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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 5th Jun 2014, 06:32
  #10921 (permalink)  
 
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flyball. Might the speed be less than 1500m/s?
Velocity of sound in sea-water Calculator - High accuracy calculation
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Old 5th Jun 2014, 07:09
  #10922 (permalink)  
 
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The PhD who investigated this acoustic data gave a very comprehensive interview on radio 18 hours ago. He is almost certain (90% confidence) the noise was NOT MH370.

He feels more likely it represented a small earthquake or ice breaking off Antarctic shelf.

He did say low frequency sounds (at or below lower limit of human hearing) can be detected many thousands of km away. Main variables are:
1. topography of the bottom (helpful if the ocean bottom at the source sound was sloped towards the listener, as this will "lens" (reflect) noise towards the listener.
2. temperature layers (deep water channel)

He also confirmed frequencies in range of pingers would be limited to just a couple of km regardless of conditions.

Worth a listen if you are interested. Maybe available online (2gb.com). But he didn't leave much room for doubt.
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Old 5th Jun 2014, 07:29
  #10923 (permalink)  
 
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Curtin University Acoustic Signals

Ornis, you may be correct, its hard to find accurate sea surface temperature measurements for the 8th of March and it also depends on whether the plane hitting the surface caused the signal or the plane imploding under the ocean caused the signal. The acoustic sensor is located at a depth of 400m so this affects the speed as well.

Using the image Minimbar posted the final ping is about 1600km away from Perth, so this would make it 17mins for the travel time of the signal and a further five minutes the plane would need to glide (54mins).

ETH961 glided for 27mins after last engine shut down from 20,000ft, (even with hijacker interference).
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Old 5th Jun 2014, 07:37
  #10924 (permalink)  
 
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Originally Posted by slats11 View Post
The PhD who investigated this acoustic data gave a very comprehensive interview on radio 18 hours ago. He is almost certain (90% confidence) the noise was NOT MH370.

He feels more likely it represented a small earthquake or ice breaking off Antarctic shelf.
Unfortunately, I cannot access the recording. But I would be interested to know his reasoning. Has he seen recordings of a 777 ditching and imploding at depth or anything similar? If not then he is giving a 90% assumption.

The recordings of an identifiable noise (in fact two) happening at approximately the time that 370 was expected to have 'ditched' is an extreme coincidence.
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Old 5th Jun 2014, 07:54
  #10925 (permalink)  
 
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Speed of sound in water is APPROX 1500 mps but it varies with temperature, salinity, surface conditions and half a dozen other things

You use 1500mps as an approximation but it could be +/- 5%
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Old 5th Jun 2014, 07:55
  #10926 (permalink)  
 
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ACARS, Disabled or Switched off

Bilby, Desparing Traveller et al,

ACARS "was deliberately turned off" was reported early on. Now ACARS 'logs on' and 'logs off' usually on aircraft systems power up and power down. ACARS using VHF often (regularly) loses contact as the aircraft flies out of line-of-sight. There is a difference to the system between just not getting any more transmissions and receiving a log-off. So it would be possible to know if the system was shut down via a pilot input or just 'stopped' as it would if out of line of sight of VHF, fire had burned through the power supply, or the pilot had tripped a circuit breaker.
The repeated statements that someone had "switched ACARS off" rather than we received no more ACARS transmissions after the last one at cruise, implies that there is evidence of a tidy log-off. This evidence is crucial as it would settle several hypotheses - a pilot with a cockpit fire or some other emergency, does not find the correct place to log off from ACARS. SITA/ARINC should have that evidence and it should have been in the initial report.
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Old 5th Jun 2014, 07:58
  #10927 (permalink)  
 
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@IanW

The Curtin University receivers are based off Rottnest Island, pretty much due west of Perth. I gather these receivers serve a scientific purpose (whales etc).

He explained the data had been cross referenced with data obtained from different receivers based quite a way south of Perth (off Cape Leeuwin). The purpose of these receives is to help monitor compliance with the comprehensive test ban treaty. He was a little vague regarding precise details at this point, perhaps deliberately so. But I got the impression differential timing suggested a source well to the south (he did specifically mention Antarctica as a likely source).
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Old 5th Jun 2014, 08:09
  #10928 (permalink)  
 
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@IanW
The recordings of an identifiable noise (in fact two) happening at approximately the time that 370 was expected to have 'ditched' is an extreme coincidence.
As mentioned, the first acoustic transient, if originating from the final Inmarsat ping ring would have been produced approximately 50 minutes after the time of last Inmarsat ping.

The second acoustic transient was much later and would have originated approximately 4.5 hours after the last Inmarsat ping

Both signals received contain only low frequency energy, suggesting a large propagation range, and have rather different characteristics (frequency and time spread).
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Old 5th Jun 2014, 08:22
  #10929 (permalink)  
 
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Glide from 35,000ft?

Less than 15 mins.
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Old 5th Jun 2014, 08:41
  #10930 (permalink)  
 
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Hello, a first-time poster here with a couple of points I would like to contribute:

When Tim Clark talks about 3 systems disabled, he probably refers to the transponder, ACARS and SATCOM. Please note that ACARS and SATCOM are separate systems.

Transponder being disabled (turned off or failed) is self-evident.

Last ACARS transmission from the plane through SATCOM was at 1707 Z and none received after that, thus ACARS disabled.

In the Inmarsat logs, there is a gap of SATCOM transmissions between 1707 Z (after the last ACARS transmission) and 1825 Z (when the SATCOM in the plane initiated a handshake). In particular, the SATCOM modem didn't respond to a satellite query at 1803 Z. We can deduce therefore that SATCOM was disabled at least between 1803 Z and 1825 Z, and enabled at 1825 Z.
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Old 5th Jun 2014, 09:11
  #10931 (permalink)  
 
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Curtin University researchers find possible acoustic trace of MH370

IanW, a brief media presentation by Dr Duncan. The 15 minute interview I heard was much more in depth, but you might be interested in this.
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Old 5th Jun 2014, 09:19
  #10932 (permalink)  
 
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Dale C. Acars was VHF only. The systems off: VHF (Acars), HF, transponders, satellite phone. This reply will disappear soon along with your comment.
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Old 5th Jun 2014, 09:23
  #10933 (permalink)  
 
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Originally Posted by Ian W View Post
Bilby, Desparing Traveller et al,

ACARS "was deliberately turned off" was reported early on. Now ACARS 'logs on' and 'logs off' ....

The repeated statements that someone had "switched ACARS off" rather than we received no more ACARS transmissions after the last one at cruise, implies that there is evidence of a tidy log-off.
I don't think there is any 'Official' statement that ACARS was switched off or logged off. I believe the position/time of last ACARS on the various plots is that of a complete and normal ACARS transmission and there is no indication of a log off ACARS message.

The log ons at 18:25 (from memory) and the 7th ping, are the satellite communication system itself, not the ACARS communications. Further, I believe it is established fact that MH370 was not configured to have the ACARS system use the satcom link, Satcom was only onboard to provide telecommunications for Business/First class (and potentially available to the flight crew for calls).

I have little technical knowledge of the ACARS system, but it appears to not intrinsically require a log on/log off process. It seems to just be a VHF/HF/Satcom store and forward system where individual data packages are sent to the central service for storage and then periodically polled or pushed until an ACK is received or a retry limit is hit.

It is also not clear to me that the Satcom system itself has any 'logoff' function and therefore if there would be anything to distinguish between the device being turned off/ put into standby/ loosing power/ being destroyed
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Old 5th Jun 2014, 10:05
  #10934 (permalink)  
 
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Originally Posted by mm_flynn View Post

I have little technical knowledge of the ACARS system, but it appears to not intrinsically require a log on/log off process. It seems to just be a VHF/HF/Satcom store and forward system where individual data packages are sent to the central service for storage and then periodically polled or pushed until an ACK is received or a retry limit is hit.

It is also not clear to me that the Satcom system itself has any 'logoff' function and therefore if there would be anything to distinguish between the device being turned off/ put into standby/ loosing power/ being destroyed
The logon sets up the store and forward system and checks that you are a subscriber to ARINC or SITA messaging systems. Similarly, the SATCOM sets up a link at the lower protocol layers that also allow check of subscription against the aircraft ID, or you would not be able to start the SATCOM phone or other uses of the SATCOM system. These actions all happen on power on and are 'transparent' to the pilot. This is what was meant by the Earlier statements about 'pilots not knowing how to switch the comms systems off'. From the pilot perspective the comms can be switched off - but they are actually still connected at the network level in case the pilot wants to switch the higher level application on again.
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Old 5th Jun 2014, 10:42
  #10935 (permalink)  
 
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@IanW

Thank you for the explanations.

What I've taken away from this very interesting discussion is that possible the ground would know if the system had been tidily shut down because a logoff message would have been received, but that the existence of such a message hasn't been explicitly disclosed publicly. As you quite rightly say, if that evidence exists, it is crucial.

The preliminary report simply states:
It was later established that the transmissions from the Aircraft Communication and Reporting System (ACARS) through satellite communication system occurred at regular intervals starting before MH 370 departed Kuala Lumpur, Malaysia at time 12:56:08 MYT and with the last communication occurred at 01:07:49 MYT.
I was a bit surprised to read that paragraph, as I had been under the impression that ACARS was VHF only on this flight. Like others, I've also been under the impression that the 1:07:49 message was a routine engine report.
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Old 5th Jun 2014, 13:09
  #10936 (permalink)  
 
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Originally Posted by DespairingTraveller View Post
I was a bit surprised to read that paragraph, as I had been under the impression that ACARS was VHF only on this flight. Like others, I've also been under the impression that the 1:07:49 message was a routine engine report.
I suspect that the report conflates the Satcom infrastructure (which logged twice in flight, and is the source of the pings), with the ACARS system (which provides store and forward text and data messaging from the flight deck and various aircraft systems). But ultimately, it is irrelevant in that we know when the last ACARS message was transmitted and we know the Satcom infrastructre was connected for many hours after that.

IanW,
Understood - My point was more on the logoff side. It doesn't appear that either system (SatCom or the ACARS store/forward network) have any intrinsic need to have a logoff function. From those with more technical knowledge, is there a logoff message the would or would not be expected in certain circumstances?

I have believed that both are like a transponder in that you know it is not 'on' when it stops responding/sending rather than something like a logout messaging being sent. As such, it is not possible to to deduce the 'Why' from a loss of ACARS or Satcom (or transponder) data. It is intinguishable between the device being shut down in a controlled way (i.e turned off in the normal way), suddenly issolated from power, failed, or destroyed.
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Old 5th Jun 2014, 13:29
  #10937 (permalink)  
 
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logon and logoff

I think you will find that the reason for a logon and log off is so that the network knows the aircraft is available to receive traffic in the ground - air direction.
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Old 5th Jun 2014, 15:39
  #10938 (permalink)  
 
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Can't work out how to paste the image here.

I have calculated the solar terminator for 0018 UTC on March 8 2014, and the link below seems to work.

http://www.timeanddate.com/scripts/s...=20140308T0018


So if plan was to ditch around first light, this would suggest a long way SW along the final (7th) arc. Somewhere close to the initial air search area a long way WSW of Perth.

The further NE along the 7th arc the flight ended, the longer the plane was flying in daylight.

Last edited by slats11; 5th Jun 2014 at 15:55.
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Old 5th Jun 2014, 17:44
  #10939 (permalink)  
 
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The level of presumption here is really quite surprising. Tim Clark, President of the company that operates the largest B-777 fleet, and might just have access that we don't mentions, in an apparent off-the-cuff interview, that there were three things that his qualified crews would not know how to do, THAT WERE DONE and the presumption here is - OH! he must mean VHF com, Transponder(s), and ACARS? So how many 777 qualified pilots don't know how to manage those things? For example, do all aircrew know how to access the flight deck of an aircraft to which they are not assigned?

Isn't it time for a reality check?

Clearly, there is something else and I suspect that as a major operator with the responsibility he has, Mr Clark may know more that he can openly say? So what you, or we, should really be thinking about is what three things could have contributed to the loss of this aircraft that aircrew would not likely know about,but others might? And why is it he assumes that this knowlege boarded the flight and could do so again? Seems to discount all of those fire theories, meteors and structural failure too.

There are far more important issues in play here than LF noise picked up on hydraphones and an anxious lady sailor seeing an aircraft in the early dawn (when it is still dark at sea-level).

It seems that Tim Clark is still asking exactly what was below deck in the hold; amongst other things? That seems to have been brushed aside; as soon as someone found batteries. What else is there that remains unknown about the freight and the people onboard?

Why, then, is it assumed all will be known once the aircraft is found, if it is? Just what do you think the DFDR will reveal about the how and why?

It is time to stop sweating the small stuff and consider the bigger picture.
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Old 5th Jun 2014, 19:39
  #10940 (permalink)  
 
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Astra Mike makes a good point in closing:

quote "It is time to stop sweating the small stuff and consider the bigger picture"

The big picture now is the 29th May press release by JACC, where we are informed the next steps are as follows:

1. A review of all existing information and analysis to define a search zone of up to 60,000 square kilometres along the arc in the southern Indian Ocean.
2.Conducting a bathymetric survey to map the sea floor in the defined search area.
3. Acquiring the specialist services required for a comprehensive search of the sea floor in that area.

Simply put, this means.
1. Try and decide where to look next, then having made up their minds where to look,
2. have a peep to see where it is flat and where it is not, then
3. get the boys and their equipment on site.

It will take them till end of August to do No1 and at least another 12 months to do the rest.

Could it be that in the interim some debris may wash up on someone`s shores.
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