AirAsia plane's tail may be lifted to retrieve black boxes

[webfact]

AirAsia plane's tail may be lifted to retrieve black boxes
By ACHMAD IBRAHIM

PANGKALAN BUN, Indonesia (AP) — Strong currents and blinding silt thwarted an attempt by divers on Thursday to find AirAsia Flight 8501's black boxes, which are believed to still be in the recently discovered tail of the crashed plane.

The flight data and cockpit voice recorders are crucial for determining what caused the jet carrying 162 passengers and crew to vanish on Dec. 28, halfway into a two-hour flight between Surabaya, Indonesia, and Singapore.

Four bodies recovered Thursday raised the total to 44, Indonesian Search and Rescue Agency chief Henry Bambang Soelistyo said.

Days after sonar detected apparent wreckage, an unmanned underwater vehicle showed the plane's tail, lying upside down and partially buried in the ocean floor.

Divers looking for the black boxes on Thursday were unable to make it past currents and 1-meter (3-foot) visibility, Soelistyo said.

He said efforts will be intensified Friday to raise the tail — either with a lifting balloon or crane.

Ping-emitting beacons in the black boxes still have about 20 days of battery life, but high waves had prevented the deployment of ping locators, which are dragged by ships.

Three ships equipped with six ping locators were in the search area in the Java Sea, said Nurcahyo Utomo, an investigator of the National Commission for Transportation Safety.

Based on pictures taken by divers, he believed that the black boxes were still in their original location in the plane's tail.

"Once detected, we will try to find and lift up the black boxes as soon as possible," he said.

Officials are hopeful many of the bodies not yet recovered are inside the fuselage, which is thought to be lying near the plane's tail. Divers reaching the tail Thursday said they did not see bodies trapped in the broken-off tail section.

It's not clear what caused the crash, but bad weather is believed to have been a factor. The pilot told air traffic control he was approaching threatening clouds, but he was denied permission to change altitude because other planes were nearby. The plane soon lost contact.
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Associated Press writers Niniek Karmini and Ali Kotarumalos in Jakarta contributed to this report.


-- (c) Associated Press 2015-01-09

[Robby nz]

I know what its like trying to dive in zero or near zero vis and coupled with the short bottom time at that depth it will be making the divers job extremely difficult and dangerous.

I read an article written by a reporter who went out on one of the boats supplying the ships on station at the site, they were taking a black box locater set up out and it took them something like 6 hours battling high seas and strong winds to get to the ship.

When they got there they managed to get the locator on to the ship but it was to dangerous to transfer the technician to operate it or the inflatable needed as part of the set up, so the went back home with only half the job done.

Looks like they are doing a good job in the conditions they have to deal with. They desperately need a break in the weather.

[roasty]

I know what its like trying to dive in zero or near zero vis and coupled with the short bottom time at that depth it will be making the divers job extremely difficult and dangerous.

How deep is it? I've heard depths between 30 and 50m.

[neverdie]

How far is it from the rest of the fuselage ?

[Soutpeel]

I know what its like trying to dive in zero or near zero vis and coupled with the short bottom time at that depth it will be making the divers job extremely difficult and dangerous.

How deep is it? I've heard depths between 30 and 50m.

If they are diving on air at 50m, bottom times will be quite short,

Diving saturation would be the way to go as regards bottom time but doesn't help if there are strong currents about

[george]

Pings detected in search for AirAsia flight 8501

Indonesian search and rescue teams tasked with trying to locate the wreckage of missing Air Asia flight 8501

believe that signals from the plane’s black box recorder have been detected ...

Full story: http://www.streetwisejournal.com/pings-detected-search-air-asia-flight-8501/4232/

[Basil B]

How far is it from the rest of the fuselage ?

I do not think they have found the main fuselage, and it may not be intact...

[Robby nz]

I know what its like trying to dive in zero or near zero vis and coupled with the short bottom time at that depth it will be making the divers job extremely difficult and dangerous.

How deep is it? I've heard depths between 30 and 50m.

30 to 50 m is correct.

I have only been down to a little over 30m a few times and at that depth bottom time is very short and assent has to staged and be done very carefully to avoid the bends (decompression sickness) particularly at max bottom time.

This is because of the pressure involved, the deeper you go the quicker you use your air. This means you have to conserve air for the assent. If you were to carry more air you could stay down longer but then you have to do a longer staged assent to slowly decompress

50m is really out of the range of normal SCUBA gear, which looks to be what they are using from photos I have seen, going that deep is really only a bounce dive where you would touch bottom then start an assent.

Saturation diving that someone mentioned is an entirely different thing, that is where divers virtually live in a pressure chamber on the bottom and conduct dives out from there, this means that they stay at about the same pressure for days and sometimes weeks at a time. When they do come up they come up in a special pressure chamber and are then transferred to a decompression chamber where there they are decompressed to normal atmosphere over a carefully arranged time frame.

This is only done where long term work at depth needs to be done and needs careful planning, specialised gear and specially trained divers which they would not have and anyway the conditions of rough sea, strong currents and heavy silt would make their use impossible.