1: In the water (sea)
If an airplane crash occurs in the water, it will be very difficult to recover the black box.
For example, the plane finally crashed into the sea.
Although the seawater seems calm, there are many undercurrents and ocean currents below the sea level. These undercurrents and ocean currents keep the water in constant motion.
When an aircraft crashes, the underwater beacon installed on the outside of the black box will short-circuit as soon as it touches water, and the buzzer will emit ultrasonic pulses with a frequency of 37.5kHz. This sound is clearly audible even under water, 8 kilometers away. This situation can last automatically for up to 30 days.
Because the black box relies on electricity, after 30 days, the power of the black box will be exhausted, and it will be hopeless to find the black box.
2: A serious explosion occurred
The plane had a serious explosion before it hit the ground, causing damage to the black box, making it impossible to recover the black box.
If the plane crashes in a mountainous forest and explodes, it may trigger a wildfire, causing the black box to be exposed to the shock wave released by the explosion and the fire.
Before answering this question, we need to know what a black box is?
First of all, the "black box" is not black, but orange/red. "Black Box" is someone's nickname.
Its real name is "Electronic Flight Recorder".
It is divided into two parts:
One is the "flight data recorder", an instrument used to record aircraft flight and performance parameters, such as the aircraft's altitude, speed, heading, Flight parameters such as climb rate, descent rate, acceleration, fuel consumption, landing gear extension and retraction, Greenwich Mean Time, as well as aircraft system operating conditions and engine operating parameters can all be recorded by it.
One is the "cockpit voice recorder", which is simply a radio call recorder that records various conversations on the plane. For example: conversations between the pilot and the ground command organization, conversations between the pilot and co-pilot, speeches by the captain and flight attendants to passengers, or threats, explosions, abnormal engine sounds, and various sounds in the cockpit.
Because after an air crash, the aircraft often disintegrates or is even destroyed by fire, so the "black box" was manufactured with this situation in mind.
In appearance, in order to withstand the violent impact and high temperature flames when the plane crashes, the outer shell of the black box has a very thick steel plate and many layers of thermal insulation and anti-impact protection materials
In terms of location, In order to be as safe as possible, the black box is usually installed in the safest part of the tail of the aircraft. This position is the least likely to be damaged in the event of a crash.
At the same time, when the plane crashes, the black box can withstand a 30-minute barbecue in a flame of 1100°C, can withstand the squeeze of a 2-ton object for 5 minutes, and can be burned in gasoline, engine oil, kerosene, batteries, Soaked in acid and sea water for several months.
After seeing this, do you think the "black box" is very strong? But not all "black boxes" are damaged or can be found in all air crash rescues.
It is actually not easy to find the black box if it is in the following two situations:
1: In the water (sea)
If the plane crashes in the water It is very difficult to recover the black box.
For example, the plane finally crashed into the sea.
Although the sea water seems very calm, there are many undercurrents and ocean currents below the sea level. These undercurrents and ocean currents keep the water in constant motion.
When an aircraft crashes, the underwater beacon installed on the outside of the black box will short-circuit as soon as it touches water, and the buzzer will emit ultrasonic pulses with a frequency of 37.5kHz. This kind of sound can be clearly heard even under water at a distance of 8 kilometers.
This situation can automatically last for up to 30 days.
Because the black box relies on electricity, after 30 days, the power of the black box will be exhausted, and it will be hopeless to find the black box.
2: A serious explosion occurred
The plane suffered a serious explosion before it hit the ground, causing damage to the black box, making it impossible to recover the black box
The plane crashed The explosion behind the mountainous forest area may cause a wildfire, causing the black box to be exposed to the shock wave released by the explosion and the fire.
Such damage could damage the outer shell of the black box, burning away the thin layers of silica and aluminum inside.
(Reference Science)