to ac: read properly .....from google translate....your guess is as good as mine i guess!
but more to the point:
http://www.nst.com.my/latest/font-color-red-missing-mh370-font-aviation-expert-suggests-6-reasons-fo...
Under Water Beacon (ULB) can emit a signal for hundreds of milesbut if the black box is covered with debris or falls into a trench at the bottom of the sea, then the strength and range of the signal would be lower.
The ELT and beacons use their own batteries and electrical failure does not affect them.
"The batteries of the beacons of the black box beacon are designed to last 28 days. If the black box beacon battery dies and the plane is not located within that time, then the only hope is to find the debris and try to work backwards from there on," he said..."...
....the area where plane last tracked was over sea but not over deep water 'trenches'
