Back in the late early 1940's, when Igor Sikorsky was developing his helo and training pilots for the
USCG, he sat in the left seat and the student pilot sat in the right seat. The
U.S. Army only wanted the helo for reconaissance or observation duties.. The USN say the potential ASW use, but didn't want to tell the Army how to develop the flying machine. Eventually most of the military testing and development went to the USCG. Since the first military (USCG) helo pilots learned to fly from the right side, that became the PIC position. The early USCG helo pilots eventually taught the USN and Army pilots how to fly.