Flight recorder

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Both side views of a cockpit voice recorder, one type of flight recorder

A flight recorder is a recorder placed in an aircraft for the purpose of facilitating the investigation of an aircraft accident or incident. For this reason, they are required to be capable of surviving the conditions likely to be encountered in a severe aircraft accident. They are typically specified to withstand an impact of 3600 g and temperatures of over 1,000 °C. Early attempts at making flight recorders were made by François Hussenot in July 1941 at the Marignane flight test center, France; they were essentially photograph-based flight recorders. In 1947, Hussenot grounded the Société Française des Instruments de Mesure (today part of the Safran group) with an associate, so as to market his invention, which came to be known as the hussenograph.^[1] At about the same period of time, in 1953, Australian engineer Dr. David Warren conceived a device that would record the voices and instruments reading, when working with the Australian Research Laboratories.^[2]

In order to facilitate recovery of the recorder from an aircraft accident site they are required to be coloured bright yellow or orange with reflective surfaces. All are lettered "FLIGHT RECORDER DO NOT OPEN" on one side in English and the same in French on the other side. To assist recovery from submerged sites they must be equipped with an underwater locator beacon which is automatically activated in the event of an accident.

There are two types of protected Flight Recorder, Flight data recorder (FDR) and Cockpit voice recorder (CVR). In some cases, the two recorders may be combined in a single FDR/CVR unit.

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 of the requirement that they survive an accident. They also require specialist 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.

Many modern aircraft systems are 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.

Cockpit video recorders have been suggested but are not yet required. The rationale is that what is seen on an instrument by the pilots of an aircraft is not necessarily the same as the data sent to the display device. This is particularly true of aircraft equipped with electronic displays (CRT or LCD). A mechanical instrument is likely to preserve its last indication but this is not the case with an electronic display.