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| mentalfloss.com |
Black box is a generic term used to describe
the computerized flight data recorders carried by modern commercial aircraft.
The Flight Data Recorder (FDR) is a miniaturized computer system which tracks a
variety of data regarding the flight of the plane, such as airspeed, position,
and altitude. This device is typically used in conjunction with a second black
box known as the Cockpit Voice Recorder (CVR), which documents radio
transmissions and sounds in the cockpit, such as the pilots' voices and engine
noises. In the event of a mishap, the information stored in these black boxes
can be used to help determine the cause of the accident.
Black boxes have been used since the earliest
days of aviation. The Wright brothers carried the first flight recorder aloft
on one of their initial flights. This crude device registered limited flight
data such as duration, speed, and number of engine revolutions. Another early
aviation pioneer, Charles Lindbergh, used a somewhat more sophisticated version
consisting of a barograph, which marked ink on paper wrapped around a rotating
drum. The entire device was contained in a small wooden box the size of an
index card holder. Unfortunately, these early prototypes were not sturdily
constructed and could not survive a crash.
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| autospeed.com |
In the 1940s, as commercial aviation grew by
leaps and bounds, a series of crashes spurred the Civil Aeronautics Board to
take the importance of flight data more seriously. They worked with a number of
companies to develop a more reliable way of collecting data. Rising to the
challenge, General Electric developed a system called the "selsyns,"
which consisted of a series of tiny electrodes attached directly to the plane's
instruments. These sensors wired information to a recorder in the back of the
plane. (Recorders are typically stored in the plane's tail section because it
is the most crash-survivable area of the plane.) GE engineers overcame a number
of technical challenges in the design of the selsyns. For example, they
cleverly recognized that the high altitude conditions of low pressure and
temperature would cause the ink typically used in recording devices to freeze
or clog the pens. Their solution was a recording system that relied on a stylus
to cut an image into black paper coated with white lacquer. However, despite
their efforts, the unit was never used in an actual flight. Around the same
time, another engineering company, Frederick Flader, developed an early
magnetic tape recorder; however, this device was also never used.
Black box technology did not advance further
until 1951, when professor James J. Ryan joined the mechanical division of
General Mills. Ryan was an expert in instrumentation, vibration analysis, and
machine design. Attacking the problem of FDRs, Ryan came up with his own VGA
Flight Recorder. The "V" stands for Velocity (airspeed);
"G" for G forces (vertical acceleration); and "A" is for
altitude. The Ryan Recorder was a 10 lb (4.5-kg) device about the size of a
bread box with two separate compartments. One section contained the measuring
devices (the altimeter, the accelerometer, and the airspeed indicator) and the
other contained the recording device, which connected to the three instruments.
Ryan's basic compartmentalized design is still
used in flight recorders today, although it has undergone numerous
improvements. The stylus and lacquer film recording device was replaced by
one-quarter-inch (6.4mm) magnetic tape, which was in tum replaced by digital
memory chips. The number of variables that recorders can track has also
dramatically increased, from three or four parameters to about 300. FDRs can
now track such in-flight characteristics as speed, altitude, flap position,
auto-pilot mode, even the status of onboard smoke alarms. In the early 1960s,
the airline industry added voice recording capability with the Cockpit Voice
Recorder (CVR). But perhaps the most significant advance in flight recorder
manufacture has been the improvements made in its construction, allowing the
units to better withstand the destructive force of a crash. Early models had to
withstand only about 100 Gs (100 times the force of gravity), which is loosely
equivalent to the force of being dropped from about 10 ft (3 m) off the ground
onto a concrete surface. To better simulate actual crash conditions, in 1965
the requirements were increased to 1,000 Gs for five milliseconds and later to
3,400 Gs for 6.5 milliseconds.
Today, large commercial aircraft and some
smaller commercial, corporate, and private aircraft are required by the FAA to
be equipped with a Cockpit Voice Recorder and a Flight Data Recorder. In the
event of a crash, the black boxes can be recovered and sent, still sealed, to
the National Transportation Safety Board (NSTB) for analysis.
Periodicals
AlliedSignal Aerospace Catalog. AlliedSignal, Inc.
Baldwin, Tom. "Black boxes Built to
Survive Doom." Journal of Commerce and Commercial, July 29, 1996,
p. lB.
Goyer, Robert. "The Secrets of Black
Boxes." Flying, December 1996, p. 88.
Sendzimir, Vanda. "Black Box." American
Heritage of Invention & Technology, Fall 1996.
— Randy Schueller
Source: Black Box
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