On our DC-3 the cowl flaps had been modified. The upper cowl flaps had been removed and replaced with a fixed metal strip that had holes for cooling. The bottom cowl flaps operated the same as unmodified DC-3s.
As stated previously the three positions were/are Open-Trail-Closed. We used open for takeoff, trail for climb and closed in cruise.
I don't know if you can tell from this photo of my DC-3 or not.
