Black box is the most important and direct evidence to judge the cause of flight accidents. Although it is called a black box, its color is not black, but a common name. Its official name is flight information recording system. In electronic technology, all instruments that only pay attention to their input and output signals without paying attention to their internal conditions are called black boxes. Flight information recording system is a typical black box instrument. For convenience, people in the industry call it a black box and spread it to the society. The public only knows that there is a black box on the plane.
The flight information recording system includes two sets of instruments: one is the cockpit voice recorder, which is actually a tape recorder. From the beginning of the flight, it kept recording all kinds of sounds in the cockpit, such as conversations, telegrams and so on. But it can only keep the sound for 30 minutes, and then stop recording. The second part is the flight data recorder, which instantly records all kinds of data on the plane on magnetic tape. Early recorders can only record more than 20 kinds of data, but now they can record more than 60 kinds of data. There are 16 kinds of important required data, such as acceleration, attitude, thrust, fuel quantity, rudder position and so on.
Using these two recorders, usually after a flight, the relevant personnel play back the records to reproduce the errors or faults that have been found. Maintenance personnel can easily find the location of the fault by using it; Pilots can use it to check the shortcomings of aircraft flight performance and operation and improve flight technology. Once the plane crashes, this recording system becomes the most direct basis for accident analysis. In order to ensure the authenticity and objectivity of the recording, the driver can only consult the recorded contents, but can't control the work of the recorder or change the recorded contents.
In order to ensure that the recorder can be preserved even after the plane crash, it must be placed in the safest place of the plane. According to statistics, the tail under the tail is the safest place on the plane, so this "black box" was installed here. The black box is put into a heat-resistant and earthquake-resistant container (or two containers) made of special steel. This container is spherical or rectangular. It can withstand the impact of its own gravity 1000 times, withstand the high temperature of 1 100℃ for 30 minutes without damage, and can be soaked in seawater for 30 days without water.
In order to find it easily, ICAO stipulates that this container should be painted with striking orange instead of black or other colors. Equipped with automatic signal generator, it can transmit radio signals to facilitate air search; It is also equipped with an ultrasonic underwater positioning beacon, which can automatically send out an ultrasonic signal for 30 days after the black box falls into the water. With the protection of these technical measures, most black boxes can be found after the plane crash, whether they are violently hit, burned by fire or falling into the deep sea. According to its records, aviation accident analysis business has taken a big step forward.
Source: People's Daily Weibo Comprehensive Civil Aviation Administration of China website