Why is it difficult for a black box to become a “cloud box”?

After an air crash, all eyes will be on the black box. The black box is an important component in an aircraft, recording a large amount of data about the flight process. Once a plane crashes, the black box can serve as the main data support to restore the cause of the air crash.

After the China Eastern Airlines accident, everyone was looking forward to finding the black boxes as soon as possible. After six days of searching, both black boxes were finally found and have been sent to Beijing for decoding and analysis.

Finding the black box of a crashed plane has never been an easy task. The occurrence of an air crash means that the plane may face explosions, high temperatures, crashes into the sea, etc. The black box faces many harsh conditions of damage and may even disappear. There is still no trace of the black box of Malaysia Airlines. It is too difficult to find a small piece of black box at the explosion site, in the deep sea, or in the mountains and forests.

Many people may wonder, with the rapid development of technologies such as AI, 5G, and the Internet of Things, and some aircraft already connected to Wi-Fi, why don’t black boxes upgrade their ability to transmit data in real time? This would help experts analyze the cause of the accident as quickly as possible. If you want to answer this question, you need to go back to the design and features of the black box.

The indestructible body

Many people have heard of the black box on the plane, but most of them probably don’t know that there are actually two black boxes on the plane. There are two types of black boxes commonly used in the current civil aviation industry, including the Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR).

FDR, as the name implies, records data parameters related to the aircraft's operation, engine, speed, heading and other working conditions. It can record at least 25 hours of flight data. CVR records the sounds in the cockpit, including conversations between pilots, various background sounds of cockpit machines, such as voice warnings, control sounds, flap and landing gear handle operation sounds, and aircraft encountering weather conditions (thunder, heavy rain, hail) sounds. CVR can record at least 2 hours of cockpit voice. After two hours of recording, it will automatically rewind and start recording again. If an air crash occurs, the previous two hours of recording will be completely retained.

The activation of the black box means an air crash. The plane will land quickly and hit the ground, which will produce a large impact force, causing explosions and fires. Therefore, in order to protect the black box, its shell must be resistant to strong impact and high temperature. The shell of the black box is usually made of titanium steel metal, which can withstand a huge pressure of 3400g (g refers to the acceleration of gravity). The protective layer of the shell can be maintained at a high temperature of 1100℃ for 30 minutes.

Air crashes do not rule out the possibility of falling into the deep sea, so the requirements for waterproofness and water pressure resistance of the black box are also relatively stringent. Generally, the outer shell is required to be able to withstand water pressure at a depth of 20,000 feet.

Regardless of whether the plane falls into the deep sea, mountains or woods, in order to enable ground search and rescue personnel to find the black box as soon as possible, the black box that falls after the accident will automatically transmit a radio signal. Even if it falls into the water, the black box is set to transmit signals underwater. The black box beacon transmits a signal once a second, and the transmission time can be up to 30 days. Searchers can use a signal receiving device to detect the location of the black box.

We can see that the performance and demand indicators of the black box are both high. If some modules for real-time data transmission are installed on the black box to enrich its functions, will the investigation of accidents be more convenient?

The “ladder to heaven” of Yunxiazi

The black box plays an indispensable role in outlining the full picture of the accident. If the aircraft can exchange information with the ground in real time in the air, it will be upgraded from a black box to a "cloud box" and get rid of the limitations of the black box. The investigation of the accident will undoubtedly be the most convenient. Many people are calling for improvements in the design of the black box and the improvement of the aircraft's monitoring system. However, it is not a simple matter to achieve such an upgrade of the black box.

Since the birth of the black box, its most basic requirement is to save data, which is also its most important function. From the perspective of hardware equipment, the black box has relatively strict restrictions on size and energy consumption. If a module that transmits signal data in real time is carried, it will be too power-consuming for the black box. We know that based on the set requirements, the black box needs to be equipped with a separate power supply. After the aircraft accident, it needs to have at least 30 days of power to transmit signals. For some internal instrument requirements, the possible exhaustion should be minimized. If a data transmission module with huge power consumption is installed, the convenience of subsequent search and rescue personnel cannot be guaranteed. Once it falls into the deep sea, the short window for transmitting signals is a real needle in a haystack for searching for a black box.

If we ignore its power consumption properties, transmitting data on an airplane is also a major challenge. The network connection signal on the airplane is unstable. On some Air China flights, if you experience Wi-Fi, you will find that the network signal and speed are poor. Whether the aircraft provides network signals through base stations or satellites, it will be limited by factors such as the terrain, weather conditions, and the location of satellites. At present, there is no mature technology that allows aircraft to transmit data in real time and transmit such a large amount of data. If you want to install some signal processing modules, as mentioned above, you will fall into a vicious cycle of huge power consumption.

For airlines, the probability of an air crash is very small. If they really spend resources on synchronous transmission or cloud storage, there are thousands of flights flying around the world every day, so many planes and data, and these data cannot be used in most cases. It is difficult for airlines to advance.

On the ethical level, there will also be disputes over security and privacy when it comes to data transmission. Some information related to aircraft may be hacked and manipulated, which will add an extra layer of threat to both commercial security and flight safety.

Whether it is due to cost or the characteristics of the black box itself, there are too many obstacles to the synchronous transmission and cloud storage of the black box. The black box is an important component for post-event response. For normal flights in most cases, the recorded data is meaningless. The black box after the accident is the most precious.

Assuming that huge resources need to be invested, under the same conditions, it may be a more likely option to directly use these costs and resources for flight safety.

Avoid tragedy from happening again

The investigation of flight accidents is not an easy task even with a black box. It takes a process and a certain amount of time to decrypt the black box and investigate the cause of the accident. The time required to decrypt and announce the cause varies depending on the specific air crash. We can see from the analysis and investigation time of previous air crash accidents that some investigation results were released in a few months, some took a year, and there were even cases where no results were obtained.

The 2020 Kobe Bryant plane crash, which is closer to our timeline, took a year to conclude. In 2010, the Yichun “August 24” air crash in China took nearly two years to investigate before an announcement was made. In 2014, Malaysia Airlines flight MH370 disappeared, and there is still no trace of the plane and the black box, so there is no way to talk about the results of the air crash investigation, and it is a long way off.

Finding the black box is only the first step. Subsequent data extraction and analysis will take a long time. The black box data only provides part of the information for analyzing the cause of the accident.

For some situations without sensors and monitoring, the black box will not record these situations: bird strikes or foreign object impacts and blows on the aircraft, wing skin separation, horizontal tail surface separation, vertical stabilizer surface separation, aircraft external parts separation, etc. These are all without sensors and monitoring signals to monitor in real time, and there will be no records of these situations in the black box. Without a special description from the crew, it is difficult to speculate on the cause of the accident.

Only when the data from the black box is combined with the on-site investigation can a logically rigorous and complete investigation conclusion be drawn. After the black box enters the decoding stage, the continued excavation and research of the accident site will not stop. For example, investigations such as the distribution of the wreckage at the scene will help understand the posture of the aircraft when it landed, the angle of impact, etc.; the position of the control surface and other information can also be analyzed through the wreckage of the aircraft, which can be cross-compared with the data recorded in the black box to provide evidence for the accident investigation.

We know that most air crash scenes are tragic, and the number of wreckage of large passenger planes can even reach 100,000. The study of these wreckage is like playing a high-level puzzle. The investigation of air crashes is also a process of investigation and solving cases. Confirm the components in the wreckage that has been deformed by the explosion, check whether there are any abnormalities in its state, and find the truth among the thousands of fragments. This process is destined to be difficult and time-consuming.

Especially when the black box suffers a certain degree of damage, the repair and interpretation of the black box data and the correction of errors will prolong and affect the investigation results.

The black box was designed with the most demanding environments in mind, but there are also some rare events that may happen, such as the failure of the black box's multiple protection measures and a large amount of data security redundancy. Such extreme situations are completely worthless for accident investigations, and it is hard to say whether there will be any investigation results in the end.

The black box is the basis of air crash investigation. With the data from the black box, all conclusions can be traced. Detailed and clear causes of air crashes can give airlines a chance to make up for their losses. We can also learn lessons from these tragic accidents and continue to increase the number of aviation safety days.

During flight activities, no one wants to see the black box, after all, the appearance of the black box means the occurrence of an air crash. But after the disaster, people are eager to find the black box quickly and decode the information quickly to comfort the deceased. We also hope that the black box can be further improved with the development of technology, so that the truth can avoid the cycle of tragedy.