Ok. The entire time i was in the navy. "left downwind approved" or "enter left downwind" was the way to instruct an aircraft on the upwind to enter the downwind.
we used the term "left closed" as a preventative control method.
"tower, VVLL23 request downwind."
"LL23, left closed traffic approved, report the 180 (base) with the gear each pass."
this told the pilot he could turn downwind with out permission, he would call the tower at the baseleg and we would give him his clearance... then he would do his approach, and turn downwind at his discretion. we actually had a rule at our facility that we could have 4 (maybe it was 6) a/c operating in "left closed." we just told each one who to follow, and that was it. they turned downwind at their own discretion.
now, when we would get airforce airplanes in our pattern, they didnt understand this. i had to spell it out to them every time. "left closed" to them, was "left downwind."
and where i'm working at now, it's the same way. (i work at an army tower as a civilian contractor.) they all use the term left closed to tell an aircraft left downwind.
is "left closed" actually defined anywhere?