@Shadoko

I would suspect the identical lines to belong to one data block that was transmitted in sub-blocks which were logged with the time stamp of the time when the block was completed.

I agree on the time resolution being 20µs. Taking into account it's round trip time and 1µs corresponds to 300m at speed of light, the line of sight resolution is 3km. With an elevation angle of ~45° the lateral resolution on the surface would be ~4.5km.

Long SATCOM messages will presumably be split into the initial signal unit that identifies the type of message, and multiple subsequent signal units containing the rest of the data. Could also be retransmissions, but I'd expect to see some kind of 'NAK' message from the aircraft before anything was retransmitted.

Hadn't noticed that until you mentioned it, but it seems likely. Given the low bit-rates of the channels, I'm not sure you could measure it to microsecond accuracy. That would also be consistent with the 10km accuracy mentioned in the 'considerations on defining the search area' document. Twenty microseconds looks like about 6km to me.

Ian W

Thanks for the clear explanation http://www.pprune.org/rumours-news/5...ml#post8492799

I note you had previously said: "the Malaysian ATC followed the book pretty well. They were not responsible for the aircraft which had been handed off and accepted by Ho Chi Minh center."

I just wonder where the certainly about handover and acceptance comes from. There are some anomalies:

(1) The Malaysian Preliminary Report does not say that the aircraft had been handed over and accepted.

(2) Both the Preliminary Report and the "Action Taken" document specify a lot about what KLATCC did to find the aircraft. For example in the PR "Thereafter KLATCC initiated efforts involving MAS OPS Center, Singapore ACC, Hong Kong ACC and Phnom Penh ACC to establish the location of MH 370. No contact had been established by any ATC units and thus the Rescue Coordination Centre (RCC) was activated at 05:30 MYT". Discussing what KL did is all rather beside the point if it is HCM's task and responsibility to contact the aircraft. Would it not have been HCM's responsibility to activate a search? [I do understand that much of this activity would be necessary to respond when HCM "asked Subang - 'Is MH370 still with you - he's not talking to me'".]

(3) Vietnam apparently denied responsibility Vietnam requests Flight 370 information after Malaysian claims | DTiNews - Dan Tri International, the news gateway of Vietnam saying "“In fact, there is no evidence that the aircraft had passed through the “Igari” way-point and entered our country’s airspace,” said Lai Xuan Thanh, Director of CAAV.". [I do understand that handover and entering the countries airspace are not necessarily the same thing].

I'm not trying to construct any conspiracy theory, I agree with you, peacetime, no threats apparent etc. I am just curious to understand. It seems pretty clear that HCM had probably accepted the aircraft, as they were the first to raise a query with KL, but the curious points above remain.

Raw data PDF
 

OleOle: Yes, 4.5 km. And because they are very cautious (and from data not absolutly steady when the a/c was stationary) they double it to ±10 km.

Another thought: After the handshakes at 19:41, 20:41, 21:41 and 22:41 there was no handshake at 23:41. It was (long time ago!) presumed as a "miss". But it is well explained by the sat call (from ground) of 23:15: this call attempt reset the one hour timer and so the next handshake was at 00:15. But no "ring" because C-channel BTO is not filed.
Seems consistent?

If you compare the PSR track (in the recent ATSB document) to the map on this post ...
http://www.pprune.org/rumours-news/5...ml#post8364326
It seems pretty clear that someone was aware of the PSR track very quickly after the incident. The "E" box being the area where they lost PSR coverage.

I do wonder what altitude the aircraft was at when it passed Butterworth.

Raw data PDF
 

"Raw data PDF": 18:25 - Log-on Request, initiated from the aircraft terminal. This is the end of the link lost period that began at sometimes between 17:07:48 and 18:03:41.

What it the meaning of that?
- a trick (before turning South) from somebody who handled the a/c knowing it had have to be "viewed" on a west route?
- an automatic sat link after HF was available along the route above Malaysia and lost again?
- some automatic data Tx from a so big change in flight caracteristics it had to be "signaled" for frequency or BFO adjustment between sat and a/c?
- ... ?

It would be interesting to know what were the subsequent "user data".

I believe if you make a sharp turn and blank out the aerial, comms with sateliite has to be restablished. presumably from aircraft end.

That's certainly a possible cause, but I would expect the aircraft to try to log on again soon after the turn. In this case, it appears to have been out of comms for at least 22 minutes.

I don't know whether there's any way it could have thought it was still logged on, but not have responded to messages from the ground? If it was still receiving the satellite signal, it should presumably have received those messages and been able to respond.

HrdoAcoustic Detectors
 

I found this from ATSB interesting:
Low frequency hydroacoustic signals present in the Indian Ocean are being examined to determine whether they can provide any information to help define the search area. These signals are recorded by hydrophones as part of the United Nations Comprehensive Nuclear-Test-Ban-Treaty Organisation (CTBTO) or the Integrated Marine Observing System (IMOS).

Way above my pay grade but wouldn't one have expected it to be done long ago?

I assume that as well as the U.N. hydrophones it is entirely possible that there are military arrays as well?

The Vietnamese have indicated that they saw the plane turn around but they didn't give any details as to whether this occurred before or after the transponder was turned off, but if we assume that it occurred after the transponder was turned off we will know that Vietnamese primary radar tracked the flight as early as 1:22 local time. The Thai government has stated that they first picked up the flight at 1:28 'flying in the direction opposite from the MH370 plane, 'back toward Kuala Lumpur' (paraphrased.) The Malaysians have remained vague and the Indonesians have left it up to the reader to read between the lines to know that they tracked the flight at all. (see my post above)

As to the Vee shaped flight path in the diagram:

I see no reason to think the flight went near Butterworth; the pilot had brought the plane down to low altitude to avoid (at least) Thai radar, and ground speed was suffering as a result; he (or she) would have wanted to clear Thai/Malaysian airspace as quickly as possible so I predict a turn towards MEKAR somewhere around 5°36'25.08"N 101° 6'29.92"E (or about 45nm ENE of Butterworth.)

Extract of the explanations in the PDF:

- ACARS Messages are Ground to Air.
- link lost period that began at sometime between 17:07:48 and 18:03:41 due to electrical power issues?
- why no more Ground Initiated to Air Telephony Calls ?

Both Ground Initiated to Air Telephony Calls tried 1 minute before the caller gave up. Even though nobody picked up the phone, the terminal itself acknowledged it was there. Was it ringing in the a/c? Was the caller on the ground aware, that the terminal was still alive?

I haven't looked at the precise times, but I would presume either the airline or ATC called when they disappeared and couldn't be contacted by radio, then called again when they were overdue at their destination. Not much point calling every ten minutes if no-one is responding.

Somewhere there will be a record of who made that call.
Has that information been made public?

It's infuriating how coy the Malaysians are being about the plane's PSR altitude profile after the transponder datastream stopped. This information is so critical to understanding what may have happened.

This is quite exactly 1 hour after the last SSR response.
I bet this is not coincidence and there is some technical explanation behind it.

Also: the 00:19 Log-on request was explained as a system restart after flame-out and subsequent RAT or battery kicks in or whatsoever. How then is the 18:25 Log-on request explained? There would have been no flame-out before that time. Generators failed? APU not started? Low altitude? There must be a technical reason for that, too.

It is probably this report from Ho Chi Minh that they had seen the aircraft turn back (presumably on PSR) that was why the Malaysians took on the RCC role rather than the Vietnamese who were meant to be the control authority, or the Singaporians whose airspace the loss of contact occurred in. It is another reason that the loss of contact appears too well timed to be coincidental with an in flight emergency. The subsequent track and profile of the aircraft was also not what one would expect from an aircraft with a severe emergency. This is no doubt why the Malaysians seem to think this was a criminal act.

Quote:
23:13 - Ground Initiated to Air Telephony Call - Zero Duration (Not Answered)
Somewhere there will be a record of who made that call.
Has that information been made public?


I have followed this thread from the very beginning and I believe this call was made by someone from Malaysia airlines. I can't find the exact reference but I remember reading it in a transcript that someone (perhaps maintenance personnel) called the plane when the controllers couldn't see it on radar.

Threemiles,

The 18:25 logon was initiated by the aircraft, if you refer to the Inmarsat BFO graph it mentions possible turn. Had a tight turn been initiated that shadowed the SATCOM beam, this would have been when the aircraft reacquired the satellite (bank reduced to the point of reacquisition).

Cheers

Looking at the relative positon of the aircraft and satellite I don't think a left turn wound have screened the aerial but a right hand would, remember the chinese video to the pax, that had a right hand turn??

I don't think a turn causes a logon. This would generate endless logons when airplanes fly holdings or so.
To me a logon would happen after some kind of system restart. As if you boot your windows computer.
I do not see a difference in the sequences at 18:25 and 00:19, that makes it strange when the latter was very firmly associated to a power up.
I would believe that this system behaviour is essential to the investigation and it should be replayed on board a real life flight. My feeling is that there is more involved than just a manual intervention by someone onboard.