The FAA is proposing to amend the digital flight data recorder (DFDR) regulations of Parts 121 and 135 to prohibit filtering of original parameter sensor signals. During several accident investigations, the NTSB found that some DFDRs were filtering signals before they were recorded. “As a result, the data being recorded did not accurately reflect the aircraft’s performance or the movements of the flight controls,” the agency said. The FAA projects that the de-filtering modification would cost about $16,025 per airplane, although not all manufacturers agree. Comments on the proposal are due by February 13.