Now that both black boxes have been found, can we recover the truth? Why isn't the data transmitted back to the ground in real time?

Experts in this article:

Liu Yuxuan, Tianjin Foreign Studies University

Qizheng Yi, Composite Materials and Engineering, Shenyang Aerospace University

This article was reviewed by Lin Wenjie, engineer, senior researcher at Chuanduo Think Tank

On the seventh day after the March 21 China Eastern Airlines accident, at around 9:20 a.m., firefighters found an orange tank at the search site. Experts confirmed that it was the second black box of China Eastern Airlines flight MU5735, and the overall appearance was relatively intact. The discovery point was 40 meters away from the impact point and 1.5 meters below the surface.

According to previous reports, the first black box was found at the accident scene at around 16:30 on the 23rd, and was initially determined to be the cockpit voice recorder.

So:

What is the difference between the two black boxes? What are their uses?

If we find the black box, can we restore everything?

The data recorded by the black box is so important, why can't the data be sent back to the ground in real time?

Let’s find the answer together today.

What is the difference between the two black boxes of Boeing aircraft?

A complete black box system mainly consists of a flight data recorder (FDR) and a cockpit voice recorder (CVR).

The flight data recorder can record various types of flight data, including a total of 200 types of data from flight attitude to flight trajectory.

The cockpit voice recorder can record various conversations on the aircraft. It has multiple audio tracks, which can record conversations between pilots and the ground control tower, conversations between pilots, broadcasts from the captain and flight attendants to passengers, various abnormal sounds and various sounds in the cockpit.

Find the black box

Can the whole truth be restored?

Not necessarily. Although black boxes can usually withstand various extreme conditions, they may still be damaged under certain extreme conditions.

In the history of aviation, there have been many cases where the black boxes in aviation accidents were severely damaged. For example, in the Indonesian SJ182 crash on January 9, 2021, the accident flight dived and crashed at high speed, and one of the black boxes was found to be broken and disintegrated. In this case, it becomes very difficult to recover and read the data. In the Lauda Air Flight 004 accident on May 26, 1991, the flight data recorder was severely damaged due to a violent impact and no data could be read.

The cockpit voice recorder (CVR) of Indonesian flight SJ182 was severely damaged. Source: Reuters

In the "March 21" air crash, the Civil Aviation Administration reported that the first black box of China Eastern Airlines flight MU5735 was delivered to the decoding laboratory in Beijing by a special person on the evening of March 23. Data download and analysis are in progress. However, the possibility of damage to the storage unit cannot be ruled out at present.

As for the time required for repair, it depends on the damage of the black box, which can take a few days or half a year. Generally, the decryption work is done by professional civil aviation accident investigation agencies. If the damage is serious, the airline staff will also send technicians to participate in the decryption work or send it back to the original manufacturer for restoration.

On March 23, at the core area of ​​the crash site of China Eastern Airlines MU5735 flight in Teng County, Wuzhou, Guangxi, soldiers of the Armed Police Guangxi Corps found one of the two black boxes. Xinhua News Agency (Photo by Xu Dong)

The data recorded in the black box is so important.

Why can't it be transmitted back to the ground in real time?

Although communication technology is developing rapidly nowadays, it is probably not that easy to synchronize all the data in the black box with the ground.

First of all, the black box's mission is to save and protect data as the top priority, and other functions are less important. In order to withstand various harsh environments and ensure that data is not damaged, the black box's hardware system cannot take into account the task of uploading data.

Secondly, the black box must operate with limited power for a long enough time to ensure that it continues to work in the event of an abnormal aircraft situation.

Moreover, once the plane falls into the water, the power supply of the black box must ensure the normal operation of the underwater positioning beacon for at least 30 days. Installing a data transmission system requires a new power supply, which will greatly increase the size of the black box, bringing great challenges to the original protection and reliability.

Thirdly, the current civil aviation system can already monitor a variety of aircraft data in real time. If all the detailed information of each aircraft is uploaded back to the ground, the amount of data is too large, which will bring inconvenience to normal work.

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In simple terms, the black box only works in special low-probability situations. If data is transmitted to the ground in real time, a large amount of unnecessary junk data will be generated.

Most importantly, to synchronize all data, an excellent network environment is required. Readers who have experienced the network environment on an airplane must know that the network connection on an airplane is not stable, and it is not an easy task to output airplane signals stably for a long time.

The search has not stopped, and the decoding work of the black box is in progress. This may be a long and arduous process. But we must trust the experts and wait patiently for the results of the accident investigation to surface.

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