Every time a tragic aviation accident occurs, you’re likely to hear the news mention something about the hunt for the plane’s black boxes. These units are said to contain vital information that can reveal why a particular airplane might have crashed. Since the 1950s, the data inside black boxes has helped accident investigators, airline manufacturers, and aviation professionals improve flight safety for everyone.

A Black Box is able to withstand many accident scenarios without sustaining damage. Before being put into use, they are tested to see if they can withstand an impact with a concrete wall at 750 kilometers per hour (about 466 miles/hour), a static load of 2.25 tons for at least five minutes, a maximum temperature 1,100 degrees Celsius (2,012 Fahrenheit) for one hour and water pressure found in depths of up to 6,000 meters (about 19,700 feet).

They are a significant contribution to airline safety, but have you ever wondered how they actually work

1. They’re actually made of two components: the flight data recorder and cockpit voice recorder.

Technically there isn’t one single “black box” on each plane. Instead, there are two parts — the flight data recorder (FDR), and the cockpit voice recorder (CVR). During a flight, the FDR tracks information about the plane itself, like its direction and speed, while the CVR records audio of the crew’s conversations, radio transmissions, engine sounds, and alarm noises.

Sometimes they can be combined together in one unit, but they are often two separate devices. They’re also quite expensive to make. The standard flight data and cockpit voice recorder system can cost anywhere from $10,000 to $15,000 to produce.

2.Human error is one of the primary reasons black boxes exist.

It’s true that inventions are born out of human necessity. In the 1950s, an Australian research scientist named David Warren helped to investigate the repeated plane crashes of the first commercial jet airliner, The Comet. He proposed that if researchers had knowledge of what happened on the plane moments before it went down, it would help them figure out how to improve the next flight.

While mechanical failure is a very real possibility, it’s been noted by several sources that the most common cause of airline crashes is pilot mistake. This is arguably why the CVR (cockpit voice recorder) exists, and not solely the flight data recorder.

3.The locations of black boxes can be traced in the bottom of deep oceans thanks to a special tracking component.

Every flight data recorder contains a tool called an underwater location beacon (ULB). This makes it possible for investigators tofind it if a plane crashes into a body of water. Once underwater, it sends out an acoustic signal that searchers can detect with a special receiver.

Finding the FDR and CVR from a plane that’s crashed into an ocean can still be tricky. In order for the signal to be heard, one has to be within a 15-mile range of the beacon. On top of that, the battery life only lasts for 30 days after it’sbeen submerged.

However, it’s not impossible. Two years after the 1987 crash of South African Airways295, investigators found the plane’s cockpit voice recorder 16,000 feet below the surface.

4.Black boxes are usually placed in the airplane’s tail because that’s where the least damage will occurs.

Even though the CVR records cockpit audio, the recording device itself doesn’t sit up front with the pilots. Typically the pilot area is fitted with several microphones, but the actual device that stores the recordings is hidden in the tail of the plane. This prevents the FDR and CVR from being completely destroyed in a crash since the tail typically feels the impact last.

As Joe Janes of the Information School at The University of Washington said, “Planes rarely back into mountains.”

5.Airplane black boxes are extremely durable.

According to National Geographic, all FDR equipment undergoes extensive tests prior to being placed on an airplane, just to be sure they can handle the stress of an accident.

The Australian Transport Safety Bureau reports that flight data recorders can withstand fires up to 1,100 degrees Celsiusand a continuous pressure force of 5,000 pounds for up to five minutesIn addition, they can endure water pressure at depths up to 20,000 feet.

6.Only a special committee is allowed to listen to black box data.

Once an FDR or CVR has been recovered from a plane crash site, it gets transported to a special lab for analysis. After the data is extracted, a panel of exclusive aviation VIPs, everyone from industry experts, airplane manufacturers, and FAA officials, meet to review its contents. They then piece together the audio recordings and information from the FDR and try to deduce what happened in the moments leading up to an incident. The rules regarding who gets to be involved in the investigation are very strict and highly regulated by The US National Transportation Safety Board.

In fact, the US Congress explicitly forbids CVR audio recordings from being released to the public. They only publish the written transcript of the CVR data after the official safety hearing occurs.

What are the colors black box?

Although they are called ‘black boxes,’ aviation recorders are actually painted bright orange. This distinct color, along with the strips of reflective tape attached to the recorders’ exteriors, help investigators locate the black boxes following an accident. These are especially helpful when a plane lands in the water.