luckypierre

Interesting speculation on the new PPRuNe poster's part. Has an internal consistency with the early suspected waypoint behavior.

EsherFlyer

Isn't that just a very long way round of 'proving' that if both Oz and CN teams heard the same ping then the source may lay somewhere in-between them ? But could they have done that? While I understand (to a limited extent) the refraction and other 'redirection' effects on sound underwater I haven't seen anything to suggest that they would hear things at ~50 times the anticipated ping range.

I don't understand the supposed significance of both the ping detection locations being on the -PER air route. If the respective ships had been 100km east or west then this 'coincidence' wouldn't have arisen, but the pings may still have been heard. Alternatively someone may have already figured out that the air route could be significant, which is why the ships were searching on it @:-).

It'd be interesting to have some insight on how the search locations are chosen from the vast range possible. The intersection of the Inmarsat arc and standard air route does sound interesting, as do some of the deeper topological features, etc depending on which theory you subscribe to. Has anyone seen a chart of with all the ideas and search areas overlaid?

M@rcoPolo

No way - the two locations are 600 Kms apart !

vkykam

Surely everyone is hoping that these are indeed signals from the recorders of the MH370, but can someone explain how or why it makes sense for the distance between pinger detection location 1 and pinger detection location 4 to be almost 30km apart?

According to Wikipedia the range of the 37.5KHz transponder pinger is 6-7km in good conditions, so even if the plane was at the center of the 4 pings, that's still a good 14-15km away...

luckypierre

Sensitivity of USN towed locator?

M@rcoPolo

Don't forget they are chasing two separate sources and the ping #2 is the one that detected 2 separate pings so it could make sense if one of the black boxes is located somewhere between ping #1 and ping #2 and the other one in the middle of pings #2, 3 and 4...

Anyway what I find almost too good to be true is that looking at http://www.jacc.gov.au/media/release...l/mr_014-2.jpg all 4 ping detections are almost right on the "satellite handshake calculation" which I presume refers to the last partial ping. Surely this is either extremely lucky (no way the arc calculated thanks to doppler analysis can be so precise) or if this is indeed the final resting place of MH370 the location must be based on a more accurate data source that they are not willing to disclose...

lewko

My speculation is that the detection distance capability of the TPL is more than has been published. The plan was always to tow the TPL back and forth across the estimated flight path and hope they get lucky. Someone always wins the lottery.

I just wonder what the Chinese heard?

JohnMacWW

The range of the pinger is not really that set because it is not so much a question of the range of the pinger, but the listening capability of the device that is attemping to hear it. Back in my submarine days (Fast attack Los Angeles Class sub) we would sometimes here very odd quiet things from a long way away. The water antenuates (removes energy) of the ping which is essentially a sound wave moving through the water. So the farther it travels the weaker it gets and thus is "quieter". But for our sub, we were so quiet we could here that much better. Sound waves can also get reflected off of transitions in water conditions. Mostly that means thermal or salinty layers. Very analogous to looking through a window that also partly reflects your image back. So the sound wave can hit a transition (a layer) and some of it can reflect off in a different direction etc. (Think echos here also as an analogy)
So we would sometimes get a signal coming from above us when the source of the noise was probably below us. Layers could be used to hide our own sounds as well. Our listening systems (passive sonar) were incredibly capable and we woudl sometimes get a sound source coming at us from two directions and you had to decide which one was the more liekly to be accurate bearing.
Anyways, you can hear a whisper a long way away is the space around you and the whisperer is quiet enough. So those pings radiate out, getting quieter and quieter, sometimes sending bounces and reflections in different directions and one moment might be "heard" at a real long distance and the next not.

polarbreeze

I notice that HMS Echo is still searching in that southern area. Anyone know what that's all about?

Need to distinguish between the undersea search area and the surface search area. Ocean Shield is doing its TPL thing in one area, while there is a large surface search area almost due west of that where several ships seems to be engaged in a surface search. Presumably these two areas are related through estimates of drift of any surface debris.

NewbieRunner

I suggest you read the transcript of the JACC press conference posted in the news thread. Here's an extract of the Q&A session.

polarbreeze

Sure but I was hoping for more insights than that. And it turns out there is an update: the latest from marinetraffic.com has HMS Echo heading up to join Ocean Shield.http://www.marinetraffic.com/en/ais/...1b9a33ef6e4261

EsherFlyer

<redacted>

Assuming these images and my interpretation are correct, this 'overview' one shows the satellite-predicted 'somewhere along this line' arc in red and the 'out of fuel' range in white. Jumping to this one and assuming that the colours are the same a less complex theory is that it just ran out of fuel there.

polarbreeze

I think someone else mentioned this but I didn't see any good answer to it yet:

It was my understanding that the Inmarsat data yielded an arc (mostly represented by a red line) whose accuracy was thought to be in the order of 100 miles or so. Now, jumping the gun a bit to assume the Ocean Shield really has found the pingers, we find that they're exactly smack dab on the red line. Did I miss a step where additional data scrubbing put the red line down with much better accuracy; or was Ocean Shield really, really lucky (in the north-south direction too BTW); or could there be other data that has directed the search more precisely?

Somebody suggested Australian radar could be at play here - anyone have any information about that?

EsherFlyer

One (speculative) suggestion I'll offer is that although each arc may have an amount of error if you assume a constant speed then that will help 'respace' them. So if the hourly arcs were notionally 420, 460 and 450 nautical miles apart you could calculate an assumed average speed of ~435knts and replot the lines to fit that assumption.

Has anyone see a 'back plot' from Ocean Shield's search position across the satellite arcs at various speeds to see if it leads back to the right origin?

Alternatively, as I think we mentioned above, I wouldn't be surprised if a submarine from some nation or other had passed by the area in the last month and detected something to help direct the surface search.

lewko

In the JACC press conference The naval rep said their sub was "not equipped" for this kind of search.

About the location, Angus said they acted on the belief that the seventh 'half' ping was at the time and point of impact. That seems to be correct. With a time of impact they were able to calibrate a line back through the other ping arcs to get an approximate landing coordinate. That would be the 'back plot' you are asking about.

Angus also said that quiet operation was the key to hearing a weak signal and separating it from noise. Only Ocean Shield will be in the water at the search site. They will drop up to 85 microphones that will listen at a depth of 1000 m. The intent is to get a geographic picture of the sound sources.

I am hoping for the best, although I wonder if all those mics hanging 1000 m down won't interfere with the 4000+ meter cable towing the TPL.

Angus was asked about the discrepancy between the 37 KHz frequency of the FDR and the 33 kHz that was detected. He didn't provide an explanation but he said they were satisfied that they had probably detected the right signal.

The question that immediately popped into my mind was whether the sono-buoy mics were re-calibrated to the actual frequency that is being sent. The sensitivity is given as 37 +/- 1khz which seems like it would tune out the actual frequency of 33khz.

I have a lot of confidence they are doing this correctly. The Ocean Shield detected the signal very soon after they started searching. Inmarsat's ping arcs and the calculation of speed and fuel used from the earlier radar hits was spot on. This is absolutely amazing and shows how technology has moved ahead since the Air France crash.