Like many inventions, versions of an airplane “black box” were independently invented
by several people, in this case beginning around the 1930s and 1940s. As for the version
that began being installed on commercial aircraft, it was invented in response to a tragic loss
of life. A De Havilland Comet 1, the world’s first commercial jet-powered airplane, disintegrated
over India in early 1953. Of the 43 passengers and crew members, none survived. Australian
chemist Dr. David Warren joined an expert panel looking into the cause of that crash
and two other crashes involving the Comet 1. Australia had a vested interest in the
success of the Comet because of its possible use by Australian airlines for a route between
Australia and the United Kingdom.
While Dr. Warren was an expert in fuel research, the plane crashes resonated with him for another
reason; his father died in 1934 when the plane he was on crashed into the ocean off Australia’s
southern coast; investigators never discovered the cause of that crash. Warren’s part in
the investigation of the Comet accident led him to believe that a simple voice recorder
located on the plane during the crash would have saved the investigators time and energy
trying to determine what went wrong. “If a businessman had been using one of these
in the plane… and we could find it in the wreckage and we played it back, we’d say,
‘We know what caused this.’”
Warren drew on his background in electronics, experience he gained from building “crystal
sets” or unpowered radio receivers in school, and he created a prototype of the ARL Flight
Memory Unit. This device recorded both conversations in the cockpit and a small number of instrument
readings for up to four hours of the flight. Once the four hour recording time had been
reached, the recording device recycled and recorded over the oldest information. While
the ARL Flight Memory Unit prototype, named in part for the Aeronautical Research Laboratories
where Warren worked, showed success during flights conducted by the Australian Department
of Civil Aviation, the Australian government and military failed to show further interest
in the device.
In 1958, a British official visiting Australia learned of Warren’s Flight Memory Unit and
invited him to England to continue work on the device with scientists and manufacturers.
It soon went into production in England and in the United States before being installed
in aircraft around the world. In an ironic twist, Australia became the first country
to require all turbine-powered airplanes weighing over 12,500 pounds to have these devices onboard.
So how did the ARL Flight Memory Unit become known as a black box? That’s a bit of a
mystery, especially considering that within the industry it is almost never called this
and the devices themselves are a color called international orange which allows them to
be more easily found at the site of a plane crash. That said, the first known instance
of these devices being called a “black box” was very early on at an Aeronautical Research
Council meeting in August of 1958. The man who called it that was one E. Newton. Why
he did so isn’t known.
As such, there are a number of theories about how the term “black box” came about. One
theory states that the name came from the fact that the boxes were often blackened and
charred from fires occurring after the crash. Given the first known instance of someone
calling it this was about the time Warren was invited to England to further his work
on the devices (before they were widely installed on planes, other than for testing purposes),
this seems unlikely. Another, much more plausible, theory is that it’s a holdover from WWII
where the Royal Air Force used to refer to various experimental devices put on planes,
such as the Oboe targeting system, as a “black-box.” Another very plausible explanation is that
it is originally from the engineering practice of calling a system that takes input, does
something to it, then gives some output, without specifically referencing the internal workings
of the device- how it actually accomplishes the thing it’s meant to do- a “black box.”
Either way, the nickname was (and still is) particularly popular with members of the media,
while aviation experts almost always refer to them as flight data recorders.
As for modern black boxes, they have undergone a number of improvements over the years, though
the basic thing they do is the same as the original. Specifically, they consist of two
separate devices: the Cockpit Voice Recorder (CVR) and the Flight Data Recorder (FDR).
The CVR records all of the noise inside the cockpit. That includes the conversation between
the crew members, radio transmissions, any alarms, the sounds of the controls being used,
and even noise from the engine and air moving around the plane. Today, CVRs record a total
of two hours of audio before the newest audio recording overwrites the oldest part of the
recording.
The FDR records a variety of flight data, though the exact requirements depend on things
like the age and size of the plane and what sort of equipment is on board. However, all
black boxes are required to record, at a minimum, the pressure altitude, indicated airspeed,
magnetic heading, normal acceleration, and microphone keying. The final item, microphone
keying, lets investigators match the data with the CVR recording. While the FDR records
on the same endless-loop principle as the CVR, it records a total of 25-hours before
overwriting the oldest information.
Black boxes need to survive the impact of the crash along with any fire that might occur
afterwards if they are to be of any use to investigators. While they occasionally change
in response to crashes, recorder crash-worthiness standards typically require boxes be able
to survive such circumstances as a 1,100° Celsius fire for an hour, 33 km/s² of acceleration
for 6.5 milliseconds (about what would be produced in a crash at 310 mph), and being
immersed in saltwater at specific depths, among other such specifications. The placement
of the black box in the tail of the plane also raises the likelihood of survival as
the tail section doesn’t usually bear the brunt of the crash impact. Additionally, a
locator beacon is included which can also help investigators find the black box if the
aircraft crashes in the water as it emits a “pinger” signal for at least thirty
days (and it will soon likely be raised to a ninety day requirement).
Thanks to the Malaysian Airline Flight 370 crash, a marked upgrade in how flight data
recorders work has also been proposed, utilizing more modern technology since the last major
overhaul of the “black box.” The most significant change, and perhaps the most helpful,
suggested is to decentralize the box. Instead of just having an on-board recording, add
in a system for broadcasting in real time the data it’s storing to some central database
on the ground. This way, even if the on board recorder can’t be located (such as when
the plane itself can’t be found), the ground crew still has the data they need to analyze
what caused the crash, and with last broadcast coordinates, even more accurately
where to
start looking for
the plane and potential survivors.