

Ask HN: Why do airlines still use "black boxes" ? - asciilifeform

Why not substitute a real-time satellite uplink? This would eliminate the need for expensive and often unsuccessful oceanic search expeditions of the kind we are now hearing about.
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aristus
There is constant data sent out by most aircraft already. The black box is for
when shit goes very wrong, like when a plane is on fire, out of power, with a
big hole in it, falling like a rock and spinning like a top.

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Sephr
I still don't see why only a black box should be used for that. As long as a
satellite uplink is powered by a separate external power source, none of these
factors will stop a transmission.

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dmv
or you are flying through an electrical storm...

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timr
Yep. Commercial airliners already have a number of redundant power sources,
located in different parts of the plane, wired in different pathways for
maximum operational redundancy. There were even studies to done to find the
parts of a jet that are least affected by eddy currents due to electrical
storms....yet the black box can operate even when those different redundant
systems fail.

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anigbrowl
From : [http://www.eng-
tips.com/viewthread.cfm?qid=246491&page=1](http://www.eng-
tips.com/viewthread.cfm?qid=246491&page=1) _Again, any single box is not the
problem. It's the receiving end. Picture the FAA receiving 8000 planes worth
of a minimum of 88 data streams at 50 Hz at 12 bytes each. That would be a
minimum of about 4 Gbps data stream, and allowing for collisions and whatnot,
you're around 20 Gbps datastream capacity.

Guess where the hackers are going to concentrate their efforts. And given the
large number of access points required to make that all happen, guess how
often the database will be compromised._

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dcurtis
You only have to transmit data when something is wrong. You can use software
to determine when to start sending updates.

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anigbrowl
Remind me not to hire you for anything mission-critical.

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garnaat
The new planes like this Airbus do actually transmit real-time maintenance
data. So, there were something like 10 transmissions from the plane that
apparently include large amounts of data regarding the systems that were
failing and when.

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noss
The cost in retrieving the black box is the least of worries, don't you think?

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wglb
Consider the fact that aircraft/control tower conversations are done over AM
radio, a very ancient technology as these things go. Why so old, you might
ask, in the vein of your question. First, there is an infrastructure cost--
towers everywhere, airplanes everywhere have AM transmitters and receivers
already.

Probably the only viable alternative that is still reliable would be single
sideband (SSB), but that would be a infrastructure change as well.

If you consider what is required to do a digital encoding including
handshaking, synchronization and the like, you are less likely to have a less
reliable system. If in the midst of an AM transmission you get a static crash,
it likely deletes one word. In a digital system, you might well have to
resync, like a modem.

So some of these systems need to be very reliable under all sorts of harsh
conditions. The questions I would ask, is 1) do the satellites already exist
2) how many of them and 3) are they visible everywhere there are airflights?
and finally 4) how expensive is this network to maintain?

My guess is that the cost of such a network is a lot greater than a few black-
box searches. Additionally, for really difficult crashes, they retrieve every
possible piece of the airplane, at an expense that makes finding the black box
seem small: <http://en.wikipedia.org/wiki/TWA_Flight_800>

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brandon272
I was wondering the same thing myself today. My first argument would be that
if data is getting into a black box, there's no reason it couldn't also get
into a satellite transmitter and out into space in the same amount of time and
with the same reliability. As for available bandwidth, how unrealistic is that
bandwidth availability? How much data is being fed into a black box during a
flight?

The idea of a distributed network among commercial aircraft and ground
stations as a method of transmitting the data also seems like an exciting
prospect, and perhaps less expensive than relying on satellite communications,
though I know nothing of the range or viability of such a platform.

In any case, a system to complement a black box would require large
expenditures by governments and airlines. But, how valuable is that data?
Pretty valuable, I think.

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sokoloff
Sure it could get "out into space", but in order to be useful, it has to get
"out into space AND pointed at a satellite" which is a substantially harder
problem especially in any upset or unusual attitude.

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raquo
Why don't they make black boxes floatable?

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aconbere
I suspect that a floating object increase the range over which you have to
search. If you object sinks to the bottom, at least you know about where it
ended up.

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jules
Let it send a signal.

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stan_rogers
Aircraft have floating, jettisonable radio beacons (Emergency Locator
Transmitters) that transmit on the international guard frequency 121.5MHz
(with intentional harmonic distortion that allow reception on the military
guard frequency of 243MHz). That frequency is monitored by SARSAT (Search and
Rescue Satellite) in North America -- the middle of the South Atlantic may not
be monitored, since the automated search notifications would not necessarily
reach anyone able to do much about it. Local air control stations will attempt
to determine the position, but ultimately it's usually someone with a portable
directional receiver that pinpoints the actual source of the signal.
(Occasionally a unit will begin transmission due to mishandling or
malfunction, and I spent far too much of my time in the air force trying to
sort through ejection seat packs and spare ELTs to find an overambitious
backup gone wrong.) ELTs are also normally located on any floatation rafts the
aircraft may be carrying.

The aircraft itself will also carry an underwater acoustic beacon (pinging at
about 40KHz) or two so that underwater wreckage can be located once the
general area has been established by the ELT that should have been jettisoned
on impact. Both items (the ELT and the UAB) have limited battery life -- they
pump out huge signals relative to their size. By convention, the UAB is
located in the same general area as the FDR and CVR longitudinally.

In the case of the Air France flight incident, it would seem that the ELT did
not work or was at a significant distance from the crash site by the time the
search reached the position. That the black boxes (the FDR and CVR) are
expected to be recoverable at this point seems to indicate that the UAB did
work (it would have been detected by a sonobuoy dropped by the search
airplane, which looked to me like it was equipped with anti-submarine warfare
equipment, judging by the MAD boom on the tail).

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run4yourlives
Yeah, the video seems to suggest one of the first rescue aircraft on the scene
was a p-3 Orion variant, of which Brazil flies 8.

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mreevery
Redundancy is cheap.

Keep the present system and add a second automatically jettisoned flash memory
copy of all data that is designed to float if at sea. It would also transmit a
signal that would include its GPS location if possible.

Jettisoning could be set to occur at a given altitude, a given set of data
values or a given acceleration/deceleration values.

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oomkiller
Well one reason is that black boxes are probably more reliable than a
satellite link, and can operate when the plane splits in half. Also, the
previously mentioned issue with the large amount of data that would be
generated by all of the airplanes.

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grinich
How is the data stored in the black box? Solid state?

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JimmyL
New ones are solid state, older ones are continuously-looping magnetic tape.

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simplegeek
Good question. Likewise, I've always wondered why don't they have parachutes
in aeroplanes :(

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noonespecial
The percentage of actual crashes in which a parachute would do anyone any good
is likely vanishingly small.

You can't use them when too high up (not enough O2) or too low (not enough
time to deploy). Most crashes take place on takeoff or landing.

Of the problems that do happen that would take you through a "jumpable"
altitude, you can only make the jump if you 1) have time, 2) have enough
airplane left to jump out of. If a big whole ripped in the plane while in
flight at 30k feet, you are very likely already unconscious or dead.

There are other issues related to the fact that commercial airliners are not
made to be jumped out of at speed. Its difficult or impossible to open their
doors during flight (with good reason). Even if you could get them open, there
may not be a jump trajectory from some doors that doesn't provide a personal
introduction to wing or engine part. Also, you cannot jump and live from a
plane going 300 knots. The plane would have to decelerate to near stall to
make it safe and if its already crashing, maneuvering at the edge of
performance is not likely.

Also, consider that professional and military jumpers are highly trained, in
top physical shape, and the landing sites are carefully chosen to avoid
injury. As a fun thought experiment, take Rosanne Bar, put her in a small
canopy "emergency chute", and drop her, at random, over the Arizona desert.
(She was on her way to Vegas, baby). Calculate survivability.

Chutes for everyone would be expensive, heavy and probably only be beneficial
in single digit percentages (or even sub single) of all crashes. They would
very likely cause more problems than they would solve.

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jdbeast00
i'm sorry but i just don't buy the 'chutes aren't worth it / wouldn't work'
argument. i'm confident that in the next few decades we'll have better safety
systems in planes, it will just take a few really smart engineers. people will
still die in planes, sure, but in the cases where chutes or whatever will
help, there will be huge benefits.

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noonespecial
Strangely chutes on planes might _be_ worth it, but maybe not like you think.

<http://en.wikipedia.org/wiki/Ballistic_Recovery_Systems>

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tdupree
This is an intriguing idea, has anybody heard of any research done for this
regarding passenger airplanes?

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Zak
Based on the article, I'm guessing large passenger jets are some time off. BRS
is currently working on systems for very small business jets.

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michaelawill
Why don't they make the whole plane out of the black box?

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asciilifeform
Aside from the usual reasons given (a plane consisting mostly of steel armor
could not get off the ground, etc.) it would make no difference to the
passengers. Falling to the ground from altitude will kill you even if you are
sitting inside an indestructible box, simply through rapid decceleration.

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drhowarddrfine
Cause black goes with everything.

