the portable ELT's will also activate automatically when immersed.
I think a likely scenario is that on impact, the device became immersed enough to cause automatic activation.., but it never floated free of the wreckage. Then, the piece of wreckage to which it was attached popped up to the surface where it remained for a few minutes, broadcasting the 406mhz signal to satellites. Then,as trapped air escaped from that piece of wreckage, it sank, bringing the ELT with it, and the signal was no longer received by the satellites.
more or less the same thing could have happened with a fixed ELT that activated upon impact.
ELT's have unique identifiers that are broadcast with the distress signal, and it's possible that if the transmission was of long enough duration, they know whether it was a fixed or portable ELT that sent the signal.
The portable ELT's are actually designed to operate while floating in the water. So, if you ever find yourself in a life raft with an ELT.., what you are supposed to do is activate the ELT - if it hasn't activated automatically - and tie it with a lanyard to the life raft.., and let it float in the water alongside the liferaft. You are not supposed to keep it with you in the life raft.
Last edited by x_navman; 31st May 2016 at 23:51.