If a ship (like the Shadow Caster for example) has a fixed primary weapon and a turret primary weapon on its card may it fire both in the same activation? Or is the turret still considered a special attack?

Only one per engagement unless an upgrade or ability specifies otherwise.

You just have two options for where to shoot from.

i second that: just 1 attack. but your primary weapon has 2 attack arcs available to choose from.

Perfect! That makes sense as the double arc turret works the same way. Thanks!

1 hour ago, Cpt Horatius said:

Perfect! That makes sense as the double arc turret works the same way. Thanks!

Depending on the ship, you may still want to have your primary and secondary arcs overlapping, anyway. For the Lancer Pursuit Craft, Ketsu Onyo really wants her targets in both arcs, while both Sabine and Asajj want their enemies in their both arcs; the mobile arc for their abilities, and the primary arc for the extra attack die.

Meanwhile, most HWK-290 pilots that run Moldy Crow want to keep the two arcs separate, to maximize their ability coverage. Jan Ors, Kyle Katarn, Roark Garnet, Palob Godalhi, and Torkil Mux all look at targets in their "firing arc," which includes both Primary (from the title) and Turret options.