After a Crash
Although they are called "black boxes," aviation
recorders are actually painted bright orange. This
distinct color, along with the strips of reflective
tape attached to the recorders' exteriors, help
investigators locate the black boxes following an
accident. These are especially helpful when a plane
lands in the water. There are two possible origins
of the term "black box": Some believe it is because
early recorders were painted black, while others
think it refers to the charring that occurs in
In addition to the paint and reflective tape, black
boxes are equipped with an underwater locator
beacon (ULB). If you look at the picture of a
black box, you will almost always see a small,
cylindrical object attached to one end of the
device. While it doubles as a handle for carrying
the black box, this cylinder is actually a beacon.
If a plane crashes into the water, this beacon
sends out an ultrasonic pulse that cannot be heard
ears but is readily detectable by sonar and
acoustical locating equipment. There is a
submergence sensor on the side of the beacon
that looks like a bull's-eye. When water touches
this sensor, it activates the beacon.
The beacon sends out pulses at 37.5 kilohertz
(kHz) and can transmit sound as deep as 14,000 feet
(4,267 m). Once the beacon begins "pinging," it
pings once per second for 30 days. This beacon is
powered by a
battery that has a shelf life of six years. In
rare instances, the beacon may get snapped off
during a high-impact collision.
In the United States, when investigators locate a
black box it is transported to the computer labs at
National Transportation Safety Board (NTSB).
Special care is taken in transporting these devices
in order to avoid any (further) damage to the
recording medium. In cases of water accidents,
recorders are placed in a cooler of water to keep
them from drying out.
U.S. Department of Defense
U.S. Navy Lieutenant Junior
Grade Jason S. Hall (right) watches as FBI Agent
Duback (left) tags the cockpit voice recorder
from EgyptAir Flight 990 on November 13, 1999.
"What they are trying to do is preserve the state
of the recorder until they have it in a location
where it can all be properly handled," Doran said.
"By keeping the recorder in a bucket of water,
usually it's a cooler, what they are doing is just
keeping it in the same environment from which it was
retrieved until it gets to a place where it can be
After finding the black boxes, investigators take
the recorders to a lab where they can download the
data from the recorders and attempt to recreate the
events of the accident. This process can take weeks
or months to complete. In the United States,
black-box manufacturers supply the NTSB with the
readout systems and software needed to do a full
analysis of the recorders' stored data.
If the FDR is not damaged, investigators can
simply play it back on the recorder by connecting it
to a readout system. With solid-state recorders,
investigators can extract stored data in a matter of
minutes. Very often, recorders retrieved from
wreckage are dented or burned. In these cases, the
memory boards are removed, cleaned up and a new
memory interface cable is installed. Then the memory
board is connected to a working recorder. This
recorder has special software to facilitate the
retrieval of data without the possibility of
overwriting any of it.
A team of experts is usually brought in to
interpret the recordings stored on a CVR. This group
typically includes a representative from the
airline, a representative from the airplane
manufacturer, an NTSB transportation-safety
specialist and an NTSB air-safety investigator. This
group may also include a language specialist from
Federal Bureau of Investigation and, if needed,
an interpreter. This board attempts to interpret 30
minutes of words and sounds recorded by the CVR.
This can be a painstaking process and may take weeks
Both the FDR and CVR are invaluable tools for any
aircraft investigation. These are often the lone
survivors of airplane accidents, and as such provide
important clues to the cause that would be
impossible to obtain any other way. As technology
evolves, black boxes will continue to play a
tremendous role in accident investigations.