Flight data recorders: filtered data

This regulation controls how flight data recorder (FDR) signals may be processed before recording. "Filtering" means altering the original sensor signal in ways beyond basic digital conversion, formatting, or removing frequencies outside the sensor's range.

For Part 135 operators, filtered data must still meet the accuracy requirements in the applicable appendix. For certain critical parameters (like pitch, roll, and heading), if filtering prevents meeting those standards, operators must either remove the filtering or prove they can reconstruct the original sensor values from the filtered data—and get FAA approval of that reconstruction method.

The regulation required operators to check their aircraft by 2011 and take corrective action by 2014. Since April 2014, no Part 135 aircraft may filter these critical parameters unless the operator has FAA-approved reconstruction procedures on file. This ensures accident investigators can access accurate flight data even when some signal processing occurs.

*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.*