Quote Originally Posted by Don Yarbrough View Post
Dane,

D-Window refers to the windows aft of the opening side windows, named for the traditional "D" shape on traditional Cubs.

All of the windows on the PA-18 have letters in the parts manual, starting with the front left "A" window (which sort of looks like an "A"), then the two slider windows B, C, and the two D windows in the back which are interchangeable p/ns, then the swing up window on the right is "E".