IEEE Spectrum September, 2010 - 10

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On 1 June 2009,
Air France Flight 447,
an Airbus A330-200,
crashed into the
Atlantic Ocean,
killing all 216
passengers and
12 crew members. No one
knows why the plane fell
out of the sky, because
no one has ever found
its black box.
beyond the
black box

instead of storing
flight data on board,
aircraft could easily
send the information
in real time to the
ground

viktor koen

by krishna m. kavi

spectrum.ieee.org
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NA * iEEE SpEctrum * AuguSt 2010

08.BlackBox.NA.indd 46

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7/16/10 9:17 AM

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AuguSt 2010 * iEEE SpEctrum * iNt

08.BlackBox.NA.indd 47

THINKING OUT
OF THE BOX

rishna M. Kavi
["Beyond the
Black Box," August]
has the right idea for
supplementing blackbox data so that all the
information isn't lost if
the black box is.
But Kavi writes
that "the boxes were
painted black in those
days to fend off the
stray rays of light that
might have ruined the
photographic film that
stored the data." David
Warren launched the
line of instruments we
have today by recording
cockpit voice and flight
data on wire, a medium
partially replaced a
decade later by magnetic
tape. Until tape's
digital bandwidth later
blossomed, five and then
eight channels of analog
data were incised by a
polygraph onto stainlesssteel foil. The recorder
developed by François
Hussenot and Paul
Beaudouin in 1939 was
based on photography.
This device needed its
film changed with every

NA * IEEE SPECTRUM * SEPTEMBER 2010

7/16/10 9:17 AM

flight and never made it
out of test aircraft into
commercial aviation.
Warren never
invented a black box.
He painted his 1956
prototype red before
getting the Australian
Department of Civil
Aviation to review it.
The department later
wrote that "Dr. Warren's
instrument has little
immediate direct
use in civil aviation."
Warren pushed on with
prototype refinements,
prompting his boss to tell
him, "If I find you talking
to anyone, including
me, about this matter, I
will have to sack you."
Jerry Nelson
IEEE Member
McLean, Va.

NO DAZE AT FCC

aving read "Radio
Daze" [Spectral
Lines, July], I must say
that the Federal Communications Commission
already recognizes and
embraces the way today's
tinkerers work and
has done so for many
years-in the amateur
radio service. The FCC

allocates frequencies in
the MF, HF, VHF, UHF,
and microwave spectrum
for amateur radio experimentation. Modifying
commercial radio
equipment and homebuilt antennas is legal in
the amateur service.
The FCC isn't trying
to rain on anybody's
parade, but protecting
radio users from harmful
interference is its responsibility. Limiting effective
radiated power from the
antenna system is one
way to meet that goal.
Donn Dengel
IEEE Senior Member
Palatine, Ill.

Senior Editor David
Schneider (call sign
N2LVD) replies: Indeed,
Part 97 rules give amateurs a lot more leeway
for experimenting. But
you'd need to control
both ends of the connection, and there would
be encryption and
content restrictions. In
any event, the point of
my essay was that the
FCC nicely recognizes
homebuilt devices under
Part 15-it's just that its
definition of homebuilt
seems a bit musty.

MONTE CARLO
NO SURE BET

wish author David
Patterson ["The

Trouble With Multicore,"
July] had explored
his algorithms for
computing the value of
pi in greater depth. The
Gregory-Leibniz series,
which he used as an
example of a sequential
algorithm, is fairly easy
to parallelize for n terms
over N processors. Even
more important, though,
parallelizing the Monte
Carlo algorithm holds its
own pitfalls. Many of the
most popular routines
for random-number
generation are not safe
to use in this context. In
some cases, multiple
threads executing in
parallel could repeatedly
receive identical "random"
numbers, which would
produce results no
better than those of a
single processor.
Dan Breslau
IEEE Member
Chicago

David Schneider responds:
Dan Breslau brings
up some important
practical issues. He
could also rightly point
out that the GregoryLeibniz series converges
too slowly to be useful.
We chose these examples
to illustrate as simply
as we could that the
same problem could be
solved in a sequential
or parallel fashion.

CORRECTIONS
In "Careers: Where the Jobs Are" [July], Gordon Day
should have been described as the past president of
IEEE-USA.
In The Data ["Who Has the Fastest Internet?"
August], we incorrectly reported South Korea's average Internet connection speed as 11.7 megabytes per
second. The correct speed is 11.7 megabits per second.
SPECTRUM.IEEE.ORG

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Table of Contents for the Digital Edition of IEEE Spectrum September, 2010