What rank in the coast guard pilots a helicopter?

The rank of a Coast Guard Helicopter Pliot varies. Because the pilot will have to have completed flight training, the minimum rank is Lt(jg) (O-2), but more than likely all pilots will have made full Lt (O-3) by the time they pin on their wings.

The highest rank for a pilot is typically a LCDR (O-4). By the time an officer is selected for CDR (O-5), they are typically not in the flight line. At the same time, provided they maintain their flight qualifications, CDR's can be pressed into flight service in emergent situations.