<image>Given that the quadrangular pyramid $$P-ABCD$$ has a base that is a parallelogram, $$PA \bot $$ plane $$ABCD$$, $$PA=AB=AC=4$$, and $$AB\bot AC$$. Points $$E$$ and $$F$$ are located on segments $$AB$$ and $$PD$$, respectively. 

$$(1)$$ Prove: Plane $$PDC \bot $$ plane $$PAC$$;
$$(2)$$ If the volume of the triangular pyramid $$E-DCF$$ is $$4$$, find the value of $$\dfrac{FD}{PD}$$.