Over the years there were a number of refinements in the aircraft. The original hydraulic gear and flap actuation system was redesigned in 1968 introducing electric flaps. In 1969 the FAA issued Type Certificate A18CE and the aircraft built under that design were designated the "A" series "Super Vikings". Aside from refinements already made to late Viking 300 models, the new 300A Vikings (17-30A, 17-31A and 17-31ATC) had a gross weight increase to 3,325 lbs. The original complex fuel system with five tanks and two fuel selectors allowing eight possible combinations of selector settings was simplified to a left, right and auxiliary system in 1974. In 1979 the Continental powered Vikings sported a fully enclosed nosewheel thanks to a redesign of the engine mount. This necessitated the use of cowl flaps for the first time on the Viking but resulted in a 12 mph increase. In 1979 production of the Lycoming powered 17-31A ceased. In 1996, the Continental IO-550 was made available as an option.