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Quote: Quoting jcxroberts (Reply 303 from previous part): People really think Australia would have missed this plane ? I don't, they use the same radar systems as the U.S., more or less. Jindalee has coverage over that area.

This has been discussed at length in previous parts.

Quote: Quoting nupogodi (Reply 305 from previous part): JORN is fancy, but if they weren't looking, they wouldn't have seen it. Yes. Australia could have "missed it". You know, *it* being something they weren't looking for, over a thousand miles offshore...

      

You can find out a surprising amount about Jindalee from this Australian Air Force fact sheet. The important point is that JORN has to have its energy focused on a particular area or 'tile' within its range to potentially be able to detect a moving metal object. How likely is it that the relevant Australian authorities were alerted in time to even start using JORN, and who would have told them where to point it?

[Edited to include, and then to remove, reply to decoder. Now posted separately below]

[Edited 2014-04-22 23:51:23]

Quoting cbrboy (Reply 1): How likely is it that the relevant Australian authorities were alerted in time to even start using JORN, and who would have told them where to point it?

Considering they had everyone looking around SE Asia for a week, I doubt they'd even be told to be ready to look, let alone where to look.

Patience is the key. They found the AF, they will find the MH. I do not understand why people blame InMarSat, the system was never meant to be used in that way. So even if their calculations are way off (which I do not think) they are not to blame. We might be looking at the first case in which an airliners was directed in a way to make it disappear forever. That is a first.

[Edited 2014-04-22 23:58:54]

[Edited 2014-04-22 23:59:22]

Quoting seahawk (Reply 3): I do not understand why people blame Immarsat, the system was never meant to be used in that way.

Who was blaming Inmarsat? They've done fantastic work. It'd be nice to have a full writeup on the methodology and the whole dataset and honestly, knowing academics in aerospace, they'd love to provide it and share it (just to show off) but their hands are tied. I hope if anyone working for Inmarsat is reading this forum, they don't think the world doesn't appreciate their work...

(Also if you're having trouble spelling it - International Maritime Satellite. InMarSat)

[Edited 2014-04-22 23:30:53]

Regarding the apparent unlikeliness of Ocean Shield detecting the pings so early into such a massive search, it would suggest one of two things:

A) They got extremely lucky.

B) They got better data than is made public.

Such data could include a range of classified or proprietary information, such as JORN radar data, better quality satellite data, an accidental detection by undersea assets such as submarines or early warning acoustic detector networks similar to SOSUS, or more tangentially, a seismographic station detecting the aircraft hitting the water.

Quoting decoder (Reply 5):

IMHO both your A) and B) apply. Presumably the authorities have Inmarsat's 'ping rings' for all of the pings, plus I would not be surprised at data having been gathered from one of the other sources you mention, with the exception of JORN.

From thread 56:

Quoting 9MMPQ (Reply 204): I have no idea where you get this ''fact'' from but it completely ignores the entire cargo process as it exists which already starts from the shipper onwards.

Quoting bluesky9 (Reply 284): Yes it turns out it is probably going to far to call this a "fact". It is widely reported on the internet, though I wouldn't call the sources authoritative . Some specifically mention that the X-Ray scanning was out. It was mentioned by some posters here gr325 Reply 238 Part 24 - quoting tweets from @TheLeadCNN & @flyingwithfish (these tweets exist, though I cannot see whether this was actually retweet from CNN) , also Dalavia Reply 344 in Part 24, nm2582 Reply 118 Part 25 - reported rumours cargo wasn't scanned, PlanesNTrains Reply 188 Part 26 says "cargo not screened on this flight", slinky09 Reply 28 Part 26, "Some reporters have talked about cargo not being screened", and others.

It's one of these things in the investigation that do not take normal procedures into account & the next thing you know it gets taken so far out of context that people start assuming all there was onboard was unsafe cargo. Because this is then found all over the web it starts to become accepted as a fact. I just figured putting up a reply and answering on something like this which does of course amount to a drop in the ocean but nevertheless.

Another example today is the news that investigators are considering going over what they have so far again. Now over breakfast i've been reading the news and already that has spun into:

1: Investigators consider rethink on investigation so far.
2: Sources close to investigation say rethink considered as aircraft may have ended up elsewhere.
3: Sources close to investigation say aircraft landed elsewhere.

Now i might have the benefit of checking up on several sources of news together with some aviation industry inside knowledge but from time to time i still get surprised about some of the stories out there. I guess nowadays we can all be a source close to the investigation that can not be named.

Surprised Waihopai didn't pick up MH370? I'd have been utterly floored if they had.

Quoting decoder (Reply 5): Regarding the apparent unlikeliness of Ocean Shield detecting the pings so early into such a massive search, it would suggest one of two things: A) They got extremely lucky. B) They got better data than is made public.

There is unfortunately a third alternative:

C) The acoustic pinger Ocean Shield detected was not that of MH370 but some random pinger related to fishing, ocean research or something similar, and therefore the true final resting place of MH370 is not in the current underwater search area
 

They just mentioned on ABC news that debris of some kind has washed up on shore in WA. The debris have been secured and photos sent to investigators to see if it's related to MH370.

edit: twitter links from an abc reporter

https://twitter.com/BeauPearson/status/458891091354193920
https://twitter.com/BeauPearson/status/458894880333234176

[Edited 2014-04-23 02:23:59]

[Edited 2014-04-23 02:24:46]

Quoting 9MMPQ (Reply 7): I guess nowadays we can all be a source close to the investigation that can not be named.

Now that certainly opens up for perspectives almost beyond imagination!

Quoting LandSweetLand (Reply 10): They just mentioned on ABC news that debris of some kind has washed up on shore in WA. The debris have been secured and photos sent to investigators to see if it's related to MH370.

The age are covering this also, lets hope its not junk!!

http://www.theage.com.au/national/po...nd-on-wa-beach-20140423-3747z.html

source:http://www.themercury.com.au/news/world/malaysia-airlines-plane-missing-debris-washes-up-as-tony-abbott-says-search-wont-be-abandoned/story-fnj3ty5y-1226892871899

Regarding the debris: ""The more we look at it, the less excited we get.""

http://news.ninemsn.com.au/national/.../possible-mh370-debris-found-in-wa

Nevertheless interesting. If it pans out, it would seem to indicate that the current search area is not the right place, and that the actual crash site must have been more like at 40 degrees south latitude.



Squares are possible search areas; diamond is where the debris washed up. Note that arrow by Augusta is a little misleading: the warm water current in red hugging the West Australia coast is the Leeuwin Current that actually flows toward the south.

The Leeuwin Current, according to most Aussie press reports I've read this morning, carries a lot of stuff with it and deposits it near Augusta. The current search could still be right.

Quoting WarrenPlatts (Reply 15): Nevertheless interesting. If it pans out, it would seem to indicate that the current search area is not the right place, and that the actual crash site must have been more like at 40 degrees south latitude.

I can't be that sure, that map does not do the Leeuwin current any justice at all as it comes down from much higher off the WA coast & here it does not show any southern current along the coastline at all. But even then i have my doubts if we can nail it down just like that. Apart from all the bad weather they have had the remnants of a tropical cyclone have also passed through the area.

Let's see what they make out of it. The one thing we have learned from this search so far is that there is a ton of junk out there so who knows what this could turn out to be.

[Edited 2014-04-23 05:29:44]

Sorry, still can't find documentation about how to quote from previous threads.

Quoting WingedMigrator: Most aviation buffs think that the speed of sound varies with density (ask around you, you'll be amazed!) but it actually only varies with temperature.

I learned something today   

People have been asking what else could have caused the underwater pings, if it wasn't the black box. I think it could have been an echosounder used by ships for navigation and bathymetric surveys. Turns out 33 kHz is a typical, standard frequency used to probe deep depths.

https://en.wikipedia.org/wiki/Echo_sounding#Hydrography

https://www.atlas-elektronik.com/fil...products/001_PDF/ATLAS_DESO_30.pdf

Also, when probing deep depths, the ping rate is slowed down to 1 Hz--i.e., 1 ping per second.

http://www.km.kongsberg.com/ks/web/n...1F5EDC1256FA300360548?OpenDocument

[Edited 2014-04-23 06:24:09]

Quoting ExpatExp (Reply 18): Quoting WingedMigrator: Most aviation buffs think that the speed of sound varies with density (ask around you, you'll be amazed!) but it actually only varies with temperature. I learned something today

So did I. That should mean on a cold day at sea level in Arctic Canada (-40C) the speed of sound is the same as at any altitude anywhere with an air temperature of -40C. Correct?

Quoting art (Reply 20):

Yes, for most practical purposes, according to Wiki:

http://en.wikipedia.org/wiki/Speed_o...ications_for_atmospheric_acoustics

[Edited 2014-04-23 08:37:49]

Quoting Finn350 (Reply 9): The acoustic pinger Ocean Shield detected was not that of MH370 but some random pinger related to fishing, ocean research or something similar

The four pinger detections did have a directional component to them - north to south. I searched but could not find a map of the ocean currents for the underwater search area. I wonder what direction both the surface and underwater currents were moving? The batteries may not have died, but just moved out of the area.

[Edited 2014-04-23 08:49:32]

Quoting WarrenPlatts (Reply 19): People have been asking what else could have caused the underwater pings, if it wasn't the black box. I think it could have been an echosounder used by ships for navigation and bathymetric surveys. Turns out 33 kHz is a typical, standard frequency used to probe deep depths.

The underwater search are was cleared of other vessels, so I don't think that it could have been an echosounder of another vessel (or that of Ocean Shield, surely they had switched off their own echousounder if any).

Was the airline safety card found by a recycling worker ever determined to be a hoax? It made sense to me at the time, but others seemed to think it was unrelated. The facility where it was found is on the east coast of Australia near Melbourne; however, this particular facility receives shipments from Busselton to process. Maybe someone was picking up trash of the beach, put it into the recycling, and then it was shipped to the east coast.

Someone posted on Reddit that this particular card was an old version and has been replaced by a newer version. This was taken as to have debunked the idea that this card came from MH370. Who can say with 100 percent certainty that if a safety card is replaced, that all previous versions are removed from the plane? Couldn't this card have been put in a drawer, a cabinet, or remained anywhere on the plane after it was discontinued?

I bring this up again because of the new potential piece of debris taken to the Busselton police department.

[Edited 2014-04-23 09:27:38]

Quoting 65mustang (Reply 24): I bring this up again because of the new potential piece of debris taken to the Busselton police department.

Yeah, one or the other pieces of the puzzle would just be circumstantial, but both of those, if there's a Busselton connection in there somewhere, are somewhat more compelling.

I must admit, the fact that the Bluefin-21 hasn't brought any images of anything of interest up from the ocean bed is a little disheartening, but then the realist in me remembers that underwater searching is a slow and steady business.

Quoting 65mustang (Reply 24):

If that's accurate, it's very unlikely that the card came from 9M-MRO.

http://www.reddit.com/r/pics/comment...at_work_today_in_australia/cgis96t

Quoting LTC8K6 (Reply 21): Yes, for most practical purposes, according to Wiki: http://en.wikipedia.org/wiki/Speed_o...stics

Thanks. Grasping the math(s) would challenge me before a bottle of vin blanc. Fortunately one ceases to attempt challenges after one!

Quoting Finn350 (Reply 23): Quoting WarrenPlatts (Reply 19): People have been asking what else could have caused the underwater pings, if it wasn't the black box. I think it could have been an echosounder used by ships for navigation and bathymetric surveys. Turns out 33 kHz is a typical, standard frequency used to probe deep depths. The underwater search are was cleared of other vessels, so I don't think that it could have been an echosounder of another vessel (or that of Ocean Shield, surely they had switched off their own echousounder if any).

The place was near a major shipping lane (2 shipping lanes actually). Ships have these things and leave them on as a matter of course in order to avoid uncharted shoals, etc. Also, simple fish finders use 33 kHz at times. There are numerous potential explanations for the observed pings.

Consider the fact that 80% of the search area has been searched. Odds are if something was there, they would have found something by now. But instead, nothing has been found. I'm hoping they find something, but I'm betting they will not....

Quoting WarrenPlatts (Reply 28): Consider the fact that 80% of the search area has been searched. Odds are if something was there, they would have found something by now. But instead, nothing has been found. I'm hoping they find something, but I'm betting they will not....

When the WHOI Remus AUV found AF447 it was on the 18th mission of Phase 4 of the search.

Bluefin-21 just completed it's 9th mission of this particular phase and has only completed roughly 2/3 of the search area.

Even if 80% of the search area was complete, as you said, it does not lower the odds of finding wreckage. Imagine, for example, that you have 10 matchboxes sitting on a table, and one has a penny underneath. You uncover 8 of those boxes and don't find the penny. Would you still say, "odds are if a penny was there, we would have found something by now?" Of course not, you keep searching until you've searched everything, then make a determination.

"Bluefin-21 AUV is currently completing mission ten in the underwater search area. Bluefin-21 has now completed more than 80 per cent of the focused underwater search area. No contacts of interest have been found to date.

The focused underwater search area is defined as a circle of 10km radius around the second Towed Pinger Locator detection which occurred on 8 April."

http://www.jacc.gov.au/media/releases/2014/april/mr033.aspx

Quote: Up to 10 military aircraft and 12 ships will assist in today's search for missing Malaysia Airlines flight MH370.

What is the purpose of the flights? It seems rather too late to be searching for surface debris from the ill-fated flight. Will the flights be stopped soon? I would also say that it seems rather too late for ships to be searching for surface debris (if that is what some of them are doing).

A little more information on several points canvassed in this thread from this ABC News story. The ABC has apparently been told the material washed ashore at Augusta is metallic and about 2.5 metres long.

Quote: Australia has vowed to keep searching for the missing plane as autonomous underwater vehicle Bluefin-21 nears the end of its first full mission. Search officials have said that once the Bluefin-21's current mission, 2,000 kilometres north-west of Perth, is finished, they will redeploy the submarine to other areas yet to be determined. Prime Minister Tony Abbott says the search strategy may change if seabed scans from the drone fail to turn up any signs of debris. "We may well re-think the search but we will not rest until we have done everything we can to solve this mystery," he said. "The only way we can get to the bottom of this is to keep searching the probable impact zone until we find something or until we have searched it as thoroughly as human ingenuity allows at this time." Malaysia's cabinet has approved the appointment of an international team to investigate the plane's disappearance, the country's acting transport minister Hishammuddin Hussein said. "The main purpose of the international investigation team is to evaluate, investigate and determine the actual cause of the accident so similar accidents could be avoided in the future," he said. Mr Hishammuddin added that the Malaysian government has had talks with state oil firm Petronas and other unidentified entities to expand the deep-sea search in the southern Indian Ocean.

Quoting KIAS (Reply 29): Quoting WarrenPlatts (Reply 28): Consider the fact that 80% of the search area has been searched. Odds are if something was there, they would have found something by now. But instead, nothing has been found. I'm hoping they find something, but I'm betting they will not.... When the WHOI Remus AUV found AF447 it was on the 18th mission of Phase 4 of the search. Bluefin-21 just completed it's 9th mission of this particular phase and has only completed roughly 2/3 of the search area. Even if 80% of the search area was complete, as you said, it does not lower the odds of finding wreckage. Imagine, for example, that you have 10 matchboxes sitting on a table, and one has a penny underneath. You uncover 8 of those boxes and don't find the penny. Would you still say, "odds are if a penny was there, we would have found something by now?" Of course not, you keep searching until you've searched everything, then make a determination.

The problem is there is an unknown probability that the penny is under a different set of 10 matchboxes, on an unknown, entirely different table, possibly in an entirely different house. If we knew for sure that the wreckage was in the search area, then searching 80% of it doesn't affect the probability of finding the wreckage in the search area--it still would be 100%. But given that we don't know if we have the right haystack in the first place, after having searched 80% of it without a trace of solid evidence, it's becoming increasingly evident that the current search area is in the wrong place. When they search all 100% of the search area without finding anything, it'll be back to square one, and all bets are off....

Quoting art (Reply 31): What is the purpose of the flights? It seems rather too late to be searching for surface debris from the ill-fated flight. Will the flights be stopped soon?

It's not too late and they will not be stopped anytime soon. As was said by an Australian Defense Minister David Johnston:

Quote: There will be some issues of costs into the future but this is not about costs. We want to find this aircraft. We want to say to our friends in Malaysia and China this is not about cost, we are concerned to be seen to be helping them in a most tragic circumstance.

Currently, the search area is set to cover about 14,650 square miles. By contrast, the Indian Ocean is 28,400,000 square miles. There is a lot of ocean out there, and a lot to cover, even though the search is contained to a relatively small sector.

You can learn more about Australian standarized SAR protocol here: http://natsar.amsa.gov.au/Manuals/Se...Manual/documents/NATSARMAN2011.pdf

Namely the parts about Sector Search and Expanding Square Search.

As for if they may find something, note that there are a lot of components which may float, even after all this time. Since cost is not a factor, the search protocol must continue.

Quoting WarrenPlatts (Reply 33): The problem is there is an unknown probability that the penny is under a different set of 10 matchboxes, on an unknown, entirely different table, possibly in an entirely different house. If we knew for sure that the wreckage was in the search area, then searching 80% of it doesn't affect the probability of finding the wreckage in the search area--it still would be 100%. But given that we don't know if we have the right haystack in the first place, after having searched 80% of it without a trace of solid evidence, it's becoming increasingly evident that the current search area is in the wrong place. When they search all 100% of the search area without finding anything, it'll be back to square one, and all bets are off....

I understand your point, but that's not how SAR works. The needle may very well be in a different haystack, but the point is that you won't know until you've search 100% of it. You can't call it off at 80%. If you did that, you could overlook it. SAR procedures are very formalized for this purpose.

If they search 100% it won't be back to square one. It will be on to the next phase, where one area is crossed off and a new one started.

[Edited 2014-04-23 14:05:09]

Quoting WarrenPlatts (Reply 33): after having searched 80% of it without a trace of solid evidence, it's becoming increasingly evident that the current search area is in the wrong place.

Well, no.

Whether you think you are in the right place or not, you are no more likely to find it in the first 5% than the last 5%.

Only when you have searched 100% do you know it was the wrong place.


Jimbo

Quoting nupogodi (Reply 281): And remember, these estimates (9 years at 30km^2/day) are based on 100,000km^2 search area ... And over such a long period of time, debris might get buried ... you'd need to look at anything remotely interesting with sub-surface sonar ...

Sedimentation rate will be on the order of a few micrometers per year. Any debris will not get buried for a long time. No need for seismic surveys.

https://en.wikipedia.org/wiki/Pelagic_sediment#Red_and_brown_clays

Quoting bond007 (Reply 35): Whether you think you are in the right place or not, you are no more likely to find it in the first 5% than the last 5%.

Yes, agreed, provided they did *not* prioritize which parts of the search area were searched first based on beliefs about where in the search area the plane (or FDR / CVR) was most likely to be.

That aside, I understood the probability issue simply to be that if, say, there was only a 10% chance (made-up percentage) the plane was in the search area, and treating each part of the search area as equally likely to contain the plane, then if 80% has already been searched to no avail there is only a 2% chance the plane is in the search area. Not a reason to call off the search, agreed, but still a bummer....

The above is wrong if there is reason to think that the likelihood of the plane being in the search area does *not* decrease as the percentage of the search area that does not have the plane increases. Is there reason to think that (I don't know)??

Were the debris washed ashore off WA ( described as a "metal sheet with rivets" ) discarded as related to MH370? Or are they still performing test to the piece? I can't find any news about the subject.

Rgds.
G.-

Quoting Gonzalo (Reply 38): Were the debris washed ashore off WA ( described as a "metal sheet with rivets" ) discarded as related to MH370? Or are they still performing test to the piece? I can't find any news about the subject.Rgds.G.-

Looks like it is unrelated....

http://www.cnn.com/2014/04/23/world/asia/malaysia-airlines-plane/

Quote: (CNN) -- A metal object that washed ashore far from the area where investigators are looking for Malaysia Airlines Flight 370 is "not likely to be of use" in the search for the missing plane, a top Australian official said. "Analysis of the photos is enough not to warrant further analysis of the material," Australian Transport Safety Bureau Chief Commissioner Martin Dolan said Thursday.... The next logical step after the underwater search is to "rethink all of the information we have at hand," ocean search specialist Rob McCallum told CNN. An expanded search area might include the last 370 miles of the plane's flight path, perhaps 15 miles on either side, he said.

http://www.dailymail.co.uk/news/arti...links-missing-Malaysian-plane.html

Quote: Unidentified material that washed ashore in Australia and is being examined for any link to the lost Malaysian plane is unlikely to have come from the jet, an official revealed today. The Australian Transport Safety Bureau had been scrutinising photos of the object, which washed ashore six miles east of Augusta in Western Australia state. But Martin Dolan, chief commissioner of the bureau, said an initial analysis of the material - which appeared to be sheet metal with rivets - suggested it was not from Malaysia Airlines Flight 370. Mr Dolan said: ‘We do not consider this likely to be of use to our search for MH370. At this stage, we are not getting excited.’ He added that the analysis of the material would likely be completed overnight and a formal statement issued tomorrow.

ATSB is satisfied that Debris that washed ashore in WA is NOT from 9m-mro.

http://www.perthnow.com.au/news/wash...-atsb/story-fniztvnf-1226894191865

This image was first posted by Finn350 almost three days ago in the previous part. Please pardon my repeating it, as it is germane to the current discussion.

The current underwater search is being conducted in a 10km radius around Ocean Shield's Pinger Detectiion #2. I'm presuming that's because it was roughly in the centre of the four separate detection locations. The logical step would be to make the next search either around one of the other three pinger detection locations or immediately adjacent to the first search area.

[Edit - quote and text below added]

Quoting KIAS (Reply 34): The needle may very well be in a different haystack, but the point is that you won't know until you've search 100% of it. You can't call it off at 80%. If you did that, you could overlook it. SAR procedures are very formalized for this purpose. If they search 100% it won't be back to square one. It will be on to the next phase, where one area is crossed off and a new one started.

I think we have to understand the current 'haystack' being searched as a large area around the four pinger detection locations. The initial 20km diameter circle being searched is just a small part of the first haystack. I don't think any official has claimed that the aircraft is definitely in that circle.

[Edited 2014-04-23 15:58:33]

[Edited 2014-04-23 16:02:06]

One thing about the search is definite..

If the plane is found, I gurantee it will be found in the LAST place we look for it.

My lost keys are always found in the last place I look for them.


Mark

Quoting MarkAK (Reply 42): If the plane is found, I gurantee it will be found in the LAST place we look for it. My lost keys are always found in the last place I look for them.

Well.... when you find the thing you were looking for, you stop the search, so technically everytime we finnally see the thing, it is "in the last place we look for"....     

On a side note, the pingers are probably the most intriguing part of the last days/weeks.... the ocean is not so quiet apparently!!

Rgds.
G.

Quoting bond007 (Reply 35): Well, no. Whether you think you are in the right place or not, you are no more likely to find it in the first 5% than the last 5%. Only when you have searched 100% do you know it was the wrong place. Jimbo

But Warren is correct - when you've searched 80% of a search area and not found anything, if there is a chance it's not in the search area at all, then with every additional portion searched it becomes less likely it's there at all. In other words, at 80% searched without result, it's more likely you are in the wrong place than at 5% without result.

On the other hand, if you know that you've got "the right haystack" it becomes increasingly probable that you'll find it on the next pass you take.

It's only at the very beginning that the the first 5% is as likely to yield a result as the last 5%.

And if it was a circular search region, there would be non-uniform probabilities through the search region - the most likely location will be in the centre. The periphery is less likely.

Only if you are searching for a moving target will the probability of finding it be equal on every pass.

I just heard on the news that when the US President meets the Malaysian PM on Sunday in Malaysia (as part of this current Asia-Pacific trip) MH370 discussions will be on the agenda. There was also mention that at this stage Obama has no plans to visit the Malaysian opposition leader.

Quoting cbrboy (Reply 41): The current underwater search is being conducted in a 10km radius around Ocean Shield's Pinger Detectiion #2

What if the Bluefin just missed it by a couple of Kms? What if MH 370 is sitting let's say 12/13 Kms from pinger detection #2?

From a mathematical perspective (although I hated stats as almost everyone does), searching 80% of the search zone says absolutely nothing about the probability of whether the wreck is in the search zone.

If you make a statement like "every 'positive' area of 100km^2 will have a piece of wreckage in 1km^2 about 10% of the time" (like 10km^2 with wreckage in 100km^2 on average), then if you search 80km^2 and find no wreckage at all, the probability of that happening is quite low (0.9^80) so you can say your search area is very likely not a 'positive' area.

Now, in our case the wreckage is not randomly distributed. I mean yes theoretically if you think about it, it's randomly somewhere in the search area, but the act of searching a piece of the area and searching another piece of the area are *independent events*. We know nothing about the properties of the search area in general, we can't say "because we haven't found it, it's probably not there". What we can say is that, if we figured we'd have 50% chance to find it in 100km^2, but we've searched 80km^2, now all we can say is that we have a 50% chance to find it in the remaining 20km^2.

I hate stats. But these searches are independent events. Not finding it doesn't reduce our probability of finding it.

(In a very basic example, if you are sure you have a fair coin, getting 5 tails in a row does not mean your chance of getting heads on the 6th flip is worse than 50%)

Quoting nupogodi (Reply 47): From a mathematical perspective (although I hated stats as almost everyone does), searching 80% of the search zone says absolutely nothing about the probability of whether the wreck is in the search zone.

I agree.

I'm not sure if this has been asked before, but how capable is this equipment of detecting wreckage if it is in very small pieces and under a lot of silt on the sea floor? How deep could the silt be if it is under the silt? Would it even be detectable?

Also, I assume that a side-scan sonar device is attached to the Bluefin-21, if so, would the same device be attached to the REMUS 6000 if it was brought in? Or, would there be differences in the sonar equipment that both devices use thus meaning one might be better than the other (without considering the fact that the REMUS 6000 can obviously go deeper)?

What is considered an "optimal allocation of effort" in search is to divide the search area into a series of x/y cells. You then use Bayesian statistics (see here: http://en.wikipedia.org/wiki/Bayesian_search_theory) in order to find it. You formulate which area is the most likely to contain the wreck, based on your hypothesis. You search that square. If you turn up empty, it lowers the probability of the wreck being in that square and raises it in others. You then continue to search uniformly over every maximum-probability cell, adjusting as you go. But - you concede to search all, down to the lowest probability, in order. This is a very simplified presentation of the procedure but hopefully you get the idea.

This does NOT mean if you search 80%, and don't find anything, that the chances of you finding something in the total search area is lower!

[Edited 2014-04-23 19:12:43]