RICHMOND, Va. – A loss of oxygen is a leading theory for why an unresponsive business jet flew off course and over the nation’s capital Sunday before it crashed in rural Virginia. But federal investigators are just beginning to look for answers, and experts cautioned against jumping to conclusions.
The Cessna Citation took off from Elizabethton, Tennessee, headed for Long Island's MacArthur Airport. Once over Long Island, it inexplicably turned around and headed south, flying straight over Washington, D.C. before crashing in Virginia, k illing the pilot and three passengers.
“By far the most likely suspect is some sort of a pressurization issue,” said William Waldock, a professor of safety science who teaches aircraft accident investigation at Embry-Riddle Aeronautical University in Prescott, Arizona.
“It went up to 34,000 feet and basically stayed there — all the way up, all the way back,” Waldock said. “The turn (away from New York and back south) is a little perplexing. But it kind of depends on what kind of autopilot system the aircraft had.”
The Sunday crash wasn’t the first time a flight ended up far from its destination under mysterious circumstances.
WHAT IS HYPOXIA?:
Hypoxia is the condition that occurs when someone’s brain is deprived of adequate oxygen. If untreated, it can be fatal.
In aviation, hypoxia can happen if a non-pressurized plane flies above 10,000 feet without supplemental oxygen or if there is a rapid decompression during a flight, or a malfunction of the oxygen or pressurization systems, according to the Federal Aviation Administration.
Oxygen pressure decreases as altitude increases. It’s the reason planes are pressurized and why mountaineers carry supplemental oxygen on high-altitude climbs. It’s also the reason flight attendants explain to passengers how to use oxygen masks in the unlikely event that cabin pressure is lost during a commercial flight.
THE EFFECTS OF HYPOXIA
“It's something that happens slowly. It’s almost like you’re getting groggy, and you just can’t, you can’t piece things together. And eventually you lose consciousness,” said Anthony Brickhouse, a former member of the National Transportation Safety Board who is now an associate professor at Embry-Riddle Aeronautical University and director of its Aerospace Forensic Lab in Daytona Beach, Florida.
Waldock, Brickhouse's colleague in Arizona, added that the pilot would have had about 45 seconds to a minute to put on an oxygen mask.
“Whatever hit him, hit him fast enough to where the pilot didn’t really have too much time to get on the emergency oxygen system,” Waldock said. “That type of aircraft usually has a an emergency mask for the pilot, called a pressure-demand mask, that actually force feeds oxygen into your lungs. At 34,000 feet, you really can’t move air volume in and out."
The fighter jet pilots who caught up with the business jet said its pilot appeared to be slumped over and unresponsive, according to two US officials briefed on the matter. The officials were not authorized to discuss details of the military operation and spoke on condition of anonymity.
The fact that the pilot could be seen through the windows could mean that the aircraft did not have a “catastrophic” pressurization failure, Waldock said. If it had, the interior windows would have frosted over from quickly changing pressure at 34,000 feet. Plus, there likely would have been other damage to the plane, which kept flying.
Brickhouse, the other Embry-Riddle professor, said that aircraft are often set to fly on autopilot “so if the pilot goes hypoxic or loses consciousness, that aircraft is just going to fly whatever route it was programmed to fly,” he said.
Brickhouse said it's unclear why the plane suddenly turned around in New York and headed south again. He said it's possible the pilot was disoriented and may have “tried to reprogram a flight computer or something like that.”
“That's definitely something that investigators will be looking into,” Brickhouse said.
Flight tracking sites showed the plane suffered a rapid spiraling descent, dropping at one point at a rate of more than 30,000 feet (9,144 meters) per minute before crashing in the St. Mary’s Wilderness.
Waldock said the plane likely ran out of fuel, given its rapid descent and the lack of a very large fire at the crash site.
“There’s quite a few, over the years, pressurization-issue accidents that look very similar to that type of behavior,” he said.
OTHER CRASHES INVOLVING HYPOXIA:
— One of the most well-known crashes involving hypoxia was the 1999 crash of a Learjet that lost cabin pressure and flew halfway across the country on autopilot before running out of gas and crashing in a South Dakota pasture, killing professional golfer Payne Stewart and five others.
— Among multiple theories in the 2014 disappearance of Malaysia Airlines Flight 370 carrying 239 passengers and crew was a slow or sudden decompression, causing a loss of oxygen, that could have killed everyone on board. If oxygen levels dropped, a loud, automated warning would have alerted the pilots to put on their oxygen masks and immediately descend below 10,000 feet, where there is enough oxygen to breathe without aid. But aviation experts said in that case the plane should have kept flying automatically toward Beijing and been visible on radar.
— Greek investigators said pilots on a Cypriot airliner did not realize an automatic pressurization system was set to “manual” when a loss of cabin pressure and oxygen led to hypoxia and the plane’s crash in Greece in 2005, killing all 121 people on board.
— In January 2018, Dr. Bill Kinsinger, of Edmond, Oklahoma, had been flying his Cirrus SR22T to Georgetown, Texas, to collect a disabled dog that was destined for a foster home in Oklahoma. But he never landed at the suburban Austin airport and overshot his destination by hundreds of miles. Authorities believe he may have lost consciousness due to hypoxia.
Finley contributed from Norfolk, Virginia.