Is there any schematic how they work? if I'm understanding what I see in the photos, the bottom part is moveable and the bottom opening size varies, plus there is the anti-ice rubber boot.
TIA
Vedran
IIRC there isn't any movable part for the slot type. These are the fixed ones and work like those attached outside. The larger angle of attack of the wing and smaller speed the more of the air runs into the slot going out at the tops and causing increasing of the lift.
These bottom openings weren't adjustable rather. It is a light trick. The colours there and the angle the images were taken with make this. The areas around the openings and the inner surfaces of the slots were painted black. Also because there were the inspection/accessing hatches. You may notice them in the enlarged shot of your first image posted above and others below here. In other words the black rectangles at the bottom were a kind of the techical markings/ stenciling making easier to notice the openings. However the factory way of making the slots could have varied in order to make them simpler in construction and attaching for the the different batches of the PV-1. In these shots you may notice these were made in two versions.
Thank you Wurger!
Your 4th photo clearly shows the deicing rubber boots for the slots (including fixing profiles as per the erection manual) and the 5th photo shows the slots sans the boots. We are making progress!
Cheers,
Vedran