It's supposed to be an extremely low amount and the fuel pick-ups are placed such that it should never be a problem but there have been cases where water in the fuel caused problems, including at least one notorious crash where the cause was identified to be fuel contamination.
It's supposed to be an extremely low amount and the fuel pick-ups are placed such that it should never be a problem but there have been cases where water in the fuel caused problems, including at least one notorious crash where the cause was identified to be fuel contamination.