Originally they were tape, however modern FDR's use solid state technology to record unto 25hours of data.
There are a few things that every airliner in the world is required to have. Two of these are the flight data recorder and cockpit voice recorder. The flight data recorder in a bright orange box typically weighs less then 20 pounds.
The manual states FDR flight data recorder there is also the flightdeck voice recorder
bright orange, black isn't easy to find in a crash site
Black box
The black boxes are two separate devices, the Cockpit Voice Recorder (CVR) and the Flight Data Recorder (FDR) Old CVRs recorded thirty minutes of sound, new data replacing old data. New CVRs record two hours of sound. FDRs can record 17-25 hours of data.
The "Black box".
Black Box
If a plane crashes due to some cause then we can find out why the plane crashed with the help of Flight Data Recorder. If there is nothing they could find in the Flight Data Recorder, they could rely on the Cockpit Voice Recorder.
There are two types of black boxes aka flight recorder, the flight data recorder (FDR) and the cockpit voice recorder (CVR).
The 'Black Box' .The Black Box Flight Recorder is part of modern aircraft equipment as we still have air crashes. The other side of the flight data recorder is the flight deck voice recorder. Although most people still talk about a black box in fact it is painted bright orange to stand out from other parts of a crashed aircraft.
It is not really black, but still called "black box". It is a flight data recorder.There are two "black boxes" on modern day aircraft. One is the Cockpit Voice Recorder (CVR) used to record cockpit, intercom, and pilot to controller communications. The other is the Digital Flight Data Recorder (DFDR) used to record aircraft flight control inputs, flight parameters (speed, altitude, etc.), and system performance. The primary use for both is in accident investigation. This record remains intact even after accidents also.
Nothing is waterproof, especially considering the high stresses involved in an airplane accident. The flight data recorder is water resistant. It is also designed to minimize the probability of data loss even if it does get wet internally.