The Sauer S 1800 is a family of German four-stroke aircraft engines, certified according to JAR 22-H (CS-22 subpart H)[1] [2]
The engine is based on the Volkswagen air-cooled engine, extensively modified for aircraft use and all the parts are custom made. They are certified according to CS-22 subpart H[3] and can therefore be used in motorgliders and light aircraft that are certified as CS-VLA[4] and CS-LSA[5]