Flight Data Recorder - Design

Design

The design of today's FDR is governed by the internationally recognized standards and recommended practices relating to flight recorders which are contained in ICAO Annex 6 which makes reference to industry crashworthiness and fire protection specifications such as those to be found in the European Organisation for Civil Aviation Equipment documents EUROCAE ED55, ED56 fiken A and ED112 (Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems). In the United States, the Federal Aviation Administration (FAA) regulates all aspects of U.S. aviation, and cites design requirements in their Technical Standard Order, based on the EUROCAE documents (as do the aviation authorities of many other countries).

Currently, EUROCAE specifies that a recorder must be able to withstand an acceleration of 3400 g (33 km/s²) for 6.5 milliseconds. This is roughly equivalent to an impact velocity of 270 knots (310 mph) and a deceleration or crushing distance of 450 cm. Additionally, there are requirements for penetration resistance, static crush, high and low temperature fires, deep sea pressure, sea water immersion, and fluid immersion.

Modern day FDRs receive inputs via specific data frames from the Flight Data Acquisition Units (FDAU). They record significant flight parameters, including the control and actuator positions, engine information and time of day. There are 88 parameters required as a minimum under current U.S. federal regulations (only 29 were required until 2002), but some systems monitor many more variables. Generally each parameter is recorded a few times per second, though some units store "bursts" of data at a much higher frequency if the data begins to change quickly. Most FDRs record approximately 17–25 hours worth of data in a continuous loop. It is required by regulations that an FDR verification check (readout) is performed annually in order to verify that all mandatory parameters are recorded.

This has also given rise to flight data monitoring programs, whereby flights are analyzed for optimum fuel consumption and dangerous flight crew habits. The data from the FDR is transferred, in situ, to a solid state recording device and then periodically analyzed with some of the same technology used for accident investigations. In other cases the data is downloaded from the aircraft's Quick Access Recorder (QAR), either by transfer to a portable solid state recording device or by direct upload to the operator's headquarters via radio or satellite.

FDRs are usually located in the rear of the aircraft, typically in the tail. In this position, the entire front of the aircraft is expected to act as a "crush zone" to reduce the shock that reaches the recorder. Also, modern FDRs are typically double wrapped, in strong corrosion-resistant stainless steel or titanium, with high-temperature insulation inside. They are usually bright orange. They are designed to emit an underwater locator beacon for up to 30 days, and can operate immersed to a depth of up to 6,000 meters (20,000 ft).