Black Boxes
 How long can aircraft black boxes last underwater
and still provide useful information
--Nancy S, Albuquerque, NM
"American 1420, Little Rock approach, roger. We have a thunderstorm
just northwest of the airport moving, uh, through the area now..," Little Rock
tower warns the American Airlines pilot of bad weather conditions at 4:34 a.m.
on June 2, 1999.
A "black box" recorded the cockpit conversation, which ran
another 14 minutes until American 1420 crashed and burned
on landing.
Safety investigators use the aircraft's two "black boxes" to
determine the cause of the crash and to prevent similar
accidents in the future. The boxes, not black but bright orange
for visibility, contain the flight data recorder and the cockpit
voice recorder. These boxes meet stringent survival specifications and, to answer your
question: can function in water for 30 days. Here are some FAA endurance regulations.
- an impact of 3,400 G's. This is equivalent to going 400 miles an hour, slamming on
the brakes, and stopping within 18 inches.
- flames at 2,000 degrees Fahrenheit (hotter than molten rock) for 30 minutes.
- water pressure at 20,000 feet below the surface (the ocean floor), withstanding the
corrosive effects of salt water, and pinging a sound a second for 30 days so divers
can locate the box.
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