The China Eastern jetliner was flying between the cities of Kunming and Guangzhou on March 21 when it nosedived into a mountainside, disintegrating on impact and killing all 132 people on board.
The cause of the disaster, China’s deadliest plane crash in more than 30 years, is not yet known.
“NTSB investigators are assisting the Civil Aviation Administration of China with the download of the cockpit voice recorder from China Eastern Flight 5735 in our lab in Washington,” spokesman Peter Knudson said in an email. He declined to give any details of this work.
The other black box from the plane, the flight data recorder, has also been found, and it too could help solve the mystery of what went wrong. This recorder contains crucial information such as the speed of the aircraft, its altitude and heading. It was found March 23 and sent to Beijing for analysis.
While parts of this recorder were seriously damaged, the data storage unit appears relatively intact, Zhu Tao, director of safety at the Civil Aviation Administration of China (CAAC), told reporters last weekend.
The aircraft went down near Wuzhou in southern China after losing contact with air traffic control.
Tracking website FlightRadar24 showed the jet sharply dropped from an altitude of 29,100 to 7,850 feet (about 8,900 to 2,400 metres) in just over a minute. After a brief upswing, it dropped again to 3,225 feet, the tracker said. There is no data for the flight after 2:22pm.
The cockpit voice recorder will likely provide investigators with details of communications between the flight’s three pilots, which is one more than is normally required on board the Boeing plane.
Earlier on Friday, the NTSB said a team of three investigators had left for China to assist in the crash probe. The NTSB said “investigators will limit interactions with those outside of investigation similar to safety protocols at Beijing Olympics, which will allow them to begin work immediately without a quarantine.”
The team includes the US accredited representative Sathya Silva, who is an NTSB senior aviation accident investigator. An NTSB spokesman said the US team was traveling on a commercial flight. It was not clear if the team will travel to the crash site in China and for how the long team will be in China but it could be several weeks.
The NTSB also said a small team from Boeing is also traveling China to assist in the investigation.
CAAC News, a publication under the Chinese aviation regulator, said on Saturday that the NTSB group of seven investigators and technical advisers had arrived in China. Under an international agreement, the NTSB has the right to participate since the plane was designed and built in the United States.
On Thursday, Chinese state media said the cause of the crash must be determined as soon as possible, following a meeting of China’s highest decision-making body helmed by President Xi Jinping.
Information about the crash must be released in an open, timely and transparent manner, state media said in a report on the meeting of the seven-person Standing Committee of the Communist Party’s politburo, China’s top leadership.