Flight data recorders

This regulation requires Part 121 air carriers to equip large airplanes (those certified for high-altitude or turbine-powered operations) with flight data recorders (FDRs). The specific parameters that must be recorded—ranging from basic data like time, altitude, and airspeed to more detailed information like control surface positions and engine thrust—depend on when the airplane was type certificated and manufactured.

Older aircraft have less stringent requirements, while newer aircraft must record more parameters using digital recording methods. The recorder must operate continuously from takeoff roll to landing roll.

Recorded data must be retained for at least 25 hours of operating time, but no more than 60 days under normal circumstances. However, if an accident or reportable occurrence terminates a flight, the carrier must remove and preserve the recording media for at least 60 days. This preserved data becomes crucial evidence for accident investigations.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*