It is a striking orange color, why is it called a "black box"?

Black Box

Flight Data Recorder

Can record the aircraft during flight

Detailed information

The black box is a device that records flight data and cockpit conversations. It can record 25 hours of flight data before the aircraft stops working and communication recordings ranging from 30 minutes to 2 hours.

The flight data includes flight altitude, speed, heading, climb rate, descent rate, acceleration, fuel consumption, landing gear extension and retraction, Greenwich Mean Time, aircraft system operating conditions and engine operating parameters, etc. The communication recording mainly records the conversation information between the captain, co-pilot and crew members in the cabin.

Today we will study:

How was the black box invented?

Is the black box black?

What other little-known facts about the black box?

The evolution of the black box

In 1939, French aviation engineers Francis Husnot and Paul Baudoin invented a recording device that can record the most important information of an aircraft, such as its speed and altitude, on 88mm film in a similar way to taking photos. After landing, take out the film to restore the state of the flight. However, the film is disposable and very expensive, and this device is only suitable for aircraft that have landed smoothly. If the aircraft crashes, the film will be destroyed, so this recording method is only used for test flights of new aircraft models.

▲ The first generation black box

During World War II, British engineers improved the flight parameter recording device by using a steel needle to carve the curves of various parameters on copper foil. In this way, even if the plane caught fire or crashed, the data at that time could be retrieved. However, copper foil is heavy, the amount of data recorded is very limited, and the price is high, so it is only used on military aircraft. This is the first generation of black box, which can only record five flight parameters such as heading, altitude, airspeed, vertical overload and time .

▲ The second generation black box

In 1956, the first flight data recorder for civil airliners was born in Australia. Its inventor, Dr. David Warren, invented the second-generation improved black box while studying aviation fuel. The working principle of the new black box is similar to that of an ordinary tape recorder, but a protective shell with impact resistance and fire resistance is added to the tape recorder. The second-generation black box can generally record dozens of parameters, and a cockpit audio recorder also appeared at the same time .

▲ The third generation black box

The third generation of black boxes appeared in the 1990s. With the rapid development of microelectronics technology, black boxes began to use semiconductor memory to record data. The third generation of black boxes generally record hundreds of parameters, and their functions have gradually extended from flight accident investigation to daily pilot monitoring, aircraft fault diagnosis and maintenance .

▲ Modern black box

The new generation of black boxes can record video information, the number of parameters recorded is as many as several thousand , and can regularly transmit the key data of the black box through data links such as satellites. However, due to the influence of communication bandwidth, signal blind spots and meteorological environment, the real-time data transmission method cannot completely replace the role of traditional black boxes. In addition, a new type of jettisonable black box has also appeared, which can automatically separate from the aircraft body when the aircraft crashes, and has the functions of floating on water and radio and satellite positioning.

The black box is not black

In electronic technology, all instruments that only focus on their input and output signals and not their internal conditions are called black boxes. The flight information recorder system is a typical black box instrument. For convenience, people in the industry call it a black box.

The black box is one of the electronic recording devices used exclusively on aircraft. Generally, there are two black boxes, one is the cockpit voice recorder and the other is the flight data recorder. Each mechanical part and electronic instrument of the aircraft is equipped with sensors connected to the black box, so the black box can record data from various instruments.

Although we call this flight parameter recorder a black box, its surface is not black. In order to make it easier to find it, the International Civil Aviation Organization stipulates that this container should be painted a striking orange-red instead of black or other colors. Some black box shells will also have reflective strips with "FLIGHT RECORDER, DO NOT OPEN" written on them.

Black Box Knowledge

1. Where is the black box installed?

The black box is usually installed at the tail of the aircraft, specifically below the rearmost vertical tail. According to statistics, the tail below the tail of the aircraft is the safest place on the aircraft.

The black box will be placed in one (or two) heat-resistant and shock-resistant containers made of special steel. This container is spherical or rectangular. It can withstand impacts 1,000 times its own gravity, withstand high temperatures of 1,100°C for 30 minutes without being damaged, and be immersed in seawater for 30 days without getting wet.

2. Can the black box itself send out radio signals?

There is no radio transmitter on the black box, so the recovery work on land mainly depends on the search and rescue team's manpower. The black box has bright colors on the surface, and the search and rescue team can search for the black box based on this feature. This is the only way to recover the black box on land.

3. What kind of signal can the black box actively send to the outside world?

The only component of the black box that can send signals to the outside is called an underwater beacon (ULB). The underwater beacon is activated when it encounters water, and sends a sound wave signal with a frequency of 37.5KHz once a second (note that it is a sound wave signal), and can work continuously for 30 days.

4. How to detect the acoustic signal of the black box?

The sound wave signals emitted by the black box underwater can only be detected by sonar in the water. However, due to the small size and power of the black box's underwater beacon, under normal circumstances, the ship-borne sonar can only receive the black box sound wave signals within a range of several kilometers at most, and the effective detection range of small handheld sonar is only a few hundred meters.