Chances of locator beacons transmittors working
1) Fixed ELTs(Qty 2) - Works only in case of over land crashes.
2) Portable ELT(Qty 1) - Someone has to turn it on and not under water
3) Beacons on rafts(Qty 8) - Need salt water contact to activate, but has to be above water level to transmit.
4) ULBs on CVR/FDR(Qty 2) - Underwater only, limited range, limited life.
Big assumption these are maintained properly.
So sonar sweeps and ROV visual searches have better probability than these.