The RAF's helicopter crewmen, who are WSOs, as the link above describes, are all trained to man the guns fitted in a hostile environment. However, that is just a small part of their job as they load the aircraft, assist in the navigation, etc.
The RAF's green helicopters used to have navigators, and there are still one or two flying, but it's not a career route open any more, not least that we stopped all navigator (Weapon System Officer) training about 3 years ago.