The battleships have a gun tube with a chamber and breech on the end. Projectiles, all one diameter, are rammed straight in. In Airwolf how do the varying sized missiles get loaded into the tubes? There's no way for them to load. The whole tube is outside the chopper. They have yo use a star trek transported to get the missiles into the tubes.

Check out the Iowa class battleships - each turret has three barrels but can only fire one at a time. The idea is that subsequent turrets can fire while the first is being reloaded.
So the three missile tubes could be to fire one at a time while the others reload, or (as you note) that each tube is a single shot.
It would have been far more realistic to show missiles on launch rails, but that would mean needing more stock footage (to show different loadouts), the possibility of continuity errors, and more expensive SFX to show the missile igniting and launching.
So for the most part - yeah, TV land practicality more than anything.
Philo's Law: To learn from your mistakes, you have to realize you're making mistakes.

I the ep Airwolf II, the Redwolf chopper only had one.
It was a ridiculous idea. Aside from the fact that they used missiles totally incorrectly, eg. air to ground for air to air etc they are all different diameters and lengths and would never fit a pod launch system like that. The loading mech would be virtually impossible as would loadout space.
In the end a fun TV show. Ignore the tech stuff.