA, had undergone routine service, during which the engine and pylon had been removed from the wing for inspection and maintenance.

McDonnell-Douglas's removal procedure called for the engine to be detached from the pylon before the pylon was detached from the wing. However, seeking greater efficiency, American Airlines, Continental Airlines and United Airlines had developed alternate procedures that saved approximately 200 man-hours per aircraft. The airlines stated that "more importantly from a safety standpoint, it would reduce the number of disconnects (of systems such as hydraulic and fuel lines, electrical cables, and wiring) from 72 to 27."

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In their new procedures, American, Continental and United removed the engine and pylon assembly as a single unit. United used an overhead crane to support the engine and pylon assembly, while American and Continental supported the engine and pylon assembly with a forklift.

American and Continental had learned that if the forklift wasn't exactly positioned, the engine and pylon assembly would rock back and forth and jam the pylon against the wing's attachment points. Forklift operators had to rely on voice and hand gestures because they couldn't see the juncture between the pylon and wing. During maintenance on tail number N110AA, there was a shift change, and the new shift found that the pylon had jammed on the wing, and they had to reposition the forklift.

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This repositioning caused unseen structural damage to be done to the wing's pylon attachment points. Then, like a ticking time bomb, tail number N110AA continued to fly an additional eight weeks, with the damage increasing with every takeoff and landing.

Following the crash of Flight 191, an inspection was made of the DC-10 fleets of the three airlines. Inspectors found the United Airlines DC-10s were fine, but several DC-10s at American and Continental had the same fatal flaw to their pylon mounts as Flight 191.

Two weeks after the crash of Flight 191, on June 6, 1979, the U.S. Federal Aviation Administration suspended the DC-10's type certificate, grounding all DC-10s under its jurisdiction. It also enacted a special air regulation banning all DC-10s from U.S. airspace. This prevented foreign DC-10s not under FAA jurisdiction from flying over the U.S. Once the FAA was satisfied that maintenance procedures were primarily at fault and not the actual design of the aircraft, the type certificate was restored on July 13, 1979, and the special air regulation was repealed.

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A History of Accidents

However, the damage done to the DC-10's reputation was not so easily restored. Prior to Flight 191, the DC-10 had already been involved in two other crashes: on June 12, 1972, near Windsor, Canada, American Airlines Flight 96 experienced an explosive decompression after its left rear cargo door blew out. The rapid decompression in the cargo hold caused the floor of the passenger compartment to partially collapse, restricting some of the control cables that led to various flight control hydraulic actuators.

The plane's rudder deflected to its maximum right position, and the engine in the plane's tail shut down. The pilots still had control of their ailerons, the right elevator and the horizontal stabilizer. By applying tremendous back pressure on the yoke, and coming in at high speed for an emergency landing, the pilots were able to land safely at Detroit Metropolitan Airport.

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The cause of the accident was determined to be a problem in the cargo door latching system, which had failed to latch completely while not giving any indication to the crew. A separate locking system, which was supposed to ensure that this couldn't happen was inadequate.

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McDonnell Douglas instituted a number of minor changes, but on March 3, 1974, the rear cargo door of Turkish Airlines Flight 981 blew open, causing that aircraft to go out of control. It crashed in a forest near Paris, France, killing all 346 people on board, and giving it the dubious distinction of being the deadliest crash in aviation history until the 1977 Tenerife airport disaster.

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Just five months after the crash of Flight 191, on October 31, 1979, a DC-10 operating as Western Airlines Flight 2605 crashed in Mexico City. That crash was attributed to low visibility and an attempt to land on a closed runway. Less than a month later, on November 28, 1979, a DC-10 operating as Air New Zealand Flight 901 flew into Mount Erebus on Ross Island, Antarctica, killing all 237 passengers and 20 crew on board. That accident is New Zealand's deadliest peacetime disaster, and the deadliest accident in Air New Zealand's history.

10 years later, on July 19, 1989, another DC-10 flying as United Airlines Flight 232, lost its tail-mounted engine, which caused the loss of many of its flight controls. It crash landed at Sioux City, Iowa, killing 111 passengers, but 185 survived.

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In spite of all this, the DC-10 went on to have a long career as both a passenger and cargo aircraft, and DC-10 production didn't end until 1988. Many retired passenger DC-10s have been converted to cargo use as MD-10s. They are a part of the FedEx Express fleet. In 2000, American Airlines retired its last DC-10s after 29 years of service, and in February 2014, Biman Bangladesh Airlines flew the last ever DC-10 passenger flight.

The Boeing 737 Max

On October 29, 2018, a Boeing 737 Max 8 airliner flying as Lion Air Flight 610 took off from Jakarta, Indonesia heading to Pangkal Pinang. 12 minutes after takeoff, it crashed into the Java Sea killing all 189 passengers and crew on board.

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 Just four and a half months later, on March 10, 2019, Ethiopian Airlines Flight 302 crashed shortly after takeoff from Addis Ababa, killing all 157 people on board. This second crash raised concerns about the safety of the 737 Max and caused countries around the world to ground their fleets.

The history of the 737 Max is one of hurried change. In 2011, Boeing re-engineered its workhorse 737 aircraft in an effort to compete with Airbus's A320neo, which had newer and more efficient engines. During testing, Boeing discovered that the 737 Max's new fuel-efficient engines were heavier than the older engines, and changed the aerodynamics of the plane. They caused the plane's nose to pitch up under certain conditions.

To counter this problem, Boeing introduced MCAS, the Maneuvering Characteristics Augmentation System. MCAS, which was activated by Angle of Attack data, and would automatically trim the horizontal stabilizer to bring down the nose. When Lion Air Flight 610 taxied down the runway, the information coming from its Angle of Attack sensors was off by 20-degrees. This should have caused a warning light to appear in the cockpit, but that light wasn't part of an additional-cost package that Lion Air hadn't purchased.

Once in the air, the erroneous Angle of Attack data caused the MCAS system to repeatedly activate, driving the jet’s nose into a fatal dive. Ethiopian Airlines Flight 302 experienced a similar loss of control shortly after takeoff.

On March 13, 2019, shortly after President Trump and Boeing CEO Dennis Muilenburg said that they were voluntarily grounding the 787 Max 8 and 9, the U.S. Federal Aviation Administration said that it was "ordering the temporary grounding" of all Boeing Max airplanes. According to an earlier article on this site, "the last time the FAA issued such an order was for the McDonnell Douglas Corp.'s DC-10 in 1979." While the future of the 737 Max hangs in the balance, it's probably a good time to review the history of the DC-10.

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