Malaysian Airlines MH370 contact lost
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There has been a lot of expert posts about acoustic properties through water. Salinity, depth, temperature layers etc..
Added to this, what about the geography of the ocean floor?
If the wreckage sits within a valley then this will certainly make it harder to detect the cvr/fdr pings?
Could this be the reason that the 2+ hours capture time with Ocean Shield happened when the towed pinger locator wasn't at its full depth - so was possibly more likely to pick up a signal for a longer period of time?
I.e less affected by peaks and troughs of the ocean floor..
Added to this, what about the geography of the ocean floor?
If the wreckage sits within a valley then this will certainly make it harder to detect the cvr/fdr pings?
Could this be the reason that the 2+ hours capture time with Ocean Shield happened when the towed pinger locator wasn't at its full depth - so was possibly more likely to pick up a signal for a longer period of time?
I.e less affected by peaks and troughs of the ocean floor..
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@Johny B
Yes the lack of real news or spin theories is postive
The Australian newspaper has a headline that proclaims that we have foubd the haystack and now to find the needle but nor much else..
And another has some details on further reducing the size of the haystack...from ABC auz Malaysia Airlines MH370: Search crews confident missing plane's locator beacon still running - ABC News (Australian Broadcasting Corporation)
"However, the plans have been put on hold until another signal is received, or it is certain the batteries in the black box recorder have expired.
The international search team is focusing on a 600-kilometre arc in the southern Indian Ocean, about 1,600km off the West Australian coast.
US navy captain Mark Matthews is in charge of the equipment detecting the signals.
He says while there is a chance the battery is still working, crews will keeping using their towed equipment, rather than underwater submersibles.
"It's an operational trade-off. The ground I can cover in one day using the towed pinger locator would take me six days with an autonomous underwater vehicle," he said.
"I'm going to keep using my towed pinger locator until I'm prepared to say, 'You know what? The beacons are no longer transmitting'."
He says there is cautious optimism from the sounds that have been picked up.
"The frequency, it was a repetitive signal every second, the pulse whip was about 10 milliseconds in length - that's appropriate for the signal," he said.
"The only thing that was a little off was the frequency of the transmission but based on the age of the beacons and talking to the manufacturers, it is still a signal of interest."
Yes the lack of real news or spin theories is postive
The Australian newspaper has a headline that proclaims that we have foubd the haystack and now to find the needle but nor much else..
And another has some details on further reducing the size of the haystack...from ABC auz Malaysia Airlines MH370: Search crews confident missing plane's locator beacon still running - ABC News (Australian Broadcasting Corporation)
"However, the plans have been put on hold until another signal is received, or it is certain the batteries in the black box recorder have expired.
The international search team is focusing on a 600-kilometre arc in the southern Indian Ocean, about 1,600km off the West Australian coast.
US navy captain Mark Matthews is in charge of the equipment detecting the signals.
He says while there is a chance the battery is still working, crews will keeping using their towed equipment, rather than underwater submersibles.
"It's an operational trade-off. The ground I can cover in one day using the towed pinger locator would take me six days with an autonomous underwater vehicle," he said.
"I'm going to keep using my towed pinger locator until I'm prepared to say, 'You know what? The beacons are no longer transmitting'."
He says there is cautious optimism from the sounds that have been picked up.
"The frequency, it was a repetitive signal every second, the pulse whip was about 10 milliseconds in length - that's appropriate for the signal," he said.
"The only thing that was a little off was the frequency of the transmission but based on the age of the beacons and talking to the manufacturers, it is still a signal of interest."
If one combines the Inmarsat data with the assumed flight path data, one gets two lines which intersect at nearly a 90° angle. The intersection point is almost exactly half way between the two ping sightings by the Chinese vessel HaiXun01 at S25°E101° and the Ocean Shield at S21°E104°. This means that the most likely place where MH370 went down is approximately S23°4.24’ E102°27.58’, which is the only point to lie on both the 40° arc and the L894 flight path. Given the short time remaining in the pinger lifetime, it would be well worth searching around this location.
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@Double07.
Yes that is very good work!
Looking at the AMSA search maps earlier in the week, they showed a "predicted" flight path that wasnt straight, rather was arched as it headed toward WA....would that fit with your proposed route from Indonesia??
I have tried to extrapolate the same arc backwards but I am not technically advanced enough to do it!!!....But I would imagine that someone could....If the angle of the arc inwards was back-tracked on the same arc to north of Indonesia, could that give an indication of route?
Yes that is very good work!
Looking at the AMSA search maps earlier in the week, they showed a "predicted" flight path that wasnt straight, rather was arched as it headed toward WA....would that fit with your proposed route from Indonesia??
I have tried to extrapolate the same arc backwards but I am not technically advanced enough to do it!!!....But I would imagine that someone could....If the angle of the arc inwards was back-tracked on the same arc to north of Indonesia, could that give an indication of route?
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Originally Posted by portmanteau
an indonesian military chief said " the aircraft was not detected flying over our territory" which is not the same as saying we never saw it.
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This means that the most likely place where MH370 went down is approximately S23°4.24’ E102°27.58’, which is the only point to lie on both the 40° arc and the L894 flight path. Given the short time remaining in the pinger lifetime, it would be well worth searching around this location.
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Hi-frequ audio directionality
Hi frequency audio at 30K+ is very high, and highly directional. I wonder of the towed array lost the pings as it moved into the "shadow" of a submerged mountain range. To experience the effect you only need a hi-fi. Put on some music with a lot of top and put your hand between the woofer and your ear- should be little effect on the bass because low frequencies are less directional. Now do the same between tweeter and ear- top loss, right? Now imagine the effect of a mountain between pinger and array, when the ping is over 10KH higher than most hi-fi set-ups go. the cut off "shadow" would be very abrupt.
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USN Captain Mark Mathews said: "The frequency, it was a repetitive signal every second, the pulse whip was about 10 milliseconds in length - that's appropriate for the signal."
I thought the Dukane Seacom ULB MH370 was outfitted with has a signal interval of 0.9 seconds. Teledyne/Benthos models have a 1 second interval.
I thought the Dukane Seacom ULB MH370 was outfitted with has a signal interval of 0.9 seconds. Teledyne/Benthos models have a 1 second interval.
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Nice work. Your assumption about the flight path taken, is very plausible as well, as it would be much more convenient to enter a set of waypoints to navigate by than use Heading Select mode (obviously). Your other assumptions also seem to all line up, so hopefully the team at JACC/AMSA are thinking on the same wavelength as you.
Haixun 01 reported hearing pings ~150 nm off L694. Ocean Shield heard them almost directly (within 20 nm) underneath M641. They are so far apart that it's impossible for the same pinger to be heard in both places. If we assume that MH370 was following air routes (not an unreasonable assumption), it's more likely that it was on M641, Ocean Shield's report is the real deal and Haixun's report is false.
It's also possible that Australians thought of this before us, and that they were checking that spot precisely because it is at the intersection of an Inmarsat arc and a flight corridor. (Otherwise the chances of stumbling on a working pinger in the amount of time they spent working with a TPL are too vanishingly small.)
M641 is a priori more likely than L694. If you were going to fly from Strait of Malacca to Perth while following flight corridors and waypoints all the way through, NILAM KALOX IKASA is the shortest route. Timing is wrong (it gets you to the supposed crash site in under 5 hours unless you go <400 kts). Double07's proposed route does a better job of avoiding Indonesia, but it involves a lot of unnecessary and complicated zigzagging and it's still a bit too short.
In either case, logic is still missing in action (what else is new?) Is this not a suicide but a spectacularly botched hijacking to Australia now? IGARI to Learmonth (NW Australia) is 4 hours at cruise speed if you don't try to avoid any radars and simply head south. Running out of fuel and ditching in the ocean because you chose a route that takes nearly twice that time would be head-scratching, to say the least.
And finally, there's Doppler. I'm not too confident in any reconstructions or interpretations of Doppler any more, but I don't think that either of those routes agree with it.
I would submit it is logical - albeit logic serving an outcome we find deeply disturbing and incomprehensible.
If it wasn't for the satellite pings (a detail perhaps not known about or somehow overlooked), we likely would have no idea what happened. But strip away the satellite stuff, and everything else fits with a desire to disappear without trace.
Why? Who knows. But history is full of people who chose to disappear.
Who has been harmed by this? That provides best guess at motive. Well the Malaysian government has been horribly exposed on the world stage. It has generated ill feeling between Malaysia and China (not what he Malaysian government would want).
I am not suggesting it was a particular pilot who supported the opposition. We can't conclude that. But someone (could have been other than pilot) who wanted to damage Malaysia for some reason.
If it wasn't for the satellite pings (a detail perhaps not known about or somehow overlooked), we likely would have no idea what happened. But strip away the satellite stuff, and everything else fits with a desire to disappear without trace.
Why? Who knows. But history is full of people who chose to disappear.
Who has been harmed by this? That provides best guess at motive. Well the Malaysian government has been horribly exposed on the world stage. It has generated ill feeling between Malaysia and China (not what he Malaysian government would want).
I am not suggesting it was a particular pilot who supported the opposition. We can't conclude that. But someone (could have been other than pilot) who wanted to damage Malaysia for some reason.
Props are for boats!
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Thanks Finn47,
Lets hope they get some solutions and act on it. The fact they are looking at the Lithium Ion battery rules again is good as well. They were only re-written last year due the UPS- Dubai and the Asiana Cargo - Jeju Island accidents and have confused many.
ICAO has just announced a two-day meeting in May, covering several topics mentioned here, such as new guidelines on ULBs and deployable flight recorders:
Quote:
"The unprecedented and unusual circumstances of flight MH 370 have been particularly difficult for civil aviation officials to resolve and the lack of definitive answers has been much harder still for the victims' families to come to terms with. They, above all, will benefit from a fuller explanation of this accident," he added.
Aliu also said ICAO recently added a new guideline on underwater locator beacon (ULBs) which will take effect in 2018.
ICAO’s Flight Recorder Panel is reviewing new methods to speed up process of determining accident sites, deployable flight recorders and the triggered transmission of flight data.
Furthermore reviews will be conducted on aviation security, travel documents as well as requirement for the transport of lithium batteries.
MH370 Tragedy: ICOA to meet on global tracking - Latest - New Straits Times
Quote:
"The unprecedented and unusual circumstances of flight MH 370 have been particularly difficult for civil aviation officials to resolve and the lack of definitive answers has been much harder still for the victims' families to come to terms with. They, above all, will benefit from a fuller explanation of this accident," he added.
Aliu also said ICAO recently added a new guideline on underwater locator beacon (ULBs) which will take effect in 2018.
ICAO’s Flight Recorder Panel is reviewing new methods to speed up process of determining accident sites, deployable flight recorders and the triggered transmission of flight data.
Furthermore reviews will be conducted on aviation security, travel documents as well as requirement for the transport of lithium batteries.
MH370 Tragedy: ICOA to meet on global tracking - Latest - New Straits Times
USN Captain Mark Mathews said: "The frequency, it was a repetitive signal every second, the pulse whip was about 10 milliseconds in length - that's appropriate for the signal."
I thought the Dukane Seacom ULB MH370 was outfitted with has a signal interval of 0.9 seconds. Teledyne/Benthos models have a 1 second interval.
I thought the Dukane Seacom ULB MH370 was outfitted with has a signal interval of 0.9 seconds. Teledyne/Benthos models have a 1 second interval.
It's a 10 ms pulse of 37.5 kHz ultrasound, repeated every 0.9 seconds. That's a duty cycle of 10/900 or about 1.1%.
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Thermoclines and Oceanic Ensonification
Any student of ASW (anti-submarine warfare) would be familiar with the fact that deep ocean areas contain barriers to the direct propagation of sound. Whether or not a sound penetrates a layer depends upon the relative densities, the steepness of the temperature gradient within and between the layers and mixing characteristics at the layer's periphery. There's little mixing at great depths.
It's not unusual for sound to bounce between layers with little loss in dBA and finally reach the surface layer in an annulus (think the area enclosed by two concentric circular rings), once the thermocline's extremities are reached (i.e. due mixing or shelf shallowing in water depth). That "surfacing" can be hundreds of miles away (i.e. 100's of miles away from the source). Nuclear subs use this characteristic of sound to hide beneath or between layers of different temperature, salinity or density. A good airborne sonar operator could distinguish between first and third CZ's (Convergence Zones) due to the fuzziness / distinctiveness of the sonics. However for a "bottomed" source, the topography will make a difference also (think "shouting in a canyon and the resultant directionally deflected echo effects).
Any ship crossing a CZ annulus could do it (unknowingly) at a quite shallow angle and remain in detection for 150 minutes or cross it at an acute angle (eg outer circumference direct to annulus centre) - and ths maintain contact for only 13 minutes.
It's just another (but very debilitating) weakness of the pinger system - in comparison with a satellite relay of streamed system and GPS data before aircraft impact.
37.5 khz acoustic is particularly vulnerable to a channeled sonic bounce between layers. It's one reason why the USN settled upon VLF and ULF broadcasts for reliable contact with its boomers on station. RF or acoustic, within the ocean's layers, it makes little difference.
Chasing a pinger's weak emanations in deep water is like chasing your tail.
It's not unusual for sound to bounce between layers with little loss in dBA and finally reach the surface layer in an annulus (think the area enclosed by two concentric circular rings), once the thermocline's extremities are reached (i.e. due mixing or shelf shallowing in water depth). That "surfacing" can be hundreds of miles away (i.e. 100's of miles away from the source). Nuclear subs use this characteristic of sound to hide beneath or between layers of different temperature, salinity or density. A good airborne sonar operator could distinguish between first and third CZ's (Convergence Zones) due to the fuzziness / distinctiveness of the sonics. However for a "bottomed" source, the topography will make a difference also (think "shouting in a canyon and the resultant directionally deflected echo effects).
Any ship crossing a CZ annulus could do it (unknowingly) at a quite shallow angle and remain in detection for 150 minutes or cross it at an acute angle (eg outer circumference direct to annulus centre) - and ths maintain contact for only 13 minutes.
It's just another (but very debilitating) weakness of the pinger system - in comparison with a satellite relay of streamed system and GPS data before aircraft impact.
37.5 khz acoustic is particularly vulnerable to a channeled sonic bounce between layers. It's one reason why the USN settled upon VLF and ULF broadcasts for reliable contact with its boomers on station. RF or acoustic, within the ocean's layers, it makes little difference.
Chasing a pinger's weak emanations in deep water is like chasing your tail.
Last edited by Runcible; 9th Apr 2014 at 10:11. Reason: sp/typo
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I would submit it is logical - albeit logic serving an outcome we find deeply disturbing and incomprehensible.
If it wasn't for the satellite pings (a detail perhaps not known about or somehow overlooked), we likely would have no idea what happened. But strip away the satellite stuff, and everything else fits with a desire to disappear without trace.
If it wasn't for the satellite pings (a detail perhaps not known about or somehow overlooked), we likely would have no idea what happened. But strip away the satellite stuff, and everything else fits with a desire to disappear without trace.
The "original" southern track scenario, with the crash in the roaring 40's, was weird but at least could make some sense in the way you describe: as a disappearance without a trace in the middle of nowhere.
But this new track does not even "work" as a disappearance. It leads in a definite direction: towards Perth airport. If MH370 continued on this track and had enough fuel, in another 1.5 hours it would end up in Perth.
Here's the route via M641, extended to logical conclusion:
SkyVector: Flight Planning / Aeronautical Charts
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[Not a pilot] Thanks, Double07. I am trying to deduce from your note whether people are able to take, e. g., the sixth ping and make an arc for it, and then the fifth ping, etc., to try and determine the path from last voice contact based on average speed. I am not able to determine if that is what you have done or not.
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mm43 nailed it.
Houston confirmed that Ocean Shield found 2 instances of acoustic event again, as mm43 forecasted hours ago.
link to mm43's post9623 earlier
http://www.pprune.org/8425618-post9623.html
link to mm43's post9623 earlier
http://www.pprune.org/8425618-post9623.html
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"Two more pings have been detected by the Australian ship Ocean Shield in the search for flight MH370. Air Chief Marshal (ret) Angus Houston, the head of the search's Joint Agency Co-ordination centre, announced the development during a press conference in Perth on Wednesday afternoon.
It revives hope the missing Malaysia Airlines plane's black box is still transmitting data days after its batteries were due to run dead.
Crew on the Ocean Shield deploy the towed pinger locator. Photo: AP
Mr Houston said expert data analysis on previously detected signals had found they were not of natural origin, further boosting hopes of a breakthrough.
It revives hope the missing Malaysia Airlines plane's black box is still transmitting data days after its batteries were due to run dead.
Crew on the Ocean Shield deploy the towed pinger locator. Photo: APMr Houston said expert data analysis on previously detected signals had found they were not of natural origin, further boosting hopes of a breakthrough.
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Excellent news 
Does the pinger detector sled have an IRU and vector sensors or is it just a dumb hydrophone ?
Regardless they presumably now have a cross fix on the position and can launch the AUV...
Does the pinger detector sled have an IRU and vector sensors or is it just a dumb hydrophone ?
Regardless they presumably now have a cross fix on the position and can launch the AUV...
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I THINK he said that they won't deploy the UAV until they can pin point the ping because it takes 6 times as long underwater as it does on the surface.