What Are Flight Data Recorders?

A Flight Data Recorder (FDR) is a device used to record and collect specific aircraft performance parameters from an array of sensors, storing them in a medium designed to survive an accident. Historically, an FDR is one of two types of “flight recorders” carried on aircraft, the other being a cockpit voice recorder (CVR). Today, the two are often combined into a single unit, but must meet the flight recorder equipment requirements outlined in ICAO Annex 6 for the operation of aircraft.

According to the provisions in ICAO Annex 6, a Type 1 FDR must record all parameters required to accurately determine the flight path, speed, attitude, engine power, configuration, and operation of an aircraft. Type II and IIA FDRs, on the other hand, are expected to record parameters required to accurately determine the flight path, speed, attitude, engine power, and configuration of lift and drag devices. Despite having slightly different objectives, either variant is installed in the most crash-survivable part of the aircraft, which is usually in the tail section.

The data collected in the Flight Data Recorder (FDR) system can help investigators determine whether an accident was caused by pilot error, an external event, or a system problem. The availability of this data has contributed to airplane system design improvements, allowing engineers and operators to predict potential difficulties as planes age. For instance, FDR data can be used to monitor the condition of a high-hour engine, and evaluating such data can be useful in making a decision about when to replace an engine before failure occurs.

By regulation, newly manufactured aircraft must monitor at least 88 important parameters, some of which include time, altitude, airspeed, and heading. Additionally, some FDRs have the capacity to record the status of more than 1,000 other in-flight characteristics that can aid any aircraft investigation, items being monitored ranging from flap positions to auto-pilot mode, smoke alarms, and many others. It is worth noting that an FDR verification check is carried out annually to verify that all mandatory parameters are recorded.

History of Operation

Until the introduction of solid-state flight recorders in the late 1980s, CVRs and DFDRs of the 1960s and 70s used magnetic tape as their primary recording medium of choice. There were a variety of tapes and tape transports used by a wide range of recorder manufacturers, some of the most widely used being mylar, kaption, and metallic variations. Still, the tape transports were even more varied, using designs like coplanar reel-to-reel, coaxial reel-to-reel, endless loop reel packs, and endless loop random storage.

A majority of DFDRs necessitate a flight data acquisition unit (FDAU) to provide an interface between the various sensors and the DFDR. The FDAU is responsible for converting analog signals from the sensors into digital signals that can be multiplexed into a serial data stream suitable for the DFDR to record. However, the recording capacity of the rape DFDR is limited by the length of the tape, making it suitable for only the first generation of wide-body transports until digital avionics were introduced. By the 1980s, solid-state flight recorders marked the most significant advancement in the evolution of this technology, expanding recording capacity, crash/fire survivability, and recorder reliability.


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