Text / Liu Liang
On March 21, a Boeing 737 of China Eastern Airlines crashed in Teng County, Wuzhou City, Guangxi Province, with 132 people on board.
As an important flight data recorder, the black box records a lot of important information during the flight and becomes the key to deciphering the cause of the flight accident.
According to the latest information disclosed by the State Council investigation team at a press conference on the evening of March 22, at present, no survivors have been found on the plane during the rescue process.
The press conference also mentioned that the two black boxes on the plane will be searched as soon as possible.
On the same day, Guo Qing, an associate professor of the School of Aeronautics at Northwestern Polytechnical University, answered a number of key questions about the black box in an exclusive interview with China News Service Guoshi through train.
The country is a through train: After an aviation accident, it is often mentioned that the "black box" is the key to finding the cause of the plane crash.
What is a black box?
Black boxes are also called "flight recorders".
There are generally two flight recorders installed on passenger aircraft, one is the aircraft data recorder, which is responsible for recording data such as flight speed, altitude, time, engine speed, and the deflection angle of the aircraft rudder surface; the other is the cockpit voice recorder, responsible for Record plane calls to the ground, crew conversations, and various sounds in the cabin.
The country is a through train: why is the black box so important?
The black box can provide investigators with the flight situation of the aircraft in the period before the crash. It is an important source of evidence for accident analysis and a data source for making correct judgments about the accident.
The country is a through train: what is the "pressure resistance" indicator of a "black box" in general?
In order to withstand the violent impact force and high temperature burning flame of the black box when the plane crashes, the black box shell usually has a very thick steel plate and many layers of thermal insulation materials to protect against impact.
Usually the black box can withstand a high temperature of 1100°C for half an hour to an hour, and can withstand a gravity impact of about 100G when the plane crashes.
It can withstand more than 4,000 meters of deep water pressure, and is not afraid of long-term immersion in seawater.
The main function of the black box is to provide multiple data records of the aircraft, rather than the positioning function, so its positioning function is not strong, usually only sends out pulse signals, and the time is limited, but generally more than 30 days.
The country is a through train: in the category of passenger aircraft, is the "black box" performance of different types of aircraft the same?
In the general category of passenger aircraft, the "black box" performance indicators of different types of aircraft are basically the same.
The country is a through train: Some netizens asked that the black box is highly resistant to pressure in an accident, why is it not used in the manufacture of aircraft structures.
What do you think?
The black box is a part of the aircraft, and it is also a very important part. Compared with the aircraft, the black box is small in size, more like a small luggage for a passenger, so it can be made of heavier materials, and there is no need to consider the weight issue too much.
However, the entire manufacturing process of the aircraft controls the weight very strictly, because the increase in weight will reduce the flight performance and economy of the aircraft. Now relatively new passenger aircraft are using a large number of composite materials, which is also a prerequisite for ensuring strength and rigidity. Lose as much weight as possible.
Such as Airbus A350XWB and so on.
The country is a direct train: Why can't the data of the black box be synchronized by the "cloud" to avoid the difficulties caused by search?
It should be technically possible for the black box to transmit data wirelessly and synchronize with the cloud.
However, when the plane is flying normally, the data stored in the black box is useless. This data is only used for analysis after the plane has an accident.
That is, the plane's black box data only works after an accident.
There are about tens of thousands of aircraft flying every day in the world. If the data of each black box is transmitted and saved in real time, it will cause a lot of data garbage, and it will also bring trouble to the really useful later data analysis.
The country is a direct train: Although it is called a black box, most of the relevant black box pictures found on the Internet are orange or red items. Why?
The idea of installing a sound recorder in the cockpit was proposed in 1954. At that time, all the electronic instruments in the aircraft were placed in a black square box of uniform size and shape, and the sound recorder was placed in the strongest black square. in the box.
In 1957, the US Civil Aviation Administration stipulated that aircraft weighing more than nine tons must be equipped with flight recorders to enhance the protection of the aircraft.
In 1965, the Aviation Administration decided to paint the black square box mounted on the aircraft "orange" or "red".
Once the plane crashes, the appearance of the black box will be very conspicuous and easier to find.
By 1965, almost every airline in the world had switched to orange or orange-red flight recorders, but still kept the name "black box".
In order to make the black box more eye-catching, the shell of the black box is bright orange and equipped with a light-emitting strip.
The country is a through train: what are the ways to find the black box?
Usually, the way to find the "black box" is to search and rescue personnel to carry out a dragnet search near the plane crash site, using metal detectors and search and rescue dogs, such as drones, unmanned vehicles and other advanced equipment.
The country is a through train: Is there a critical time window for finding black boxes?
The search for the black box must be as fast as possible. With the passage of time, the strength of the signal emitted by the black box will gradually weaken with the consumption of electricity. The longer the time, the more difficult it is to search for the black box.
The country is a through train: what are the difficulties in finding black boxes at present?
Because the crash site of the China Eastern Airlines plane is in a mountainous area with complex terrain and dense jungles, the size of the black box of a Boeing 737 aircraft is usually about 60x20x20cm, so it is very difficult to find a black box with a size similar to the size of a small express carton in the densely forested mountainous area. It is difficult to judge the posture and speed at the moment before the crash, which also brings great difficulties to the search for the black box.
The country is a direct train: how can I find the black box, and is there any other way to know the cause of the accident?
To determine the cause of the plane crash, you can also start from other aspects, such as investigating the plane's maintenance records, the records of replacement parts, the pilot's psychology, and whether the plane was hijacked and other reasons.
These can be used as auxiliary means to determine the cause of the crash. The accident investigation team definitely hopes to find a black box to restore the most real scene before the crash.
China is a through train: where is the black box located on the plane?
The black box is generally located at the tail of the aircraft. If the aircraft crashes, the tail of the aircraft is usually the last part to be hit, so putting it at the tail of the aircraft increases the possibility of saving the black box.
The country is a direct train: if you find the black box, how long will it take to decipher the contents?
The interpretation time of the black box depends on the seriousness of the crash of the aircraft, which may be several days or several months.
The country is a through train: who will interpret the data?
Finding the black box is generally interpreted by a professional civil aviation accident investigation agency. There are many international agencies that can interpret it. Boeing will also send technicians to participate in the interpretation, or send it back to the Boeing headquarters for interpretation.