Saturday, March 26, 2022

Almost 22,000 Feet in 72 Seconds: Plunge of China Eastern Plane Puzzles Experts

Boeing 737 crash in southern China was among the fastest jetliner descents ever recorded

The Wall Street Journal 
By Benjamin Katz, Micah Maidenberg and Mike Cherney
March 25, 2022 7:06 am ET

It was one of the fastest descents of a commercial aviation jetliner in history.

China Eastern Airlines Flight MU5735 had been flying normally for just over an hour on Monday when it suddenly nosedived, plummeting more than 21,000 feet in 72 seconds. After the fall appeared to be briefly arrested, the plane stopped transmitting data, crashing into green mountains in southern China.

Video footage captured by a mining company’s surveillance camera showed the aircraft almost perpendicular to the ground in its final moments before it crashed, while attempts by air-traffic controllers and other nearby jetliners to contact the pilots after the aircraft started hurtling to the ground went unanswered.

It is “extremely unusual to see an aircraft in a full nose dive,” one industry safety official in the U.S. said. “Many of us are scratching our heads.”

The vertical speed of the descent reached almost 31,000 feet a minute at one point, according to data from tracking provider Flightradar24, mystifying experts. With very limited information available so far, it leaves open a range of possibilities as to how the Boeing 737-800 carrying 132 passengers and crew met its fate.

The Aviation Safety Network, operated by the independent safety advocacy group, the Flight Safety Foundation, and which maintains a flight accident database going back to 1919, said it identified eight examples of accidents since 1985 where a plane quickly descended in an abnormally steep way or fell out of the sky at high speed.

Previous falls from high altitudes have had a range of causes, said Jeff Guzzetti, the former director of the Federal Aviation Administration’s accident investigation division. Investigators need to winnow down possibilities: Anything from a small structural failure to a malfunctioning autoflight or autopilot system to a pilot becoming disoriented to some kind of intentional act could have played a role, he said.

“Everything’s on the table,” said Mr. Guzzetti, who isn’t involved in the investigation, while adding that the probe is in the very early stages.

So far, there are few clues to help determine what happened. Only one of the aircraft’s two black boxes—believed to be the cockpit voice recorder—has been recovered. Black boxes, which are colored bright orange to assist searchers trying to identify them in the debris of a crash, are installed in the tail of the jet to help safeguard the devices in a crash.

The voice recorder typically keeps a rolling two-hour record of the sounds in the cockpit. The second black box is a flight-data recorder that can track more than 1,000 flight characteristics from the plane’s basic conditions, such as airspeed and altitude, to the status of smoke alarms or the positioning of the wing’s flaps.

Recovering that data, especially if the recorder has been damaged by fire, could be a long, painstaking process, according to Graham Braithwaite, who trains air accident investigators at England’s Cranfield University.

A senior official with China Eastern told reporters earlier this week that the plane was in good working order and the crew was qualified and in good health at the time of departure. The pilots were both experienced—one was among the country’s first batch of pilots trained to fly modern commercial aircraft and on the cusp of retirement.

China’s aviation regulator will lead the investigation, and the National Transportation Safety Board has appointed a senior air-safety investigator as a U.S. representative, the NTSB has said.

Zhu Tao, a spokesman for the Civil Aviation Administration of China, on Thursday said basic information about the incident has been submitted to the International Civil Aviation Organization and to the NTSB.

Meanwhile, search and rescue teams on Thursday found parts of a plane engine, officials said. They continued to look Friday for the second black box, missing passengers and wreckage.

Matthew Gray, former head of training at Australia’s Qantas Airways Ltd., said investigators will likely focus on what would cause an airplane to go down at such a steep angle.

“It’s the very steepness of the attitude which is the most confounding and confronting thing about this,” he said.

Other past crashes where planes rapidly fell out of the sky well after takeoff in a steep manner or quickly descended likely occurred for a variety of reasons, according to official accident reports.

In 1999, EgyptAir Flight 990 rapidly pitched nose-down not long after takeoff from New York’s John F. Kennedy Airport to Cairo, reaching a speed as high as 39,000 feet a minute and an average descent rate of 20,000 feet a minute during a second dive during the accident, according to a report from the NTSB.

All 217 people on board the plane were killed when the aircraft crashed into the Atlantic Ocean 60 miles south of Nantucket, Mass. The NTSB said in its analysis that evidence indicated the flight’s relief first officer manually disconnected the plane’s autopilot while alone in the cockpit and idled the engines.

The NTSB report didn’t say why he acted the way he did. After the crash, some investigators believed the pilot acted deliberately, and the Federal Bureau of Investigation assisted in the investigation, according to the safety agency.

During an AirAsia accident in 2014 that killed 162 people, the plane lost altitude at a rate of 20,000 feet a minute during one stretch, according to a report about the incident from Indonesian authorities. Several factors contributed to the crash, including an electrical interruption to a flight computer that caused the autopilot function to disengage and crew actions that resulted in the plane entering a prolonged stall condition they couldn’t recover from, according to the report.

In Monday’s crash, data showing that the China Eastern aircraft regained altitude for a brief period suggests that the pilots could have tried to pull up the plane and recover from the rapid descent, former Qantas pilot Mr. Gray said.

The aircraft suddenly appeared to gain altitude, climbing almost 1,200 feet in 10 seconds, before its nose again turned to the ground and it hit the mountainside, Flightradar24’s data show.

It is possible that a malfunction occurred at 29,000 feet that sent the plane into a rapid dive, and that when the crew tried to pull up the plane, a secondary failure occurred, sending the plane down at such a steep angle, Mr. Gray said.

Mr. Braithwaite, the Cranfield professor, cautioned that that preliminary tracking data may have been thrown off by the extreme conditions that the aircraft underwent before the crash, and may have caused it to transmit some false data.

The 737 NG family of jets has one of the best safety records in commercial aviation after almost 25 years in service. Noting that record, Mr. Braithwaite said the aircraft is designed with multiple safeguards to prevent a midflight incident, especially at such an extreme angle. “They don’t just drop out of the sky like this,” he said.

Alison Sider contributed to this article.

China Eastern Airlines, Boeing 737-800, B-1791 performing flight MU-5735

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