Whenever an air crash occurs, one of the most important tasks of the accident investigation team is to find the "black box" on the plane. This small box about half a meter long holds the last information before the plane crash, which is the most direct evidence to judge the cause of the accident. The black box includes two sets of instruments: one is flight data recorder (FDR), which can record the flight parameters of the aircraft in real time. The important data such as speed, altitude, heading, thrust and acceleration of the aircraft are included, and the recording time range is the last 25 hours. The other is the cockpit call recorder (CVR). After the flight starts, the four sound tracks on the instrument begin to record the calls between the pilot and the air controller, the dialogue between the pilot and co pilot, the crew's broadcast to passengers, and various sounds in the cockpit (engine sound and alarm sound). The recording time is about 2 hours. After the recording is full, it will automatically rewind and record from the beginning. In the race against the clock accident accountability, the process of looking for the black box seems too long. Moreover, the black box is not invincible. It may be destroyed by explosion, damaged by seawater, or even lost like the black box of Malaysia Airlines mh370. So why not synchronize the black box data to the cloud in real time to facilitate investigators to extract it quickly? Can black box data be synchronized with the cloud in real time? Compared with the era when the black box was invented, today's communication technology has been greatly developed, and Wi Fi can be connected to aircraft. We can also see the speed and altitude data of China Eastern Airlines passenger plane in the last period of time from the Internet, which has been shared in real time. However, it is not so simple to make the black box synchronize all data clouds. The main task of the black box is to save data. The performance of other aspects is very poor, so it is unable to carry the operating environment required for data synchronization. Over the past few decades, storage technology has been greatly improved. In the past, the black box was equipped with disk, and now most aircraft use solid-state flight data recorder (SSFDR). In order to resist the strong physical impact, the black box cannot use the general high-capacity storage devices such as hard disk and SD card. In fact, the data storage capacity of the black box is less than 1% of that of ordinary laptops. It usually has only 1 ~ 4G storage space to keep all system files, and can't perform operations and other tasks. We can't simply add a hard disk or SD card to expand the memory of the black box Secondly, in terms of hardware, the weight, size and energy consumption of the black box are strictly limited. The design of the black box requires that it can operate with limited power for long enough. The black box is equipped with independent power supply to ensure that the recording instrument can continue to work when the aircraft is abnormal; Once the black box falls into the water, the power supply will maintain the underwater positioning beacon for at least 30 days. In this way, the energy consumption of the instruments inside the black box should be reduced as much as possible, and it is too electricity consuming to install a data transmission module. Finally, the synchronous storage of such critical data requires a very stable network environment, but the network on the aircraft can not do so at present. This is probably the most important reason. If you've used Wi Fi on the plane, you'll find that its network speed is slow and its connection is unstable. Wi Fi on the aircraft mainly relies on two technologies to access the Internet, namely, the base station network on the ground and the satellite network in the sky. Satellite location, terrain, weather conditions and other factors will affect the stability of the network. However, the black box needs to ensure continuous and complete data recording, which can not be achieved by Wi Fi on the aircraft, radio, radar, satellite telephone and other systems. On planes equipped with Wi Fi, passengers can surf the Internet during the cruise phase ｜ pixabay In addition, some experts mentioned in an interview that it is not necessary to synchronize the massive data of each aircraft in real time. The current civil aviation system has been able to monitor the speed, altitude and other data of the aircraft in real time, and the aircraft can also communicate important information with the ground through satellite telephone; However, if the detailed flight data and cockpit dialogue of all aircraft are synchronized in real time, the amount of data is too large and it is not helpful for management. In fact, the vast majority of flight accidents occur in the take-off and landing stage of the aircraft, and the damage degree of the aircraft is relatively light. In this case, it is very simple to find the black box and extract the data. Even if the plane disintegrates, the black box is still there Although the name is black box, it is actually eye-catching bright orange and equipped with reflective strips for search and rescue personnel to find. In order to ensure data security, the aviation industry has made detailed provisions on the installation position, power supply mode, impact resistance and high temperature resistance of the black box. The black box is generally installed at the tail of the aircraft. According to the statistical data, this is the least easily damaged part after the aircraft crash. Its outer layer is wrapped with heavy stainless steel plate and thermal insulation layer, which can withstand the impact of up to 3400 gravitational accelerations, the high temperature of thousands of degrees Celsius and the pressure of 6000 meters of water depth, so as to protect the data storage elements from damage. In order to be easier to find after falling into the water, the black box is also equipped with reflective strips and underwater positioning beacons. The underwater positioning beacon can continuously send ultrasonic waves for at least 30 days, which is convenient for search and rescue personnel to locate in the water. However, in a few cases, the positioning beacon will fall off due to the impact of the air crash. Schematic diagram of black box structure ｜ Encyclopedia Britannica The birth of the black box The invention of the black box originated from a series of tragic accidents in the beginning of civil aviation. In 1949, a British airline launched the world's first jet airliner, de Haviland comet. But then, from 1952 to 1954, seven comet crashed successively, killing 110 people. First shot in 1952 by "comet Dylan" To investigate the cause of the accident, the British Civil Aviation Authority set up a team of experts in Australia (which was still a British colony at that time), including 28 year old David Warren, a chemist who studies aircraft fuel. In the course of the investigation, Warren encountered a major difficulty: there was too little data available. At that time, some military test aircraft had been equipped with flight data recorders, but this was not applied to the field of civil aviation. The narration of the witness can also provide irreplaceable and important information, but few people survive an air crash. To know what the pilots and passengers experienced at the last moment before the accident, a tape recorder needs to be installed in the cabin. Therefore, Warren combined the flight data recorder with the cockpit recorder and wrapped it in a solid shell, hoping to provide valuable information for the investigation after the air crash in this way. David Warren and the first generation black box prototype ｜ National Museum Australia At first, Warren's superiors were not interested in the idea, so Warren had to spend the weekend developing prototypes in his garage. But with the passage of time, the value of the black box has been recognized and began to be gradually put into use. Although the modern black box has some technical upgrades, it generally retains Warren's design. With the help of the black box, the aviation industry can better learn from each accident and become safer and safer. But it happened that the black box could not be found in some particularly major air disasters, such as Malaysia Airlines mh370 air crash. It is hoped that the development of technology can bring further improvement to the black box, so that every accident can find the answer and the tragedy will not repeat itself. reference [1] https://www.nma.gov.au/defining-moments/resources/black-box-invented [2] https://www.britannica.com/technology/flight-recorder [3] https://science.howstuffworks.com/transport/flight/modern/black-box.htm [4] https://science.howstuffworks.com/transport/flight/modern/black-box-data-stored-in-cloud.htm [5] Wiseman Y. Can flight data recorder memory be stored on the cloud? [J]. Journal of Aviation Technology and Engineering, 2016, 6(1): 3. [6] Airworthiness standard for transport aircraft (ccar25), Civil Aviation Administration of China. (Xinhua News Agency)