20. Do you know black boxes?
Black boxes are flight recorders placed in an aircraft for the purpose of making it easier to know how the accidents happened in flight.
An airplane actually has two black boxes. The flight data recorder catches the information, which can discover whether human error or instrument problems contributed to an accident. The cockpit (驾驶舱) voice recorder records pilot voices and cockpit sounds.
The black boxes are not black. They are painted bright orange to help with their
recovery after accidents. The outside is with stripes of reflective tape (反光带). The black boxes are usually placed in the tail of a plane where they are more likely to survive a crash. A flight data recorder is required to store at least 25 hours of flight information. A cockpit voice recorder is required to record at least 2 hours of audio information.
For the black boxes to survive a crash, they are built to be waterproof, fireproof, shockproof, heat and pressure and corrosion resistant (耐腐蚀). The black box must be able to hold 3, 400 times the force of gravity, when the airplane goes down at the speed of about 500 km/h. It must also survive flames up to 1, 100 degrees Celsius for one hour, and the boxes should be able to give out a signal once per second while put under 6, 000 meters of saltwater for at least 30 days.
How is data from black boxes picked up?It needs special skills to physically bring the black boxes back. Investigators may need to clean and dry the black boxes and download data from them. It takes time to download and get the information from data. If the storing units go wrong, it will take longer time, either days or months.
So, the black boxes are very important to explain to everyone what happened during the flight.