BLACK BOXES

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Context

China’s aviation authority announced that a flight recorder, commonly known as “black box”, “from China Eastern MU5735 was found.

What are Black boxes?

These are two large metallic boxes containing recorders that are required to be kept on most aircraft, one in the front and the other in the rear.
The recorders record the information about a flight, and help reconstruct the events leading to an aircraft accident.
Black boxes are a blazing, high-visibility orange in colour, so that crews looking for them at a crash site have the best chance of finding them.

Types

The cockpit voice recorder (CVR) records radio transmissions and other sounds in the cockpit, such as conversations between the pilots, and engine noises.
The flight data recorder (FDR) records more than 80 different types of information such as altitude, airspeed, flight heading, vertical acceleration, pitch, roll, autopilot status, etc.
Black boxes are mandatory on commercial flights. Their purpose on aircraft is not to establish legal liability, but to identify the causes of a mishap and, therefore, help to prevent adverse incidents in the future.

History

The use of black boxes dates back to the early 1950s, when, following plane crashes, investigators were unable to arrive at a conclusive cause for the accidents.
An Australian scientist named David Warren is often credited with their invention.

Technicalities

In the initial days of the black box, a limited amount of data was recorded on wire or foil. Thereafter magnetic tape was used, and modern models contain solid state memory chips.
The recording devices, each weighing about 4.5 kg, are stored inside a unit that is generally made out of strong substances such as steel or titanium.
They are insulated from extreme heat, cold or wetness. The FDR is located towards the tail end of the aircraft because that is usually where the impact of a crash is the least.
To make black boxes discoverable under water, they are equipped with a beacon that sends out ultrasound signals for 30 days.