The flight data recorder (FDR) is designed to record the operating data from the plane's systems. There are sensors wired from various areas on the plane to the flight-data acquisition unit, which is wired to the FDR. So whenever the pilot flips a switch or twiddles a knob, the FDR records each action.
In the U.S., the Federal Aviation Administration (FAA) requires that commercial airlines record a minimum of 11 to 29 parameters, depending on the size of the aircraft. Magnetic-tape recorders have the potential to record up to 100 parameters. Solid-state FDRs can record hundreds or even thousands more.
On July 17, 1997, the FAA issued a Code of Federal Regulations that requires the recording of at least 88 parameters on aircraft manufactured after August 19, 2002. Here are a few of the parameters recorded by most FDRs:
- Pressure altitude
- Vertical acceleration
- Magnetic heading
- Control-column position
- Rudder-pedal position
- Control-wheel position
- Horizontal stabilizer
- Fuel flow
Solid-state recorders can track more parameters than magnetic tape because they allow for a faster data flow. Solid-state FDRs can store up to 25 hours of flight data. Each additional parameter recorded by the FDR gives investigators one more clue about the cause of an accident.