Mmmmmm ...
....
The Bo105 mentioned earlier in the thread dont have dump capability as a standard feature, it comes with the internal extra tank ...
... sorry ol' chap but that is incorrect ... go find the option supplements manual of the flight manual and all will be revealed !!
IIRC the internal (2x 200l slipper tanks) do not connect to fuel dump they flow into the main tank and only from there can the contents can be dumped.