Violent Wind, Flying Debris: What Happens in a Plane Rupture

(Bloomberg) -- When even a small hole suddenly opens in a jetliner miles above the Earth, it unleashes hurricane-like forces. Everything that’s not strapped down is 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 on Tuesday, when a Southwest Airlines Co. plane lost a window at 32,500 feet, killing a woman who was partly sucked out of the cabin -- they’ve led to grisly results.

Violent Wind, Flying Debris: What Happens in a Plane Rupture

“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 if 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.

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’s president of the consulting firm Air Safety Engineering LLC.

The pressure within the cabin of the Southwest jet would have been roughly three times the pressure outside at the plane’s altitude. Far lower changes in the earth’s air pressure can cause the intense winds from hurricanes or storm fronts.

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

Violent Wind, Flying Debris: What Happens in a Plane Rupture

Hansman estimated that the air flowing outside damaged Southwest Flight 1380 would have generated 800 to 1000 pounds (363 to 454 kilograms) 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.

While she was outside the craft she would have been buffeted by air rushing past the jet. The plane was traveling at 496 miles (798 kilometers) per hour when the engine failed, according to data compiled by the website.

A medical examiner in Philadelphia, where the Boeing Co. 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.

Pressurized Cabins

“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.

Violent Wind, Flying Debris: What Happens in a Plane Rupture

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.

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.

Cargo Doors

According to an NTSB report, the man was pulled entirely through the opening of roughly 16- by 10.5-inches. 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.

In 1972, an improperly latched cargo door came off an American Airlines plane 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.

Turkish Airlines

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 crash site.

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.

Somalia Bomber

Even pilots have been partially ejected. A British Airways captain was flung from a BAC-111 jet in 1990 at 17,300 feet when the windscreen blew off shortly after the plane departed from Birmingham, England, according to a report by the U.K.’s Air Accidents Investigation Branch.

The pilot “found himself half way out of the aircraft through his windscreen aperture,” the report said. He recalled lying on his back and trying to breathe before losing consciousness. Crew members, who were holding him by the waist, thought he’d died, but the pilot began kicking his legs shortly before the plane landed.

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

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

And in 1988, 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.

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

©2018 Bloomberg L.P.