BEIJING — China Eastern Airlines Flight 5735 was at 29,100 feet in a clear afternoon sky over the hills of southern China, seemingly poised for a smooth landing in Guangzhou. The plane, a Boeing 737-800 NG, was only seven years old. One of China’s most experienced pilots was one of three pilots in the cockpit.
But then, at 2:20 p.m. on March 21, the plane collapsed.
Air traffic controllers made frantic calls that went unanswered. The pilots did not send Mayday messages. The plane fell over 20,000 feet to 7,400 feet in less than a minute. Then it reached 1200 feet in about 15 seconds, before making a final plunge into a hill covered with bamboo and banana trees. The plane was almost exactly vertical and approaching the speed of sound when it tore into the soft earth, drifting pieces of the plane up to 20 meters deep in the mud. Two pieces of a wingtip landed seven miles away.
Investigators, including a seven-member team from the United States that arrived on Saturday, are trying to understand what happened in the final minutes before the plane crashed headlong, killing all 132 people on board.
Every plane crash investigation presents unique challenges. But this one, China’s worst air disaster in more than a decade, is even more of a mystery because the plane was destroyed by the extraordinarily high speed of its impact, at an angle of essentially 90 degrees. At the end of the search last week, rescuers said they had recovered 49,117 pieces from the wreckage.
China also maintains an unusually tight hold on information, censoring discussions and speculation online and allowing limited coverage of the disaster. Chinese officials have been closely monitoring much of the information about the crash. Families of the victims have been checked to prevent them from talking to journalists or organizing protests. The names of the pilots have not been officially released, although a state newspaper in Hong Kong published them anyway.
Much depends on what data can be recovered from the aircraft cockpit voice recorder and data recorder. The so-called black boxes are designed to withstand crashes, but experts say the severe impact of these may have damaged the recorders to the point that some data was lost. The flight data recorder ended up five feet underground and could not be removed until firefighters removed a large tree root above it.
According to Peter Knudson, a spokesman for the NTSB, the National Transportation Safety Board in the United States helped China download information from the cockpit voice recorder at a lab in Washington.
The tragedy has raised questions about the country’s record of flight safety in an important year for top Chinese leader Xi Jinping, who will be seeking a third term at a Communist Party congress. China Eastern and its subsidiaries grounded 223 Boeing 737-800 jets for security checks, a third of their total fleet. The Standing Committee of the Politburo, the country’s highest governing body, said at a meeting led by Mr Xi last week that officials should determine the cause of the crash as soon as possible.
Officials overseeing the search said they found some key aircraft components, including parts of the engines and landing gear. They attempted to mimic the plane’s flight path using data from air traffic control radars and examined possible clues as to what baggage and mail had been placed on the plane.
Officials have promised to release preliminary conclusions within 30 days of the crash, in accordance with the timelines set out in the Convention on International Civil Aviation, a global agreement. That agreement also requires the participation of representatives of the aircraft manufacturer and the transport safety regulator from the manufacturer’s home country. The National Transportation Safety Board said Monday that investigators from the United States were not required to go through the usual lengthy quarantine when they arrived in China on Saturday. Instead, the team was allowed to go directly to the crash site, with some restrictions on their movements.
State media reports of the crash are limited. A branch of Jinan Daily, a state publication from a town 1,000 miles away, published interviews with a farmer near the crash site who described seeing black smoke coming out of the plane and another farmer who described seeing white smoke. . A surveillance camera in a distant mine captured the final seconds of the plane’s vertical descent. There was no smoke at all in those images.
“Nothing really seems to make sense here,” said Peter Marosszeky, a half-retired Boeing executive aerospace engineer and technical advisor who is now the general manager of Aerospace Developments, a research and development company based in Sydney, Australia. Black smoke would indicate fuel burning, while white fumes could be leaking fuel, but eyewitness accounts are often unreliable in crash investigations, he added.
Plane crash experts typically study the details that trickle out from a crash investigation for signs of a mid-air collision or explosion, mechanical problems or a pilot’s suicide. Virtually the entire plane crashed in one spot, reducing the chances of a terrorist bombing or other high-altitude accident occurring, experts said. According to Zheng Xi, the fire chief of the Guangxi region, where the crash took place, no remains of explosives were found on the rubble.
A farmer’s discovery of a piece of the plane seven miles west of the crash site initially sparked speculation among experts that the plane had some sort of midair breakup. But Chinese authorities later confirmed that the fragment, plus a much smaller fragment found a mile away, were pieces of one of the plane’s winglets, which are wingtip extensions that produce extra lift. Air crash experts said it was not surprising that such lightweight parts could land far from the site.
“It’s a winglet, so it’ll fly like a wind — it won’t come down like a piece of aluminum, it’ll fly around,” said John Goglia, a retired NTSB board member who has worked on investigations into plane crashes in the area. the world for more than half a century.
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Marriages and divorces. Faced with a rapidly rising divorce rate, China enacted a rule that forces married couples to undergo a 30-day cooling-off period before officially breaking up. The measure appears to have been effective in reducing divorce, but is unlikely to help a demographic crisis fueled by a decline in the number of marriages.
Damage to a winglet or the loss of a winglet would not significantly alter a pilot’s ability to stay airborne, Mr Goglia added. “It wouldn’t cause a nosedive, and it’s possible it broke off as the plane approached supersonic speeds,” he said.
Aviation Partners Boeing, a Boeing joint venture with a wingtips manufacturer that makes winglets for the 737-800, declined to comment on the discovery of the winglet fragments.
Aviation experts, including Mr Goglia, focused in particular on the vertical position of the aircraft at the time of impact. Commercial aircraft are designed so that their natural tendency is to flatten out in flight. Achieving a true nosedive requires constant, extreme force on the horizontal stabilizers on either side of the aircraft’s tail, Mr. Marosszeky.
The horizontal stabilizers control the pitch of an aircraft – whether the front of the aircraft tends to go up or down. The question for experts is whether the nose of the plane was pushed down because of a technical malfunction or because of a decision by a pilot.
Martin Craigs, the chairman of the Aerospace Forum Asia, a Hong Kong-based trade group for aviation equipment suppliers, said that during the China Eastern crash, the aircraft’s ability to fly almost perfectly straight down, without sliding or fluttering , helped demonstrate that “it is clearly not a terrorist bomb.” But he didn’t rule out an intentional crash.
He cited the 2015 crash of a Germanwings flight with 150 people on board as an example of suicide by a pilot. “Nothing should be ruled out – remember that a few years ago we had a pilot purposely fly a plane into the Alps.”
Amy Chang Chien and Li You research contributed.
