China Eastern crew did not reply

The Civil Aviation Administration of China (CAAC), in an initial briefing on the loss of the China Eastern Boeing 737-800 (B-1791), says air traffic controllers monitoring traffic in the Guangzhou flight information region saw the aircraft enter a steep descent and attempted to make contact, but “received no reply”.

Flight MU5735 was just over an hour into its journey from Kunming to Guangzhou at 29,000ft when the fatal descent began.

At present, says the CAAC, investigators are searching for the flight data recorder and cockpit voice recorder. The aircraft hit the ground at high speed and wreckage is widely spread. As a precaution the agency has declared all China’s 737s grounded for checks, although it has not been specific about what checks may be required, and a safety review of aviation infrastructure like ATC and maintenance organisations has been ordered.

China is proud of its safety record, and had not seen an airline fatal accident on its territory since August 2010 when a Henan Airlines Embraer EMB190 crashed on approach to land in fog at Yinchun Lindu airport.

China Eastern crash today

Crashes these days are incredibly rare, but a fairly new Boeing 737-800 of China Eastern Airlines has crashed in China on a domestic scheduled flight from Kunming to Guangzhou. It looks as if none of the 132 people on board have survived.

This incident is unusual in the sense that crashes very rarely happen in the cruise – that is, during the en-route section of the flight. This is because the crew has no high workload to deal with at that time, the engines are operating at a gentle cruise power, and the airframe is not under stress from manoeuvring.

According to the FlightRadar 24 tracker, the aircraft stayed on the same heading towards its destination while it descended toward the point of impact with the mountains. If it had broken up in the air because of sabotage or a catastrophic structural failure, it would almost certainly have spiralled down. But this aircraft was quite young, so structural failure can almost be ruled out.

We have no reports of a distress call to ATC, yet the aircraft began a descent. There was no reason for the crew to have adopted a descent profile at that point, because the descent toward its destination airport did not need to begin for another ten minutes.

If the crew had adopted a deliberate emergency descent because of sudden cabin decompression, it would have levelled at 10,000ft or thereabouts, whereas the last height reported by the tracker was 3,325ft.

The last time – indeed the only time – I saw a flight profile like this, the aircraft involved was the Germanwings A320 that crashed in France in March 2015, and the cause of that, according to the official investigation, was the copilot deliberately crashing the aircraft because of his mental state.

At this point, however, there is no direct evidence to support this conclusion regarding China Eastern and flight MU5735.

The most compelling evidence so far, as is often true so soon after a loss, is what did not happen. A Mayday call did not happen, although during a descent from 29,000ft there is plenty of time to make one.

The investigators will be trying to find out why that was.

Post Script on 19 May 2022: The Wall Street Journal has quoted US NTSB officials working with the Chinese authorities on the crash investigation as saying that the cockpit flight controls appear to have been manipulated deliberately with the apparent intention of crashing the aircraft. The NTSB press office will say only that it is for the Chinese authorities, in charge of the investigation, to make any such statements, and so far they have not done so.