Boeing KC-97 Stratofreighter
The Boeing KC-97 Stratofreighter is a four-engined, piston-powered United States strategic tanker aircraft based on the Boeing C-97 Stratofreighter. It replaced the KB-29 and was succeeded by the Boeing KC-135 Stratotanker.
Source: Wikipedia — Boeing KC-97 Stratofreighter (CC BY-SA 4.0)