Flight 370 - the Australians regain the signal

Which must be fast fading at this date.  No matter, they seem to be zeroing in on our lost plane.

Via the BBC:

  "Teams searching for the missing Malaysia Airlines plane have reacquired signals that could be consistent with "black box" flight recorders.

An Australian vessel heard the signals again on Tuesday afternoon and evening, the search chief said.

Signals heard earlier had also been further analysed by experts who concluded they were from "specific electronic equipment", he said."

ACM Houston said it was important to refine the search area as much as possible before sending down the Bluefin 21 underwater drone to search for wreckage.

"Now hopefully with lots of transmissions we'll have a tight, small area and hopefully in a matter of days we will be able to find something on the bottom," he said.

Other key points made by ACM Houston:

• The more signals received the easier it is to pinpoint a location. Signals seem to be fading, which is consistent with black box batteries going flat
• Vessels on the surface can cover the same search area six times faster than those underwater
• The ship that is searching for the signals has switched everything off apart from its engines to avoid noise
• Searchers have no idea what the sea bed looks like in the search area. They think it may be silty
• Silt is bad news. It can be thick and can hide things in a way that rock does not
• Dozens of sonar buoys with microphones attached will now be dropped 304m (997ft) below the surface to help listen for signals

Experts at the Australian Joint Acoustic Analysis Centre had also analysed the first two signals heard over the weekend, he added.

Their analysis showed that a "stable, distinct and clear signal" was detected. Experts had therefore assessed that it was not of natural origin and was likely to be from specific electronic equipment."

Continue reading the main story

One might wonder what the bottom is like in this area:

"Owing to strong geostrophic currents and consequent scouring of the sediments, the Wharton Basin, the southern Mascarene Basin, and parts of the Southwest Indian and Australian–Antarctic Basins have little or no sediment (Kennett, 1982). Sediment in these areas, when present, is mostly brown clay."

"There are strong bottom currents, with speeds approaching 10–20 cm s−1, in the Wharton Basin and the southern Mascarene Basin, and in parts of the Southwest Indian Basin and Australian–Antarctic Basins, resulting in minimal sediment deposition (Kennett, 1982; Gage and Tyler, 1991)."

Kennett, J.P., 1982. Marine Geology. Prentice-Hall, Englewood Cliffs, NJ, 813 pp.

I'm not sure if that is good or bad.  Strong currents might spread things out over miles, and make it dangerous for submersibles to maneuver, but it is the environment that they will have to work in.