I wrote briefly about DASH (Drone Anti-Submarine Helicopter) in this post.
DASH was a failure for several reasons. It was too cheaply-made, with multiple sources of single-point failure which would result in the loss of the drone. Because of DASH's small size and the fact that no transponders were installed, they had a propensity to disappear from radar and once that happened, they were effectively lost. There was also no feedback from the drones to the ships; so the controllers had no idea what a drone might be doing at any given moment.
35 years after DASH was canceled, the Navy began trying again to operate drone helicopters rom ships, though not for ASW. But that'll probably come to pass in the not-so distant future.
2 hours ago