The Russians are starting trials with a radar roughly equivalent to the Longbow for the Kamov Ka-52 helicopter, with a roughly 30km range. (paid subscription required)
The cost for the 2nd seat and radar that were added in the upgrade from the Ka-50 is that a lot of the armor has been removed to keep weight below 10 metric tonnes.
Mostly I’m posting this for the picture, because I’ve always found the coaxial helicopters to look “cool”