RE FLOATING ELTs:
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.

Radar
 

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.

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

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.

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,

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.

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.

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.

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:

http://www.hr-smith.com/images/stories/503-CPI.pdf

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.

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.

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.

MODS quit
 

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

: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.

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:
https://www.sita.aero/file/1569/Aircom_new_generation_services.pdf‎

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'.

Possible motive
 

slats11

Good assessment of possible motives. What's missing is
- something spontaneous
- something not going according to plan
- a change in plan.

The Earth is Unimaginably Vast
 

For those who are frustrated at the apparent inability of modern technology to find a large passenger jet even after days of searching it may help to consider the following.

The total surface of the earth covers around 510 million square kilometres.
Water covers 361 million square kilometres and land 149 million square kilometres.

Assuming that a 777 jet (or wreckage) covered an area of 50 by 50 metres (a large over estimate), then that still only represents 1/400th of a square kilometre.

Given that the theoretical range of the jet covered nearly a third of the earth's surface (call it 150 million square kilometres), investigators are looking for a single point measuring at best 50 metres by 50 metres in all of that area. So 150 million square kilometres times 400 = 1 point in 1,600,000,000 possibilities at best. That is assuming the aircraft or wreckage are visible from the air. If it is under water or has made a smaller impact crater on land, the odds become even greater against locating anything.

Obviously the investigators are doing everything in their power to try and reduce the odds by calculating the most likely flight path, but the search is going to take a long time.

Yes, we can fly around the world by jet in under two days, or in 90 minutes with a spacecraft in low earth orbit. But the earth is still unimaginarily huge, despite the wide angle shots from ISS and the blue pebble photo taken from the moon (also with a wide angle lens).

I don't disagree. As a former SAR captain I have found the dye to be fantastic however it has a lifespan. The trade off between liquid dispersal and the slow release of a gel limiting the size of the visible area is one for the scientists.


I would guess that if the search area was located in the wrong area then the intervening time between dispersing passive aids and looking for them would defeat both liquids and gels.


Self detaching ELT's and SARSAT beacons are not very common on commercial airliners as they are, generally, not out of contact for as long as this scenario therefore the area of search is normally smaller and more located.

Relative precision doesn't matter. If you can measure 1 microsecond precisely then you can also measure 250001 microseconds with the exact same absolute precision.

A very GOOD explanation of the INMARSAT system
 

For those who seem to be struggling with the SATCOM/INMARSAT operation the following gives a very good overview:

TMF Associates MSS blog » Understanding ?satellite pings??

Hopefully this will put-to-bed the repeated questions regarding this!