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[Applause]
when TWA flight 800 exploded in midair
just off Long Island on July 17th 1996
it caused the death of all 230 people on
board it was the subject of the longest
crash investigation in civil aviation
history
eventually thanks to essential
information recovered from the
aircraft's flight data recorder the
cause of the crash was revealed so how
do they retrieve and analyze the data on
an aircraft's black box
gem cache of the National Transportation
Safety Board in Washington DC has a
tough job when there's an airplane
accident it's down to him to make sense
of the data recorded by two vital pieces
of equipment the flight data recorder
known as the black box and the cockpit
voice recorder if you have no idea what
happened on an aircraft accident it's
very difficult to prevent another one
from happening that was just like it so
we can identify the problem and fix the
problem
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modern flight data recorders cost
upwards of $15,000 each by law they must
record 88 separate elements of the
flight including time airspeed heading
and altitude
most modern boxes however are capable of
recording over 1,000 individual data
streams meanwhile the cockpit voice
recorder uses a continuous loop of
magnetic tape that completes a cycle
every 30 minutes so it has the last half
hour of sound from the cockpit both
these boxes are typically painted orange
and are equipped with an underwater
locator beacon this beacon is activated
when a sensor comes into contact with
water and will send out a signal every
second for 30 days but to be of any use
to air accident investigators this
intricate technology needs to survive
some of the worst accidents known to man
the box is designed to withstand an
impact three and a half thousand times
its own weight
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the exterior is made from quarter-inch
thick stainless steel while inside and
aluminum housing is surrounded by
fireproof insulation an inch thick
finally bicarbonate of soda is shaken
into the container to absorb heat but
short of crashing a plane there's only
one way to ensure these defenses are
tough enough meet Gary Kirsten he's made
a life's work of trying to destroy black
boxes and thankfully it doesn't seem to
be doing very well
the first test uses a heavy weight
dropped onto the boxes most vulnerable
axes this test is a pretty severe test
wherein we take a 500 pound weight with
a hardened steel pin on it rockwell 42
very hard steel we're gonna drop it from
ten feet here we go
shut the door I'm arming the dropping
mechanism
we're armed okay everybody here we go
fire in the hole yep we have any impact
let's see what we got
here's the hardened steel pin a very
bent pin but barely a mark on the black
box having survived a crash impact the
next major challenge for a black box is
surviving high temperature fuel fires
we're gonna perform a one hour
high-temperature fire test this is the
same unit that went through the
penetrating resistance test
you guys ready back there the box is
subjected to a minimum of one hour at
2,000 degrees Fahrenheit
yeah the crucial data chips in the black
box have survived becoming toast this is
what the circuit card looks like after a
fire test you see the Flex print is all
burnt and charred and melted off but the
card itself that has the important data
on the memory chips is in perfect
condition
back at the National Transportation
Safety Board Jim can retrieve the data
from the box by plugging it into his
computer
for more severely damaged boxes the
memory chips inside can be removed using
a heat gun and read from directly
meanwhile damaged voice recorders often
have to be cut open to retrieve the
valuable magnetic tape inside thanks to
Jim's analysis of this simple piece of
tape investigators were eventually able
to discover the cause of the TWA flight
800 accident
initially investigators suspected a bomb
had caused the crash however after an
extensive investigation another
explanation emerged the airplane was was
perfectly normal the flight recorder
looked great the voice recorder was fine
and then all of a sudden it just ended
so we spent a lot of time figuring out
the last quarter of a second of the
voice recorder and the last few frames
of flight data recorded what was going
on with that aircraft two brief sections
of interference on the voice recorder a
fraction of a second before the
explosion led investigators to realize
the accident had been caused by an
electrical short circuit which had
ignited fuel in the center tank the
voice recorder was was very telling we
actually had a lot of information to
prove that it was not a terrorist
explosion it was actually a fuel fuel
air explosion as a result of this
crucial piece of evidence the Federal
Aviation Authority recommended changes
to the design of the center fuel tank
and the installation of electrical
components and thanks to the existence
of the flight data recorders and flying
is now safer than ever before