Editing Flight recorder (section)

=== Additional equipment ===
Since the 1970s, most large civil jet transports have been additionally equipped with a "[[quick access recorder]]" (QAR). This records data on a removable storage medium. Access to the FDR and CVR is necessarily difficult because they must be fitted where they are most likely to survive an accident; they also require specialized equipment to read the recording. The QAR recording medium is readily removable and is designed to be read by equipment attached to a standard desktop computer. In many airlines, the quick access recordings are scanned for "events", an event being a significant deviation from normal operational parameters. This allows operational problems to be detected and eliminated before an accident or incident results.

A '''flight-data acquisition unit''' (FDAU) is a unit that receives various discrete, analog and digital parameters from a number of sensors and [[avionic]] systems and then routes them to the FDR and, if installed, to the QAR. Information from the FDAU to the FDR is sent via specific data frames, which depend on the aircraft manufacturer.

Many modern aircraft systems are [[fly-by-wire|digital or digitally controlled]]. Very often, the digital system will include [[built-in test equipment]] which records information about the operation of the system. This information may also be accessed to assist with the investigation of an accident or incident.