What the press calls the
black box on an
Airplane. Actually, there is more than one "
black box:" the most important ones are the
Flight Recorder and the Cockpit voice recorder, also known as a CVR.
The CVR is not black, it's bright day-glo Orange, so it can be spotted after a crash. It consists simply of a continuous loop of tape that records the last 30-45 minutes of what happens in a cockpit. This along with the Flight recorder can give investigators insight into what happened and can reconstruct the accident.
Sometimes this doesn't work right, because the incident can happen an hour before landing and the CVR stops recording, such as in some hijackings. In one case the hijacker switched off the CVR circuit breaker, and tried to crash a FedEx plane into the headquaters. A member of the flight crew noticed it and switched it back on. Later in court, the tape provided clear proof of what happened, catching the person say, "This is an axe, I'm going to kill you"(paraphrased).