Devices that record data about an aircraft and/or its cockpit environment, so as to aid in accident investigations or troubleshooting/maintenance. Use this tag for questions about flight recorders in general, or about types of flight recorders other than an FDR or CVR; use the [flight-data-recorder] or [cockpit-voice-recorder] tag if the question is about one of those specific kinds of recorders.
Flight recorders are devices which, as the name indicates, record information about the aircraft, its systems, and/or the cockpit environment whenever the aircraft is operating. The first flight recorders were invented during World War II; types practical for commercial airline use were developed in the 1950s, and became mandatory for large airliners in most jurisdictions in the 1960s and 1970s (smaller commercial aircraft were not generally required to carry flight recorders until much later, and most general-aviation aircraft in most jurisdictions usually don't have to, even today).
The two main types of flight recorders are the flight-data-recorder, or FDR (newer versions of which are often referred to specifically as the digital flight data recorder, or DFDR), which records parametric data about the aircraft and its systems, and the cockpit-voice-recorder, or CVR, which records cockpit audio; the two are sometimes combined, to form what is known as a cockpit voice and data recorder or combined voice and data recorder (CVDR), or as a digital voice and data recorder (DVDR). Other types include:
- The quick access recorder, or QAR, records information about an enormous number of aircraft parameters (often far more, and sampled more frequently, than the FDR). Unlike the FDR, which can be quite inconvenient to routinely retrieve data from (FDRs are optimised for crash-survivability, not for easy routine access), the QAR stores data in a format making it very easy and simple to access, usually by recording the data onto a standard removable storage device (the first QARs used tape cartridges; these were later succeeded by QARs using magneto-optical disks, and the newest QARs use flash memory cards or sticks), by providing a USB port through which data can be downloaded onto a standard laptop computer via a simple transfer cable, or both. QARs were developed to provide a means for collecting and analysing flight data for purposes such as troubleshooting, maintenance, and supervision of line operations without having to remove the FDR after every flight and truck it to a facility equipped to read out data from it. The downside is that QARs are generally not crash-protected, and are usually located in or near the cockpit electronics bay to make them easier to access; thus, they are far more likely to be totally destroyed, or unusably damaged, in an accident involving severe crash forces, postcrash fire, or both. Despite this, QARs have, on occasion, yielded useful data about the cause of a crash, and they are invaluable for analysing accidents and incidents where the aircraft landed safely (due to the facts that they usually record data in far more detail than the FDR, and can be used to crosscheck the data that is recorded by the FDR).
- The cockpit image recorder (CIR) is a more recent development; following a number of accident-investigations where the available parametric and audio data left large uncertainties in areas such as who did what when, what did who see when, or what was going on that no-one saw, investigators began to recommend that regulations be amended to require the recording of cockpit video in addition to audio. Although these recommendations started in earnest around the turn of the millennium, no regulatory authority yet requires CIRs, even for large airliners. Some companies are making light, portable video recorders, which are used by many operators of small airliners and general-aviation pilots; unfortunately, these recorders are seldom crash-protected, and often do not survive a crash.
Although flight recorders are popularly known as “black boxes”, this moniker is quite inaccurate; flight recorders are actually painted bright orange, to make them easier to find following accidents. Most flight recorders (with the exception of QARs, which are intended primarily to aid in maintenance and troubleshooting) are heavily armoured and cushioned to protect the recording medium from impact deceleration and crushing forces, together with many thick layers of insulation to shield against postcrash fire. To further increase their crash-survivability, most flight recorders (again, with the exception of QARs) are located in the tail section of the aircraft (the area most likely to survive a crash); this placement became mandatory in most countries after a number of crashes in the 1960s where the flight recorder(s) were destroyed (up until then, the most popular places to put these recorders were in the cockpit electronics bay or one of the landing-gear wells). In earlier flight recorders (which used magnetic tape, or - for many older FDRs - a strip of metal foil with data traces scratched into it), this armour and insulation covered the entire recorder, in order to adequately protect the bulky recording medium. However, newer flight recorders, which store data on solid-state flash memory, take advantage of the relative extreme compactness of this recording-medium technology to concentrate all the shielding and insulation around a small “memory module”; this allows for a lighter recorder (as there is no need to shield the parts of the recorder which store no data), while (as a small, compact, frequently-round package is easier to make super-strong than a large rectangular metal box) simultaneously increasing the survivability of the data stored in the recorder.
Following a number of crashes in which one or both recorders were lost in deep water, flight recorders are now required to include crash-activated “pinger” beacons, which send out repeating sound pulses that can be picked up by a search vessel’s sonar equipment, but flight recorders still, from time to time, require tremendous effort to recover from Davy Jones’s locker (especially if the aircraft’s wreckage is not rapidly located; the batteries in most pinger beacons are only good for about a month or so of pinging). As a result, two other potential solutions have been getting more attention lately; one is telemetry (where aircraft data is continuously streamed to a ground-based storage facility in real time), a system widely used on spacecraft and experimental-aircraft, and already used by some airliners to a very limited degree for maintenance purposes, while the other is the use of jettisonable or deployable flight recorders (already commonly used on military aircraft, though not on commercial aircraft), where the recorders are thrown free at impact and float to await recovery.
For more information about flight recorders, see Wikipedia’s articles on: