Flight Data Recorder (FDR)
The crash-protected recorder that captures aircraft parameters (attitude, speeds, control positions, systems states) for at least the last 25 hours.
Modern FDRs record hundreds to thousands of parameters at high sample rates, which is what allows an investigator to reconstruct the flight second by second and to animate it.
The casing survives high-g impact, deep-water pressure and prolonged fire; the underwater locator beacon transmits for 30 days, extended to 90 on many installations after the AF447 search.
Related terms
The recorder capturing flight-deck audio: crew speech, radio calls, alerts and ambient sound. Its contents are legally protected.
The international standard governing aircraft accident investigation. It defines who investigates, what an accident is, and that the sole objective is prevention rather than blame.
The aircraft told the crew something untrue: blocked pitot tubes, a failed angle-of-attack vane, or disagreeing airspeed and altitude indications.