China Plane Crash: How Air Accidents Are Investigated, All You Need To Know

All 132 people in the China Eastern Airlines passenger plane that crashed in China on Monday are presumed dead as rescuers could not find any survivors. 

The plane nosedived and crashed in the mountains in Tengxian County in the city of Wuzhou, according to an eyewitness quoted by China’s official news agency Xinhua. 

“The plane looked to be in one piece when it nosedived. Within seconds, it crashed,” said Chen Weihao, who saw the plane falling while working on a farm. Chen added the plane hit a gap in the mountain where no one lived.

Xinhua further quoted Chinese officials as saying that the search for the plane’s black box holding the flight data and cockpit voice recorders would be difficult.

What is the ‘black box’ and how does it help in aircraft accident investigations?

In most aircraft, what’s usually called a “black box” are actually two separate devices – a cockpit voice recorder (CVR) and a flight data recorder (FDR). These devices are the first stop for investigators. 

Several microphones are installed in a cockpit that catch all the sounds inside, ranging from spoken words to even faint clicking of switches. All of this sound is stored in CVR. This is important in investigations as it provides cockpit crew's voices, engine sounds, warnings from instruments, and every other piece of audio.

FDR stores all of the plane's operating data. There are several parameters that are tracked by FDR through the various sensors installed in the plane, which include time, altitude, speed, fuel, etc. 

CVRs and FDRs are therefore critical to reconstructing a timeline of the flight and can provide clues from either the data or sound from the cockpit about the cause of the accident.

Investigators also create video simulations of the aircraft’s trajectory from such data. 

How does an air accident investigation start?

The investigation starts by securing the site of the accident and collecting as much physical evidence as possible. They also take photographs and videos.

The investigators collect and properly store all debris and big parts of the plane that are salvaged. 

“They also conduct interviews with eyewitnesses and draw charts showing the debris field and any indications of how the aircraft hit the ground, such as the angle of impact, the distribution of debris and other details,” according to Daniel Kwasi Adjekum, an Assistant Professor of Aviation at the University of North Dakota.

Daniel adds that investigators also collect all the documents related to the plane, its crew and its recent flights for forensic analysis.

Who conducts such investigations?

There are specific technical support and probe teams that look at technical aspects of the accident, such as the air traffic control activity and instructions, weather at the time of the accident, human issues like crew experience and training, plane’s maintenance records, emergency response, safety equipment, and the aircraft’s performance and sub-systems.

“They may disassemble the crashed plane’s engines or other components and use flight simulators to attempt to experience what the pilots were dealing with,” writes Daniel. 

Forensic experts test the dead as well as survivors among the passengers as well as the crew for drugs or other substances to understand whether their conduct was compromised in any way or whether they were inebriated or in any kind of irregular mental or physical state that could have led to the accident. Bodies and physical remains are also tested by forensic experts for identification purposes. 

What’s the goal of the investigation and how is it arrived at?

Rather than blaming a person or group, the goal of the investigation is to find the cause of the accident and/or contributing factors, which may range from human error to fault in the plane’s design or external factors such as extreme weather or a bird hit. 

The findings are used to enhance aviation safety standards and improve the aircraft if any shortcomings are found, such as the case of Boeing's 737 Max aircraft involved in Lion Air and Ethiopian Airlines’ crashes in which it was found that the plane had faulty software that overrode pilots’ instructions and also that the pilots had insufficient training. 

Sometimes, the fleet of a particular aircraft type is grounded until the investigation is completed. Earlier in 2019, the Indian government had grounded the Boeing 737 Max aircraft being used by Indian airlines after the Ethiopian Airlines crash. The fleet was allowed to operate after 27 months when the Indian regulator was satisfied by Boeing’s rectifications. 

What’s the timeline of the investigation?

Within 30 days, the investigators must release a preliminary report to the International Civil Aviation Organization, which is the specialised agency of the United Nations for civil aviation. 

The final report is usually expected to follow the preliminary report before a year has passed. 

In cases where a final report cannot be released in this period, investigators release important updates or an interim report on the first or subsequent anniversaries of the accident. These reports detail the progress made so far.