By Kaye Foley

Although plane crashes are statistically rare, when one does happen, it’s the black box that is key to figuring out what went wrong.

But what is a black box and how does it work?

A black box is an electronic device stored in the tail of the plane that records flight information. Airplanes have two of them: the CVR , or cockpit voice recorder, and the FDR, or flight data recorder. And, despite the name, they’re not actually black, but bright orange, so they can be easily found. 

The CVR records conversations, air traffic control and warning sounds in the cockpit from the two most recent hours of a flight. The FDR keeps track of the plane’s vital information, like speed, altitude, engine power, fuel levels, temperature and flight controls. It records up to 25 hours of data, and after that it records over existing data. 

Black boxes can get damaged, but their “crash-survivable memory units,” which protect the memory cards, are practically indestructible. They’re wrapped in a thin layer of aluminum, an inch of high-temperature insulation and are covered in stainless steel or titanium. 

Black boxes are built to survive acceleration up to 3,400 Gs, an hour in temperatures as high as 2,000 degrees Fahrenheit and to survive being submerged in water at a depth of 20,000 feet. They have an underwater beacon that emits a pulse every second and is detectible by sonar for about 30 days. 

With hundreds of thousands of flights taking off daily around the world,, when it comes to the essential role of black boxes on planes, at least you can say, “Now I get it.”