The flight data recorder (FDR) is a flight recorder used to record specific aircraft performance parameters. A separate device is the cockpit voice recorder (CVR), although some recent types combine both in one unit. Popularly, though almost always falsely, known as the black box used for aircraft mishap analysis, the FDR is also used to study air safety issues, material degradation, and jet engine performance. These ICAO regulated "black box" devices are often used as an aid in investigating aircraft mishap, and these devices are typically one of the highest priorities for recovery after a crash, second only to bodies of victims. The device's shroud is usually painted bright orange and is generally located in the tail section of the aircraft.
Despite his 1954 report entitled "A Device for Assisting Investigation into Aircraft Accidents" and a 1957 prototype FDR named "The ARL Flight Memory Unit", aviation authorities from around the world were largely uninterested. This changed in 1958 when Sir Robert Hardingham, the Secretary of the UK Air Registration Board, became interested. Dr. Warren was asked to create a pre-production model which culminated into the "Red Egg", the world's first commercial FDR by the British firm, S. Davall & Son. The "Red Egg" got its name from the shape and bright red color. Incidentally, the term "Black Box" came from a meeting about the "Red Egg", when afterwards a journalist told Dr. Warren, "This is a wonderful black box."
Currently, EUROCAE specifies that a recorder must be able to withstand an acceleration of 3400 g (33 km/s²) acceleration for 6.5 milliseconds. This is roughly equivalent to an impact velocity of 270 knots and a deceleration or crushing distance of 450 mm. Additionally, there are requirements for penetration resistance, static crush, high and low temperature fires, deep sea pressure, sea water immersion, and fluid immersion.
Modern day FDRs are typically plugged into the aircraft's fly-by-wire main data bus. They record significant flight parameters, including the control and actuator positions, engine information and time of day. There are 88 parameters required as a minimum by current U.S. federal regulations (only 29 were required until 2002), but some systems monitor many more variables. Generally each parameter is recorded a few times per second, though some units store "bursts" of data at a much faster frequency if the data begins to change quickly. Most FDRs record 25 hours worth of data in a continuous loop.
This has also given rise to flight data monitoring programs, whereby flights are analyzed for optimum fuel consumption and dangerous flight crew habits. The data from the FDR is transferred, in situ, to a solid state recording device and then periodically analyzed with some of the same technology used for accident investigations.
FDRs are usually located in the rear of the aircraft, typically in the tail. In this position, the entire front of the aircraft acts as a "crush zone" to reduce the shock that reaches the recorder. Also, modern FDRs are typically double wrapped, in strong corrosion-resistant stainless steel or titanium, with high-temperature insulation inside. Additionally, since the recorders are sometimes crushed into unreadable pieces, or never located, most modern units are self-ejecting (taking advantage of kinetic energy at impact to separate themselves from the aircraft) and also equipped with radio and sonar beacons (i.e. emergency locator transmitter).
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