Beijing is expected to submit an early investigation report on Wednesday into last month’s China Eastern Airlines crash, when flight MU5735 descended sharply and slammed into a southern Chinese hillside – killing all 132 on board.
However, the report to the International Civil Aviation Organization (ICAO) – a United Nations body – is likely to only contain basic facts garnered by investigators, according to air accident specialists, and not analyses and conclusions on why the Boeing 737-800 plunged from a cruising altitude.
The Civil Aviation Administration of China (CAAC), which is leading the investigation, needs to submit a preliminary report to the ICAO within 30 days of the crash, according to international aviation law. The report will also be sent to the United States, where the aircraft was built.
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The CAAC has said the preliminary report would not be made public.
The flight, carrying 123 passengers and nine crew, dived from an altitude of 8,870 metres (29,100 feet) on March 21 as fast as 560km/h (31,000 feet per minute or 348mph), according to data from flight tracking website Flightradar24. It levelled off and climbed for just 15 seconds before plunging into a hillside in Wuzhou in China’s southern Guangxi Zhuang autonomous region.
The report would be based on verified information available at the time of writing, including speed, altitude, radar information and voice communication with air traffic control, Joe Hattley, a retired aircraft accident investigator at the Australian Transport Safety Bureau, said.
“The essential thing about a preliminary report is that it has no analysis, no findings, no conclusions, but there may be things like safety recommendations,” he explained.
Electronic data such as audio and radar information from air traffic control would be easy to verify, he said. But data from the flight recorders – or black boxes – needed to be decoded by specialists, who would verify the integrity of the data, given that the recorders could be damaged in the accident.
The flight data recorder and the cockpit voice recorder from MU5735 were recovered at the crash site days later and flown to Beijing for decoding.
The cockpit voice recorder, which captures conversations between the pilot and other sounds in the cockpit, was later sent to Washington to be decoded by investigators at the US National Transportation Safety Board (NTSB). The NTSB is also helping to decode information on the flight data recorder.
The preliminary report could also include other basic information, such as weather on the flight path, and the crew’s flight hours, medical certification and training, said Warren Chim Wing-nin, a spokesman for the Hong Kong Institution of Engineers’ aircraft division.
He said that in general, investigation reports began with all the facts found, followed by a list of findings based on the facts, the conclusions derived from the findings, a list of causes or probable causes from the conclusions and, lastly, the safety recommendations.
“The difference between a preliminary and an interim or final report would be its thickness,” Chim said. “A final report itself could be 100 or 200 pages long, and with attachments, as thick as a phone book.”
Hattley estimated the preliminary report would just be several pages long. The preliminary report for Malaysia Airlines flight MH370, which went missing in 2014 with 239 people on board, had five pages.
China, like other signatories to the Chicago Convention on International Civil Aviation that governs a range of areas including incident reporting, needs to follow the same set of ICAO standards and recommended practices, and is likely to produce a preliminary report of a similar breadth and depth.
An investigation into a crash as large and complex as MU5735’s could take one or two years to complete, Hattley said.
The ICAO did not directly respond to questions about whether China had sent its preliminary report or whether it had notified the UN aviation agency about “matters directly affecting safety”, which under the Chicago convention must be sent as soon as possible.
“The convention does not assign a regulatory or oversight role to the ICAO Secretariat … Questions regarding the undertaking and/or outcomes of an accident investigation should therefore be addressed to the relevant authority/authorities,” it said in an emailed reply.
On Sunday, China Eastern allowed its Boeing 737-800s to take to the skies again after grounding 223 following the crash.
Flightradar24 data shows a Boeing 737-800 flew a same-day round trip from Kunming to Chengdu on Sunday as flights MU5843 and MU5844, respectively. Another Boeing 737-800 flew the same route on Monday, with the two aircraft flying the routes on alternate days at least until Wednesday.
Boeing 737-800s mostly operated the route but had been replaced by Boeing 737-700s after the crash.
State-owned People’s Daily reported on Sunday that China Eastern Airlines was gradually letting its Boeing 737-800s return to the skies but those belonging to manufacturing batches closer to the plane involved in the March 21 crash would remain grounded for deep maintenance and evaluation.
The airline’s leading party members’ group publicity department did not respond to requests for comment by phone or email.
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