The Federal Aviation Administration (FAA) has published a final rule spurred by the November 2001 crash of an American Airlines Airbus A300-600. It prohibits filtering of certain data captured by digital flight data recorders (DFDR).

The aircraft crashed after takeoff from New York’s Kennedy International. The National Transportation Safety Board (NTSB) eventually determined that rudder inputs by the pilot, wake vortex encounters and sensitivity of the A300's rudder controls were involved.

The NTSB said filtered data has made several aircraft accident investigations difficult.

The FAA rule prohibits “filtering” of some original flight recorder sensor signals unless the data can be accurately reconstructed.

The U.S. aviation agency says “the rule improves the integrity and quality of the data recorded on digital flight data recorders while giving aircraft designers and operators more flexibility in system design and operation.”

It said during aircraft accident investigations – including the 2001 American Airlines Flight 587 accident -- NTSB found some flight data recorder systems were filtering sensor signals and the data did not accurately reflect the aircraft’s performance or the movements of the flight control systems.

Under the new rule, operators have 18 months from the effective date (referred to as reporting date) of the rule to review their DFDR systems and create a record that indicates whether the system on each aircraft is filtering any of the parameters included in a “no filter list.”

Operators that identify filtered parameters have two options.  If an operator chooses to remove the filtering, they must do so four years from the effective date (30 months after the reporting date). If an operator decides to show by tests and analyses that filtered data can be reconstructed, they have up to 18 months from the reporting date to submit that information to the FAA for approval.
 
In all cases, compliance with the rule is required four years from the effective date.

The new rule applies to approximately 7,586 aircraft and 37 helicopters operated by scheduled air carriers and non-scheduled airplane and rotorcraft operators that must have a DFDR.

The FAA estimates the cost to operators and manufacturers will be $310,000.