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What kind of equipment is the black box and why is it so important? Why is it that in the air crash rescue operation, in addition to finding survivors, another rescue focus is to search for the black boxes at all costs and sparing no effort? What secret is hidden in the black box? What role will it play in solving the mystery of the air crash?

Today, Mr. documentation will uncover the black box! I believe that through the following 9 questions, we can answer your questions.

What is a black box? Black boxes, also known as flight recorders (FLIGHT RECORDER), are installed on aircraft and are used for aviation accident investigation, maintenance and flight test equipment.

A complete black box system is mainly composed of two parts:

Flight data Recorder (Flight Data Recorder,FDR): record all kinds of flight data.

Cockpit voice recorder (Cockpit Voice Recorder,CVR): records all kinds of calls on the plane.

2. Is the black box black? Although everyone calls it a black box, it is actually a typical "misuse of words". In fact, its surface is painted bright red or orange, with reflective strips and the words "FLIGHT RECORDER, DO NOT OPEN" (flight recorder, please do not turn it on). This can have an eye-catching effect and make it easier to find in the search process.

3. How was the black box born? Black box, born in 1953, has a history of 70 years.

After World War II, the British applied jet technology to civil aircraft. De Havilland designed the earliest jet airliner, named Comet. However, from 1953 to 1954, several crashes occurred one after another, which caused heavy casualties and grounded the comet.

As a member of the Commonwealth, Australia's civil aviation department has also summoned experts to discuss the possible cause of the accident. Of all the experts present, Dr. David Warren, a scientist from the Aeronautical Research Laboratory in Melbourne, Australia, believed that most meetings and investigations could not come to a conclusion and that the person who could best explain what happened to the plane had died. Can't provide any clues. Warren realized that if the plane had equipment to record the flight, the problem would be easier to solve.

In the years that followed, after repeated experiments and failures, Warren and his colleagues finally developed a prototype black box that could hold four hours of voice and flight data in 1956, but the Australian Aviation Department reacted coolly.

In stark contrast to Australia's apathy, black boxes are popular in other countries, such as the UK.

It was not until 1977 that the black box really attracted the attention of the whole world. That year, two Boeing 747s collided on the runway of Spain's Tenerife airport, killing 583 people and injuring hundreds, in one of the worst plane crashes in the history of aircraft navigation. Thanks to the records of the black boxes, the accident soon came to light. By playing back the cockpit recordings recorded by the black boxes at the time, it was found that the main cause of the disaster was misunderstandings between pilots and misunderstandings of instructions given to the tower. Without the black box, people may never have access to this vital information, which provides an accurate direction for air crash investigators.

After the disaster of the aircraft, the important data provided by the black boxes not only greatly help people analyze the causes of the accident, but also provide direction and guidance for the improvement of the aircraft. Today's aircraft are forced to install black boxes. From the initial scratches left by needles on the metal foil to reflect the data change curve, to the use of semiconductors to store data and record video information, the black box records thousands of parameters. and the key data of the black box can be transmitted regularly through data links such as satellites.

4. Why do you call "flight recorder"black box"? the word "black box" is a British term during World War II, which originated from the development of radio, radar and electronic navigation aids in British and allied fighter planes. These often secret electronic devices are actually wrapped in non-reflective black boxes or shells, so they are called "black boxes".

When Dr David Warren demonstrated the prototype of the flight recorder in the UK, the British media rushed to report it. At that time, flight recorders did not have a name, perhaps in electronic technology, instruments that only paid attention to their input and output signals but did not pay attention to their internal conditions were all called "black boxes", or in order to attract people's attention, the British media called flight recorders "black boxes". And this call, has been called up to now.

5. Where is the black box installed on the aircraft? The black box is usually installed at the rear of the machine. Because through the statistics of flight accidents, it is found that the relative position of the tail of the aircraft is relatively high, it is usually not easy to be completely damaged after the crash, and some airborne instruments and equipment installed in the tail are not easy to be damaged, so the black box is installed in the tail position.

6. What are the components of the black box? Black boxes generally contain the following components:

Power source

Shock-proof memory cell

Aircraft interface circuit board

Underwater positioning beacon

The most important feature of the black box is its firmness and durability, and only special materials can meet this requirement. Take the anti-impact storage unit of the flight data recorder as an example, the core component of the flight data recorder is the solid-state storage unit, which is wrapped by three layers of protective materials and has strong puncture resistance and high temperature resistance.

The outermost layer is an anti-impact protective shell made of titanium steel. Titanium has the advantages of low density, high strength, stable chemical properties and not easy to react with acid. Titanium has high melting point, poor thermal conductivity and strong resistance to external high temperature.

The middle layer is an insulating layer, which is composed of glass fiber and other composite materials. Glass fiber also has the advantages of heat resistance, corrosion resistance, high mechanical strength and insulation. Different from carbon fiber, glass fiber is mainly composed of silicon dioxide, calcium oxide and alumina, which can effectively resist the impact of foreign sharp foreign bodies at high temperature.

The inner layer is a thermal insulation layer made of paraffin wax. Paraffin is a kind of latent energy storage material, which can absorb a lot of heat when it changes from solid to liquid, and the latent heat of phase transformation is large, at the same time, the volume change is small, and the phenomenon of supercooling will not occur. Paraffin wax is not only a high-quality cooling material, but also a good insulation material, which can be used for insulation protection of electrical components after melting.

Inside the insulation layer is a memory circuit board that contains solid-state memory chips. At present, some black boxes have used military-grade solid-state memory chips, and the circuit boards of the black boxes are not simple and can withstand certain shocks and temperatures. It can be said that they have "reached home" in their protection capabilities.

7. is there a high technical requirement for the manufacture of black boxes? Due to the serious impact, fire, seawater immersion, chemical solution erosion and strong lightning strike after the plane crash, there are a series of high-tech requirements for the design and manufacture of aircraft "black boxes". In this way, the recorded data in the "black box" can be well preserved even if the crashed plane is completely damaged. These technical requirements include:

Strong impact resistance: the shell of the black box is made of titanium and steel and can withstand a huge pressure of 3400g (unit of acceleration of gravity), which is equivalent to the impact of a speed of 500 kilometers per hour.

High temperature resistance: in a high temperature flame of 1100 degrees Celsius, the bearing time is as long as 30 minutes to 1 hour.

Waterproof and anti-water pressure: waterproof, the shell can withstand water pressure of 6000 meters deep.

Can send a signal: the black box dropped after the crash will automatically send a radio signal to guide rescuers to find it. If the plane accidentally crashes into the water, the underwater positioning beacon on the recorder will be activated automatically when it comes into contact with the water. the beacon transmits a signal every second for up to 30 days.

8. What information is recorded in the black box? Early recorders can only record more than 20 data. according to the basic requirements of civil aviation regulations, flight data recorders should record at least 88 data, and some can record more, depending on the model. The time range of the record is the last 25 hours, and the record of 25 hours ago has been erased.

According to MH / T 2004-2004 "Flight data Recorder Decoding parameters Specification", these 88 data include air pressure altitude, acceleration, attitude, thrust, fuel quantity, position of control surface and so on.

The cockpit voice recorder in the black box can only record cockpit sound for two hours. It records not only the dialogue between the crew and their dialogue with the tower, but also the background noise. The sound of seats pushed back, for example, can tell investigators when the captain left the cockpit, which provides a key clue to the investigation into the Germanwings 9525 crash.

9. Why are the black boxes put in the water after being salvaged? Black boxes should be placed in clean fresh water immediately after being pulled out of the water (take the 2018 LION AIR JT610 Boeing 737 crash) to prevent salt and minerals from corroding the equipment when the sea water dries. The more seriously damaged the black box is, the more difficult it is to decode it and the longer it will take.

As an objective, true and comprehensive recorder of aircraft data, the black box is the most reliable, scientific and effective means to find out the cause of the accident after the plane crash. With the development of aviation, black boxes are playing a more and more important role in daily aircraft safety maintenance, flight condition monitoring, accident elimination and fault location, and even play an indispensable role in the flight process.

Through today's popular science, we must have a preliminary understanding of the black box. If you have more questions about the black box, please feel free to leave a message in the comments area.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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