Explosive decompression at 32,500 feet. What happens?

By Alan Levin

and Ryan Beene

Bloomberg

When even a small hole suddenly opens in a jetliner flying miles above the Earth, it unleashes hurricane-like forces. Everything that’s not strapped down flies toward the opening. The wind can easily lift a person up and out of the plane.

These terrifying episodes are rare but when they occur — such as Tuesday when a Southwest Airlines plane lost a window at 32,500 feet, killing a woman who was partly sucked out of the cabin — they have led to grisly results.

“That’s why they call it an explosive decompression,” said Nora Marshall, a former National Transportation Safety Board investigator who specialized in cabin safety and accident survival. “It is extremely forceful. The differential in pressure, it’s very, very significant.”

There have been at least a half dozen cases since the 1970s in which people were heaved out of airliners after planes suddenly lost pressure, prompting a rush of air as from a burst balloon. In a handful of extreme cases, the aircraft crashed, killing hundreds of people, after decompressions severed flight controls or disintegrated the planes.

Dawn of the jet age

Examples go back at least to the dawn of the jet age, when planes flying at ever higher altitudes relied on pressurized air in the cabin so people could breathe. Three British de Havilland Comets, the first pressurized civilian jet, came apart in midair within two years of the aircraft’s debut before engineers identified a design flaw.

“There’s a fog that comes into the cabin,” Marshall said. “Papers, bags, coats, jackets, everything will head to the breach in the fuselage.”

If a sudden opening in the plane is large enough, it creates a violent windstorm at the point where the pressurized air inside the passenger cabin rushes out of the plane.

“It’s instantaneous and it’s sustained over a period of time until the pressure inside the aircraft is equal to the pressure outside of the aircraft,” said Richard Healing, a former NTSB board member who is president of the consulting firm Air Safety Engineering.

The torrent of air would be most fierce next to the opening, just like when a person puts a hand next to a vacuum cleaner nozzle, said Massachusetts Institute of Technology aerospace professor John Hansman.

800 to 1,000 pounds of force

Hansman estimated that the air flowing outside Southwest Flight 1380 on Tuesday would have generated from 800 to 1,000 pounds of force. That would have been more than enough to pull Jennifer Riordan, 43, part way out of the plane before fellow passengers could pull her back in. A medical examiner in Philadelphia, where the Boeing 737-700 made an emergency landing, concluded that Riordan, a vice president at Wells Fargo & Co in Albuquerque, New Mexico, died of blunt impact trauma to the head, neck and torso.

“Her seat belt was keeping her held down at the hips,” Peggy Phillips, a retired nurse who was on the flight told The New York Post. “The rest of her was outside the plane.”

The plane’s window cracked open when a fan blade on the left engine, which had been weakened by metal fatigue, broke loose and sent engine debris flying, according to investigators. One clue about the power of the air blasting out the opening was released by the NTSB Wednesday: no traces of the window were found in the plane.

Aircraft manufacturers spent decades mastering the enormous forces created when a pressurized cabin flies at higher altitudes.

Those forces crippled the de Havilland Comet. Over the space of 12 months ending in 1954, three planes and their passengers and crews were lost. Investigators eventually concluded that stresses from pressurization at the corner of the square windows caused their fuselages to rupture catastrophically.

Similar DC-10 accident

In the case that is most similar to Tuesday’s accident, a window-seat passenger was sucked out of a National Airlines McDonnell Douglas DC-10 near Albuquerque in 1973. The airliner’s right engine exploded and shot debris through the passenger compartment, causing the victim’s window to fly off.

According to an NTSB report, the man was pulled entirely through the roughly 16- by 10.5-inch opening. He was buckled in, but the belt was fastened loosely, the agency said. A passenger sitting next to the man could not pull him back. The body wasn’t recovered for two years.

An improperly latched cargo door came off an American Airlines plane in 1972 while it was flying 11,750 feet above Ontario, Canada, with 67 people aboard, according to an NTSB report of the incident.

The loss of pressure in the cargo hold collapsed part of the cabin floor above it, injuring 11 people and damaging cables that controlled the rudder, stabilizer flaps and a rear engine, making an emergency landing in Detroit even more difficult.

Less than two years after the Ontario accident, a Turkish Airlines DC-10 had a similar loss of a cargo hatch with far deadlier results. The door popped off about 10 minutes after the plane had taken off from Paris bound for London and had reached about 11,000 feet, according to a U.S. Federal Aviation Administration report.

Part of the cabin floor collapsed and several sections of seats were drawn out of the plane with six passengers still in them.

Damage to flight-control cables caused the plane to crash in a forest outside Paris. All 346 people on board died, including the ejected passengers whose remains were found eight miles away from the site of the crash.

Nine people died in 1989 when a United Airlines jet decompressed shortly after taking off from Honolulu. A cargo door broke loose at about 23,000 feet, causing the cabin floor to cave in and flinging away several rows of seats. A flight attendant who was clinging to a seat leg was pulled to safety by passengers, according to the NTSB.

Some terrorist bombings have led to similar scenarios. One man was sucked out of a Daallo Airlines jetliner about 15 minutes after takeoff from Mogadishu Airport in Somalia in 2016, according a database maintained by the Flight Safety Foundation.

The plane had reached 12,000 feet and a small explosion — believed to have been from a bomb carried aboard by the man — blew a hole in the fuselage, causing decompression. The plane was able to return to the airport.

Another well-known example of decompression occurred in 1988 when an Aloha Airlines flight attendant plunged to her death after her plane’s roof, which had been weakened by corrosion, tore open at 24,000 feet. The case illustrates how quickly such events transpire.

“She was gone before anybody could recognize it,” Marshall said.