2002
letter
the Safety Board indicated that the flight 587investigation revealed that vital flight control surface position information was notdirectly recorded on the accident airplaneâs FDR because of the SDAC filter (see section1.11.2). The Board believed that the filtered data supplied by the SDAC did not meet theaccuracy requirements under dynamic conditions called for in 14 CFR 121.344
AppendixM. The Safety Board stated that the presence of filtered data was âsurprising anddisappointing
â considering the FAAâs actions regarding SafetyRecommendationsA-94-120 and -121 (see section 1.18.7.1). Specifically
the Boardindicated that it accepted the FAAâs assertion that the issuance of the 1997 final rule(which precluded the use of a filter and added the requirement for a dynamic testcondition) and AC 20-141 (which specified test procedures for recorded parameter dataunder static and dynamic conditions)
as well as the work of POIs
would ensure thatoperators would not record filtered FDR data.The Safety Board believed that the FAA needed to take immediate steps to identifythose A300 airplanes that recorded filtered flight control surface data and to takecorrective actions as soon as possible to bring these airplanes into compliance withexisting regulations. The Board also noted that it was important for the FAA to completethe review called for in Safety Recommendation A-94-121 to ensure that all aircraft thatrecord filtered data are identified and brought into compliance with regulations as soon aspossible. In addition
the Board expressed concern that older aircraft
which have nothistorically recorded filtered data
could be retrofitted with new or upgraded avionics thatsupply filtered data to the FDR. The Safety Board requested that
within 30 days
the FAAadvise the Board
in writing
of the steps that the FAA intended to take to address theproblem involving A300 airplanes that record filtered data and to identify and correct anyother aircraft that are similarly recording filtered data.In a March 6
2002
letter
the FAA stated that
when Safety RecommendationsA-94-120 and -121 were issued
it surveyed all transport-category airplane manufacturersto determine if FDR data on their airplane models were filtered. The FAA indicated thatthe manufacturers might not have had a clear understanding of what filtered data meant inthe context of Safety Recommendation A-94-121 and that
as a result
the manufacturersdefined âfilteredâ as they saw fit. The FAA further indicated that Airbus reported that theFDRs on its airplanes did not record filtered data.The FAA recognized that it gave assurances to the Safety Board that the wordingof its 1997 final rule on data filtering would preclude the recording of filtered flightcontrol position data on most transport-category airplanes. However
the FAA stated thefollowing regarding the wording of the final rule:
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