Vlucht MH370 Malaysia Airlines - waar blijf je nou? #40

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Op donderdag 10 april 2014 20:28 schreef ATan het volgende:

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Want?

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SYDNEY—An air crew hunting for Malaysia Airlines Flight 370 detected an underwater signal in the search zone on Thursday in what might be the latest ping from the missing jet’s “black box” flight recorders.

“The acoustic data will require further analysis overnight but shows potential of being from a man-made source,” said Air Chief Marshal Angus Houston, who is leading the search operation that is increasingly focused on a remote patch of the southern Indian Ocean where the missing plane is thought to have gone down.

Air Chief Marshal Houston said the signal was detected by a P-3 Orion military aircraft that was conducting an acoustic patrol near the area where four previous signals had been picked up by the Australian defense vessel Ocean Shield.

He didn’t clarify how the aircraft identified the signal, but Australia sent a P-3 Orion plane to drop 84 sonar buoys on Wednesday broadly in the same spot where the Ocean Shield was towing a U.S. Navy black box detector. Each sonar buoy from the Orion is equipped with a set of underwater microphones that unspool on wires to a depth of 1,000 feet.

The buoys send data through a radio system back to the aircraft for analysis–a technique typically used to track enemy submarines attempting to evade surface radar. Dropped in a pattern across the search area, the buoys could help to triangulate the source or sources of four signals picked up by the Australian navy since April 5.

Thursday’s announcement was the first underwater detection reported from an air crew and the fifth such signal picked up in the immediate area this week. The detected pings have led authorities to believe they are closing in on the missing jet’s likely final resting place.

“The more effort we put into location of where the transmission is coming from, the more certainty we will have that we will find something on the bottom of the ocean,” Air Chief Marshal Angus Houston said Wednesday.

The previous reported signals, picked up twice on Tuesday, were weaker than the initial pings detected over the weekend, suggesting the recorders’ batteries were close to running out of power. Beacons on the plane’s two flight recorders have an estimated battery life of about 30 days before they stop emitting signals. It has been more than a month since the plane disappeared.

Earlier Thursday, Australia’s Joint Agency Coordination Centre said that more than a dozen planes and 13 ships were patrolling an area of 57,923 square kilometers (22,364 square miles) of the southern Indian Ocean northwest of Perth—the narrowest zone yet in a close to five-week-old search for the jet, which disappeared en route to Beijing from Kuala Lumpur on March 8.

Authorities said air sorties had spotted a large number of objects in the search zone, but those items fished out of the water by ship crews weren’t from the missing plane, according the Australian authority leading the multinational hunt. While planes and ships are continuing to scour the surface of the sea for debris, search officials are placing their biggest hopes on homing in on the possible black box signals.

Investigators believe Flight 370 ran out of fuel and crashed into the ocean after vanishing from civilian radar as responsibility for communicating with the plane was being handed from Malaysian ground control to Vietnam. It was carrying 239 passengers and crew.

Ocean Shield has been sweeping a 7-mile strip of water since Friday. It is towing a U.S. Navy device nearly 2 miles beneath the ocean surface, listening for sounds from the black boxes. Other vessels, including the Chinese ship Haixun 01, are also doing an underwater search of an area farther south, though they haven’t detected any new signals since late last week.

Unless search crews can pinpoint a more precise location for the signals detected by Ocean Shield—which are up to 15.5 miles apart—undersea vehicles hunting for plane wreckage on the ocean floor would need to cover a zone of about 502 square miles, according to the U.S. Navy, which is coordinating the underwater search. The submersibles travel at walking pace, meaning it could be weeks rather than days before any debris is found.

Air Chief Marshal Houston said that search crews still needed hard evidence, such as a photograph of the wreckage, to declare the plane has crashed.

To avoid interfering with the delicate search for signals, authorities are holding back on deploying any other ships or underwater vehicles, though Air Chief Marshal Houston indicated Wednesday such a move wasn’t far away. Choosing to deploy the Bluefin-21, a torpedo-shaped submersible drone strapped to the Ocean Shield’s deck, would mark another switch in the search, effectively signaling an end to hopes of more signals from the black boxes.

Authorities think the seabed is covered with a thick carpet of silt that might be distorting the signals and could also handicap any undersea vehicles sent to look for plane wreckage using sonar initially and later video cameras. The silt also may hide debris from Flight 370 that likely scattered over a wide area as it sank to the ocean floor, they said.

The two-year underwater hunt for the black boxes of Air France Flight 447, which crashed into the Atlantic Ocean in 2009, provides sobering lessons in the search for Flight 370. The ocean floor in the Air France crash was nearly 2.5 miles deep, with forbidding peaks and valleys. It took small robotic submarines provided by the Woods Hole Oceanographic Institution nearly 60 trips under the surface before the black boxes were discovered.

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Op donderdag 10 april 2014 20:31 schreef ATan het volgende:

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Site Blocked!
This web page at <url malicious website> has been blocked by Bluhell Firewall

Lekkere website

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Op donderdag 10 april 2014 20:47 schreef Unstoppable het volgende:

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Ocean Shield is het enige schip in het zoekgebied waar de signalen worden opgepikt, meerdere schepen zou problemen opleveren (omgeving zo stil mogelijk houden). Wel hebben ze een zooitje boeien met hydrofoons eraan in het gebied gedropt. De boeien hebben een hydrofoon die 1000 voet onder de waterspiegel hangt, boei heeft een radio aan boord, signaal gaat naar vliegtuig dat een speciale acoustic processor aan boord heeft. Aangezien het doel hiervan is om een positie te bepalen kun je aannemen dat de timing etc wel goed zit, dit is immers cruciaal voor het hele proces

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Op donderdag 10 april 2014 21:08 schreef ATan het volgende:

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Dat systeem klinkt als een onderzeeboot opsporingssysteem.
Is dat systeem een passieve of actieve sonar? Luistert het wel op de frequentie van de black boxes? Is het specifiek bedoeld voor het luisteren op deze frequentie? Want het zou kunnen dat het ontwerp gericht is op het ontvangen van de ping van de actieve sonar en minder geschikt is voor andere bronnen. Het verhaal klinkt nu alsof de rest van de schepen en vliegtuigen beter thuis kunnen blijven.

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Op donderdag 10 april 2014 21:14 schreef Unstoppable het volgende:

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De rest van de schepen en vliegtuigen zoeken grotendeels naar wrakstukken, behalve twee andere schepen die meer zuidelijk zoeken (naar de blackbox) en de P-3 Orion die de boeien dropt en de info processed die het terugstuurt.

Ocean Shield is aan het zoeken met behulp van een TPL-25 van de US Navy
http://en.wikipedia.org/wiki/Towed_pinger_locator

Verder verwijs ik je naar dat artikel ik net heb heb gepost

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Op donderdag 10 april 2014 21:47 schreef MartijnA3 het volgende:
Wat ik wel vreemd vind is dat een towed pinger locator kan luisteren naar een gebied van max 3700m breed. Toch zijn er op 4 plekken pings gehoord, met als grootste afstand 30km van elkaar.

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Op donderdag 10 april 2014 22:00 schreef gebrokenglas het volgende:

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Ja, dat verbaast mij ook. Wat zou kunnen is dat door sterke underwater currents, of doordat bepaalde lagen water van verschillende temperatuur is, het geluid meegenomen of afgebogen wordt. Wat dus ook het weer wegvallen van het signaal kan verklaren.

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Op donderdag 10 april 2014 22:10 schreef Nieuwschierig het volgende:

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c = 1449,2 + 4,6T - 0,055T² + 0,00029T³ + (1,34-0,01T)(S-35) + 0,016d

c = geluidssnelheid (m/s), T = temperatuur (°C), S = zoutgehalte (‰), d = waterdiepte (m)

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Op donderdag 10 april 2014 22:00 schreef gebrokenglas het volgende:

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Ja, dat verbaast mij ook. Wat zou kunnen is dat door sterke underwater currents, of doordat bepaalde lagen water van verschillende temperatuur is, het geluid meegenomen of afgebogen wordt. Wat dus ook het weer wegvallen van het signaal kan verklaren.

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Op donderdag 10 april 2014 22:14 schreef gebrokenglas het volgende:

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ehhh...

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Op donderdag 10 april 2014 22:22 schreef ATan het volgende:

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Okee goed werk Nieuwsgierig, dat is dus grofweg de geluidssnelheid onder water op zee, maar hoever kan het geluid gaan onder water bij welke amplitude voordat het uitdooft?

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Op donderdag 10 april 2014 22:38 schreef Nieuwschierig het volgende:

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Van walvissen is bekend dat ze met soortgenoten 500 km verderop kunnen communiceren. Dus niet alleen een ping uitwisselen

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This "channeling" of sound occurs because of the properties of sound and the temperature and pressure differences at different depths in the ocean. The ocean is divided into horizontal layers in which the speed of sound is greatly influenced by temperature in the upper layers and by pressure in the deeper layers. As temperature decreases, the speed of sound decreases, and as pressure (depth) increases, the speed of sound increases. Sound waves bend, or refract, towards the area of minimum sound speed. Therefore, a sound wave traveling through a thermocline (a region of rapid change in temperature with depth) tends to bend downward as the speed of sound decreases with decreasing water temperature, but then is refracted back upward as the speed of sound increases with increasing depth and pressure. This up-down-up-down bending of low-frequency sound waves allows the sound to travel many thousands of meters without the signal losing significant energy. The depth of this “channel” varies in different oceans depending on the salinity, the temperature, and depth of the water. At low and middle latitudes, the SOFAR channel axis lies between 600-1200 m below the sea surface. It is deepest in the subtropics and comes to the surface in high latitudes, where the sound propagates in the surface layer. Scientists often take advantage of the properties of the SOFAR channel. We have learned that by placing hydrophones at just the right depth (that is, at the axis of the sound channel) we are able to record sounds such as whale calls, earthquakes and man-made noise that occur many kilometers from the hydrophone. As a matter of fact, sometimes we can hear low-frequency sounds across entire ocean basins!. Image courtesy of Sounds in the Sea 2001, NOAA/OER.

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Sound in water is reflected at the surface and the bottom, as well as at boundary layers. The bottom material affects the strength of both reflection and absorption. Water salinity and temperature affect boundary layer conditions and angles of refraction. The frequency of the sound affects refraction, in similar fashion to the refraction of light of different wavelengths. Sound can be channeled underwater in the same way that images can be 'channeled' in air to produce mirages. The problem is further complicated by sea-bed topography - peaks and canyons can reflect or blank a signal.

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Op donderdag 10 april 2014 22:41 schreef ATan het volgende:

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Ik bedoelde eigenlijk dat Amplitude in decibel nog mist in je formule rechts, met Afstand in meters links en Geluidssnelheid in m/s ook naar rechts.

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Op donderdag 10 april 2014 21:12 schreef matthijst het volgende:
Nee joh, ze doen maar wat daar. Het gerucht gaat dat die boeien eigenlijk blikjes zijn met en touw eraan en dat er dan in de helicopter een Maleier (zo noemen ze die hier schijnbaar) zit die ook een blikje aan zijn oor zet en dan hoopt dat hij wat hoort. Het vreemde is dat de frequentie voor het menselijk oor niet hoorbaar is, maar dat geeft alleen maar aan wat een amateurs ermee bezig zijn.

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Op donderdag 10 april 2014 23:08 schreef Nieuwschierig het volgende:

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Die formule zegt niets over hoorbare afstand. Allen over de snelheid met betrekking tot de factoren die de snelheid beinvloeden.

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Op donderdag 10 april 2014 23:08 schreef eight het volgende:

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Ja, nu weten we het wel.

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Op vrijdag 11 april 2014 03:22 schreef matthijst het volgende:

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OK
Lachwekkend dat er elke twee dagen iemand kom die niks gelezen heeft van de afgelopen topics en dan doet alsof hij het vliegtuig wel even zal vinden vanaf z'n zolderkamer.

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Search teams looking for the missing Malaysia Airlines flight MH370 are "very confident" they have found the location of a black box, Australian Prime Minister Tony Abbott says.

"We have very much narrowed down the search area and we are very confident that the signals that we are detecting are from the black box," Abbott said from China.

Australia has been leading the search for the Boeing 777 aircraft, which went missing on March 8 en route from Kuala Lumpur to Beijing, ever since the operation was moved to the Indian Ocean.