Investigators are trying to figure out what caused the pilot and passengers to become unresponsive in a small jet that eventually crashed in Virginia on Sunday, but the tragedy has made pilots take serious considerations about oxygen when flying. woke up.
Airplane cabins are pressurized because the air is too thin to breathe at jetliner cruising altitudes. Higher density air is forced into the cabin so the passenger can breathe as if he were 8,000 feet above sea level instead of 40,000.
What happens when the cabin is depressurized?
At the highest altitudes, it takes just a few seconds before the effects of numbness, confusion, euphoria, and unconsciousness appear. Pilots may not feel a reason to act. However, failure to recognize and respond quickly can have fatal consequences.
“We’re almost there,” says former airline captain and aviation expert Les Abend. “It depends on your altitude. It depends on your health.”
Investigators did not say why they believe the pilot of the Cessna Citation business jet was found unresponsive and collapsed when a fighter plane intercepted the plane near the capital on Sunday.
The plane, with the veteran pilot and three passengers on board, left the Tennessee airport, flew toward its destination of New York, then turned south and eventually crashed in the woods of rural Virginia. Rescuers found no survivors.
But officials said investigators were looking at hypoxia, or lack of oxygen in the body, as a possible cause of the crash. Possibilities include not having proper pressurization or losing pressurization while the aircraft was cruising at about 34,000 feet, experts said. The autopilot settings, they said, would explain why the plane kept flying at that altitude until it ran out of fuel.
“It’s a mystery at first, but I think there are some indications that there may be a problem with the pressurization on board,” said CNN aviation analyst Peter Goertz, who led the investigation as executive director of the National Transportation Safety Board. said. .
Investigators will have difficulty determining the cause of the crash, as the plane was destroyed by the impact of the crash.
“They will be looking for valves, which are critical parts of the pressurization system,” Goertz said. “But I doubt they can get it.”
Barometric problems and hypoxia have contributed to past aviation accidents, including one that killed golfer Payne Stewart in 1999. The business jet lost contact with an air traffic controller while climbing to an altitude of 39,000 feet. Fighters sent to intercept the plane reported a dark cockpit and condensation or ice on the inside of the windshield. (Temperatures are very cold at high altitudes.)
The NTSB concluded that Stewart’s crash was caused by “the incapacity of the crew as a result of failure to receive supplemental oxygen after the cabin was depressurized.”
In 2005, the Boeing 737 crash, which killed all 121 people on board, is also believed to have been caused by the pressurization of the plane. Greek safety investigators attributed the crash of Helios Airlines Flight 522 to an improperly set cabin pressurization system and the failure of the crew to properly diagnose multiple warning alarms. He claimed that the incapacitation of the crew was the cause.
Investigators wrote that the symptoms appeared while the captain and a ground mechanic were troubleshooting the problem over the aeronautical radio.
The Helios crash is an example of the slow onset of hypoxia as the aircraft ascends. Hypoxia can also develop slowly if the aircraft is leaking air, such as if the aircraft doors are improperly sealed. Onset can be rapid and dramatic, such as in explosive situations.
“Explosive decompression just says, ‘Put your mask on now,’ because it’s over in seconds,” says Arbend. “You lose your cognitive capacity and you lose consciousness very quickly.”
Life-threatening hypoxia in pilots is relatively rare, but how to recognize and respond to the condition is an important part of pilot training.
“Our bodies give us clues that we’re not getting enough oxygen,” says Scott Wagner, an assistant professor of aeronautical sciences who teaches physiology to students at Embry-Riddle Aeronautical University.
He teaches his students to look for symptoms such as tingling or numbness in the extremities, dizziness, blue nail beds and lips, and euphoria.
“Sometimes people don’t rush to take corrective action because they feel that things are going well, and that’s a dangerous symptom,” Wagner said.
He takes Embry-Riddle students to a special high-altitude atmospheric chamber where the instructor can regulate the atmospheric pressure. While the pressure is dropping, he gives them simple tasks such as writing down the symptoms they are feeling or solving a math problem.
“What we often experience is that students can’t concentrate doing four or five additions in a row. They lose focus and have to start over,” he says. said.
Some students don’t quite remember how they reacted, so Wagner keeps a record of what happened on the floor.
“The students will say, ‘Yes, it all worked out.'” And they are amazed at what happened,” he said.
Experts say passengers should be aware that pressurization problems are extremely rare. Pilots don special oxygen masks, scramble planes into dense air, and train to react quickly.
Passengers need to react quickly when orange oxygen masks fall from the ceiling.
This instruction is part of all flight attendant safety briefings. But some experts say passengers may not be paying attention or realizing the importance of the message. When a Southwest Airlines flight lost pressure in 2018, killing one passenger, images posted on social media showed other passengers wearing masks incorrectly.
Masks cover the nose and mouth and, as instructed by flight attendants, passengers must put them on themselves before helping others.
“Grab it and put it to your face, because you’ll need it,” Abend said. “The best thing you can do is grab it, because no one can help you when you’re hypoxic.”