Not on Hercs. Herc fuel tanks are vented to atmosphere. Unlike a fighter which requires a pressured fuel system to keep fuel flowing in aerobatics a Herc's is just pumped from the tank to the engines. Their is almost no pressure in the tanks at all. That is why the external tanks have two pumps, keep fuel flowing if one fails.

The main reason why the RAF Herc tanks leaked is they are flexible bag tanks. They need to be kept wet at all times to stop them cracking and leaking. Never happend in the RAF. They we so seldom used that they would dry out especially around the fixtures and fitting. Small leaks would start and leak into the dry bays around the tank and come out of the drains at the back of the main undercarriage.

Dax