In the 1st season (which we just finished -- reruns start this week), we see Scott take the center seat once in "A Taste of Armageddon". Sulu has it at least twice that I recall: in "Arena" and "Errand of Mercy". Those are also both higher stakes situations--the ship is in combat, at war in the latter episode. Now, Sulu is a Lieutenant and Scott is (presumably) a Lieutenant Commander. I say presumably because I don't know that it's ever explicitly stated, and braid on sleeve does not always match stated rank (viz. "Lieutenant Commander" Spock with two stripes and "Lieutenant" Masters with no stripe). In later seasons, especially with Takei gone to make a movie, it's firmly and explicitly stated that Scott is the 2nd Officer. But in the 1st season, it seems that Sulu might be higher up in the pecking order, which would make sense with the "Line", "Staff", "Engineering" uniform division--a Lieutenant in Line would be in, well, line to take over the conn before someone in Engineering (and certainly Staff -- no one ever thinks of giving command to McCoy, though he is senior officer when Spock is arrested in "Menagerie"). This all gets a little confused since Spock was explicitly "Second Officer" in "The Enemy Within". Who was First Officer then? In any event, by the time Spock was explicitly the First Officer on the Enterprise, who was Second Officer? Sulu or Scott? Or did they share the title, on different shifts? (There's precedent for that -- I'm reading about a WW2 merchant marine vessel that had two third mates, one of them junior).