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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 10th Apr 2014, 00:49
  #9621 (permalink)  
 
Join Date: Mar 2014
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Evaluation of ULB Signals

Does anyone know if the black box pingers stay phase stable? Its been mentioned before about folding data to get a better signal to noise. Its a common pulsar technique.
Given that the ultrasound signal exhibited very significant frequency deviation (about 33 kHz rather than the nominal 37.5 kHz) it is unlikely that the ultrasound signal itself is phase stable. Thus, digital signal processing techniques predicated on phase stability are unlikely to be of assistance. However, the ULB may have reasonable frequency stability over the short term as temperature and water pressure are static and battery voltage decays only slowly.

The situation is more promising with regard to the timing of the sound pulses. According to Air Chief Marshall Angus Houston, pulse periods of about 1.1 second were observed, indicating that the signal originated from the FDR ULB.

Pulse width and duty cycle are most likely governed by a single crystal oscillator and are thus sufficiently stable for signal integration etc. Of course, as Ocean Shield moves relative to the ULB, pulse phase will change with the effective sound path length between the ULB and the TPL.

Careful evaluation of (i) pulse phase; (ii) sound intensity; and (iii) ultrasound doppler shift of recorded signals correlated with the time and precise TPL location should help narrow the scope of further searches.
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Old 10th Apr 2014, 00:54
  #9622 (permalink)  
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oldoberon,

The small search area highlighted on the map is where The Ocean Shield is now ( Marine tracker website) and that's what they've highlighted for the sonar buoys. If my eyes are correct.

Also interesting on Marine tracker is the warship HMAS Toowoomba is already coming back from Exmouth probably for supplies to the other ships. Nice to a have a speedy supply ship. I'm wandering if these promised German Submersibles capable of 6000m are on board. Also shows HMS Echo heading towards Ocean Shields search zone as well.

Live Ships Map - AIS - Vessel Traffic and Positions - AIS Marine Traffic
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Old 10th Apr 2014, 01:20
  #9623 (permalink)  
 
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FinalIy!! After yearzzz of reading and learning (most of the time, anyway) and being seriously amused at clever comments/retorts, I can post on a topic that I have a wee bit of experience with... In my former life, I was heavily involved with offshore ROV engineering/installations, specifically the launch and recovery of such. My first out of university project was designing a towfish and it's deployment package to be used to 'talk' with an AUV. Now, I'm a mommy, who has nothing better to do (I wish!) but hang out with you guys.

Anyhoo, I'm not sure of the Phoenix towfish's exact spec, but using a depressor wing serves to decrease the length of cable necessary to be payed out to achieve depth. Without a wing, the ratio is something like 4:1, ie 4x amount of cable for a desired depth vs. with a wing, ratio becomes something like 2:1 (not sure of exactness, I'm going off of memory). I was wondering the same, whether they were using a wing. I searched a bunch looking for broader/more installation/operations view(s) - I was actually curious in the installed winch - to see if a wing was present, but haven't seen anything in the sparse amount of ops pics from the Shield. Perhaps they're using one? If I had to guess, I'd say they would want to take advantage of lesser cable payout (and others mentioned below). It's probably just that noone's taken a shot of it as it is placed on tow cable after a specified length of payout, and at this point, the 'star of the show' TPL is long gone subsea.

I do know that a towfish's design is also an important factor in determining whether a wing is deemed necessary because some designs 'fly' better than others. The design I chose for my particular application looks similar to the Phoenix one out there, yet it is a larger version where the housing (hollow inside) was deeper to accommodate the mounting of the 'modems' (one was like 20" or so tall) inside. Point being that towfish designs modelled after nature, ie think sting rays, whose electromechanical termination placement on fish is engineered correctly (our fish flew nose down several degrees) serves to help it 'fly' more consistently at depth. I agree with all points made earlier about benefits of using a wing re tow cable harmonics and isolating the termination (that's a biggie when you're talking limiting factors). Utilizing a bend restrictor (essentially a rubber 'tube' on tow cable located just after the electromech term, designed with incrementally larger diameter thicknesses along length of restrictor) serves to keep the cable from assuming too acute of an angle during operation, which is essential.

I'm thinking the reason for the chosen 2 naut speed is simply for truly zeroing in on ping location as to not 'miss it' and when ping's located, that they get enough recorded data in a specific region along path for analysis purposes. It also indeed could be to keep cable harmonics at bay, to keep lower forces on electromechanical term because higher speed equals increased drag equals higher forces at term connection (kevlar term is weaker than steel 'potted' type), and/or the tow cable's strength, ie the max design load of the cable may be encroached upon at deeper depths in cases like this at higher speeds. Kevlar's great and all, but a parted cable isn't pretty. And a lost tool is even less pretty haha.

A huge thanks to you guys for the immense knowledge and entertainment.

PS. Reason I believe a TPL AUV isn't readily available is there's rare demand for such a tool at exorbitant costs of design/manufacturing. Dolphins would definitely be cheaper to train haha.
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Old 10th Apr 2014, 01:41
  #9624 (permalink)  
 
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Acoustic Doppler Shift

The reason the pinger detectors are looking for signals over an extended range of frequencies is because the speed of sound in water varies due to pressure changes with depth as well as salinity changes.

The speed varies up to 10% depending on conditions.

This in itself is no problem if the detector and sender are at the same salinity and pressure. However if you have a detector in a different pressure and salinity layer to the source the detected frequency will be altered - doppler shifted if you will - by up to 10% either side of nominal. Pulse duration will also be affected but pulse interval won't be altered.

This also means that a signal detected by a deep towed detector will be different frequency to a shallow towed detector.

Last edited by Mahatma Kote; 10th Apr 2014 at 02:10. Reason: depth effect
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Old 10th Apr 2014, 01:47
  #9625 (permalink)  
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RAAF Learmonth being used now

Ten News Tweet :

TEN Eyewitness News ‏@channeltennews 23m
The command centre coordinating the #MH370 search moves to an RAAF base near Exmouth in W.A

This has been corrected now only the Wedgetail operation is based out of RAAF Learmonth not the Search Coordination and Control it seems to be staying in RAAF Pearce.

Thanks to ONETRACK for info.

Last edited by Sheep Guts; 10th Apr 2014 at 02:53. Reason: Update of info
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Old 10th Apr 2014, 02:11
  #9626 (permalink)  
 
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Observed ULB Ultrasound Frequency Stability

However if you have a detector in a different pressure and salinity layer to the source the detected frequency will be altered - doppler shifted if you will - by up to 10% either side of nominal.
Not so.

The frequency of sound transmitted by the ULB may be impacted by the water pressure etc. in which the transducer operates. However, for a stationary transmitter-receiver (hydrophone) pair, the frequency received will be identical to that transmitted.

Slight frequency variations could, of course, occur if the effective transmission path length through the ocean water between transmitter and hydrophone changes due to currents, changes in temperature, salinity, pressure etc.
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Old 10th Apr 2014, 02:18
  #9627 (permalink)  
 
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So now we are asked to believe that this plane flew for 5-6 hours at about 250 knots? Is that even possible? What could that tell us about the events before the turn southward?
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Old 10th Apr 2014, 02:28
  #9628 (permalink)  
 
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(alph2z) If you plot a straight great circle line from NILAM to the magnetic south-pole you get extremely close to the search site of Ocean Shield* (last satellite ping not shown but passes over search site).

NILAM (western tip of Indonesia) is at the upper left of the image. Search site is small yellow thumbnail west of northern Australia. Magnetic south-pole is in lower right corner of image.

[180 degree magnetic heading from western tip of indonesia]
IMHO, I don't think so: magnetic declination is very low (around 1W) near Bandah Aceh: http://upload.wikimedia.org/wikipedi...8/Mv-world.jpg
With a 180 magnetic heading from western tip of Indonesia, you will fly quite true South at the beginning, with the track slowly turning East and more and more faster. I don't know how to draw the track on GEarth map.
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Old 10th Apr 2014, 02:38
  #9629 (permalink)  
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South African Airways 295 CVR recovered at 4900m

This is interesting except they didn't get the FDR. Lets hope they can get both with MH370. Its a tough ask.

South African Airways Flight 295 - Wikipedia, the free encyclopedia
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Old 10th Apr 2014, 02:45
  #9630 (permalink)  
 
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@Sheep Guts - I don't think that that news item is particularly correct about the "command centre" moving to Learmonth.
Perth is the sensible centre for command due to the availability of every requirement - from fuel, to food, to communications, spares and servicing.

Learmonth has been activated as a base for the Wedgetails. It's normally operated in a "ready" state - but its location and the much lower availability of all necessary requirements to support this huge operation, would make it a poor choice for overall command.

I doubt very much whether Chinese military Iluyshins will be allowed to operate from what is an important Australian military airbase.
I'm hazarding an educated guess there's military stuff at Learmonth that's a whole lot more sensitive, military-wise, than what's at Pearce.

Learmonth base activated for MH370 search | usanews.com
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Old 10th Apr 2014, 02:49
  #9631 (permalink)  
 
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ULS for search maps

mesoman:
AMSA :: Australian Maritime Safety Authority
For 4-10-14 map try:
https://s3-ap-southeast-2.amazonaws....area_close.pdf
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Old 10th Apr 2014, 02:58
  #9632 (permalink)  
 
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Information Sheet on Bluefin-21 AUV

A general information sheet on the capabilities and specifications of the Bluefin-21 Underwater Autonomous Vehicle (AUV) is available at
http://www.bluefinrobotics.com/asset...duct-Sheet.pdf
This is the vehicle that will be sent down to attempt to find, map and photograph the wreckage.
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Old 10th Apr 2014, 03:58
  #9633 (permalink)  
 
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The following from AMSA provides a more detailed look at todays search areas. The Sonar buoy drop is in the area Ocean Shield is currently working (marked by a very small yellow triangle).

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Old 10th Apr 2014, 04:41
  #9634 (permalink)  
 
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The Sonobuoys that will be dropped as listening devices in the larger search area are indeed broad spectrum passive listening devices. The modifications to the aircraft equipment might allow for a narrow frequency spectrum to be more closely monitored so that the returned signal will only scan the chosen frequency range around 37.5kHz
The modifications to the aircraft were to temp-fit new sonobuoy receivers and software capable at looking at the extended frequency range of the sonobuoys they are using.

The sonobuoys continuously transmit their wideband acoustic data which is received by the aircraft. The crew will then focus their attention in the higher frequency bands but all frequencies are available for display at the receiver.
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Old 10th Apr 2014, 05:32
  #9635 (permalink)  
 
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AIS update

AIS for Ocean Shield updated at 04:50 UTC.
Still on the same 113 pass at 1.7KTS

Echo has slowed from the original 15.5KTS to 11KTS but still on original heading with possible ETA in search zone of ~11:00 but it seems likely to stay out of the immediate area until OS has completed the TPL scans
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Old 10th Apr 2014, 06:00
  #9636 (permalink)  
 
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Originally Posted by TRW Plus
So now we are asked to believe that this plane flew for 5-6 hours at about 250 knots? Is that even possible? What could that tell us about the events before the turn southward?
You might want to read silvertate's post #9728 which went up a couple of hours before your post; he explains IAS - TAS and how altitude affects ground speed.

Another factor is how far north MH370 flew in order to not have raised any undue attention from the Indonesians. The last reported radar sighting of MH370 was in the vicinity of waypoint NILAM (Lat: 6.756389 Lon: 95.976389) An Indonesian spokesperson has stated that MH370 did not pass over Indonesian territory so we know the flight did not make its turn south at that point but how far north beyond NILAM it may have traveled is open to question. Probably the shortest conceivable route would have it going to NOPEK (6 36' 14N 94 25' 0E) and then possibly to NISOK ( 3 2' 54N 92 0' 0E) and from there joining airway M641 south.

However if the flight had followed that route, its path northbound from the Malacca Strait and the turn south would have been visible to Indonesian radar and that might have caused the Indonesians to add two and two and suspect they were seeing the missing Malaysian airliner. So it is possible that it continued on northward from NILAM until it was sure to be beyond Indonesian radar.

And of course the flight altitude would affect the range of visibility to Indonesian radar; and that information is unknown.
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Old 10th Apr 2014, 06:39
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An Indonesian spokesperson has stated that MH370 did not pass over Indonesian territory
No, they aren't saying that. They are saying they do not have it on radar and have no evidence that it skirted Indonesia / Sumatra. That's quite a different statement.

Some research into Indonesia radar capabilities leaves me feeling strongly that MH370 could have headed south across Indonesia from IGARI or WMKN or WMKD.

A common theme here - Indonesia seeing nothing; Malaysia radar reports untrustworthy; Thailand unable to hang their had on a 'strange' return - Singapore saying nothing - adds up to an uncomfortable picture for all of them -- MH370 most certainly crossed airspace of one or more yet no one knows where. That's the only 'conspiracy' theory that makes sense and it's simply one of embarrassment.

A route south from near the last known point (hand off to Ho Chi Minh) can't be ruled out at all. Overcomplicating things and relying on radar reports or capabilities that seem to be quite unreliable has caused most to look elsewhere.

IMO the current ping locator search is happening where it is happening based on flight at FL120 on close to due south heading from somewhere on the north east side of Malaysia due to a failed approach, likely all dead on board.

We'll find out soon.
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Old 10th Apr 2014, 08:00
  #9638 (permalink)  
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The Malaysian Govt states that "criminal" events occurred with Flt 370.
They then stated that non of the passengers were of interest in their investigation! So which is it?
Andy...remember 9/11? Different airlines, different cities...same type plane.
It is important to keep an open mind, that's why the World was caught with their pants down on 11/9!

As I have said many times before on this thread, it is more than likely to have been something that was previously un-considered prior, just like AF447! My money is still on a catastrophic event!
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Old 10th Apr 2014, 08:03
  #9639 (permalink)  
 
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Lots of concentration on the civilian ships (and ADV) searching for some wreckage, how about any submarines ?

The RN sent a nuclear sub - no updates as to where she might be.

The Australians have some ( 4 ????? ) Collins class submarines which were subject to a very acrimonious procurement process - here there has been no mention of their deployment.

And, of course, the US has a few subs knocking around.

Submarines have extremely sophisticated underwater listening equipment and the lack of publicity is odd.
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Old 10th Apr 2014, 08:22
  #9640 (permalink)  
 
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Originally Posted by phil gollin
Lots of concentration on the civilian ships (and ADV) searching for some wreckage, how about any submarines ?

The RN sent a nuclear sub - no updates as to where she might be.

The Australians have some ( 4 ????? ) Collins class submarines which were subject to a very acrimonious procurement process - here there has been no mention of their deployment.

And, of course, the US has a few subs knocking around.

Submarines have extremely sophisticated underwater listening equipment and the lack of publicity is odd.
Submarines do indeed have extremely sophisticated underwater listening equipment and the lack of publicity is normal and exactly what would be expected.
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