An airplane’s digital flight-data recorder, or “black box,” holds massive amounts of data, documenting the performance of engines, cockpit controls, hydraulic equipment and GPS systems, typically at regular one-second intervals throughout a flight. Inspectors use such data to reconstruct the final moments of an accident, looking for telltale defects that may explain a crash. 

http://web.mit.edu/newsoffice/2011/black-box-analysis-0912.html
飞机“黑匣子”什么样子？