oviano: I should have been less cryptic. Sorry. :)

There was nothing "sudden" about their progress in the search. This search has been going on for over a month. We in the public are not priviy to all of the details of what they consider, what they reject, and what their cueing and trigger information have been.

Part of what they are doing involves the process of elimination, and making the most of such clues as are available. If we let the drama infested media influence our understanding of this search, we can fall into the trap of assigning traits like 'sudden' to events that unfolded over time for the search team and various national authorities.

They were indeed searching huge areas, but the areas have been shrinking every few days. Nothing strange, nothing sudden.

What took a lot of people by surprise (myself included) was the public announcenment that the early searches in the South China Sea and Malucca Straits needed to be abandoned, and a search far off the coast of Australia in the middle of nowhere granted precedence.

As I understand the background of this search, the indicators that this was a better course of action did not arrive suddenly, but were derived from the process of vetting and analyzing the sparse information available. No drama: plodding detective work.

I thought it was the 'boring' work of ongoing detail analysis of the Inmarsat data coupled with more refined analysis of 777 performance characteristics that fit to the pattern of known arcs and dopplers that lead to deploying listening assets in the 'small arc' where Haixun 01 and Ocean Shield were operating.

It seems quite likely that after a lot more hard analysis of the acoustic data they will have localised a reasonable search area and then in several weeks will have found the wreckage with the side scan sonar.

Nothing particularly sinister in all of this analysis and thinking taking a lot of time.

IATA code coincidence...
 

Using IATA codes instead of ICAO reveals a bizarre coincidence:


Originally heading for PEK
Turned west to PEN
Turned south to PER


All of which are MH served destinations, alphabetically ordered same as above...


772 FMC uses ICAO codes though, does it not?

Why new location
 

It was the realisation that the aircraft was flying lower.

The resulting faster IAS, slower TAS, and thus slower groundspeed - and the resulting shorter range - meant that the search location had to move along the last ping-ring towards the northeast. Simple, really.

What we don't yet know, is why they suddenly realised that the aircraft flew at low-level.


P.S. If someone can post the fuel-burn/altitude tables for 1,000' and 10,000', it would be fairly easy to calculate roughly how low it flew.

Also it is possible a classified asset heard it first and a hint was dropped to get everyone in range of the pinger ;)

I think the reasoning was the reverse. Assume last ping was at out-of-fuel. That gives a fuel burn rate which can then be reverse looked up to find the cruise levels/speeds that would result in that burn rate now fit those speeds/levels to the several INMARSAT rings the one that most closely fits tells you where on the final ring the aircraft was out-of-fuel. Use simulation of aircraft behavior when fuel is out at that level/speed, then generate a new search area. Pingo :D

It was the analysis of the INMARSAT data that lead them to the current search area, much the same as AF447.

In response to posts regarding the difficulties posed in recovery operations in the particular search area I would add as follows.
I understand the search area is over the Wharton Basin. A deep drilling operation of the sea bed of this basin has been carried out some years ago for scientific purposes. I would imagine the search effort being conducted employ the benefit of the knowledge gained from this survey. Detailed information on the deep drilling survey, bottom depths and deposits may be found at the following links.

http://www.deepseadrilling.org/26/volume/dsdp26_09.pdf

http://www.deepseadrilling.org/22/vo..._appendixI.pdf

http://www.deepseadrilling.org/26/volume/dsdp26_36.pdf

As pointed out by hamster3null this location is also in the area where flight path M641 crosses the projected position curve for the last ping.

No, there was no INMARSAT analysis performed in the case of AF447, it wasn't needed.

MH 370 altitude
 

Not entirely correct.

While the Imarsat data gave the general area to look in, the final ping-ring still gives us an arc a thousand nautical miles or so long. All the search zones were along that arc - but which segment of that arc is correct?

There needs to be a method of fine-tuning the information.





Amended due to post 9719 by Ian W below.

You are right that the fuel burn remains the same, for all the various speed/altitude scenarios, because the fuel load is known and the time is known. But we still have various potential tracks depending on the speed/altitude of the aircraft.

You can have a high-TAS-speed flight at high altitude - and end up south and west of Australia. (Yellow track.)
You can have a low-TAS-speed flight at low altitude - and end up north and west of Australia. (Purple track.)

So we come back to the same question I posed above - what made the search teams decide that the low level scenario was the more likely? Although the burn-rate is a known factor, there are still numerous speed/altitude combinations that will achieve that same fuel burn. Thus there still must be some other information that prompted a look towards lower and thus altitudes/slower TAS speeds (the purple line). Perhaps it became likely that the aircraft never climbed again, after its assumed descent to to low level while skirting Malaysia.



Note how each hourly ping lies on the same ping-ring, but end up hundreds of miles apart - even though the fuel burn is the same for each hour flown.
These tracks below are for illustration only, and are not to any exact speed-scale. *

http://i59.tinypic.com/57cwz.jpg

They MAY do this if they want to make a tighter turn, but you really try to avoid this when towing, as you lose all the time turning and not searching.
Typically you run a racetrack type of search pattern to optimize the depth and the search area.
While it is called mowing the lawn, it is not efficient to directly overlap paths, you just keep moving the entire racetrack over...

http://i60.tinypic.com/xpyhbm.jpg

"Analysis by the British satellite company Inmarsat and the UK's Air Accidents Investigation Branch (AAIB) was cited on Monday by the Malaysian prime minister as the source of information that has narrowed the location where the Malaysia Airlines flight MH370 may have crashed into the southern Indian Ocean to a corridor a couple of hundred miles wide."

The new method "gives the approximate direction of travel, plus or minus about 100 miles, to a track line", Chris McLaughlin, senior vice-president for external affairs at Inmarsat, told Sky News"

For AF 447, BEA used the sat data to narrow the search area when it was found by Swire Seabed...it was found long after the pingers stopped working.

a "towed pinger locator remotely operated vehicle" doesn't make any sense. Neither does an ROV for locating pingers. Any ROV has a huge disadvantage: propulsion noise. I can't think of any advantages, it would still need to be tethered to a mother ship. So why exactly would you want an ROV for that?

The Blufin 21 platform can be equipped with a PL, no problem. There is at least one from the US Navy on Ocean Shield.

Currently, it can be also be outfitted with sidescan, magnetometer, and video...it is completely autonomous...

EDIT: You program the path of the fish, and to surface at intervals to charge and send data. You can program it to surface at contact as well.

That is certainly a possibility and has been used before.

«look here» to a trusted ally then take it overtly from there.

RS, I am quite certain it is not the Capt driving the search pattern parameters. Why would I mention your name?

Coding course paths for surface and subsurface vessels is much the same as a coded flightpath for an aircraft.

When mapping, a surface vessel is typically on a coded course. When towing an array, the coded turns must take into account the towfish depth and dynamic properties. The fish must stay at depth for proper mapping overlap.

Look at the search pattern that I provided, and you will see that it is much more efficient.

I have been providing mapping patterns for autonomous underwater platforms for telecommunications cable laying for several years, so commercially, we understand how to map effectively. When one is paying for fuel, one learns to be efficient.

EDIT: I would also take note of the TPL shown in the image above. (post 9682) IF that is the actual configuration, it is not correct, which is likely why they have to tow it so slowly. A higher speed tow would involve a towfish depressor weighted wing in front of the array. The wing would keep it at depth with far higher speeds, about 7kts instead of 2...

You misunderstand.


We know (or at least assume we know) the initial track of the aircraft to loss of radar contact
We know the fuel load the aircraft carried and the last miss-ping gives us the out-of-fuel time therefore we know the burn rate.
That burn rate can be achieved in a limited number of ways - assume it is relatively constant from loss of radar contact.

Then use the different levels and speeds that give that burn rate and see which fit the ping rings.

We may of course be having a noisy agreement - but the burn rate is simple - time of flight and known fuel upload adjusted for initial tracked flight. Assumption necessary is that the aircraft maintained a steady cruise.

Agreed, but AIS data I have just seen from Ocean Shield indicates they are more focused around 21°06'S 103°54'E, and the latest positions indicate the vessel is crabbing its way to the north again on 293°/113°T tracks.

http://oi57.tinypic.com/4ixwlk.jpg

The latest position at 10/04:50 UTC is 21°08.5'S 104°10.2'E and heading 113°T. The speed is currently 1.7 KTS.

I am curious why OS continues all by herself?
The other search area has 6 search vessels..

http://i62.tinypic.com/11iztis.jpg