Flight data recorder

In aircraft, the flight data recorder (FDR) and the cockpit voice recorder (CVR) are used to record aircraft and pilot behavior in order to analyze accidents, and are usually called "black boxes" by the news media.

The main purpose of the device is to reduce the manufacturer's liability by correctly assigning blame to the failing assemblies or persons. The famous, secondary use is to analyze accidents to prevent future failures.

Traditional black boxes use potentiometers attached to strings. The strings are actually steel wire, bolted to the controls and flight surfaces. As the surfaces move, the resistances of the pots change, changing the frequency of an oscillator. The oscillator's electronic howl is wired to a recorder. The howl is better than just recording a voltage because the howl cannot be affected as easily by stray currents or magnetic fields. The howls, along with the pilot's incoming and outgoing audio, are recorded on a continuous loop of magnetic tape or wire.

Black boxes are often poorly maintained, because they are not critical to flight. There is a growing sentiment that they should be reliable, solid-state digital systems. Additionally, since they are often crushed into unreadable pieces, or never located, there is a move to make them self-ejecting, and brightly colored, with radio and sonar beacons.

External Links

• The Black Box: An Australian Contribution to Air Safety
• Flight Data Recorders: How They Work and What They Reveal
• How Black Boxes Work (Seven page article with links)