The EC135 is merely a follow on from the Bo 105 ??
Wasn't the bo105 originally designed as an anti-tank helicopter ?
The only similarity I can see between their fuel systems is that they have overflow pipes and transfer pumps to fill the supply tank (in an EC135 that is tanks, plural)..... Just like many other helicopter fuel systems, so what's so unusual about that?
Surely a supply tank is there to ensure a dedicated engine 'supply' of fuel, regardless of what else is happening in the the fuel storage system and with the attitude of the helicopter?