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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 17th Mar 2014, 14:55
  #5181 (permalink)  
 
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Ian W:
"The pings carry the ID of the sender - that is how INMARSAT know what to do with the ping, reject it or accept it and what level of service it should get. If you get a cell phone and turn it on - the first thing it does is start pinging the networks with its IMEI - the networks that do not service that phone take no notice the ones that do respond. So in this case no ACARS data but electronic identity data."
This post implies that the AIRCRAFT initiates the ping.
Other posts have stated that the SATELLITE initiates the ping.

Obviously both can't be right. The pings seem to be a critical part of the information available right now.
Can someone with firsthand knowledge of SATCOM/ACARS architecture help us out here?

Assuming the ping data for MH370 are Kosher (Halal?), how 'accurate' are the range/distance estimates (aka the red arcs) that have been generated?
Are we talking +/- 10km? 50km? 200km?
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Old 17th Mar 2014, 14:58
  #5182 (permalink)  
 
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Amen

Agreed FakeSealion.

As yet, there has been no MOTIVE for any of that.

Human Factors or mechanical failure. I struggle with the latter if the plane was airborne for 5+ hours and there were NO comms effort made by anyone aboard via any means. I think the only additional salient and sobering fact is that MH370 is not airborn anymore. However, there is an industry and SLF that need to find out why.
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Old 17th Mar 2014, 14:59
  #5183 (permalink)  
 
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The oil rig worker seems strangely elusive since the email.
....and he probably would not describe it as an "oil rig" if he was a genuine worker on whatever form of oil thingy it actually was.
So my best guess is that is was yet more lies and disinformation.
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Old 17th Mar 2014, 15:01
  #5184 (permalink)  
 
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Can you seriously suggest that circa 200 cell phones can be "blocked" from around 2000ft to landing and thereafter, for about 8 days without one single text getting out to the outside world?
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Old 17th Mar 2014, 15:02
  #5185 (permalink)  
 
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WTG BARREL: " Question: have you considered that that report could be simply inaccurate or false?"

CNN 11AM EST Just announced that the Malaysian Government has corrected this time element, and says ACRS was NOT (necessarily) OFF at time of Goodnight!
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Old 17th Mar 2014, 15:03
  #5186 (permalink)  
 
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Originally Posted by dsc810 View Post
The oil rig worker seems strangely elusive since the email.
....and he probably would not describe it as an "oil rig" if he was a genuine worker on whatever form of oil thingy it actually was.
So my best guess is that is was yet more lies and disinformation.
That is well observed. The text of the email was precise, yet that term is distinctly 'plane'-like for a professional to use in that context.
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Old 17th Mar 2014, 15:04
  #5187 (permalink)  
 
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A big elepant in the room.

The inmarsat data is derived from ACARS pings.
The press releases say that ACARS had been deliberately switched off.

MAKE UP YOUR MIND.

Theory - ACARS can communicate via VHF and via satellite.
The VHF antenna or its cable were damaged (depressurisation or structural ?) but the ACARS unit was NOT switched off, it simply switched to using the satellite.

Either someone is lying or this takes us back to a catastrophic failure rather than human intervention.
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Old 17th Mar 2014, 15:04
  #5188 (permalink)  
 
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SEENITALL #5243 page 263

Asking a question is fine -- just so long as you have done your own research to see whether or not that question has been asked and answered (multiple times maybe) previously. Not to do this is lazy and wastes everyone else's time.
my statement re "the question you are afraid to ask because it may may you look dull" was a principle not just aimed at this thread or your comments, I also I believe your answer was not specifically to me.

With regard to your reply I joined at page 65, my routine is every morning (I am retired) pick up at the page I left read through to last posting, noting any I want to comment on if they are still there when I go back i comment. I am sure many others do not follow this system
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Old 17th Mar 2014, 15:04
  #5189 (permalink)  
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Originally Posted by NigelOnDraft;8383361[*
It was a 2 crew flight, Capt would not "go back to rest". He might go out to use the toilet, but any "rest" would be in his seat.
Don't confuse SOPs with Cultural practice.

I asked some days ago about the cultural practice amongst the airline pilots or about the cultural practice of this captain.

If all the company pilots adhered strictly with the rules then you are correct. But we know they don't. Remember the FO was acknowledged to have had passengers in the cockpit. If that rule was breached it suggests that there was laxity in other areas.
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Old 17th Mar 2014, 15:04
  #5190 (permalink)  
 
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To dsc810 -

Actually 'oil rig' is how most of those who work on mobile drilling rigs would describe them. That is what this vessel is - a deepwater capable semi-submersible rig.

So the language used sounds right - even it seems unlikely the sighting was of MH370. Not impossible.
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Old 17th Mar 2014, 15:10
  #5191 (permalink)  
 
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Originally Posted by rigbyrigz View Post
WTG BARREL: " Question: have you considered that that report could be simply inaccurate or false?"

CNN 11AM EST Just announced that the Malaysian Government has corrected this time element, and says ACRS was NOT (necessarily) OFF at time of Goodnight!
Thanks, would you please provide the link?
Trying to make a sense out of "ACARS was not necessarily OFF at time of goodnight".
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Old 17th Mar 2014, 15:13
  #5192 (permalink)  
 
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it's got nothing to do with being "Blocked"... The cellphones, if they manage to log on to a cell at all, will also be logging on to multiple other antennas. The system blocks them out as it knows they are likely to be airborne, before they overload the network.

I would suggest that multiple hijackers and a bin bag would solve the problem after landing...
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Old 17th Mar 2014, 15:14
  #5193 (permalink)  
 
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cell phones and the like.....

I hate to be a pessimist but IF the flight excursion to 45,000 feet did occur, then it might explain lack of phone signals texts etc.....
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Old 17th Mar 2014, 15:14
  #5194 (permalink)  
 
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Theory - ACARS can communicate via VHF and via satellite.
The VHF antenna or its cable were damaged (depressurisation or structural ?) but the ACARS unit was NOT switched off, it simply switched to using the satellite.

Either someone is lying or this takes us back to a catastrophic failure rather than human intervention.
It cant really be that, if it disintegrated then how are signals still being sent 8 hours after it took off, that's pretty much evidence that it was still intact up until 08:11 ,

The rig worker may have seen a bright light in the sky that could have been anything, then the next day hears a plane might have crashed near his area and its human nature to just draw conclusions of your own....(still personally think this was a hoax)

Last edited by Livesinafield; 17th Mar 2014 at 15:15. Reason: spelling
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Old 17th Mar 2014, 15:15
  #5195 (permalink)  
 
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I suspect some journalists (and others in the mix) are following this thread and at times discover fields of follow-up inquiry.

SO:
Summary:
ACARS reported at 1:07 (maybe with the left turn pre-programmed waypoint maybe not
F>O> (or someone) signed off 1:19 no mention of problems
ACARS DID NOT "send" the scheduled 1:37 update
BUT it was still ON (CB not pulled or circuits disrupted) for all latter handshake attempted pings, with the satellite

Leaves this technical question i think:
What would be the causative factor that, with ACARS ON, the 1:37 report (and others) was skipped?
How/what would switch ACARS to satellite from other broadcasting method?
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Old 17th Mar 2014, 15:17
  #5196 (permalink)  
 
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Waypoint change in 1:07 ACARS message?

If you wanted to "steal" an aircraft (and I don't) wouldn't you want it to look like it had simply disappeared? Presumably they'd have been flying on LNAV (maybe VNAV too). Since there is circa 10 miles IIRC without radar cover between Malaysia and Vietnam what was to stop whoever was flying choose heading select towards IGARI, enter VAMPI as next waypoint in the FMC, turn further 40° right after IGARI still on heading select then go back to LNAV? Now you see us, now you don't!

777 drivers, does the content of outgoing ACARS messages show on EICAS or MCDU? If it does, maybe it was noticed, hence the turning off of ACARS. Transponder off would have been a given, to appear "invisible".

Lets just hope MH370 is found soon.
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Old 17th Mar 2014, 15:20
  #5197 (permalink)  
 
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re cellphones.

Just collect them off the passengers under duress and put them in a metal box.

Faraday cage lets no signal in or out.
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Old 17th Mar 2014, 15:20
  #5198 (permalink)  
 
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Any chance that the oil rig worker might have seen a missile fired in the general direction of the plane, possibly a near-miss that convinced whoever was then flying to take evasive action?

Obviously he didn't see the plane itself, unless all of this later info about a westward flight path is false.

But if so, this missile would have been fired rather early in the sequence of events to suggest anything other than a very early recognition of a hijacking. That could only have come about if the legit pilots somehow communicated the fact before the handover and radio silence, possibly without alerting the hijacker(s). The missile would have changed that dynamic.

Also, would a missile be visible further away than a burning aircraft as the oil rig observer reported? That might make it more plausible since I think we established the oil rig was about 300 miles from where the plane last made radio contact and most indications now suggest an immediate westward jog after that. So in other words, a missile fired eastward that missed or failed to have its intended result, soon afterwards seen by one oil rig worker who happened to be looking in the right direction.

Question would then be, who fired it, and why didn't they continue their attack? The other point I considered was that a smaller aircraft flying off the system somehow came to grief after a close brush with MH 370, and that one came down in the sea. I'm saying smaller only because anything larger than a private jet would have been reported missing too.
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Old 17th Mar 2014, 15:22
  #5199 (permalink)  
 
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Originally Posted by Cheerio View Post
That is well observed. The text of the email was precise, yet that term is distinctly 'plane'-like for a professional to use in that context.
I personally have discounted that area (well had until the news that MAS now saying acars was not necessarily turned of before last vhf message)

However the rig worker may have deliberately used a non professional/generic description to not confuse the intended readers.
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Old 17th Mar 2014, 15:27
  #5200 (permalink)  
 
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About the satellite pings

I note many posts referring to earlier pings and asking the question why no information has been released concerning anything other than the “last ping.” Maybe I can shed some light on this.

Summary
1) It is most unlikely that data relating to anything other than the most recent ping would be retained onboard the satellite, and
2) Each ping must necessarily contain an unique identifier.

Communication satellites generally use time division multiple access (TDMA) to enable them to service many “clients” simultaneously. This works as follows: the satellite allocates time slots to each client for them to uplink their data, so that in normal operation client A transmits a brief burst of data then Client B, client C and so on. The whole sequence repeats many times per second in so-called frames. For this to work, the sat’ needs to keep a record of all its potential clients and the time slot(s) allocated to each one. This is the TDMA scheduling table and it is maintained by the satellite’s on-board computer.

Periodically, the satellite broadcasts a channel access frame, inviting any new client wanting to use the satellite’s services to identify itself and the services it wants to access. The timing of the replies received during the channel access frame enables the satellite to work out the most suitable time slot(s) to allocate to that client. Note that in doing so, the satellite has implicitly calculated the round-trip time for radio waves to that client.

Once a client (aircraft, sat-phone, etc.) has established channel access it periodically pings the satellite to check its time slot allocations. (Hello this is client XYZ. My time slot is 36ms after the frame. Is that still OK?) If the client has moved significantly, the satellite may notice the timings have changed and update its TDMA tables with a new time slot for that client. Note that all of this TDMA stuff is merely to maintain access to the satellite if needed and has nothing to do with actual data transfer, which is negotiated separately as and when needed.

The operative word is update in that paragraph. When the tables are updated, previous values are overwritten and lost. There would be no reason to log or down-link all the technical details of the TDMA protocol as that information has no commercial value to the satellite operator.

When a client falls silent, its entry will remain in the TDMA tables until expunged to make room for a new client. It would appear that Inmarsat were able to interrogate their bird before this happened and down-link the data for MH370. Unless the satellite was logging useless, out-of-date information, this record would contain only the most recent ping data.
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