The flight engineer on a B-17 was essentially a flying ground crewman. His job was to monitor mechanical operation of the aircraft. If fuel leaks occurred, landing gear were stuck, turrets were jammed, or other problems resulting from battle damage or flak, it was the responsibility of the engineer to recognize the problem and try to repair it. A flight engineer sometimes made the difference in whether or not a plane returned home. The engineer was also responsible for manning the top turret gun. Since enemy fighters frequently attacked from above, this position was crucial to defense of the aircraft.