ChristiaanJ
Pockets of dye marker spread through the aircraft might be a help. Maybe one should go into each life vest?
And contrary to radio-active tracers, they would need no other equipment in the first search aircraft on the spot except the Mk 1 eyeball.
Updating the specs of the "pingers" in the recorders might help as well.
'Crying for help' a couple of days, then go to 'listen and reply' mode, with modern technology in the same unit housing, should be feasible.
The dye marker proposal seems simple enough, but by the time you think through what will happen to any liquid bearing the dye after mixing with fresh / sea water in its journey to the surface, the dispersion could be quite significant. The release of this marker dye needs to be in a controlled manner over time, else you finish up with dye on the surface along with any other debris. No different to what we have already witnessed. To implement the dye proposal will be fraught with a whole lot of constraints, e.g. the safety aspects of ensuring it will not be released in other than predetermined situations.
On the other-hand, the cry / listen mode for the pinger is a relatively simple technical solution - software plus exchanging the uni-mode "pinger" for a bi-mode "echo sounder". Battery life in the listen mode would then be extended for many months, as the listen on to off ratio need not be high. A hardware exchange for the existing FDR / CVR is the only implementation required.
mm43