black box

Popular name for the unit containing an aeroplane's flight and voice recorders. These monitor the plane's behaviour and the crew's conversation, thus providing valuable clues to the cause of a disaster. The box is nearly indestructible and usually painted orange for easy recovery. The name also refers to any compact electronic device that can be quickly connected or disconnected as a unit.

The voice recorder records in a 30-minute loop, so that the last minutes of a flight can be listened to if there has been an accident. The flight data recorder functions on a 25-hour loop. Neither recorder is battery operated so, as happened in the 1998 Swissair crash that killed 229 people, the final data may be missing as power gets cut off. The only part of a blackbox that is battery operated is its underwater locator, that will transmit a signal for 35 days after the crash to aid its location.

The maritime equivalent is the voyage recorder, installed in ships from 1989. It has 350 sensors to record the performance of engines, pumps, navigation lights, alarms, radar, and hull stress.