A Boeing 737-800 passenger plane of China Eastern Airlines with 132 people crashed in Wuzhou, Guangxi, on March 21. After the accident, none of the passengers aboard survived. Two black boxes were found on March 23 and 27, respectively, but in severely damaged condition. The investigation now is underway, with many mysteries remaining unanswered.

The first mystery is China Eastern Flight MU5735’s pilots’ profiles

The chief pilot, identified by the state-owned Ta Kung Pao company as Yang Hongda (杨鸿达), was an industry veteran with more than 6,000 flight hours. Notably, the first co-pilot, Zhang Zhengping (张正平), had an impressive resume. Meanwhile, the second co-pilot had 556 flight hours.

Zhang Zhengping, with 40 years of flying experience, worked for China Yunnan Airlines, which later merged with China Eastern, accumulated 31,769 flight hours, and trained more than 100 pilots.

According to the Chinese-language Wall Street Journal, Zhang Zhengping was a “five-star captain.” He had rich experience in commercial aviation and served as an instructor for the flight’s captain, Yang Hongda.
Gao Fei, a Chinese-American pilot with 26 years of flying experience, said, “Aside from working for an airlines’ management, the highest position of a pilot could be a CAAC designated check airman. However, somehow Zhang was demoted to a first officer, losing his decorated status and taking a significant hit on his salary.”

Gao also did not rule out the possibility of the pilot’s emotional distress as well as a safety hazard for the airline.

According to public information, in China, a captain or check airman’s average annual salary was at least $120,000, while a co-pilot’s annual salary was around $46,000, a significant difference.

Secondly, Flight MU5735’s speed of the descent

According to the Wall Street Journal, this was one of the fastest descents of a commercial aviation airplane ever recorded.

After more than an hour of normal flying, China Eastern Airlines flight MU5735 suddenly nosedived, falling more than 21,000 feet in 72 seconds. Shortly after it started to fall, the jet stopped transmitting data and plunged to a mountainside near Wuzhou city, Guangxi province, southern China.

According to data from tracking service provider Flightradar24, at one point, the vertical speed of the descent reached nearly 31,000 feet per minute, puzzling experts.

Jeff Guzzetti, the former director of the Federal Aviation Administration’s accident investigation division, told Wall Street Journal that previous falls from high altitudes had had a wide range of causes. Investigators need to sort out many hypotheses: from a small structural failure to a malfunctioning autoflight or autopilot system to a pilot becoming disoriented to some kind of intentional act.

Thirdly, the plane’s vertical position at impact
As the New York Times reported on April 4, aviation experts have paid attention to the aircraft’s vertical position at impact.

Based on the video footage captured by a mining company’s surveillance camera, the aircraft plunged almost perpendicular to the ground in its final moments. Air-traffic controllers and other nearby jetliners had tried to contact the pilots after it shot to the ground, but to no avail.

John Goglia, a retired N.T.S.B. board member, said that the natural tendency of commercial airplanes is to level off in flight.

In addition, according to Peter Marosszeky, who is now the managing director of Aerospace Developments, a research and development company in Sydney, Australia, to achieve a true nosedive, the horizontal stabilizers on either side of the aircraft’s tail must be under constant, intense force.

The horizontal stabilizers control a plane’s pitch. The question is whether the nose of the plane was pushed down due to a technical malfunction or a pilot’s decision.

Martin Craigs, the Chairman of the Aerospace Forum Asia, a Hong Kong-based trade group for aviation equipment suppliers, said that the plane’s ability to fly almost exactly straight down, without gliding or fluttering, shows that “it’s clearly not a terrorist bomb.” He also did not rule out a deliberate crash.

Matthew Gray, former training chief at Australia’s Qantas Airways, said investigators would likely focus on what would trigger an airplane to fall at such a steep angle.

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

According to official accident reports, there are various reasons for other accidents where planes quickly fell out of the sky well after takeoff in a steep manner or rapidly descended.

In 1999, EgyptAir Flight 990 rapidly headed nose-down shortly after takeoff from New York’s John F. Kennedy Airport to Cairo. According to a National Transportation Safety Board report, it reached 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.

No one among the 217 people on board survived after the aircraft crashed into the Atlantic Ocean 60 miles south of Nantucket, Massachusetts. In an analysis, the National Transportation Safety Board said that evidence indicated the flight’s relief first officer manually disconnected the plane’s autopilot while alone in the cockpit, idling the engines.

The report didn’t say why he might have acted that way.

Fourth, a battle for control of a China Eastern Airlines flight

Flight data provided by air traffic monitoring service FlightRadar24 has shown a battle for control of a China Eastern Airlines flight on March 21. It suggests the plane pulled out of a 22,000 foot nosedive and briefly started climbing before slamming into the ground in a second dive.

The data suggests the plane was at an altitude of 29,100 feet when it went into a high-speed dive at 2:20 pm, losing altitude at a maximum rate of about 348 mph.

After twenty seconds into the dive, the rate of descent slowed. The dive was further arrested over the next 45 seconds until the plane leveled off 7,425 feet above the ground. It then began climbing.

About 15 seconds later, at 8,600 feet, the plane went into a second dive.

About 30 seconds later, the plane crashed into the ground, in a wooded area of Teng county, near Wuzhou city.

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

Gray said malfunction might have occurred at 29,000 feet that sent the plane into a rapid dive. A second failure occurred when the pilots tried to pull up the plane, sending the plane down at such a steep angle.

The Cranfield professor Braithwaite noted that the preliminary tracking data could have been thrown off by the aircraft’s harsh conditions before the disaster, causing it to transmit some false data.

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