
The Search for MH 370 (Inmarsat) - wglb
http://journals.cambridge.org/download.php?file=%2FNAV%2FS037346331400068Xa.pdf&code=99d6daf127f9c88ca22b52fd9ff5084a
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phkamp
I've looked over the calculations and I think they are making a very shaky
assumption.

The BFO-bias is calibrated why the plane is on the ground, and they assume it
is constant over time, temperature, air-pressure etc.

This is probably not a valid assumption under any circumstances, given that
there is no atomic frequency standard involved and probably not even an OCXO.

Given that MH370's inmarsat-terminal was powered off for something like an
hour during which environmentals may have been extreme and even outside specs,
the assumption of a constant bias certainly have no legs to stand on in this
particular case.

If the terminal used something like a 1PPM milspec 100MHz TCXO, I would guess
is that the BFO bias could be anywhere between 0 and 300Hz after the 18:25Z
logon.

I have not tried to replicate their trajectory estimation using this
uncertainty, but by eye-balling it, it vastly increases the uncertainty of the
resulting location.

The validations they have done using other aircrafts involves BFO's running in
nominal mode throughout, and therefore provides no information about how the
BFO bias might change after power on/off or extreme environmentals.

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wglb
Do you have any sense of an alternative to their very shaky assumption, or are
they essentially boxed in by the available numbers?

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sillysaurus3
How long can an airplane's black box last before degrading due to natural
causes? Forever?

More precisely: Assuming the black box survived the crash intact, and assuming
that it will be located between 1 and 1,000 years from now, is it guaranteed
we'll be able to pull useful data off of it? I wonder what the engineering
process is like for one of those things...

EDIT: Apparently, the key component of a flight data recorder is its Crash
Survivable Memory Unit (CSMU). This manufacturer claims a lifetime of 30
years:
[http://www2.l-3com.com/edi/crashsurvivable.htm](http://www2.l-3com.com/edi/crashsurvivable.htm)

More info:
[https://www.aea.net/AvionicsNews/ANArchives/TechSpeakMar10.p...](https://www.aea.net/AvionicsNews/ANArchives/TechSpeakMar10.pdf)

The CSMU is rated for 30 days of saltwater submersion. Obviously, the only
scenario it'll be submerged in saltwater outside of the lab is if the
recorder's housing cracks. So, assuming the recorder survived the crash, I
wonder which would degrade first: The housing or the memory unit? If the
housing fails, then the memory unit is toast, since it's only rated for 30
days of saltwater. The manufacturer guarantees the CSMU will last 30 years,
but it seems like as long as it stays dry then it might last for much longer.
I wonder how long it's theoretically possible to extract useful data off of it
assuming it stays dry.

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baudehlo
Which is really only relevant if it's ever found. The ocean is HUGE.

~~~
melling
Well, if we assume that we're looking for an aircraft with a few large pieces,
and it's only a matter of time before cheap autonomous submersible vehicles
become common, then it probably will be found some day. Might take a decade or
two, but at some point we'll extensively map the rest of the oceans.

~~~
baudehlo
I guess the question becomes who is going to pay for these robots? They'll
need the ability to dive deep, explore, and then come up for "air" (a
recharge). Those aren't going to come cheap. Perhaps the undersea cable
conglomerates but it's hard to imagine the use-case for mapping inaccessible
areas.

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MichaelGG
Extend past a few decades. A post-scarcity society would almost certainly
search every square metre of the ocean for this airplane, assuming humans are
still making decisions.

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stouset
You say "post-scarcity" like it's an inevitable scenario. Resources are
finite. Energy is finite. Exponential growth doesn't last forever.

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toomuchtodo
> Energy is finite.

With enough renewable energy from the sun, there is very little we're
constrained by

[http://www.sandia.gov/~jytsao/Solar%20FAQs.pdf](http://www.sandia.gov/~jytsao/Solar%20FAQs.pdf)

"All together, the technical potentials can be estimated to be: Solar
electricity: 89,000 TWc · (1-0.708) · (1-0.0345) · (0.3) = 7,500 TWc Solar
fuels: 89,000 TWc · (1-0.708) · (1-0.0345) · (0.1) = 2,500 TWc Solar thermal:
89,000 TWc · (1-0.708) · (1-0.0345) · (0.225) = 5,600 TWc

These are huge potentials, dwarfing by many orders of magnitude those of the
other."

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parados
Hopefully this is not too much off-topic but one of my best school friends was
murdered on flight UTA772 in 1989 (he wasn't the target of the bomb, just one
of the consequences). Seven years later his mother forwarded me his camera
that had been discovered in the wreckage. It was pretty beaten up but it
seemed to me that there was still a film in it. I managed to ease the film out
undamaged but by now it was way past its process by date and had been lying in
the desert for a while so I wasn't at all optimistic about the latent image.
With technical help from Kodak and a very good lab we eventually managed to
get some usable images off the film. To my amazement there was, when greatly
enlarged, one picture of him. Grainy and colour distorted but definitely him.
This picture was some source of comfort to his family as his body was never
discovered which, as is always the way with these things, adds immensely to
the distress.

So on MH370 there might be other useful sources of data in the wreckage apart
from the FDR.

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brc
Often the wreckage itself tells a big story, assuming most of it can be found
in a debris field. It can certainly say whether it broke up in the air or hit
the water intact, for a start. Then you can look for bomb explosions or other
types of explosions. Even the location of the wreckage would fill in large
parts of the story which is currently unknown.

The interesting thing to me is how much money,collectively, are we (and the
term is loose because I don't know who is paying) prepared to spend to find
this wreck?

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ximeng
Malaysia and Australia sharing about 50 million dollars.

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curtis
In comparison, Wikipedia shows the unit cost for a 777-200ER as $261.5
million.

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chris_va
Random question: Why do black box pings stop after 30 days of 1 ping/second,
instead of an exponential tail off for the next few decades?

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damian2000
Battery life ... I think the 30 days figure is the minimum spec, but in
reality it can go on longer, depending on age of battery, i.e. when it was
last replaced.

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cnvogel
This video has a teardown of an old flight data recorder (tape based), with a
ultrasound pinger/locator beacon(at about 3 minutes into the video).

[http://youtu.be/mQehX0rVYuY?t=3m48s](http://youtu.be/mQehX0rVYuY?t=3m48s)

Here's some technical information about this particular beacon.

[http://www.sea-
avionics.com/lc/cart.php?target=productDetail...](http://www.sea-
avionics.com/lc/cart.php?target=productDetails&model=DK-100&substring=DK-100)

It says that the shelf-life of the battery is only 6 years (which probably
means that it will lose some significant part of its total capacity over 6
years). Having a device operate for "decades" surely will need different power
sources. (even if cutting down on average power consumption drasticly, by only
emitting one ping per week or so...)

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leoc
Sure, but exponential slowdown over maybe six months seems achievable, and
would likely have been very useful in the case of MH370.

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mikeash
I think it just comes down to this being an extremely conservative field, and
these systems get implemented based on past experience.

Before MH370, basically nobody anticipated having to search for a commercial
airliner with no idea where it went besides that it was vaguely somewhere
within a continent-sized patch of ocean. The 30-day period was considered to
be enough. Even with MH370 it could have been enough if the Malaysian
authorities hadn't been so unbelievably incompetent as to waste an entire week
searching the wrong ocean when they had data which definitively showed it went
elsewhere.

It's similar to the question of why airliners don't periodically report their
position using GPS and satellite data, since they basically have the
capability already. The answer is that nobody really thought it was necessary,
since tracking airplanes through other means worked fine right up until it
didn't.

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kyrra
Link does not work on mobile (at least for my iPhone).

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bobbles
Here's a TL:DR for you: "The analysis presented in this paper indicates that
MH370 changed course shortly after it passed the Northern tip of Sumatra and
travelled in a southerly direction until it ran out of fuel in the southern
Indian Ocean west of Australia. A potential flight path has been reconstructed
that is consistent with the satellite data, indicating a last contact location
of 34·7°S and 93·0°E, but it is stressed that the sensitivity of the
reconstructed flight path to frequency errors is such that there remains
significant uncertainty in the final location."

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mfsampson
Ah, nice. A factual document about this. Can't believe they have already
brought out books about this when the aircraft is still missing.

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nikatwork
Assuming the conclusion is correct, what would be the most likely explanation?
Pilot murder/suicide?

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m-app
Might be a lack of oxygen, similar to Helios Airways 522?

[http://en.wikipedia.org/wiki/Helios_Airways_Flight_522](http://en.wikipedia.org/wiki/Helios_Airways_Flight_522)

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leoedin
That doesn't really explain the dramatic change in course. To essentially do a
180 degree turn and fly the opposite direction there must have been some sort
of pilot input into the navigational system.

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mnw21cam
It's amazing how stupid people can be when oxygen deprived. My dad had
decompression chamber training with the Aussie air force. They gave everyone a
clipboard questionnaire with some simple puzzles. In oxygen-deprived state
most people were writing off the edge of the clipboard and on their legs.

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TillE
True, but it doesn't really fit with disabling the transponders and changing
course moments after communicating normally with ATC.

Any theory other than deliberate action seems to rely on several major
coincidences. Not strictly impossible, but definitely not the most plausible
option.

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goshx
TLDR: we still don't know where it is.

