As the second black box was found on March 27, subsequent decoding work is under process. The exterior of its data-storage unit is relatively complete despite the fact that other parts of the device have been severely damaged.
Whenever an air crash occurs, one of the most important tasks of the accident investigationis to find the black box on the plane. This small box about half a meter long holds the last information before the plane crashed, which is the most direct evidence to investigate the cause of the accident.
The black box includes two sets of devices: 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 of the flight. The other is the cockpit voice recorder (CVR). After the flight starts, the four sound tracks on the CVR 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 including 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.
The process of searching for the black box seems too long in the investigation of the accident. 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?
Is it feasible for the Cloud synchronization?
Compared with the time when the black box was invented, today's communication technology has been greatly developed, since WiFi can be connected to aircraft. However, it is not simple to make the black box data be synchronized in Cloud.
The main property of the black box is to save data. The performance of other aspects is rather 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.
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 to 4G storage space to keep all system files and cannot perform tasks such as computing.
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 it to operate with limited power for long enough. The black box is equipped with independent power supply to ensure that the recording device 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 energy-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 WiFi on the plane, you'll find that its network speed is slow and its connection is unstable. WiFi 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 WiFi on the aircraft, radio, radar, satellite telephone and other devices.
In addition, some experts mentioned 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.
Even if the plane disintegrates, the black box can be found
Although its 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 statistics, the tail 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 and the pressure of 6000 meters of water depth, so as to protect the data storage part 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 the black box due to the impact of the air crash.
The invention 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 Havilland Comet. But then, from 1952 to 1954, seven airliners of De Havilland Comet crashed successively, killing 110 people. 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 crew 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.
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.