The Walter NZ 40 was an unsuccessful, three-cylinder, air-cooled, radial engine for aircraft use built in Czechoslovakia by Walter Aircraft Engines in the late-1920s.
Using common cylinders and parts from the earlier Walter NZ 60 (Novák-Zeithammer) engine the NZ 40 was the last in this series of engines.[1] Problems with imbalance causing vibrations lead to the type being redesigned as the NZ 45. This version underwent a type test in early 1932 but the problems were not fully resolved and the engine did not find any aircraft application. Very few of these engines were produced before being replaced in the range by the Walter Polaris.[2]