China Eastern Flight MU5735 Crash: Black Box Sent for Analysis as Search Widens Near Wuzhou

On Wednesday night, a damaged black box recovered from the wreckage of China Eastern flight MU5735 was sent to a laboratory in Beijing. By Thursday, officials said, the work of downloading and analyzing its data was underway. Zhu Tao, head of the aviation safety office at the Civil Aviation Administration of China, told reporters in Nanning that the box holds the cockpit voice recorder, and that he could not rule out damage to its data storage unit.

The Boeing 737-800 was carrying 132 people when it crashed on Monday in a village in Tengxian County, in the city of Wuzhou, in the Guangxi region. No survivors have been found. Of the plane's recorders, only one black box has been recovered so far. A cockpit voice recorder captures voices, audio alerts and background sounds such as engine noise or switches being moved. The flight data recorder, a separate unit, stores speed, altitude, direction, pilot actions and the performance of key systems.

Investigators want that data because of how the flight ended. MU5735 fell from 29,100 feet to 9,075 feet in two minutes and 15 seconds before striking a mountainous area. Hu Xiaobing, a professor at the School of Safety Science and Engineering of the Civil Aviation University of China, told state-run CGTN that the crash was unusual because it was vertical. For reasons not yet known, he said, it seemed to him the pilots may already have been unconscious during the steep descent. That is one expert's impression, not an investigative finding.

On the ground, the search moved forward on Thursday. Pieces of engine wreckage were found, and Zhu said the main impact point had been basically determined. Most of the wreckage lay within a radius of about 30 metres of that point, he said, and the debris reaches as deep as about 20 metres underground.

Zheng Xi, head of the fire brigade of the Guangxi Zhuang Autonomous Region, gave the tally handed to the investigation team: 183 pieces of aircraft wreckage, some remains of victims, and 21 pieces of victims' belongings. Rescuers widened the search area on Thursday even though rain has hampered the effort for days.

The weather and terrain have made the work hard. Rain caused waterlogging at the core crash site and raised the risk of small landslides, Zheng said. The mountain road is narrow and slippery, so large rescue vehicles and equipment could not get in. East of the core site lies mainly virgin mountain forest, steep and heavily wooded, which makes searching harder still.

The airline has responded as well. China Eastern and its subsidiaries temporarily grounded 223 Boeing 737-800 aircraft and began a sweeping safety overhaul, Liu Xiaodong, head of its publicity department, told a press briefing. All the grounded aircraft are being checked and maintained to the highest safety standards, he said, to confirm they meet airworthiness requirements.

Families have been arriving. By Thursday morning, 305 relatives of 56 passengers had reached Wuzhou, and more than 200 of them had visited the crash site.

What comes next depends largely on the laboratory in Beijing: whether the damaged cockpit voice recorder yields usable data, and whether the second recorder is found.