The lost Air France jet

StephenGiles

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Having made 6 flights to Agentina from England and others to Peru and Ecuador, the thought often occurred to me, when standing in the galley eating fun sized mars bars at various times through the night, not being able to sleep,  - do the flight controllers know where we are? We have been reminded that there is no radar over a big chunk of the Atlantic in the last few days!
 

MartyMart

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That's a very sad loss .... and yes it makes you think about that "out of range" area.

I fly almost every week in and out of Europe so I "try" very hard not to think too much about it
..... after 20 years and many thousands of flights I am beginning to NOT enjoy them !!

Hope it doesn't become a big problem for me in the near future.

MM
 

JohnRoberts

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The good news is we generally learn from such catastrophic failures to better avoid them in the future, the bad news is a 3 mile long debris field in deep water will not make it easy to find the black box.

RIP

JR
 

Svart

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They've been mulling over putting bidirectional GPS equipment in planes for years.  This would allow you to track the plane via GPS.  For some reason the cost of this is too much for airlines to consider doing it yet cellphone companies can put these devices in every new phone.

WTF

Yet again the airline industry fails us and it's sad that it's always a terrible loss that will give them a kick in the pants to get this moving along.

 

deuce42

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Whilst it's no consolation to the passengers or their now grief stricken loved ones, the amount of plane related deaths is actually very low compared to any other form of transport.  It's the enormity of the loss when it happens that makes plane crashes seem so scary for us, i.e hundreds of people going down in a huge piece of metal. If a car crashes and 2 people die (which happens daily in every country on the globe) we seem to accept it as fact of life, yet if we add up the number of car related deaths it would far exceed any air disaster.

Marty, I don't fly as frequently as you do, but maybe you might feel a little better if you consider that before a plane takes off, at least theoretically, there are people performing safety checks  etc. If you had driven or taken a long term bus or train on as many trips over 20 years would you be any better off? 

I wish you and everybody else on this board a safe passage for the rest of your trips:)
 

PRR

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> yet cellphone companies can put these devices in every new phone.

Many of these cellfone finders are not "global".

They do not reference satellites, Polaris, sun, moon, etc.

They work only where cellfone coverage exists.

In most of the cellfone area, multiple cells can "hear" you. They negotiate and the one which hears you best takes your call; but hands-off to another as you move around.

So if towers 47, 48, and 49 hear you, you are somewhere between them; if 47 hears you best, you are likely closer to 47 (of course this may be skewed by trees, buildings, etc).

I don't know, but "logically" another level of location can be found by comparing path delay. If tower 47 hears you and then tower 48 hears you 1 microsecond later, you are on a line 1,000 feet closer to tower 47. Three towers can, ideally, reduce that line to a point (at least a cocked hat). Strong multipath can skew this, but if the delay times exceed the known distance between towers, the anomaly is clear. Additional evidence if your cellfone has been on while moving: errors can average-out giving a firmer path to your current position.

Oddly, there is better cellfone coverage hundreds of miles in the sea off the coast of Texas than there is in Maine north of the Volvo Line. Must be all those oil wells. The airplane went down far off a poor coast; I doubt cellfone reaches. (However they have been saying the pilot "texted" a message, a verb coined for cellfones.)

I'm not sure how position data would have helped here. For one, so -many- systems failed in the last minutes, we must not assume any GPS would have functioned toward the end. For another, the general path and speed of the craft was known, simple dead-reckoning gives a probable area. Headwinds affect this, and the pilot will steer to avoid trouble; but trouble seems to have come on quickly so the error-area should be small. And indeed they found slicks fairly quickly, considering how remote the area is.

What bothers me is two slicks 60 miles apart. No explosion will do that. All I can think is that some major piece fell off, yet the rest of the plane continued at decent glide angle. If you assume a cabin-chunk falls near vertical, and the rest of the plane at 10:1 (a healthy airliner does better), then from ~~30,000 feet the plane would glide 60 miles past the chunk. Somewhat like the Hawaii Air airplane, except that one "only" lost roof-skin and landed in full control. This one may have been far more frightening.

> Yet again the airline industry fails us

"Failed"? There is a clear alternative: don't fly. Take the Queen Mary, only 5 or 6 days when she ran. Of course, while Mary ran well, some other ships went down, many with more souls lost than any airplane. Or do what most folks did before the Vikings and Columbus: avoid the sea, and if compelled to go by boat, hug the shore. Oh yeah: lot of shore-hugging boats were lost.

Yet Stephen and Marty take advantage of very affordable rapid travel for business or pleasure, repeatedly, and surely aware that nothing is certain except a tin can 8 miles high at 0.9 speed of sound is certainly risky. Marty is doing business, trade which might be less busy and profitable without rapid travel. And he could, instead, stay in London and dodge highway traffic, or go hermit on a distant farm and be killed by a bull or his tractor...

Yes, the current event can probably be "blamed" on the low cost of airline travel. There is a little too much pressure to fly in bad weather, to cover the airplane loan. And there is a little too much pressure to increase the payload/cost ratio of airplanes, leading to changes which bench-test well then crack a few years in service. And as more and more flying gets done, there is more chance of "unlikely" combinations of circumstances actually happening.

It is interesting that the Graf Zeppelin flew that route for many years, with zero excitement, not even a twisted ankle. And dirigibles are far more at the mercy of storms than 707s: their top speed is only comparable to a good storm, not 10+ times faster, their top commercial altitude is below the top of storms, while a 707 flies over most storms. And while weather radar may be thin in that area, there was none when the Graf was flying. -Most- peacetime dirigibles went down in unexpected storms (and the exceptions are instructive: the India was redesigned for such high payload that it creamed the first hill it found).
 

strangeandbouncy

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Hi


  Latest news on BBC is suggesting that there may have been a bomb on board. 4 days before there was a direct threat to the same flight.



  Kindest regards,


    ANdyP
 

Svart

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> yet cellphone companies can put these devices in every new phone.

Many of these cellfone finders are not "global".

They do not reference satellites, Polaris, sun, moon, etc.

They work only where cellfone coverage exists.

In most of the cellfone area, multiple cells can "hear" you. They negotiate and the one which hears you best takes your call; but hands-off to another as you move around.

So if towers 47, 48, and 49 hear you, you are somewhere between them; if 47 hears you best, you are likely closer to 47 (of course this may be skewed by trees, buildings, etc).

Uh no.  GPS was mandated to be installed in ALL US cellphones after 9/11.  This was under the guise of E911 for the purpose of finding someone if they call 911 from their phone.  Most phones only have an uplink, they can only report themselves on the GPS network but cannot downlink anything.

Here is an article where the police used it for good: http://www.knoxnews.com/kns/local_news/article/0,1406,KNS_347_5507506,00.html

and I'm sure that given the right circumstances, they will use it for evil as well.

Chances are good that if you've bought a cell phone anytime after about a year from 9/11 then your cell phone has the ability to be tracked by GPS satellites if you have any GPS functionality, like navigation, or not.

This is only a small part of the government's invasion into our privacy but they can't seem to help make transportation safer by mandating that an airplane have a GPS location device so that they can find it when it goes down.  Who knows how many people *might* have survived that crash only to have drowned before anyone could find them?
 

SSLtech

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Svart said:
Chances are good that if you've bought a cell phone anytime after about a year from 9/11 then your cell phone has the ability to be tracked by GPS satellites if you have any GPS functionality, like navigation, or not.

No, Your phone is NOT "tracked by GPS satellites". Only the CELLPHONE knows where it is. The satellites are much too busy doing more useful work to know where every cellphone on the planet's surface is... and where it's been.

Satellites used for GPS transmit a synchronised time-code, along with other things which they were BUILT to do. GPS is a clever way of detecting subtle differences between the arrival times of these timecode streams, which the GPS RECEIVER is then able to use to calculate position, on the surface of a notional sphere. -If you want navigation capability, what you have to do is superimpose a known terrain upon that same notional sphere surface.

But the sattelites are basically just doing the 'speaking clock' job and "talking" to your phone... they're NOT 'listening'.

-CELL TOWERS listen to cell phones. When GPS tracking is remotely enabled to find a phone, the PHONE determines its position by listening to the satellites, then relays its calculated position via subcoding within its "I'm here" response to the cell tower's "Who's here" messages. -If there's no cell towers to send the message to, there's no way to track the phone. (unless it's a satellite phone of course... but none of us own those, I have little doubt!)

Cell-tower-signal-dominance location (pretty much exactly as described by PRR) has been available since early on, and since cell towers also broadcast timing synchronisation codes, I understand that since later on -even before GPS- it may have been possible to more closely approximate location by arrival-timing comparison of TOWER signals, which helps with signal 'shadowing' and multipath issues.

I'm not a specialist, but I do know a guy who works at a major phone company, and who was pretty deeply involved with some of the developments in this field. -He tells some fascinating (to a geek-nerd at least!) stories. -If there are any detail-specific questions, I can put them to him, and see if he can explain things better than I have.

Keith
 

Svart

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GPS satellites do have uplink channels..  They just don't tell you about them.  SHSSSSSHH.  It's a secret..

 

JohnRoberts

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One thing that makes sense considering modern communications bandwidth is for the black box to be virtual and have the data stream to somewhere physically distant from the aircraft.  I suspect communication satellites don't have very dense coverage over the middle of the ocean, but give them time. People will want their youtube while flying.

JR


 

AnalogPackrat

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Svart said:
GPS satellites do have uplink channels..  They just don't tell you about them.  SHSSSSSHH.  It's a secret..

Please...all satellites have comm uplinks for control and configuration purposes.  These old GPS satellites don't have some secret monitoring capability.  Some other military satellites may well be doing this, however!

You're 5w or less omni-directional fone antenna ain't gonna provide squat for signal at the almost 13000 mile distant GPS satellite.  Said satellites were not built to monitor hundreds of millions (billions?) of fones.  The obvious and practical way to implement fone location via GPS is exactly as outlined by SSLTech.

If you don't want to be tracked either leave the fone at home or pop out the battery.

A P
 

AnalogPackrat

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JohnRoberts said:
One thing that makes sense considering modern communications bandwidth is for the black box to be virtual and have the data stream to somewhere physically distant from the aircraft.  I suspect communication satellites don't have very dense coverage over the middle of the ocean, but give them time. People will want their youtube while flying.

Good idea.  Current BB tech is still pretty primitive--tapes and all that.  Seems like flash memory is getting pretty robust these days.  Why not dump to local memory and offload to external data sink?  As for the floating thing--also a good idea, but difficult to implement with the current designs which are large, imbedded in the plane for increased survivability (and connectivity for recording).  A small digital,  ejectable unit with beacon and flotation might be possible.

A P
 

Svart

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I have intelligence from a retired Navy person who worked on the GPS uplinks.  They do indeed have uplink channels that aren't the data channels you speak of.  They are true DSSS uplink channels for transmitting through the satellites, not datalink channels used to communicate WITH the satellites.

Since I work with RF I can say with confidence that the GPS signals are some of the most robust transmission types on the planet.  The receivers and transmitters on the satellites are highly efficient.


You're 5w or less omni-directional fone antenna ain't gonna provide squat for signal at the almost 13000 mile distant GPS satellite.

GPS data can be acquired up to 10 feet underground and further underwater.  That's pretty darn good for something for such a tiny amount of power.  In RF sometimes it's not the POWER of the signal, it's the robustness and the ability of the receiver to reject noise and interferers. 

 

AnalogPackrat

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Svart said:
I have intelligence from a retired Navy person who worked on the GPS uplinks.  They do indeed have uplink channels that aren't the data channels you speak of.  They are true DSSS uplink channels for transmitting through the satellites, not datalink channels used to communicate WITH the satellites.

And you think these uplinks are used to monitor cell phone transmissions?  I don't think so.

Since I work with RF I can say with confidence that the GPS signals are some of the most robust transmission types on the planet.  The receivers and transmitters on the satellites are highly efficient.

And I don't deny that at all.  I think you misunderstood me.  I never said GPS transmissions were a problem.  What I said was that GPS satellites are not monitoring hundreds of millions of cell fones.


You're 5w or less omni-directional fone antenna ain't gonna provide squat for signal at the almost 13000 mile distant GPS satellite.

GPS data can be acquired up to 10 feet underground and further underwater.  That's pretty darn good for something for such a tiny amount of power.  In RF sometimes it's not the POWER of the signal, it's the robustness and the ability of the receiver to reject noise and interferers.  

Again, I'm not arguing about reception of GPS signals by cell fones or other devices.  You posited that cell phones were being directly monitored by GPS which is simply not true.  5w omni transmission from a cell phone + 13000 miles + noise from hundreds of millions of other devices on the same wavelengths is a bit different from what you are talking about.  The inverse square law is not your friend here...

A P


 

lofi

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Marik said:
Why the black boxes are not designed to float? It'll make much more sense, wouldn't it?  ???

then the plane would have to disintegrate in order to ensure there release.

 

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