Refuelling in missions
 

How can i refuel to a friendly port? I play the Barham mission, i am close to a blue port (Benghazi, i think) and there is no option. I am supposed to press esc and choose doc x but it'not there. Maybe because my fuel is not empty yet? It's lower than half and i have a few torpedoes left. I am thinking that maybe it's not allowed refuelling in missions but only in campaigns.