John H. wrote:

Why do you see helicopters flying with their doors open?

Open? How about 'off'. I don't recall ever seeing the damn doors.
--
John H

They were around, John. (pic of a USN HU-UD1)

http://www.fas.org/man/dod-101/sys/ac/uh-1-dvic328.jpg


You had to remove them if you had a fixed m-134 mini or a stationary
mounted M-2, but they could have been left on., just not closed. Less
weight and less turbulance.

Most had them taken off, though, unless it was an actual MED-VAC
'copter

Turbulance? in a ... chopper????