What is the black box (in planes) made of ? Normally wat does it do ?

Black boxes which usually hold the clues to a plane's crash, are built strong enough to survive bomb blasts, violent impacts and intense fires. They measure approximately 4 by 6 by8 inches and weighs about 30 kg and are kept in a case which can withstand 30 minutes of 1100 degrees C at 50,000 (Btu's) British Thermal Units per square foot per hour.

They are actually orange in color and a very high quality heat resistant paint is used, so that they can be spotted easily even at dimly lit crash sites. They are always placed in the tail end of the flight.

The black box records voice and flight data. The cockpit voice recorder continuously collects data and retains a record of the most recent 30  minutes, the conversation between the pilot and the Ground Control Room.

The flight data recorder keeps a record of the most recent 25 hours of a plane's operating data, including altitude, air speed, vertical acceleration and heading.

Flight data are recorded either by magnetic tape or in solid-state memory. Modern data recorders can long more than 200 different parameters and transmit data either 64 times or 128 times a second. Thus when recovered from the airplane crash sites the black box helps to reconstruct a clear picture of the crash.