With data from flight and cockpit recorders sometimes lost or irretrievable
following a crash, should airlines begin transmitting such data in real time to
ground stations?
After I watched a rough cut of "Crash of Flight 111" here at the NOVA offices,
a colleague who watched it with me asked, "Why don't they just beam black-box
data in real time to ground stations via satellite?" She was responding to
another colleague's remark about how unfortunate it was that, as mentioned in
the program, the flight data and cockpit voice recorders on Swissair Flight 111
had ceased recording roughly six minutes before the accident.
The New York-to-Geneva flight had mysteriously plunged into the ocean off Nova
Scotia on the night of September 2, 1998, killing all 229 people aboard. The
black boxes could have provided valuable clues as to the cause of the crash.
But without their data on the final minutes of the flight, the Transportation
Safety Board of Canada undertook what became a four-and-a-half-year, $39-million
investigation to try to determine the cause by other means.
Neither I nor anyone else in the room that day had an answer to my colleague's
question. So I decided to look into it. After talking to experts at the Federal
Aviation Administration (FAA) and National Transportation Safety Board (NTSB)
as well as in the academic and private sectors, I got my answer: They're
working on it, with intriguing possibilities not just for black-box data
transmission but also for better troubleshooting during emergencies, improved
airline efficiency and maintenance, even telemedicine. But it's easier said
than done.
Why do it?
The advantages to having continuous, real-time transmission of flight
and cockpit information are many. First, in the case of a crash, black-box
data would be available to investigators immediately. They wouldn't have to
wait for the recorders to be dug out of the ground or fished from the seafloor.
This has important implications in our age of terrorism. Authorities need to
know quickly whether a crash was terrorist-related; suspect trails grow faint
with each passing hour, much less the days or weeks it can take to recover
black boxes and analyze their recordings.
And when black-box recordings are lost, as was the case with the two planes
that struck the World Trade Center, downloaded data may be the only
data. (I should note here that if Swissair Flight 111 had had a real-time data
link, it would have quit operating at the same moment as its flight and cockpit
recorders. Like black boxes, data-link systems would rely on a plane's
electrical power, which the Flight 111 pilots shut off during their attempt to
isolate and fight the fire that eventually brought the plane down.)
A robust data link would also mean a lot more information than just black-box
data could flow, and it could flow both ways. As it is now, aircraft,
particularly when flying over oceans, are often incommunicado for long periods.
"Next to a remote desert island, it's about the only place you can hide and be
out of touch," one aviation expert told me. With a broadband communications
link, people in the air and on the ground could be in constant, detailed
contact.
This would have clear benefits, most significantly the ability to cope with emergencies.
If air-traffic controllers clearing
aircraft for takeoff could glean pilot intent from incoming data, for example,
they could reduce runway incursions, a leading cause of aircraft mishaps. "If
you're polling this data every second, and you see that a pilot who hasn't been
cleared is powering up and taking his foot off the brake, you know he's going
to move," says Jay Brown, a computer scientist at the FAA Tech Center in
Atlantic City, New Jersey. "With airplanes, it takes two or three seconds to
get them to move, so you could potentially stop a runway incursion."
During a technical
emergency, pilots could get critical advice from engineers and other experts on
the ground, who would have real-time knowledge of
that plane's engine conditions, flight-control positions, and other essential
data at their fingertips. During a hijacking, air controllers, government authorities, and other
key personnel could make more effective decisions, even warn possible targets.
Had controllers been able to detect instantly the flight-path changes and other
burgeoning anomalies on the 9/11 planes, perhaps something could have been
done, at the least, to lessen the loss of life on that tragic day. Flight
attendants could even better tend to mid-flight medical crises. Sensors attached to a
patient, for instance, could give ground-based doctors vital signs and other measurements upon
which to base potentially life-saving decisions.
Whether intentionally triggered or not, emergencies on aircraft are thankfully
rare, and it is during routine operations that such a high-bandwidth link would
be most continuously useful. If, for example, computers monitoring a data link
could alert mechanics that a certain part of a flying aircraft was in imminent
need of replacement, an airline could have that part waiting at the plane's
destination. If airline staff had a real-time sense of exactly where their
aircraft were at all times, they could better schedule personnel to greet
planes, collect baggage, and the like. If the FAA saw that an airline was
constantly monitoring an aircraft's engines—a clear safety
advantage—it might extend a required overhaul from every 15,000 hours to
every 20,000 hours, a significant cost saving to the airline.
Making it work
Several ways to develop such a system are under consideration. The FAA Tech
Center, which researches, develops, and tests new aviation equipment for the
FAA, has been working with the San Diego-based Titan Corporation on a prototype
system architecture. It relies on existing communications links such as air
phones (when an aircraft is within line of sight) and satellites (when it's
not) to transmit black-box or other aircraft or cabin data to ground stations.
Titan's Richard Goelz says the project grew in part out of the 1996 crash of
TWA Flight 800, whose black boxes took over a week to recover, at enormous
cost. "The project started with the idea that there needs to be a better way of
making data like that available without an extended search," he says.
Another company, AeroSat Corporation of Temple, New Hampshire, has a Department
of Transportation grant to demonstrate a different way of doing the same thing.
Instead of air phones or satellites, AeroSat proposes using aircraft themselves
as transmitter/receivers. When a plane is beyond line-of-sight, it would send
its data to another flying aircraft in the fleet. That second aircraft would pass the data
to a third plane, and so on down the line until
one of that airline's planes is within line of sight of a ground station and
can dump the data down. "It's like rain coming off a roof," says AeroSat's Bill
McNary: the data passes along horizontally in a high-altitude network of
daisy-chained aircraft until it can find a way down.
Regardless of approach, experts agree that the technology exists and that the
amount of data to stream is quite manageable.
So what's the delay? Cost, for starters. "Purely from an accident investigation standpoint,
airplanes almost never, ever crash," says Jim Cash, the NTSB's senior technical
advisor for black boxes. "So to be continuously sending data off an airplane
that could go its entire 40 or 50 years of flight service and never have an
incident or accident—nobody's got that kind of money, especially the
airline industry. It's still much cheaper to put a box on an airplane and just
have it run its merry life recording data that nobody will ever look at."
Costs include designing, building, operating, and maintaining the system, which
may require a series of new ground stations and/or expensive satellite time.
There are also privacy and competition issues to consider. How, for instance,
do you ensure, even with encryption, that only Singapore Airlines receives
Singapore Airlines data? And there's no guarantee that a plane under stress
won't lose its data link just when it's needed most, as would have been the
case in those final six minutes of Swissair Flight 111. For this and other
reasons, most experts agree that such systems would supplement rather than
replace black boxes.
Despite the hurdles to wireless transmission, it may not be too far off.
Aviation specialist Paul Czysz, a professor emeritus at St. Louis University,
believes that all it would take to spur an official drive for a telemetry
system would be the crash of a major jetliner over mid-ocean in which the black
boxes were unrecoverable—"a Titanic event," as he calls it. "You're going
to have to have something like this," Czysz says of a real-time data link,
"just to make sure you know what happened."
And if there's one thing that everyone—from crash investigators to
victims' families to just about anyone who ever flies—wants to know in
the wake of disastrous crashes like Swissair Flight 111, it is what happened.
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Black boxes, which are actually painted orange to make them easier to find after a crash, are built tough: inside each is a crash-survivable memory unit that can withstand exceptional heat, pressure, and violence. Yet because black boxes are occasionally lost or otherwise unable to aid an accident investigation, supplementary wireless versions that continually send their data to ground computers are in the offing.
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With no black-box data recorded during the
final five minutes and 37 seconds of the Swissair flight,
investigators had to seek clues to the disaster's cause elsewhere. Their
multiyear, multimillion-dollar investigation took place in this hangar in Nova
Scotia.
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Air-traffic controllers might be
better able to prevent runway incursions if they had access to up-to-the-second
information coming from aircraft under their guidance.
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Like many crashes in the sea, the loss of TWA Flight
800 required an extensive, costly search for its black boxes (above, the USS
Grasp at the crash site). With a real-time transmission system, flight
and cockpit data would be available instantly.
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