There are usually many unanswered questions as to what brought the plane down. Investigators turn to the airplane's flight data recorder (FDR) and cockpit voice recorder (CVR) for answers. Any commercial airplane or corporate jet is required to be equipped with a cockpit voice recorder and a flight data recorder. It is these two items of separate equipment which we commonly refer to as a ‘Black Box.’ While they do nothing to help the plane when it is in the air, both these pieces of equipment are vitally important should the plane crash, as they help crash investigators find out what happened just before the crash.
To help locate the cockpit voice recorder and a flight data recorder in the aftermath of a plane crash that occurs at sea, each recorder has a device fitted to it known as an Underwater Locator Beacon (ULB). The device is activated as soon as the recorder comes into contact with water and it can transmit from a depth as deep as 14,000 feet. Also, to help investigators find them; a Black Box is not actually black at all, but bright orange. The term “black box” is favoured by the media, but most people in the know don’t call them that.
All recorders undergo countless tests. For example, one Black Box recorder, the L-3 FA 2100 underwent testing that includes exposure to a 1,110°C fire for an hour and 260°C heat for 10 hours. It is also able to operate between -55° to +70°C and it can carries a minimum 25 hours of flight data.
Black boxes are fitted with an underwater locator beacon that starts emitting a pulse if its sensor touches water. It means that black boxes can only be detected if the aircraft is under water. If a crash happens on land, searchers only have the orange color as a visual beacon.