BAe Hawk tailplane trailing edge rivets?
 

Looking at a BAe Hawk a couple of days ago, I noticed that the trailing edge of the tailplane had very pronounced rivets holding the skins together, whereas all the other surfaces appeared to be either flush riveted or had no rivets. Are the tailplane rivets intended to act as turbulators/some sort of Gurney flap, or is it just the way it is made?

No point putting the effort into flush riveting if the boundary layer is too thick at the point to matter all that much.

They aren't there for any deliberate aerodynamic purpose.

Look at the back end of the fuselage on a Hawk as well; it's a mass of rivets as well. Same logic - the drag improvement of flush riveting is negligible.