I think the Corps still has CWO's and they go to 5 now insted of 4 being top.When I got out in 69 Capt. was about the higest rank I ever saw fling a chopper but lots of CWO's and they were great. Many enlisted door gunners from Korea era became CWO pilots durning Viet Nam days and seemed to hold their cargo more dear than the new butter bars just getting in the game.
As a side note in 66 in Nam I meet the last two inlisted pilots of the Army Air Corps in DaNang. They were teaching the Arvin pilots how to fly the old prop plane fighters.