Why does the black box remain intact in an air crash?

Each aircraft is fitted with two pieces of equipment – Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) – that are designed to survive an air crash so that the data recorded helps investigators reconstruct events preceding the crash. FDR records values of about 700 parameters related to the flight and controls and CVR records conversations taking place in the cockpit. The data is recorded in a crash survivable memory unit and housed in a cylindrical casing made of three layers that can withstand extreme heat, high impact and pressure. The black box is painted orange, not black, has reflective tape on its surface and is fitted with underwater locator beacon.