The 'maximum detection range is 2 - 3km' which is fairly useless. As became clear in the Air France search what's required is a massive pulse to give a sensible range, delivered at far longer intervals to allow battery life to be extended.
One huge 'ping' every hour, for example, would have had this plane located by now, assuming it's under water.
Fast pulses, in an environment where everything moves slowly, are a waste.