the physics of active hydrofoils in war thunder (pgh-02 and pg02) were fairly acurate before the regia marina update when they added the sparviero they adited the physics for all of them and brokethem, they now bounce all over with small waves and can barely aim and turning got much worse
active hydrofoils use computer controled surfaces under water to ride at a certain height over small waves they do not ride the surface like surface piercing foils and they maintain a certain altitude above the water wich gives them stability at high speeds and makes them more stable in general as well. the hydrofoils work like control surfaces even when the hydrofoils is hullborne. this was mostly true for both the uss tucumcari and japanese pg-02 befor the update they also turn with minimal yaw drift because of the masive vertical fins that connect the foils.
after the update active hydrofoils act like surface piering hydrofoils which is wrong
they drift making their turning slow to react. in fast ships which are already easier to beach because of the foils it makes them fairly hard to use in tight spaces.
they now also bounce all over the place with even minimal waves making aiming almost imposible in the pgh-02 with a 40mm bofors the italian ship suffers too but the japanese with its fire rate is doable but not ideal or correct.
in heavy waves somtimes these ships jump out of the water and flip over, they also are unable to sail straight in even minimal wave conditions and constant corrections are needed
in the original devlog for the uss tucumcari the video portrays correct handling of the hydrofoils
i will link videos and images for comparison to the real boat and how the hanges have cripled active hydrfoils in war thunder