My understanding of the two measurements is
1 Doppler - which is a measure of the frequency shift of the Aircraft signal when received at this earth station and is dependent on the accuracy of the 'transmitting frequency' probably more accurately the precise bit rate. For the system to work, this needs to be very very accurate but is not a 'clock' in the sense of having a specific time, just a very accurate period between each bit. This measure tells if the plane was generally North or South of the satellite. I believe based on Inmarsat knowing the satellite's movement. But doesn't tell us much about the aircraft's speed or direction of flight.

2 The Ping - which is a time delay and tells us on which arc on the Earth the aircraft is located. The general conversation implies that it is a round trip delay of a message packet, however, it appears there is also is a calculation the satellite does to tell the Aircraft station what delay it needs to use from the satellite's reference clock in order to fit into the assigned TDM slot. This would be a pretty accurate number I order for the system to work effectively (because the more accurate each station is in hitting its time slot, the less buffer is needed between slots and the more data that can be transmitted). So if the arc is determined using this piece of data, it should be pretty accurate and pretty much independent of the condition of the Aircraft station.

I am sure a real expert will correct any errors. But from my perspective it seems very unlikely that Inmarsat will have gotten the Doppler direction wrong or the arc wrong. However, where the aircraft actually was on the arc depends on the assumptions of how fast it was going, and how steady that velocity was.

Re: Inmarsat data
 

@WillFlyForCheese
Inmarsat have said that they have indeed validated their findings by running the same analysis against their data from other scheduled MAH B777 flights where the flight path is known.

Blacksheep`s commentary makes a lot of sense in setting out the limitations of satcom data analaysis carried out by INMARSAT.
INMARSAT announced that after six complete handshakes recorded at the ground station following ACARS, the a/c`s operational comms sytem stopped sending messages. INMARSAT was then able to calculate range of a/c from sat and time taken for signal to be sent and received. They then generated the well published Northern and Southern Corridors. Which seemed to cover a large chunk of mother earth and water. So got their heads back down and developed a second innovative technique which took into account the Doppler effect, which we all know from watching ambulances, police cars and for train spotters, locos. They analysed the frequency that the ground station expected to recieve and the one actually measured, which they told all is called the Burst Frequency Offset. They then checked this prediction with six other B777 a/c flying on the same day in various directions which resulted in a good match with the Southern Corridor. So off went all the troops in that direction.
So it would seem to me at least, that the whole thing is built on much theory and little hard fact. Until such time when some debris is washed on someone`s shores nothing will be known.

Nuclear Sub Added to Search
 

Now that HMS Tireless, the oldest active member of the Trafalgar class, has been added to the search, do we need to reconsider the usefulness of such an asset in light of lessons learned with AF447? In the AF case, the open literature suggests the on-board acoustic sensors were unable to locate the black boxes but we now know that the pinger on the CVR was defective when finally recovered. Perhaps some of the bright boys have added functionality, within the limits imposed by the physics of the actual sensors, to detect relevant frequencies. Sadly, Tireless, once scheduled to be retired last year, is also the only Trafalgar class not to retrofitted with the Sonar 2076 system, which the RN claims is the most advanced in the world. Seems like an odd choice on the surface (pun?) but perhaps in this case older is better while avoiding revealing just how good the new kit is.

Preliminary incident report within 30 days
 

Under the terms of the IATA/ICAO treaties, the authorities in charge of investigating an aircraft incident involving death are required to publish a preliminary report within thirty (30) days of the incident. Recent experience with the Malaysian government suggests we should set the bar for details and truthfulness pretty low. Perhaps April 7th will come and go with no report at all. After all, there is no evidence of casualties. Nor, to be precise about it, is anything definitive known about the incident/accident. It would be nice to know the assumptions, science and conclusions which underpin the search and investigation so far, but they would not necessarily be described in an accident report. It is disheartening to imagine that we may never know what happened to MH370. Even worse: we may never find out why the search took the turns it did.

Re: Inmarsat data
 

@WillFlyForCheese

I agree; as the UK AAIB have reviewed Inmarsat's work, presumably they have reviewed these tests as well. That the source data has not been made public has caused much debate here on PPRuNe.

I don't understand what Inmarsat are showing on their "Burst Frequency Offset Analysis" chart for the time-period, from take-off up to the time we are led to believe last primary radar contact was lost at approx 18:20UTC i.e. what the "Predicted Track" represents for this time period - the measured track here appears wayward but after this point it follows their Predicted Southern Track.

It is disappointing the Malaysians have not made public a definitive track from the last known position in the South China Sea at 17:20UTC, when the transponder stopped, to the position of last primary radar contact in the Strait of Malacca at 18:20UTC. (The Chinese media have released an alleged, incomplete, trace for the Strait of Malacca, but the Malaysians refused to comment on this.) I suspect that events including route/speed/altitude etc in that missing hour are key to this mystery.

Chinese radar track
 

@biggles:
The only radar track that I've seen from the Chinese (families) is in the South China Sea/Gulf of Thailand.

Is there another (Chinese version) for the Malaccan Straits?

Anwar Ibrahim talks of Malaysian Government cover up ?
 

Do not know how reliable this report is but it makes interesting reading - Anyone got anything to add to the details on radar Capture .

MH370 Malaysia Airlines: Anwar Ibrahim says government purposefully concealing information - Telegraph

@dicksorchard. Nothing like some political noise to keep people stirred up. Does BFA to help find the missing aircraft, however ... comments on the criticisms from the political opposition.
Gee, political opposition indulges in speculation about the evil in current party in power. Straight out of Politics 101 playbook. Not original. I'll suggest the man has never served a day in uniform, nor ever sat at a radar console on the mid watch. Indeed, if it was on, operating as advertised, and manned. Maybe nobody told the Air Force Planes to go. Maybe they were not in the Alert 5 status at midnight-ish on a Friday night. Fair statement. Maybe they saw it and it didn't register that something was well out of order. See above: midnight to dawn shift, your A side is probably not on watch.

@mickjoebill: why would they leave the navlights on if it's a human up to no good? If it was a "something's wrong" scenario, interesting idea there.

Regarding the 30-day prelim report requirement
 

Poster "YYZjim" recently noted the standard requirement of a preliminary report at the 30-day mark. Also noted was that one could argue as to whether the triggering event is known to have occurred - there's obviously no physical investigation site yet, etc.

In my legal view, there is unequivocally and literally zero basis to regard the incident as in abeyance. True, no wreckage (or other confirmatory physical evidence). But certainly the 30-day clock began to wind at the point in time no later than scheduled arrival plus 24 hours. I'd not want to advocate for any entity with any degree of involvement in the Mystery of MH370 that the fact of said Mystery bars the 30-day clock from starting to wind.

But that timing point is merely procedural. The substantive stuff is hinted at by YYZjim's noticing that Malaysian authorities seem not prepared to add generation of such a report to their already-overwhelmed capacities. One realizes the ICAO legal system does not presently contemplate, and perhaps does not even allow, a kind of mobilization of investigatory, legal, and technical expertise on a multi-national level. But this incident dramatically breaks the mold - and it's a fair bet that when the facts ultimately do become known, that breakage will extend far more deeply. So it is time to innovate, on the legal and administrative agency front. (I won't repeat earlier posts advocating broad outlines of such new approach.)

I think this a bit humorous, who cares about 30 days, 60 days, etc.
Cameroon didn't bother to release any preliminary report when KQ507 crashed and the final report was released like 3 years after the crash.

Possibility Set
 

A. Inmarsat got it completely right and MH370 came down in South arc.

A1. Controlled ditching left nothing on surface
A2. Debris not yet found

B. Hole in Inmarsat calculations as noted by Duncan Steel and MH370 came down in North arc.

B1. Landed in North arc and concealed. Passengers???
B2. CFIT in mountainous terrain while flying below radar.

A1 looks most probable at present.

If/when raw Inmarsat data becomes available, Duncan Steel's possibility set will be either validated or dismissed.

The big difficulty with the Inmarsat analysis is that the equipment in the a/c was in a suspect condition. Possibly it had suffered physical damage from an event or it had been switched off. For equipment that isn't designed to stop cleanly on switch off, very odd things can happen as the supply rails fall so instead of some meaningful 'ping' that everyone has been analysing, they might have been analysing a 'chirp' as the volts die. A huge amount of weight seems to be given to this analysis. I'm with the group who feels that case is not proven. The a/c might be anywhere, even landed softly enough to let some or all souls survive. I hope so.

ELT changes?
 

I've seen elt's fail because the antenna lead was ripped off the antenna at time of crash

I would like to see other methods trigger the ELT to transmit.

May I offer this:

Instead of JUST using impact G loads or even salt water emersion, how about: a timer.

During pre flight the timer is set for fuel exhaustion minus 30 minutes ( or anything you like ). It can be reset upon the ground (WOW switch for example) after safe arrival (do your checklists boys!)

But if you fly till fuel exhaustion time, its been sending out a signal for 30 minutes to aid in finding your plane.

Inmarsat publication: original docs
 

The most official (and, IMHO,,accurate) info about maths done for looking at MH370 tracks is there:
You searched for mh370 - Inmarsat
It seems all those who have tried to make their own "predictions" from published pings data are coming with too high Doppler values vs the published chart.
With the chart, Inmarsat published this:
http://www.inmarsat.com/wp-content/u...tributions.jpg
and also a worded explaination ( http://www.inmarsat.com/news/malaysi...tails-uk-aaib/ )OK, this is for the "arcs".
This follows:And this is the Doppler from which is the well known chart.

But what is D1 in above picture? Is this the part (?) of the Doppler corrected by the a/c unit (as explained by mm43: http://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost-457.html#post8416026 ) But then, what is D2?

Could be that the frequency (from the a/c) is corrected to zero Doppler (from true frequency received and internal clock), and Inmarsat made the measured from the length of the bits of data (lower "frequency" > lower Doppler)? Perhaps a stupid guess...

Not quite true - the UK has fighters on QRA that are quite regularly scrambled to assess civil aircraft, from hijack to commuter aircraft failing to flight plan or to navigate as expected; and of course the occasional Russian probing flights. This has been the case for decades. The Contiental US did not have any similar QRA capability until after 9/11 - a case of once bitten twice shy.

I see they have announced that they have deployed the towed pinger locator".

"The hunt for the missing Malaysia Airlines plane has shifted below the surface, with the "towed pinger locator" deployed on Friday to search for the black box before its batteries expire.

A stab in the dark!

However, a chance for the ship's crew to get familiar with towing the TPL25 at depth, including the constraints on speed and manouvering.

True.

We don't even know they made that assumption for some time.

As pointed out below, there was no assessed air breathing threat to the CONUS so your military was effectively stood down prior to 911.

I think many people in a similar situation would be covering their six rather than admit out right that - they didn't notice, they didn't think, they weren't looking etc etc. It needs a special culture to say - Boss I goofed and for the Boss not to cover his 6.

@ShadokoI don't think it's a stupid guess at all.

A while back in the thread there was an excellent post explaining the nature of the satellite/aircraft handshake (the "ping"). This included a requirement for the aircraft equipment to Doppler correct its transmission to the satellite.

That being so, it's also possible that Inmarsat may have done some of its analysis not based purely on the straightforward Doppler effect between aircraft and satellite, but on the residuals left after that correction took place, whether in terms of uncorrected shift or some other consequent effect.

It's also noteworthy that Inmarsat were at pains to state that they had calibrated their work against other southbound Malaysian B777 flights. The specificity of that statement implies that such a calibration may not have been valid if done against a flight by another carrier, or by another aircraft type. Or, indeed, on another routing. Perhaps the work relies, in part at least, on the specifics of the performance of the particular equipment build installed in MAS B777s??

If so, then attempts to reconstruct what Inmarsat have done based purely on the freshman physics of the Doppler effect and basic orbital mechanics are doomed to failure.



As for why Inmarsat haven't released the full details of what they have done, a few potential explanations come immediately to mind:

1. It's just too complicated for ready public consumption . These are press releases, not technical papers, after all. The Doppler effect and geostationary orbits are pushing at the limits of public understanding as it is. I am sure that those who need to know have been given full briefings.
2. If their work relies on the specific performance of the equipment build installed on the aircraft, then divulging details could well compromise the commercial confidentiality of the equipment supplier.
3. If this really is "cutting edge" science (a description that doesn't exactly apply to orbital motions and the Doppler effect, after all!), then they may see commercial opportunities for what they've done and want to protect their interests before making a full, public disclosure.

Just a few thoughts... :)