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-   -   Malaysian Airlines MH370 contact lost (https://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost.html)

toboev 17th Mar 2014 16:32

on the topic of mobile phones and why no apparent contact to/from any of them:
If you set up an open femtocell in the aircraft, would that not capture all the mobiles on board, which would all see it as their nearest and most powerful "cell tower". Any call from such a mobile would go nowhere other than the femtocell. And since mobiles wind their RF down to the minimum required, with a strong local cell tower signal they would all be on minimum RF power.

(For the record, I am not an aviation professional, nor am I a mobile phone specialist)

Mr Optimistic 17th Mar 2014 16:37

Any chance we can get clarification on the Inmarsat ping business as requested above? Since I understand that a SATCOM service for a cars was not subscribed to then neither the aircraft nor the satellite would be motivated to ping so presumably this relates to voice comms. Unless a time stamp is sent I do not see how a handshake initiated by the a/c would allow signal transit time to be calculated by the satellite.

On another issue is it now understood that the acars shutdown was not the tidy logging off procedure believed up to a few pages back.

On another issue would the a/c have been visible to Vietnam ATC at the time of last voice message.

And finally, following normal protocol, when would first voice contact have been expected with Viet ATC in relation to the time of the OK roger message?

Thank you for your patience!

Lonewolf_50 17th Mar 2014 16:40


Originally Posted by Mr Optimistic (Post 8383509)
On another issue would the a/c have been visible to Vietnam ATC at the time of last voice message.

And finally, following normal protocol, when would first voice contact have been expected with Viet ATC in relation to the time of the OK roger message?

Not sure about your second, but you can read some of LukeSkyToddler's posts in this thread regarding when Vietnam ATC was trying to make contact with MH370. Search of this thread by his user name should get you to the posts in question.
?? Just did a search, and find that I cannot dig up any of his posts. He made quite a few about hearing Vietnam ATC calling for and getting no response from MH370, as he was in the air and on that freq at the time.

Don't know what to make of this. :confused:

oldoberon 17th Mar 2014 16:42


Originally Posted by DOVES (Post 8383486)
I understand that the ELT is practically mute if itís underwater.
If it is so, also because of this ugly episode (it's not the first), from which we must learn something, is it not possible to invent something that can transmit the emergency message and its location even after a ditching?
I think of a panel that breaks down when immersed in salt water and so allowing the expulsion and emersion of the device.

Saw this idea somewhere, water soluble bags of highly concentrated fluorescent dye in wings and cargo holds,. I liked it because they were passive, ie no batteries or activation needed

Mr Optimistic 17th Mar 2014 16:44

Thanks re ATC. I read those posts relating to what another flight heard. What I don't know is whether ATC witnessed them disappear or whether they were operating by the clock only.

Re ELT. EM waves are going nowhere through water at that frequency so the thing would have to escape and swim to the surface.

island_airphoto 17th Mar 2014 16:44

These are common on boats. They break loose if submerged and come to the surface and activate themselves.
If you read the tech log, it is possible to get something like this for airplanes but not common.

GunpowderPlod 17th Mar 2014 16:47

On radar:

It seems to me that if a passenger aircraft is flying on established routes and at established flight levels with its transponder deactivated, provided it does not trespass into secure airspace, it will be ignored by military radar and invisible to ATC. This is rather worrying if I am correct.

On flight deck security. Surely it has to be improved now:

1. additional door to prevent anyone following crew through the single door when open i.e. an airlock type system

2. three flight crew, not just two, so that nobody is left alone on the flight deck while someone leaves for a break. The third member could be security instead of pilot.

diginagain 17th Mar 2014 16:50


Originally Posted by oldoberon
Saw this idea somewhere, water soluble bags of highly concentrated fluorescent dye in wings and cargo holds,. I liked it because they were passive, ie no batteries or activation needed

Some slight consideration might be given to a few scenarios. Flight in clouds, standing in the rain, or being washed, perhaps?

rigbyrigz 17th Mar 2014 16:50

Re: "Unless a time stamp is sent I do not see how a handshake initiated by the a/c would allow signal transit time to be calculated by the satellite"

The expert interviewed on CNN clearly said that at a regulated time interval (1 hour?) the satellite initiates the handshake attempt with a faint ping something like " are you there, got anything for me", and seems to id the a/c is same handprint as last time, and how far way it is based upon ping return time.

IE; The a/c did not initiate the pings we are hearing about.

oldoberon 17th Mar 2014 16:51

floatation water activated ELts are fitted to all PAX aircraft

Someone has already posted on this aircraft there was one on one of the pax doors (may have been all pax doors), BUT you have to manually release them from their stowage,

Wirbelsturm 17th Mar 2014 16:53

The ELT is embedded in a foam floatation device. It does, however, need to get free of the hull in the event of an accident as they are normally stowed within the hull space!

fluorescent dye is excellent BUT it is a short term solution as it does disperse very quickly dependant upon sea state, swell and wind.

There is a sonar locator beacon which will activate when submerged. This is normally good for 30+ days dependant upon water temperature and depth. The detection range for this device is also dependant upon depth, salinity and the isothermal properties of the water (layering). Depending upon the sensitivity of the detecting equipment (read the military won't tell you) the detectable range of the sonar locator beacon can be huge.

Pontius Navigator 17th Mar 2014 16:57

GPP, potentially correct. Except that as a non-transponder it will not have a 'friendly' track ID and the IDRO will contact the ATC to confirm identity if the track is inbound. In this case, before the turn back it would have excited no interest from the Malaysian AD.

GarageYears 17th Mar 2014 16:58

Lazy posters...
If you want to keep posting the same questions over and over, then this is going nowhere fast... how about you READ the THREAD before posting questions that have been answered over and over and over and over....

1) Rig worker - was 370 miles from the last reported position... you figure out where that puts the horizon even accounting for the aircraft being at 35Kft.... Also the fact that nothing more from the alleged source makes this even less believable.

2) Pings... The SATCOM sub-system is entirely SEPARATE from the ACARS system. The SATCOM terminal is simply one of the available transmission systems fitted to the aircraft. Just as the voice transmissions can be sent via HF, VHF, or SAT, so can ACARS messages. Therefore the act of deselecting ACARS does nothing the SATCOM transceiver itself. The INMARSAT system is effectively maintaining a "stay-alive" connection to the aircraft. The fact that the ACARS system was not subscribed to the SATCOM service isn't really relevant.

Sawbones62 17th Mar 2014 17:06

Mentioned before - ejectable, floating ELT
This is from the Tech Log thread - the ejectable, floating ELT called a Crash Position Indicator (CPI) has been around since WWIi. CPIs have fitted to helicopters, transport aircraft through the Tornado and Starfighter. The ELT is fitted into a floating "tumbling airfoil" and can contain a CVR/FDR.

Here's an example for the USAF C-141 original CPI, including multiple damage sensors throughout the aircraft and provision for a tape recorder for the CVR AN/URT-26 Crash Position Indicator

Other offshore industry and military examples can be found on Google.

The extra cost over ELTs made the CPI unpalatable for regulators and airlines, but that may change...with modern electronics it can be a very much smaller device using the 406Mhz technology and solid-state memory for FDR/CVR:


slats11 17th Mar 2014 17:09

Possible motive
1. Kidnap passengers as hostages? You would have to know that the pax on this flight were typically Chinese (most) and Malaysian. I can't imagine China would be keen to negotiate, nor to facilitate negotiations by the relatives. So this would seem a very poor choice of flight for this purpose.

2. Theft of cargo? For this to work, you would need accomplices and logistics at other end. This takes time to set up. How much notice would you have of an upcoming valuable shipment? Presumably not enough to get yourself onto that flight and organise the other end. Could it have been a spur of the moment opportunistic theft? Possibly. But the details we have suggest the reversal of course (and other things) was done very skilfully, and this suggests detailed planning. And you would still have to set up the other end. So theft seems unlikely.

3. Steal plane for some future terrorist plot? This is probably the most likely scenario for the "northern corridor." However, you would imagine the customer was most likely in the Middle East. You would also imagine the customer would like his plane stolen with the least chance of things going wrong. So why steal a plane heading east, and then have to reverse course and avoid radar of Malaysia, Thailand, Indonesia etc? There are plenty of MAS flights from KL heading to Europe or Middle East. Why not steal one of these flights? You could even cross India (legally) and then disappear - which would give you much greater range (Pakistan or Iran). For ME terrorists, an added bonus of a Europe bound flight would be a greater number of westerners. Do we know if the crew flew other routes?

4. "Southern corridor" scenario. Hard to think of a reason other than suicide and disappear. If this happened, the guy didn't want anyone to know for sure - he could have left a note, or even come up on the radio and announced his intention. Nor did he want the plane found. Reverses course and possibly flies low to avoid primary radar - unlike the customer in option 3 who has nothing to gain by playing games with radar, it is possible the pilot here enjoys the challenge of defeating radar. He then heads NW up Straits of Malacca, before turning SW when he is sure he is out of primary radar coverage. Why turn NW first? Well he does not want to be found. If he is picked up by primary radar, heading NW he looks like lots of other traffic heading out of KL or Singapore. If he went immediately SW over Malaysia and then Sumatra, this would seem unusual if anyone did see him on primary radar.

oldoberon 17th Mar 2014 17:09


Originally Posted by diginagain (Post 8383534)
Some slight consideration might be given to a few scenarios. Flight in clouds, standing in the rain, or being washed, perhaps?

and Wirbelsturm

Regarding other water sources yes, but they can be a lifed item or salt water soluble ( not good for the great lakes).

Regarding dispersal missed out that the idea was they were a gel to slow down the release and dispersal.

Still neither of you (like me) ruled them out as a good passive aid .

Still a place in the world for low tech! KISS keep it simple.

geneman 17th Mar 2014 17:14


To the precision of the ping arc:

GSM base stations have to know the timing delay between cell phone and base station. This timing delay is determined by "pinging" them. The precision of this measurement gives the distance between phone and base station with an accuracy far better than 550 meters.

That is an example for what precision is possible with everyday consumer electronics. I don't know the exact specs for inmarsat, but taking into account unfavorable geometry, I would expect a precision in the range of better than 5 km.
Given that the satellite is at an altitude of about 36,000 kilometres, a 5km precision would be about +/- 0.014% of the distance, which would be truly remarkable.

formationdriver 17th Mar 2014 17:14

MODS quit
Reading the last 70-odd pages of posts I suspect the PPRuNe moderators have been magically transported onboard # 370.
Come back.

Towhee 17th Mar 2014 17:16


So let me get this straight. Because the Captain is wearing a shirt declaring "Democracy is Dead" in protest of the overall UMNO/BN approach to government (and the obvious treatment of Ibrahim), and is a supporter of Ibrahim he is now more strongly considered to be some kind of hijacking suspect? What century are we in?

The pilot's viewpoints on politics and support of PKR are nothing special. There's quite a sizable contingent of people in MY with the same opinions and support for the opposition has been growing for years.

Secondly, Anwar Ibrahim is *not* jailed. The accuracy of modern media and "journalism" these days is just flat out appalling. It's no longer about being precise or accurate - it's completely driven by eyeballs.

Terrorists have won, haven't they? Time to burn some witches.
:ok: :ok:::ok:

It's outrageous to impugn the pilot based on his political support for an opposition candidate. Opposition, factionalism, dissent is the essence of democracy.

Unsurprisingly, these scurrilous allegations seem to be promulgated by the Daily Mail.

The DM is an aggressively right wing tabloid that mixes infotainment with ultra.conservative diatribe. It has a Nazi supporting lineage. Its US readership consists of white trailer trash and devotees of Faux news.

Malaysia is still a quasi authoritarian nation with limited press freedoms. It lacks a completely independent judiciary. It's had one party rule for way too long.

Reputable publications have covered the Ibrahim saga for years, so it surely doesn't take this tragedy to advertise the deplorable situation.

VH_BIL 17th Mar 2014 17:16

This is a fairly nice layman's description of 'ACARS pings' that have been wildly misunderstood on this thread...

Understanding ?satellite pings? ? Tim Farrar - The Malaysian Insider

For those still reading - this gives an overview of ACARS:

There are some AEEC standards documents in that document that contain the protocol definitions of ACARS.

From the document: "the AeeC Characteristic 741 for the satellite Data Unit specifies the use of an X.25 based protocol, which Inmarsat originally intended to be used for packet data communications across the AMss network. this complies with the protocol specified in the ICAO AMss standard described later in this document."

So it uses X.25 - there's some DTE address fields there.

It seems the ACARS "SATCOM" data stream in this aircraft was based on the Inmarsat Swift64 service and these terminals use an ISN which is a "12 character Inmarsat Serial Number" - so there's the layer 1 ID.

Although I haven't found those standard definition documents for this service, it seems like these 'pings' would be addressed directly to a terminal address (i.e. unicast to the specific ISN) rather than some random broadcast/multicast across the whole beam/coverage area (pointless thing to do).

X.25 can do the same thing - and the AeeC can do the same on top of that - apparently (according to AEEC 620 standard for ACARS) it uses a 7 letter IATA address (from the aircraft registration mark).

So there are three different addresses at three different layers that would be able to identify the signalling terminal.

As an aside, especially when talking about mobile/cellular phone systems, just because you know something about one system does not mean every system works similarly - (this thread contains mounds of rubbish on this topic).

Remember that there are 2G, 2.5G, 2.75G, 3G, 4G, LTE systems using Analogue, TDMA, CDMA, W-CDMA, FDD, TDD, etc all on different bands, with different design trade-offs and varied methods of implementation and completely different performance characteristics (and I haven't even mentioned the Chinese varieties like TD-SCDMA).

BTW - in the beginning "ping" was a UN*X utility designed to send ICMP packets for IP networks - named after the Sonar 'ping'.

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