The warning nobody sent: the DC-10's cargo door and Turkish Airlines Flight 981

The McDonnell Douglas DC-10 entered service in 1971, a three-engine widebody built to carry around 300 people across the country. It is the airplane the MD-11 later grew out of. Like many jets of its era, it had cargo doors in the lower fuselage that swung outward. Outward-opening doors leave more room inside for bags and freight, but they come with a catch: once the airplane is pressurized, the air inside pushes the door outward with tons of force, and the only things holding it shut are its latches.

On the DC-10, an electric motor drove the latches closed. A handler then pulled down a handle on the outside, which pushed a set of locking pins into place behind the latches. If the pins were in, the door was safe. If the latches hadn't fully closed, the pins weren't supposed to go in, and the handle wasn't supposed to go down.

In practice, the handle could be forced down anyway.

The first warning came on the ground. In May 1970, during a pressurization test at the factory, a DC-10's cargo door blew out. Douglas put it down to a mechanic's error.

The second came in the air. On June 12, 1972, American Airlines Flight 96 left Detroit with 67 people on board. Five minutes later, climbing through about 11,700 feet over Windsor, Ontario, the rear cargo door blew off.

The cabin above the cargo hold had no vents to let the pressure equalize, so part of the floor collapsed into the hold. The control cables for the tail and the center engine ran under that floor. The rudder jammed and the center engine shut down. Captain Bryce McCormick still had some control, and he had practiced steering a DC-10 with engine power alone in the simulator. He flew the jet back to Detroit and landed it. Nobody died.

The NTSB found that the door had looked closed when it wasn't: the loader had forced the handle down with his knee. It recommended two things. Make it impossible to close the handle unless the door was locked, and vent the cabin floor so it couldn't collapse.

The FAA's engineers drafted an airworthiness directive, a legally binding order that every DC-10 operator would have had to follow. It was never released.

According to later accounts, the president of the Douglas division, Jackson McGowen, called the head of the FAA, John Shaffer, and offered to handle it with service bulletins instead. Service bulletins are the manufacturer's own recommendations: airlines aren't legally required to carry them out, and they don't come with the public attention of a directive. The FAA agreed. It became known as the gentleman's agreement.

Douglas sent out its fixes. They included stronger wiring for the latch motor, a small window for checking that the locking pins were in, a placard telling handlers to verify the pins, and a metal support plate to make the handle much harder to force. The floor vents were left out. A U.S. Senate hearing would later criticize the FAA for weak enforcement and secret proceedings.

Convair, a division of General Dynamics, built the DC-10's fuselage for Douglas, including the cargo doors. Its director of product engineering was Dan Applegate. On June 27, 1972, two weeks after Windsor, he sent a memo to his boss.

He wrote that DC-10 cargo doors "will come open sometime during the twenty-plus years of use ahead for the DC-10," and that "I would expect this to usually result in the loss of the aircraft." He pointed out that the same thing had already happened in the 1970 ground test, and he argued for deeper changes to the door and the floor.

As far as the record shows, the memo never reached Douglas. By most accounts, Convair's managers worried that raising it now could make Convair responsible for the cost of the changes and for anything that went wrong; one of them reportedly called it "an interesting legal and moral problem." The memo stayed inside Convair until lawyers found it years later.

Meanwhile, Douglas kept building DC-10s, with the fixes added on the production line. Fuselage number 29 was one of them.

Ship 29 went to Turkish Airlines, which named it *Ankara* and registered it TC-JAV. On March 3, 1974, it was flying Turkish Airlines Flight 981 from Istanbul to London, with a stop in Paris.

That day there was a strike at a British airline, and many travelers were stranded at Orly. Flight 981 had empty seats, so it filled up. It left Paris with 335 passengers and 11 crew.

A baggage handler closed the rear cargo door and pushed the handle down. The placard about checking the locking pins was printed in English and Turkish, and he spoke neither. Looking through the inspection window wasn't his job, and the person who was supposed to make that check didn't do it. In the cockpit, the warning light went out.

About ten minutes after takeoff, climbing through about 11,000 feet, the rear cargo door opened. The floor above it collapsed, as it had over Windsor. This time the damage was worse, and the cables to the tail and the center engine were cut. Six passengers in the rear rows were pulled out of the airplane.

The crew had no way to control the tail. Seventy-seven seconds after the door opened, the airplane struck the Ermenonville forest, northeast of Paris. All 346 people on board died. At the time, it was the deadliest air crash in history.

Investigators started with the door. Douglas had issued a fix for exactly this failure almost two years earlier, so why hadn't it worked?

When they examined the wreckage of the door, they found that the support plate from the service bulletin had never been installed on Ship 29. The airplane's records said it had been. Douglas had designed that fix and sent it out, and the paperwork said this airplane had it. Ship 29 was flying without it.

Other parts of the mechanism were also out of adjustment. The locking pins came up short of where they needed to be, and the switch for the cockpit warning light was rigged so the light went out before the door was locked. Exactly who made those adjustments, and when, was never fully settled.

After the crash, Douglas first pointed to the baggage handler. The baggage handlers' union answered by refusing to load DC-10s until the company apologized. John Shaffer, who had left the FAA by then, argued that a directive might not have prevented it either, because the FAA relied on manufacturers to certify their own fixes and didn't check.

Four days after the crash, the FAA issued an airworthiness directive on the cargo door, the kind of binding order it had decided against in 1972. The DC-10's cargo door latches were completely redesigned. A later rule required stronger, vented floors on the DC-10 and other widebodies, and today's certification rules require cargo doors that can't be pressurized unless they are locked, with a way to see the locks directly. Airliners designed since then have to meet those rules.

The families sued. The Applegate memo came out in the litigation, and the defendants settled for an estimated $100 million, about $80 million of it from McDonnell Douglas. At the time it was reported as the largest settlement ever paid for an air disaster.

The DC-10 kept flying, and its problems didn't end in 1974: the next chapter is Chicago, 1979. Today the last DC-10s in the air are freighters and the converted very large air tankers that fight wildfires; you can watch DC-10s live on the tracker or see the air tankers when they are flying. The airplane it grew into, the MD-11, has its own story.