Flight Data Recorder (FDR)
The Flight Data Recorder (FDR) records flight parameters. The range and quantity of data recorded varies widely, depending on the age and size of the aircraft.
The minimum requirement is to record a basic group of five parameters:
- Pressure Altitude
- Indicated Airspeed
- Magnetic Heading
- Normal Acceleration (Load Factor)
- Microphone Keying
Microphone keying (i.e. the time radio transmissions were made by the crew) is recorded to correlate FDR data with CVR information.
This basic requirement has existed since the 1960's and modern jet aircraft now typically record hundreds of parameters covering all aspects of the aircraft's operation. For example, the Airbus A380 aircraft records over 3,000 parameters on its FDR.
The FDR retains at least the last 25 hours of data and, like the CVR, operates on the endless-loop principle. Modern FDR's, however, use memory chips rather than magnetic tape as the recording medium. As FDR's have a longer recording duration than CVR's they are useful for investigating both incidents and accidents.
The FDR often tells accident investigators what happened during an accident sequence.