A Southwest Airlines flight flying from New York City to Dallas turned terrifying this morning, when the left-side engine failed at 31,000 feet. Debris from the engine, which appears to have exploded, punctured the fuselage, leading to the violent depressurization of the cabin. Oxygen masks above every passenger dropped from the ceiling of the plane, and the pilots also quickly descended the Boeing 737 to below 10,000 feet, where the 143 passengers and five crew could breathe, before making an emergency landing about 15 minutes later, in Philadelphia.
The National Transportation Safety Board, which is now investigating, says that one person was killed, but did not share the cause of death. It marks the first fatality on a US airline flight over American soil since 2009.
Photos show a gaping hole where a window was on the 737, and outside a mangled mess of engine cowling, with the white-on-blue Southwest lettering crumpled like a soda can. According to a local NBC affiliate, passengers say a woman was partially drawn out of the broken window before being pulled back in.
This sort of incident is incredibly rare, and the combined engine loss and cabin depressurization presented a particularly dangerous, complicated scenario, even for well-trained pilots. We don’t yet know what caused the engine failure, or what happened inside the plane as it made its way back to the ground. But we do know how airline pilots are trained to deal with this kind of problem.
The first thing the pilots would have heard or felt is a bang, sway, or shudder, as the engine failed. They would check their instruments to back up their senses, looking for engine speed or fire warning indicators. They would have felt the depressurization, as pain in their ears. And then they would have started running through their emergency checklists.
“They get the idea ‘we’ve lost an engine, and lost pressure—we need to get down,’” says Douglas M. Moss, an aviation consultant with AeroPacific Consulting, who flies the Boeing 757 and 767.
First, the pilots put on their own oxygen masks and make sure the air is flowing. Stored in consoles, these typically look more like what fighter pilots wear than the flimsy yellow cups that drop onto passengers. Then they start heading for the ground. People can breathe at around 15,000 feet, but pilots aim to get below 10,000 to be safe. They don’t want to push an already damaged airframe into a steep dive, but drop as quickly as possible. Modern airliners can descend 20,000 feet in about 90 seconds. On the way down, having lost power on one side, the pilots would adjust their rudders, flaps, and other flight control surfaces to keep the aircraft balanced.
Based on photos and video passengers posted to Facebook, it seems most people remained calmly in their seats, with their oxygen masks on. (Many had the mask over just their mouths, but if you pay attention to the safety briefing—and this a reminder to do so—it should cover your mouth and nose, and you should breathe normally.)
The pilots don’t reach out to air traffic control until that descent is underway. “Something we teach students from day one is aviate, navigate, communicate—in that order,” says Brian Strzempkowski, who trains pilots at Ohio State University’s Center for Aviation Studies.
“They’d say mayday three times, say their call sign, engine failure, descending to 10,000 on heading of XYZ,” says Moss. The pilot, air traffic controllers, and an airline dispatch unit work to find the best airport for an emergency landing. In less critical circumstances, it may be better to fly a little farther to a larger airfield with more facilities, but in extreme emergencies—such as this one—the pilot can ask for priority, and the controllers will clear the path for her to land at the closest runway, in any direction.
As terrifying as this looks, the pilot talking to air traffic control sounded remarkably calm. “We have a part of the aircraft missing, so we’re going to need to slow down a bit,” she said.
On the ground, the airport scrambles firetrucks and other first responders to meet the incoming aircraft—just as they've practiced. Here, the pilot told ground controllers to have medics on standby. "We're going to stop right here by the firetruck," the pilot said. "Thank you guys for the help"
If the cabin is aflame or filled with smoke, passengers can use evacuation slides for a rapid exit. In this case, first responders held everyone on board until stairs could be driven up to the plane door. Then it’s a matter of getting everyone off safely. Today, the FAA issued a ground stop at Philadelphia International Airport, allowing already inbound flights to land, but stopping other traffic.
The National Transportation Safety Board is sending a team to examine the plane and interview witnesses and other relevant parties. If this was indeed an uncontained engine failure—where parts of the engine escape the cowling, or cover—that makes it a rare event. Engines are designed, and tested, to contain shrapnel if they fail or suck in a bird. The NTSB says it sees three or four such cases a year. The last was in September 2017, when when one of an Air France A380’s four engines shattered over Greenland. The plane made an emergency landing in Canada two hours later, with no serious injuries.
On this Southwest flight, the pilots and flight attendants contained the damage and prevented a very serious situation from getting any worse, says Strzempkowski. “It’s unfortunate this happened, but the system worked to prevent loss of life.” And now it’s up to the investigators and the rest of the airline industry to figure out what happened—and stop it from happening again.
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