I think in the case of a flying instructor, he/ she is the aircraft commander, and no doubt is trained to save the day when appropriate. In the case of a multi-crew environment pressumably the non-flying pilot is adequately trained to gauge the situation correctly and take control when necessary.
In both of these cases the pilots are flying legally and should have had sufficient training to enable them to take appropriate action.
In the case of a private flight it may be that you as a passenger feel the need to take control of a friends aircraft to save the day. However in this case it may well be that you are not able to fly his/ her aircraft because you don't have the required ratings, and you are also not insured.
I suspect if you did take control and there was a positive outcome you would be commended for your actions (if anyobdy ever found out), however if it all went tits-up then you would most certainly take the blame or part of it. What were you doing taking control of an aircraft you weren't adequately licensed/ insured to fly?
People in this day and age like to find someone to blame after all. Obviously it's better to not be dead!
Last edited by The500man; 19th Jan 2011 at 15:40.