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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 12th Apr 2014, 02:06
  #9801 (permalink)  
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25 meg per hour is 7 kilobytes per second (56 Kbps) per aircraft. Existing satellite internet networks can absorb that without breaking a sweat.

Also, most of this stuff is highly optional and it's stored mainly because it can be. 20 years ago standard FDRs on aircraft like the 777 had the capacity to record 64 or 128 words per second (0.77 or 1.54 Kbps). After the expansion of the list of required parameter groups in 2002, Boeing started installing FDRs capable of 3 Kbps.
I'm not so sure about the networks absorbing the bandwidth system wide for all aircraft in the air. Maybe it can.

I did look up some numbers. Data charges are in the $7 to $25 range. So assume 25MB per hour, looking at $175/hr. Maybe you can undersample, can limit the parameters. So call it $50 to $100/hr. That is just FDR; CVR is going to be a couple of voice channels at say $30/hour each.

Maybe that is enough said on this topic, but all in all, how much extra sim time per year could you give each pilot for that money?
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Old 12th Apr 2014, 02:11
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Seems to me that having a simple GPS unit that transmitted the aircraft's position every 10 minutes would go a long way toward finding a missing plane.
Transmitted to where, that is the question. Over the sea, it would have to be satellite and bandwidth on satellites is a scarce resource and is costly.
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Old 12th Apr 2014, 02:33
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Would a satcom person please step in? The raw bandwidth of a sat link is misleading. Individual A/C must either be polled (asked to transmit) or must speak up in the hope that data can be communicated. Simultaneous asychronous speakups - "collisions" - jam things up and the various originators must be separated in time, so they all get their data packets through. Because of transit time to/from the satellite(s), there is considerable latency involved, and at peak traffic times, actual throughput can be reduced to a fraction of the raw capacity of the sat channel. A small fraction.

This was covered extensively in the AF447 saga, and should be summarized here and "stickified" to reduce misconceptions. At least for the few that will read it before posing novice questions or "solutions".
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Old 12th Apr 2014, 03:18
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Satcom and all that stuff

Several recent posts have raised questions regarding satcom capacity and the possibility of packet data relay systems between aircraft to carry aircraft position information. These are valid technical questions but seem to be putting the cart before horse.

The real questions do not at this stage cover "how" but should concentrate on what it is that we are trying to achieve. Currently aircraft position information is available either on a schedule or on request by ATC using ADS and CPDLC. This information uses ACARS and is carried on VHF or satcom as is appropriate. ACARS is used primarily because the only global data network on the ground throughout much of the world is the airline data communications networks operated by ARINC and SITA and ATC units are connected to these.

This system could be extended to carry FDR data but to whom? Where would it be stored? Once these questions are answered then it will be time to start looking at the airground links to be used.

As a former colleague with a military background used to say, "Strategy is about what needs to happen; when the word 'HOW' crops up you are getting into tactics."

Let's get the big picture right before we drop down to the bit level.

Last edited by Frequent SLF; 12th Apr 2014 at 04:01. Reason: Early morning keyboard issues
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Old 12th Apr 2014, 03:55
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SS searching?

There was a stretch yesterday (within the past 16 hours) when neither Ocean Shield nor Echo were in the "box". Perhaps they were standing off while one of those which do not say where they are going nor where they have been was having a listen.
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Old 12th Apr 2014, 04:01
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There was a stretch yesterday (within the past 16 hours) when neither Ocean Shield nor Echo were in the "box". Perhaps they were standing off while one of those which do not say where they are going nor where they have been was having a listen.
More likely standing off while they dropped the sonobuoys. Wouldn't want to get tangled up in the 1000 foot cables suspending the hydrophones.

Last edited by rampstriker; 12th Apr 2014 at 17:51. Reason: 1000 feet not 1000 meters cable length - analysis software was modified, not sonobuoys
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Old 12th Apr 2014, 04:59
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Airbubba - Things are a bit different on the 777

Not with the Boeings I fly. The CVR now runs anytime there is power on the aircraft and for ten minutes after power is removed
VOICE RECORDER Switch

AUTO – The cockpit voice recorder runs from first engine start until 5 minutes after last engine shutdown (spring–loaded).

ON – The cockpit voice recorder runs until first engine start, then spring–loaded to AUTO.

there is definitely still a circuit breaker in the cockpit to disable the CVR
No CVR circuit breaker in the 777 cockpit. The circuit breaker is in the E/E compartment.
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Old 12th Apr 2014, 05:04
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Prop duffer

I'm not a supporter of the Malaysian govt. However, I cannot think of a similar precedent involving Malaysia where the eyes of the international community have been focused to such an extent on them.

There are powerful people here demanding and needing answers, from Boeing and Rolls Royce onwards. An enormous number of nations have become involved in the SAR and in checking and supplying other data towards the investigation. We don't know exactly who knows what but we do know there are numerous undisclosed assets operated by various nations and parties who already know more than we do about what is going on.

I'm believing it will not be in their interests to come up with a complete whitewash. Many epithets may be thrown around such as bumbling, inept, slow-on-the-uptake etc.

But if I'm wrong, I'll be happy to come back here and apologise, and will throw my hat into the cynics ring of all things Asian.
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Old 12th Apr 2014, 05:24
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It seems the marinetraffic web site has removed the Ocean Shield and Echo track and position histories. The "current" position and speed is still there but I can't get the tracks or histories to show up for the last 3 or 4 hours. I'd been saving them for the last several days.

Hopefully it's some kind of weekend maintenance and not a move to keep the public from seeing the action.
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Old 12th Apr 2014, 05:25
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@VinRogue
It's a shame the pinger does not work for say 10 days, then switch off until it receives an activation ping from a search asset, say submersible. The activation ping could be coded and limited to a set frequency range.
Increased complexity, yes, but problems with pinger battery life would be resolved.
Unfortunately this won't help a whole lot. The ULB is a very simple, low power piece of equipment. The key to the low power consumption is due to its simplicity. To incorporate a transpond functionality requires a detector to run on the ULB. So lets crunch some theoretical numbers.

The ULB pingers output at a level of 160 dB re 1uPa. That is equivalent acoustic energy of 0.075W, or 75mW. Assuming inefficiencies in amplification require a 10x amount of electrical power to produce that amount of acoustic power that gives us 0.75W.


The ping is 10ms long, thus the ENERGY per ping is 0.75*0.01 = 0.0075joules or 7.5mJ.


At a rate of 1 per second, gives an effective average power requirement (ignoring circuitry – which should be pretty simple for a dumb pinger) of 7.5mW.


Now, the company I work for makes underwater acoustic communications equipment. An example of a simple, high efficiency FSK detector uses approximately 77 milliwatts when running in continuous detect mode. That is 10x my estimated consumption for the simple pinger. An that is without the power requirement to generate an acoustic signal in response.



So not a practical option with the current ULB form factor.
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Old 12th Apr 2014, 08:56
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Side-scan Sonar

Maybe someone can post the tracks but it looks if HMS Echo is doing a side-scan sonar run each time ADV Ocean Shield does a slow turn.
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Old 12th Apr 2014, 09:41
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I wonder if it really makes sense to continue committing so much manpower, and materiel, to the visual search that's taking place >500 km to the West of the underwater search area. The chances of finding debris on the open ocean after almost 40 days must be tiny. Moreover, even on the off-chance that some debris is found, it would now be much too far from its point of origin to help narrow the underwater search area any further.
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Old 12th Apr 2014, 09:48
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As per a report in the ET

their summary of the search in a slide show

Flight MH370: Search teams receive signals again - Flight MH370: Search teams receive signals again | The Economic Times
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Old 12th Apr 2014, 09:50
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Finding some debris may help those still clinging to a desperate hope that their loved ones are still alive, to come to accept that this is not the case.
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Old 12th Apr 2014, 09:54
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Airline Safety Solutions from PPRUNE
ve7pnl's list of recommendations (11 April 21:27) gave me absolutely the biggest laugh I've had for months.

Through the streaming tears of laughter I'm sure many of us would see the truth of his serious underlying point.
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Old 12th Apr 2014, 10:16
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Originally Posted by sSquares
Maybe someone can post the tracks but it looks if HMS Echo is doing a side-scan sonar run each time ADV Ocean Shield does a slow turn.
The AIS data is quite sparse - sometimes 7 hours between individual tracking points:
Ocean Shield
Echo
Even the highest cost AIS membership only gives 12 hour tracking interval.
You can click on the vessel icon then "Show vessel track" to see last 9 locations mapped.

So a lot of the true track is hidden - one has to infer from speed & course.
Also the TPL is well separated from Ocean Shield. Echo is staying well back from the TPL when it is running.

The current interest seems to be near depths of 5,000m - 5,500m between -20.95 to -20.85 lat. and 103.9 to 104 lon.. That may account for suggestions this may be a very long process - it could be out of range of the Bluefin.

The seabed is sloping in that area so loss of reception may be due to that slope as well as battery levels decreasing.

Last edited by BillS; 12th Apr 2014 at 10:22. Reason: added comment and track info.
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Old 12th Apr 2014, 10:28
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Originally Posted by rampstriker
More likely standing off while they dropped the modified sonobuoys. Wouldn't want to get tangled up in the 1000 foot cables suspending the hydrophones.
Standard sonobuoys, modified processors in the aircraft.
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Old 12th Apr 2014, 10:42
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Ocean Shield & HMS Echo

The graphic below shows the most current tracks for Ocean Shield in Yellow, while those of HMS Echo are in White. The earliest TPL towing tracks for Ocean Shield are Red. The stars shown represent the approximate positions of received pings, as the data provided by AMSA wasn't specific.



NOTE: The positions are obtained via a sun synchronous satellite which is in sight of the vessels for 3 or 4 south going passes and the same for north going passes each day.

Last edited by mm43; 13th Apr 2014 at 19:19. Reason: updated to 12/20:32 UTC
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Old 12th Apr 2014, 10:53
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Unfortunately this won't help a whole lot. The ULB is a very simple, low power piece of equipment. The key to the low power consumption is due to its simplicity. To incorporate a transpond functionality requires a detector to run on the ULB. So lets crunch some theoretical numbers.
Utter blonde moment on my part! good point, forgot any receiver would require a power source too and probably in excess of that used up by the ULB.
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Old 12th Apr 2014, 11:02
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What does AIS say for the search area when MH370 went down?

Been purposefully not posting on this thread given the volumes etc but had an "interesting thought" last night.

Question: Is it possible to go back in time on AIS and look at what ships (if any) were in the current search area at the "best guess" time MH370 would have run out of fuel on that track?

Same would apply for early AIS paths crossing the track MH370 is suspected of taking.
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