Heinkel He 72

The Heinkel He 72 Kadett (Cadet) was a German single-engine biplane training aircraft from the 1930s. It was known to its pilots as Zitterrochen (Shivering Ray) because it shook wildly. It was also exported abroad, to Bulgaria, where it was used as a training aircraft. In Slovakia, they served as light attack aircraft carrying a small number of light bombs. Source: Wikipediahe