Flight Data Recorders
Missing Evidence About the September 11th Flights
Flight data recorders (FDRs) record the readings of instruments and positions of the aircraft's control surfaces over time. They are contained in black boxes that are designed to survive the worst crashes and, like the cockpit voice recorders, are recovered after crashes in order to reconstruct events.
To date, none of the contents of any of the FDRs from the two jetliners that hit the Twin Towers have been made public.
|Flight Data Recorder|
|Time recorded||25 hour continuous|
|Number of parameters||18 - 1000+|
|Impact tolerance||3400Gs / 6.5 ms|
|Fire resistance||1100 degC / 30 min|
|Water pressure resistance||submerged 20,000 ft|
|Underwater locator beacon||37.5 KHz; battery has shelf life of 6 years or more, with 30-day operation capability upon activation|